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Sample records for su-8 negative resist

  1. SU-8 negative photoresist for optical mask manufacturing

    Science.gov (United States)

    Bogdanov, Alexei L.

    2000-06-01

    The requirements for better control, linearity, and uniformity of critical dimension (CD) on photomasks in fabrication of 180 and 150 nm generation devices result in increasing demand for thinner, more etching durable, and more sensitive e-beam resists. Novolac based resists with chemical amplification have been a choice for their sensitivity and stability during etching. However, difficult CD control due to the acid catalyzer diffusion and quite narrow post exposure bake (PEB) process window are some of the major drawbacks of these resists. SU-8 is recently introduced to the market negative photoresist. High sensitivity, fairly good adhesion properties, and relatively simple processing of SU-8 make it a good substitution for novolac based chemically amplified negative e-beam resists in optical mask manufacturing. The replacement of traditional chemically amplified resists by SU- 8 can increase the process latitude and reduce resist costs. Among the obvious drawbacks of SU-8 are the use of solvent- based developer and demand of oxygen plasma for resist removal. In this paper the use of SU-8 for optical mask manufacturing is reported. All steps of resist film preparation, exposure and development are paid a share of attention. Possibilities to use reactive ion etching (RIE) with oxygen in order to increase resist mask contrast are discussed. Special exposure strategy (pattern outlining) was employed to further improve the edge definition. The resist PEB temperature and time were studied to estimate their weight in overall CD control performance. Specially designed test patterns with 0.25 micrometer design rule could be firmly transferred into a chromium layer both by wet etching and ion milling. Influence of exposure dose variation on the pattern CD change was studied.

  2. Moisture resistance of SU-8 and KMPR as structural material

    NARCIS (Netherlands)

    Blanco Carballo, V.M.; Melai, J.; Salm, Cora; Schmitz, Jurriaan

    2009-01-01

    This paper treats the moisture resistance of SU-8 and KMPR, two photoresists considered as structural material in microsystems. Our experiments focus on the moisture resistance of newly developed radiation imaging detectors containing these resists. Since these microsystems will be used unpackaged,

  3. Moisture resistance of SU-8 and KMPR as structural material for integrated gaseous detectors

    NARCIS (Netherlands)

    Blanco Carballo, V.M.; Melai, J.; Salm, Cora; Schmitz, Jurriaan

    2008-01-01

    This paper treats the moisture resistance of SU-8 and KMPR, two photoresists considered as structural material in microsystems. Our experiments focus on the moisture resistance of newly developed radiation imaging detectors containing these resists. Since these microsystems will be used unpackaged,

  4. Contact printed masks for 3D microfabrication in negative resists

    OpenAIRE

    Häfliger, Daniel; Boisen, Anja

    2005-01-01

    We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded into the negative resist to protect buried material from UV-exposure. Unlike direct evaporation-deposition of a mask onto the SU-8, printing avoids high stress and radiation, thus preventing resist wrinkling a...

  5. Contact printed masks for 3D microfabrication in negative resists

    DEFF Research Database (Denmark)

    Häfliger, Daniel; Boisen, Anja

    2005-01-01

    We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded into the ......We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded...... into the negative resist to protect buried material from UV-exposure. Unlike direct evaporation-deposition of a mask onto the SU-8, printing avoids high stress and radiation, thus preventing resist wrinkling and prepolymerization. We demonstrate effective monolithic fabrication of soft, 4-μm thick and 100-μm long...

  6. High resolution 100 kV electron beam lithography in SU-8

    DEFF Research Database (Denmark)

    Olsen, Brian Bilenberg; Jakobsen, S.; Schmidt, M.S.

    2006-01-01

    High resolution 100 kV electron beam lithography in thin layers of the negative resist SU-8 is demonstrated. Sub-30 nm lines with a pitch down to 300 nm are written in 100 nm thick SU-8. Two reactive ion etch processes are developed in order to transfer the SU-8 structures into a silicon substrate......, a Soft O-2-Plasma process to remove SU-8 residues on the silicon surface after development and a highly anisotropic SF6/O-2/CHF3 based process to transfer the pattern into a silicon substrate, with selectivity between silicon and SU-8 of approximately 2. 30 nm lines patterned in SU-8 are successfully...

  7. Volume Hologram Formation in SU-8 Photoresist

    Directory of Open Access Journals (Sweden)

    Tina Sabel

    2017-05-01

    Full Text Available In order to further understand the mechanism of volume hologram formation in photosensitive polymers, light-induced material response is analyzed in commonly used epoxy-based negative photoresist Epon SU-8. For this purpose, time-resolved investigation of volume holographic grating growth is performed in the SU-8 based host–guest system and in the pure SU-8 material, respectively. The comparison of grating growth curves from doped and undoped system allows us to draw conclusions on the impact of individual components on the grating formation process. The successive formation of transient absorption as well as phase gratings in SU-8 is observed. Influence of exposure duration and UV flood cure on the grating growth are investigated. Observed volume holographic grating formation in SU-8 can be explained based on the generation and subsequent diffusion of photoacid as well as time-delayed polymerization of exposed and unexposed areas.

  8. Comparison of High Resolution Negative Electron Beam Resists

    DEFF Research Database (Denmark)

    Olsen, Brian Bilenberg; Schøler, Mikkel; Shi, Peixiong

    2006-01-01

    Four high resolution negative electron beam resists are compared: TEBN-1 from Tokuyama Corp. Japan, ma-N 2401XP and mr-L 6000AXP from microresist technology GmbH Germany, and SU-8 2000 series from MicroChem Corp., USA. Narrow linewidth high density patterns are defined by 100 kV electron beam...

  9. SU-8 cantilever chip interconnection

    DEFF Research Database (Denmark)

    Johansson, Alicia Charlotte; Janting, Jakob; Schultz, Peter

    2006-01-01

    The polymer SU-8 is becoming widely used for all kinds of micromechanical and microfluidic devices, not only as a photoresist but also as the constitutional material of the devices. Many of these polymeric devices need to include a microfluidic system as well as electrical connection from...... the electrodes on the SU-8 chip to a printed circuit board. Here, we present two different methods of electrically connecting an SU-8 chip, which contains a microfluidic network and free-hanging mechanical parts. The tested electrical interconnection techniques are flip chip bonding using underfill or flip chip...... bonding using an anisotropic conductive film (ACF). These are both widely used in the Si industry and might also be used for the large scale interconnection of SU-8 chips. The SU-8 chip, to which the interconnections are made, has a microfluidic channel with integrated micrometer-sized cantilevers...

  10. Chemical synthesis on SU-8

    DEFF Research Database (Denmark)

    Qvortrup, Katrine; Taveras, Kennedy; Thastrup, Ole

    2011-01-01

    In this paper we describe a highly effective surface modification of SU-8 microparticles, the attachment of appropriate linkers for solid-supported synthesis, and the successful chemical modification of these particles via controlled multi-step organic synthesis leading to molecules attached...

  11. Tailoring the mechanical properties of SU-8/clay nanocomposites: polymer microcantilever fabrication perspective

    CSIR Research Space (South Africa)

    Chen, H

    2014-03-01

    Full Text Available SU-8/Clay nanocomposite is considered as a candidate material for microcantilever sensor fabrication. Organically modified montmorillonite clay nanoparticles are dispersed in the universally used negative photoresist polymer SU-8, for a low cost...

  12. High temperature SU-8 pyrolysis for fabrication of carbon electrodes

    DEFF Research Database (Denmark)

    Hassan, Yasmin Mohamed; Caviglia, Claudia; Hemanth, Suhith

    2017-01-01

    spectroscopy and Raman spectroscopy were used to characterize the pyrolytic carbon. The results show that the temperature increase from 900 °C to 1100 °C improves the electrical and electrochemical properties. At 1100 °C, longer dwell time leads to lower resistivity, while the variation of the pyrolysis...... composite experimental design was used to identify the influence of dwell time at the highest pyrolysis temperature and heating rate on electrical, electrochemical and structural properties of the pyrolytic carbon: Van der Pauw sheet resistance measurements, cyclic voltammetry, electrochemical impedance......In this work, we present the investigation of the pyrolysis parameters at high temperature (1100 °C) for the fabrication of two-dimensional pyrolytic carbon electrodes. The electrodes were fabricated by pyrolysis of lithographically patterned negative epoxy based photoresist SU-8. A central...

  13. Further outgassing studies on SU-8

    NARCIS (Netherlands)

    Melai, J.; Blanco Carballo, V.M.; Salm, Cora; Wolters, Robertus A.M.; Schmitz, Jurriaan

    2008-01-01

    SU-8 is often used as a structural material in microsystems. In this work the outgassing characteristics from such cross-linked SU-8 layers are studied using Mass Spectrometry and Gas Chromatography techniques. With these methods the composition of the released matter can be identified, also the

  14. SU-8 Based Piezoresistive Mechanical Sensor

    DEFF Research Database (Denmark)

    Thaysen, Jacob; Yalcinkaya, Arda Deniz; Vestergaard, R.K.

    2002-01-01

    We present the first SU-8 based piezoresistive mechanical sensor. Conventionally, silicon has been used as a piezoresistive material due to its high gauge factor and thereby high sensitivity to strain changes in a sensor. By using the fact that SU-8 is much softer than silicon and that a gold...

  15. Functionalization of SU-8 Photoresist Surfaces with IgG Proteins

    DEFF Research Database (Denmark)

    Blagoi, Gabriela; Keller, Stephan Urs; Johansson, Alicia

    2008-01-01

    The negative epoxy-based photoresist SU-8 has a variety of applications within microelectromechanical systems (MEMS) and lab-on-a-chip systems. Here, several methods to functionalize SU-8 surfaces with IgG proteins were investigated. Fluorescent labeled proteins and fluorescent sandwich immunoass......The negative epoxy-based photoresist SU-8 has a variety of applications within microelectromechanical systems (MEMS) and lab-on-a-chip systems. Here, several methods to functionalize SU-8 surfaces with IgG proteins were investigated. Fluorescent labeled proteins and fluorescent sandwich...... SU-8 in a functional fluorescent sandwich immunoassay detecting C-reactive protein (CRP) gave twice as high signal as compared with the other two surfaces. Immunoassays performed on bare SU-8 and CAN treated SU-8 resulted in detection limits of CRP of 30 and 80 ng/ml respectively which is sufficient...

  16. Innovative SU-8 Lithography Techniques and Their Applications

    Directory of Open Access Journals (Sweden)

    Jeong Bong Lee

    2014-12-01

    Full Text Available SU-8 has been widely used in a variety of applications for creating structures in micro-scale as well as sub-micron scales for more than 15 years. One of the most common structures made of SU-8 is tall (up to millimeters high-aspect-ratio (up to 100:1 3D microstructure, which is far better than that made of any other photoresists. There has been a great deal of efforts in developing innovative unconventional lithography techniques to fully utilize the thick high aspect ratio nature of the SU-8 photoresist. Those unconventional lithography techniques include inclined ultraviolet (UV exposure, back-side UV exposure, drawing lithography, and moving-mask UV lithography. In addition, since SU-8 is a negative-tone photoresist, it has been a popular choice of material for multiple-photon interference lithography for the periodic structure in scales down to deep sub-microns such as photonic crystals. These innovative lithography techniques for SU-8 have led to a lot of unprecedented capabilities for creating unique micro- and nano-structures. This paper reviews such innovative lithography techniques developed in the past 15 years or so.

  17. Special Issue: 15 Years of SU8 as MEMS Material

    Directory of Open Access Journals (Sweden)

    Arnaud Bertsch

    2015-06-01

    Full Text Available In 1997, the first paper using SU-8 as a material for microfabrication was published [1], demonstrating the interest of this negative photoresist for the near-UV structuration of thick layers and the manufacturing of high aspect-ratio components.[...

  18. Diffusion of water into SU-8 microcantilevers

    DEFF Research Database (Denmark)

    Liu, C.J.; Liu, Y.; Sokuler, M.

    2010-01-01

    We present a method to monitor the diffusion of liquid molecules in polymers. A microdrop of water is deposited by a piezoelectric drop generator onto the upper surface of a cantilever made of SU-8 based photoresist. In response, the cantilever bends in the opposite direction. We find that this b...... sophisticated finite element model the diffusion coefficient of water in the SU-8 polymer can be determined quantitatively from the dynamics of cantilever bending.......We present a method to monitor the diffusion of liquid molecules in polymers. A microdrop of water is deposited by a piezoelectric drop generator onto the upper surface of a cantilever made of SU-8 based photoresist. In response, the cantilever bends in the opposite direction. We find...... that this bending is mainly caused by the diffusion of water into the cantilever and the consequent swelling of SU-8. Using a one-dimensional diffusion model and assuming a simple swelling law, we qualitatively model the bending of the cantilever during in and out diffusion of water in SU-8. With a more...

  19. Arrayed SU-8 polymer thermal actuators with inherent real-time feedback for actively modifying MEMS’ substrate warpage

    Science.gov (United States)

    Wang, Xinghua; Xiao, Dingbang; Chen, Zhihua; Wu, Xuezhong

    2016-09-01

    This paper describes the design, fabrication and characterization of a batch-fabricated micro-thermal actuators array with inherent real-time self-feedback, which can be used to actively modify micro-electro-mechanical systems’ (MEMS’) substrate warpage. Arrayed polymer thermal actuators utilize SU-8 polymer (a thick negative photoresist) as a functional material with integrated Ti/Al film-heaters as a microscale heat source. The electro-thermo-mechanical response of a micro-fabricated actuator was measured. The resistance of the Al/Ti film resistor varies obviously with ambient temperature, which can be used as inherent feedback for observing real-time displacement of activated SU-8 bumps (0.43 μm Ω-1). Due to the high thermal expansion coefficient, SU-8 bumps tend to have relatively large deflection at low driving voltage and are very easily integrated with MEMS devices. Experimental results indicated that the proposed SU-8 polymer thermal actuators (array) are able to achieve accurate rectification of MEMS’ substrate warpage, which might find potential applications for solving stress-induced problems in MEMS.

  20. SU-8 Cantilever Sensor with Integrated Read-Out

    DEFF Research Database (Denmark)

    Johansson, Alicia Charlotte

    2007-01-01

    kan måles med optiske målesystemer eller ved hjælp af integrerede piezoresistorer. Dette PhD projekt beskriver design, fremstilling og indpakning af en polymer cantilever chip med piezoresistive udlæsning. Chippen er fremstillet i den epoxy-baserede negative fotoresist SU-8, på nær de integrerede guld...... resistorer. Cantilever baserede sensorer bliver normalt fremstillet i silicium men fordelen ved at bruge SU-8 er, at SU-8 er et blødere materiale som er billigere og hurtigere at fremstille. For at opnå elektrisk kontakt fra chippen til et printet kredsløbskort, er flere metoder så som flip-chip bonding...... blevet undersøgt. Chippen er blevet brugt til overfladestress målinger i væske, så som thiol binding og detektion af pH forandringer. Teoretiske beregninger af følsomheden for overfladestress og den mindste målbare overfladestress bliver også beskrevet. Til sidst diskuteres muligheden for at binde...

  1. Novel method for chemical modification and patterning of the SU-8 photoresist

    DEFF Research Database (Denmark)

    Blagoi, Gabriela; Keller, Stephan Urs; Boisen, Anja

    2007-01-01

    In this paper we describe a new photochemical method to tailor and pattern the surface of SU-8 negative photoresist. Antraquinone (AQ) derivatives were used to chemically modify and pattern SU-8 surfaces. Using AQ derivatives with electophilic moieties (AQ-E), we could chemo-selectively change...... the wetting behaviour of SU-8. The resolution limit of the AQ photopatterning method was 20 μm when using an uncollimated light source. AQ modification followed by a reaction with amino groups of Alexa-647 cadaverine and a Biotin-amino derivative proved possible modification and patterning of polymeric...

  2. Functionalized SU-8 patterned with X-ray Lithography

    DEFF Research Database (Denmark)

    Balslev, Søren; Romanato, F.

    2005-01-01

    spontaneous emission light source that couples out light normal to the chip plane. In addition we examine the influence of the x-ray irradiation on the fluorescence of thin films of dye doped SU-8. The dye embedded in the SU-8 is optically excited during, characterization by an external light source tuned...

  3. Polydimethylglutarimide (PMGI) as a sacrificial material for SU-8 surface-micromachining

    Science.gov (United States)

    Foulds, I. G.; Johnstone, R. W.; Parameswaran, M.

    2008-07-01

    SU-8 is finding increased use as a structural polymer MEMS material due to its biocompatibility, mechanical properties and low cost. The goal of this work is to expand the use of SU-8 through the creation of SU-8-based surface-micromachining processes that use polydimethylglutarimide (PMGI) as a sacrificial layer. PMGI is a deep-UV positive resist, used mainly for bilayer lift-off processes. PMGI is a good sacrificial layer candidate, as it is spinable at a wide variety of thicknesses, is photopatternable and has a glass transition temperature greater than the processing temperatures required for SU-8. PMGI is shown to be useful as a sacrificial layer for SU-8 surface micromachining processes with one freestanding layer with patterned metal, single-layer devices with more than one thickness, and two layer devices. Two classes of devices were fabricated with the developed processes. The first class of devices are compliant mechanisms, including bent-beam actuators, thermal isolation platforms and out-of-plane grippers. The second class of devices fabricated are freely moving devices such as hinged plates and gears, which require the use of true kinematic joints, such as scissor hinges, staple hinges and pin joints.

  4. Novel SU-8 based vacuum wafer-level packaging for MEMS devices

    DEFF Research Database (Denmark)

    Murillo, Gonzalo; Davis, Zachary James; Keller, Stephan Urs

    2010-01-01

    This work presents a simple and low-cost SU-8 based wafer-level vacuum packaging method which is CMOS and MEMS compatible. Different approaches have been investigated by taking advantage of the properties of SU-8, such as chemical resistance, optical transparence, mechanical reliability...... and versatility. A novel technique of wafer level adhesive bonding, which uses SU-8 as structural and adhesive material, has been developed and successfully demonstrated. Optical inspection and SEM images were used in order to measure the package lid bending and probe the encapsulation sealing. In addition......, an indirect vacuum level measurement has been carried out by comparing the different quality factors of a test cantilever resonator when this element is packed or unpacked....

  5. Electroluminescence and negative differential resistance studies of ...

    Indian Academy of Sciences (India)

    Negative differential resistance (NDR) characteristics observed at a low voltage region in blended OLED is related to the generation of guest hopping site and phonon scattering phenomenon. However, luminescence of the devices is not altered by the NDR effect. Keywords. Organic-light-emitting diodes; Alq3; TPD; PBD; ...

  6. Electroluminescence and negative differential resistance studies of ...

    Indian Academy of Sciences (India)

    Electroluminescence properties were investigated with respect to blend systems. Significant improvement in turn-on voltage and luminance intensity was observed by employing the blends technique. Negative differential resistance (NDR) characteristics observed at a low voltage region in blended OLED is related to the ...

  7. Deep proton writing of high aspect ratio SU-8 micro-pillars on glass

    Energy Technology Data Exchange (ETDEWEB)

    Ebraert, Evert, E-mail: eebraert@b-phot.org; Rwamucyo, Ben; Thienpont, Hugo; Van Erps, Jürgen

    2016-12-15

    Deep proton writing (DPW) is a fabrication technology developed for the rapid prototyping of polymer micro-structures. We use SU-8, a negative resist, spincoated in a layer up to 720 μm-thick in a single step on borosilicate glass, for irradiation with a collimated 12 MeV energy proton beam. Micro-pillars with a slightly conical profile are irradiated in the SU-8 layer. We determine the optimal proton fluence to be 1.02 × 10{sup 4} μm{sup −2}, with which we are able to repeatably achieve micro-pillars with a top-diameter of 138 ± 1 μm and a bottom-diameter of 151 ± 3 μm. The smallest fabricated pillars have a top-diameter of 57 ± 5 μm. We achieved a root-mean-square sidewall surface roughness between 19 nm and 35 nm for the fabricated micro-pillars, measured over an area of 5 × 63.7 μm. We briefly discuss initial testing of two potential applications of the fabricated micro-pillars. Using ∼100 μm-diameter pillars as waveguides for gigascale integration optical interconnect applications, has shown a 4.7 dB improvement in optical multimode fiber-to-fiber coupling as compared to the case where an air–gap is present between the fibers at the telecom wavelength of 1550 nm. The ∼140 μm-diameter pillars were used for mold fabrication with silicone casting. The resulting mold can be used for hydrogel casting, to obtain hydrogel replicas mimicking human tissue for in vitro bio-chemical applications.

  8. Immunosensing by luminescence reduction in surface-modified microstructured SU-8

    Energy Technology Data Exchange (ETDEWEB)

    Eravuchira, Pinkie Jacob; Baranowska, Malgorzata; Eckstein, Chris [Departament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Avda. Països Catalans 26, Tarragona 43007 (Spain); Díaz, Francesc [Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcelí Domingo s/n, Tarragona 43007 (Spain); Llobet, Eduard; Marsal, Lluis F. [Departament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Avda. Països Catalans 26, Tarragona 43007 (Spain); Ferré-Borrull, Josep, E-mail: josep.ferre@urv.cat [Departament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Avda. Països Catalans 26, Tarragona 43007 (Spain)

    2017-01-15

    Highlights: • The reduction of photoluminescence of SU-8 upon surface modification is reported. • Micropillar structuring of SU-8 surface results in an increased photoluminescence reduction rate (10% glass, 15% silicon). • Photoluminescence reduction rate can be a transduction parameter for the detection of antibody-antigen binding events. • The proposed sensing mechanism can be used to quantify small concentrations of antibody. • Lower limit of detection (LOD) of 28 μg/ml on silicon substrates and 42 μg/ml on glass substrates was achieved. - Abstract: SU-8, an epoxy based negative photoresist is extensively used as a structural material for the fabrication of microelectro-mechanical systems and in microelectronics technology. However, the possible applications of SU-8 for biosensing have not been explored much, mainly because of the photoluminescence SU-8 possesses in the near-UV and visible wavelength ranges which hinders fluorescent labelling of biorecognition events. In this study we demonstrate that photoluminescence of SU-8 can be employed itself as a sensing transduction parameter to produce a tool for immunosensing: the photoluminescence shows a systematic reduction upon modification of its surface chemistry, and in particular upon attachment of an antigen-antibody (aIgG-IgG) pair. We investigate the relation of the amount of reduction of photoluminescence on planar and microstructured surfaces, and we show that microstructuring leads to a higher reduction than a planar surface. Furthermore, we evaluated the dependence of photoluminescence reduction as a function of analyte concentration to prove that this magnitude can be applied to immunosensing.

  9. Using an SU-8 Photoresist Structure and Cytochrome C Thin Film Sensing Material for a Microbolometer

    Directory of Open Access Journals (Sweden)

    Guo-Dung John Su

    2012-11-01

    Full Text Available There are two critical parameters for microbolometers: the temperature coefficient of resistance (TCR of the sensing material, and the thermal conductance of the insulation structure. Cytochrome c protein, having a high TCR, is a good candidate for infrared detection. We can use SU-8 photoresist for the thermal insulation structure, given its low thermal conductance. In this study, we designed a platform structure based on a SU-8 photoresist. We fabricated an infrared sensing pixel and recorded a high TCR for this new structure. The SU-8 photoresist insulation structure was fabricated using the exposure dose method. We experimentally demonstrated high values of TCR from 22%/K to 25.7%/K, and the measured noise was 1.2 × 10–8 V2/Hz at 60 Hz. When the bias current was 2 μA, the calculated voltage responsivity was 1.16 × 105 V/W. This study presents a new kind of microbolometer based on cytochrome c protein on top of an SU-8 photoresist platform that does not require expensive vacuum deposition equipment.

  10. Using an SU-8 photoresist structure and cytochrome C thin film sensing material for a microbolometer.

    Science.gov (United States)

    Lai, Jian-Lun; Liao, Chien-Jen; Su, Guo-Dung John

    2012-11-27

    There are two critical parameters for microbolometers: the temperature coefficient of resistance (TCR) of the sensing material, and the thermal conductance of the insulation structure. Cytochrome c protein, having a high TCR, is a good candidate for infrared detection. We can use SU-8 photoresist for the thermal insulation structure, given its low thermal conductance. In this study, we designed a platform structure based on a SU-8 photoresist. We fabricated an infrared sensing pixel and recorded a high TCR for this new structure. The SU-8 photoresist insulation structure was fabricated using the exposure dose method. We experimentally demonstrated high values of TCR from 22%/K to 25.7%/K, and the measured noise was 1.2 × 10(-8) V2/Hz at 60 Hz. When the bias current was 2 μA, the calculated voltage responsivity was 1.16 × 10(5) V/W. This study presents a new kind of microbolometer based on cytochrome c protein on top of an SU-8 photoresist platform that does not require expensive vacuum deposition equipment.

  11. SU-8 as a Material for Microfabricated Particle Physics Detectors

    CERN Document Server

    Maoddi, Pietro; Jiguet, Sebastien; Renaud, Philippe

    2014-01-01

    Several recent detector te chnologies developed for particle physics applications are based on microfabricated structures. Dete ctors built with this approach generally exhibit the overall best performance in te rms of spatial and time resolution. Many properties of the SU-8 photoepoxy make it suitable for the manufacturing of microstructured particle detectors. This arti cle aims to review some emerging detector technologies making use of SU-8 microstructu ring, namely micropatte rn gaseous detectors and microfluidic scintillation detectors. Th e general working principle and main process steps for the fabrication of each device are reported, with a focus on the advantages brought to the device functionality by the us e of SU-8. A novel process based on multiple bonding steps for the fabrication of thin multila yer microfluidic scin tillation detectors developed by the authors is presented. Finally, a brief overview of the applications for the discussed devices is given.

  12. Development of untethered SU-8 polymer scratch drive microrobots

    KAUST Repository

    Valencia Garcia, Manuel

    2011-01-01

    This paper presents the design, simulation, fabrication and testing of novel, untethered SU-8 polymer microrobots based on scratch drive actuators (SDAs). The design consists of two 100×120×10μm linked SDAs, individually operated close to their resonant frequencies. The resonant frequency and deflection behavior of an individual SDA can be controlled by its shape, thickness, and stiffening design features. As a result, paired SDAs can be actuated individually or simultaneously by a multifrequency driving signal, allowing for two-dimensional displacement. The fabrication process uses SU-8 as structural material and PMGI as sacrificial material. The SU-8 provides a flexible material for the SDA\\'s plates as well as the bushing. Finally, a Cr/Au layer is blanket deposited to provide electrical conductivity.

  13. SU-8 Photolithography as a Toolbox for Carbon MEMS

    Directory of Open Access Journals (Sweden)

    Rodrigo Martinez-Duarte

    2014-09-01

    Full Text Available The use of SU-8 as precursor for glass-like carbon, or glassy carbon, is presented here. SU-8 carbonizes when subject to high temperature under inert atmosphere. Although epoxy-based precursors can be patterned in a variety of ways, photolithography is chosen due to its resolution and reproducibility. Here, a number of improvements to traditional photolithography are introduced to increase the versatility of the process. The shrinkage of SU-8 during carbonization is then detailed as one of the guidelines necessary to design carbon patterns. A couple of applications—(1 carbon-electrode dielectrophoresis for bioparticle manipulation; and (2 the use of carbon structures as micro-molds are also presented.

  14. Droplet backside exposure for making slanted SU-8 microneedles.

    Science.gov (United States)

    Kwon, Ki Yong; Bi, Xiaopeng; Li, Wen

    2013-01-01

    This paper presented a droplet backside exposure (DBE) method for making slanted microneedle structures on a flexible polymer substrate. To demonstrate the feasibility of the DBE approach, SU-8 microneedle arrays were fabricated on polydimethylsiloxane (PDMS) substrates. The length of the microneedles was controlled by tuning the volume of the SU-8 droplet, utilizing the wetting barrier phenomenon at a liquid-vapor-hydrophilic surface-hydrophobic surface interface. The experimental results showed excellent repeatability and controllability of the DBE method for microneedle fabrication. Analytical models were also studied to predict the dimensions of the microneedles, which agreed with the experimental data.

  15. SU-8 microfluidic device for scintillating particle detection

    CERN Document Server

    Mapelli, A; Haguenauer, M; Jiguet, S; Vico Triviño, N; Renaud, P

    2009-01-01

    This paper presents the study of a novel scintillation detector based on standard microfabrication techniques. It consists of a fine pitch array of hollow waveguides filled with a liquid scintillator and optically coupled to photodetectors. The detector has been fabricated by patterning the SU-8 photoresist on silicon wafers. Experimental studies have been performed by exciting the liquid scintillator contained in the SU-8 waveguides with electrons. The scintillation light produced was read out by an external photodetector. The results obtained with this set-up demonstrate the concept of microfluidic scintillation detection and are very encouraging for future developments.

  16. A High-Throughput SU-8Microfluidic Magnetic Bead Separator

    DEFF Research Database (Denmark)

    Bu, Minqiang; Christensen, T. B.; Smistrup, Kristian

    2007-01-01

    We present a novel microfluidic magnetic bead separator based on SU-8 fabrication technique for high through-put applications. The experimental results show that magnetic beads can be captured at an efficiency of 91 % and 54 % at flow rates of 1 mL/min and 4 mL/min, respectively. Integration of s...

  17. Multiplex polymerase chain reaction (PCR) on a SU-8 chip

    DEFF Research Database (Denmark)

    Christensen, Troels Balmer; Bang, Dang Duong; Wolff, Anders

    2008-01-01

    We present the detection of Campylobacter at species level using multiplex PCR in a micro fabricated PCR chip. The chip is based on the polymer SU-8 that allows integration with different microfluidic components, e.g., sample pre-treatment before PCR, and DNA detection simultaneously with or afte...

  18. SU-8-based microneedles for in vitro neural applications

    Science.gov (United States)

    Altuna, Ane; Gabriel, Gemma; Menéndez de la Prida, Liset; Tijero, María; Guimerá, Anton; Berganzo, Javier; Salido, Rafa; Villa, Rosa; Fernández, Luis J.

    2010-06-01

    This paper presents novel design, fabrication, packaging and the first in vitro neural activity recordings of SU-8-based microneedles. The polymer SU-8 was chosen because it provides excellent features for the fabrication of flexible and thin probes. A microprobe was designed in order to allow a clean insertion and to minimize the damage caused to neural tissue during in vitro applications. In addition, a tetrode is patterned at the tip of the needle to obtain fine-scale measurements of small neuronal populations within a radius of 100 µm. Impedance characterization of the electrodes has been carried out to demonstrate their viability for neural recording. Finally, probes are inserted into 400 µm thick hippocampal slices, and simultaneous action potentials with peak-to-peak amplitudes of 200-250 µV are detected.

  19. SU-8 Guiding Layer for Love Wave Devices

    Directory of Open Access Journals (Sweden)

    Michael I. Newton

    2007-11-01

    Full Text Available SU-8 is a technologically important photoresist used extensively for thefabrication of microfluidics and MEMS, allowing high aspect ratio structures to beproduced. In this work we report the use of SU-8 as a Love wave sensor guiding layerwhich allows the possibility of integrating a guiding layer with flow cell during fabrication.Devices were fabricated on ST-cut quartz substrates with a single-single finger design suchthat a surface skimming bulk wave (SSBW at 97.4 MHz was excited. SU-8 polymer layerswere successively built up by spin coating and spectra recorded at each stage; showing afrequency decrease with increasing guiding layer thickness. The insertion loss andfrequency dependence as a function of guiding layer thickness was investigated over thefirst Love wave mode. Mass loading sensitivity of the resultant Love wave devices wasinvestigated by deposition of multiple gold layers. Liquid sensing using these devices wasalso demonstrated; water-glycerol mixtures were used to demonstrate sensing of density-viscosity and the physical adsorption and removal of protein was also assessed usingalbumin and fibrinogen as model proteins.

  20. A study of SU-8 photoresist in deep trenches for silicon-embedded microinductors

    Science.gov (United States)

    Laforge, Elias; Rabot, Caroline; Wang, Ningning; Pavlovic, Zoran; McCloskey, Paul; O'Mathúna, Cian

    2016-10-01

    Epoxy-based resist SU-8 is widely used in the development and fabrication of high-aspect-ratio (HAR) MEMS structures. It has proven to be a suitable photoresist combining thick layer coating and good adhesion on silicon substrates as well as possessing good mechanical and chemical stability. However, the trend towards minia- turization and increasing packaging density has pushed the demand for challenging micro-machining processes. As an example, a novel design of a MEMS microinductor requires a dielectric permanent layer coated in deep silicon trenches in order to insulate copper windings from the magnetic material deposited in these trenches. This requires the development of a photolithography process which enables the coating of a void-free layer filling the trenches. In this paper, the use of thick SU-8 photoresist for filling deep silicon trenches is investigated. Different SU-8 formulations are analyzed, processed and results are compared. As a result, an optimized process is developed to achieve void-free filled trenches and a uniform planar layer above them, with near vertical sidewall patterns.

  1. Performance of SU-8 Membrane Suitable for Deep X-Ray Grayscale Lithography

    Directory of Open Access Journals (Sweden)

    Harutaka Mekaru

    2015-02-01

    Full Text Available In combination with tapered-trench-etching of Si and SU-8 photoresist, a grayscale mask for deep X-ray lithography was fabricated and passed a 10-times-exposure test. The performance of the X-ray grayscale mask was evaluated using the TERAS synchrotron radiation facility at the National Institute of Advanced Industrial Science and Technology (AIST. Although the SU-8 before photo-curing has been evaluated as a negative-tone photoresist for ultraviolet (UV and X-ray lithographies, the characteristic of the SU-8 after photo-curing has not been investigated. A polymethyl methacrylate (PMMA sheet was irradiated by a synchrotron radiation through an X-ray mask, and relationships between the dose energy and exposure depth, and between the dose energy and dimensional transition, were investigated. Using such a technique, the shape of a 26-μm-high Si absorber was transformed into the shape of a PMMA microneedle with a height of 76 μm, and done with a high contrast. Although during the fabrication process of the X-ray mask a 100-μm-pattern-pitch (by design was enlarged to 120 μm. However, with an increase in an integrated dose energy this number decreased to 99 μm. These results show that the X-ray grayscale mask has many practical applications. In this paper, the author reports on the evaluation results of SU-8 when used as a membrane material for an X-ray mask.

  2. Improved anti-stiction coating of SU-8 molds

    DEFF Research Database (Denmark)

    Lange, Jacob Moresco; Clausen, Casper Hyttel; Svendsen, Winnie Edith

    2010-01-01

    We have developed a simple method for the improved release of embossed poly(methyl methacrylate) (PMMA) as well as casted poly(dimethyl siloxane) (PDMS) from a SU-8 mold using vapor phase deposition of 1H,1H,2H,2H-Perfluorodecyltrichlorosilane (FDTS). We have further investigated if prior breakage...... the method for the mold fabrication as well as the vapor phase deposition of FDTS onto the mold is described; examples of released final devices using this method in PMMA and PDMS are presented. (C) 2010 Elsevier B.V. All rights reserved....

  3. SU-8 etching in inductively coupled oxygen plasma

    DEFF Research Database (Denmark)

    Rasmussen, Kristian Hagsted; Keller, Stephan Sylvest; Jensen, Flemming

    2013-01-01

    Structuring or removal of the epoxy based, photo sensitive polymer SU-8 by inductively coupled plasma reactive ion etching (ICP-RIE) was investigated as a function of plasma chemistry, bias power, temperature, and pressure. In a pure oxygen plasma, surface accumulation of antimony from the photo......-initiator introduced severe roughness and reduced etch rate significantly. Addition of SF6 to the plasma chemistry reduced the antimony surface concentration with lower roughness and higher etch rate as an outcome. Furthermore the etch anisotropy could be tuned by controlling the bias power. Etch rates up to 800 nm...

  4. Fabrication of high-aspect ratio SU-8 micropillar arrays

    DEFF Research Database (Denmark)

    Amato, Letizia; Keller, Stephan S.; Heiskanen, Arto

    2012-01-01

    to the resolution limit of photolithography. This paper describes process optimization for the fabrication of dense SU-8 micropillar arrays (2.5μm spacing) with nominal height ⩾20μm and nominal diameter ⩽2.5μm (AR ⩾8). Two approaches, differing in temperature, ramping rate and duration of the baking steps were...... compared as part of the photolithographic processing, in order to evaluate the effect of baking on the pattern resolution. Additionally, during the post-processing, supercritical point drying and hard baking were introduced yielding pillars with diameter 1.8μm, AR=11 and an improved temporal stability....

  5. Combined electron beam and UV lithography in SU-8

    DEFF Research Database (Denmark)

    Gersborg-Hansen, Morten; Thamdrup, Lasse Højlund; Mironov, Andrej

    2007-01-01

    We present combined electron beam and UV lithography (CEUL) in SU-8 as a fast and flexible lithographic technique for prototyping of functional polymer devices and pattern transfer applications. CEUL is a lithographic technique suitable for defining both micrometer and nanometer scale features...... in a single polymer film on the wafer scale. The height of the micrometer and nanometer scale features is matched within 30 nm. As a pattern transfer application, we demonstrate stamp fabrication and thermal nanoimprint of a 2-dimensional array of 100 nm wide lines with a pitch of 380 nm in connection...

  6. Micro-particle filter made in SU-8 for biomedical applications

    DEFF Research Database (Denmark)

    Noeth, Nadine-Nicole; Keller, Stephan Urs; Fetz, Stefanie

    2009-01-01

    We have integrated a micro-particle filter in a polymer cantilever to filter micro-particles from a fluid while simultaneously measuring the amount of filtered particles. In a 3,8 mum thick SU-8 cantilever a filter was integrated with pore sizes between 3 and 30 mum. The chip was inserted...... in a microfluidic system and water with differently sized polystyrene beads was pumped through the filter. Particles which are larger than the pore sizes, cannot pass the filter and will increase the flow resistance of the cantilever. With more and more captured particles the cantilever starts to deflect, which can...

  7. Negative differential resistance in Josephson junctions coupled to a cavity

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Filatrella, G.; Pierro, V.

    2014-01-01

    or external – is often used. A cavity may also induce a negative differential resistance region at the lower side of the resonance frequency. We investigate the dynamics of Josephson junctions with a negative differential resistance in the quasi particle tunnel current, i.e. in the McCumber curve. We find...

  8. Fabrication of SU-8 low frequency electrostatic energy harvester

    KAUST Repository

    Ramadan, Khaled S.

    2011-11-01

    A 1500μm × 1500μm × 150μm out-of-plane, gap closing, electrostatic energy harvester is designed and fabricated to harvest low-frequency ambient vibrations. SU-8 is used to fabricate the proof mass (1200μm × 1200μm × 150μm) and the 5 m springs. Different harvesters were designed to harvest at 50, 75 and 110 Hz. At 110 Hz, Simulations show that with an input vibration of 10 μm amplitude at the frequency of resonance of the structure, the energy harvester should generate an average output power density of 0.032μW/mm3. This is the most area-efficient low-frequency electrostatic harvester to-date. © 2011 IEEE.

  9. Gold Nanoparticles-Coated SU-8 for Sensitive Fluorescence-Based Detections of DNA

    DEFF Research Database (Denmark)

    Cao, Cuong; Birtwell, Sam W.; Høgberg, Jonas

    2012-01-01

    that use fluorescence as the predominant detection workhorse. Here, we show that deposition of a thin gold nanoparticles layer onto the SU-8 surface significantly reduces the autofluorescence of the coated SU-8 surface by as much as 81% compared to bare SU-8. Furthermore, DNA probes can easily...

  10. Novel fabrication process for 3D meander-shaped microcoils in SU-8 dielectric and their application to linear micromotors

    Science.gov (United States)

    Seidemann, Volker; Buettgenbach, Stephanus

    2001-04-01

    This paper reports on an optimized fabrication process for three dimensional coil structures such as meander or helical coils wound around in plane magnetic structures. The process consists of UV depth lithography employing AZ4562 and SU8 photo resists and electroplating of copper and nickel-iron. Furthermore SU8 is used as the embedding dielectric due to its excellent planarization properties and high structural aspect ratio. Special emphasis was laid on the decrease of via interconnect resistance by electroplating the vias and upper conductors in a single step thus avoiding a large number of resistive interfaces. This was achieved by sacrificial wiring and structured seed layers. The developed technology is applied to a variable reluctance micro motor with a novel design that avoids high friction. The presented concept makes use of a stator traveler configuration generating complementary attraction forces. The technology and design concept is presented and first results are demonstrated.

  11. Drug-resistant gram-negative uropathogens: A review.

    Science.gov (United States)

    Khoshnood, Saeed; Heidary, Mohsen; Mirnejad, Reza; Bahramian, Aghil; Sedighi, Mansour; Mirzaei, Habibollah

    2017-10-01

    Urinary tract infection(UTI) caused by Gram-negative bacteria is the second most common infectious presentation in community medical practice. Approximately 150 million people are diagnosed with UTI each year worldwide. Drug resistance in Gram-negative uropathogens is a major global concern which can lead to poor clinical outcomes including treatment failure, development of bacteremia, requirement for intravenous therapy, hospitalization, and extended length of hospital stay. The mechanisms of drug resistance in these bacteria are important due to they are often not identified by routine susceptibility tests and have an exceptional potential for outbreaks. Treatment of UTIs depends on the access to effective drugs, which is now threatened by antibiotic resistant Gram-negative uropathogens. Although several effective antibiotics with activity against highly resistant Gram-negatives are available, there is not a unique antibiotic with activity against the high variety of resistance. Therefore, antimicrobial susceptibility tests, correlation between clinicians and laboratories, development of more rapid diagnostic methods, and continuous monitoring of drug resistance are urgent priorities. In this review, we will discuss about the current global status of drug-resistant Gram-negative uropathogens and their mechanisms of drug resistance to provide new insights into their treatment options. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  12. A SU-8/PDMS hybrid microfluidic device with integrated optical fibers for online monitoring of lactate.

    Science.gov (United States)

    Wu, Min-Hsien; Cai, Haoyuan; Xu, Xia; Urban, Jill P G; Cui, Zhan-Feng; Cui, Zheng

    2005-12-01

    A microfluidic device with integrated optical fibres was developed for online monitoring of lactate. The device consists of a SU-8 waveguide, microfluidic channels and grooves for the insertion of optic fibres. It was fabricated by one-step photolithography of SU-8 polymer resist. Different channel widths (50-300 microm) were tested in terms of detection sensitivity. A wide range of flow rates were applied to investigate the influence of flow rate on signal fluctuations. The separation between optical fibre sensor and microfluidic channel and the width of fluidic channel have been optimized to maximize the detection sensitivity. It was revealed that 250 microm of channel width is the optimum light path length for a compromise between detection sensitivity and interference of ambient light. The independence of detection signals on flow rates was demonstrated within the range of flow rate (0.5-5 ml/hr) tested. Compared with conventional lactate detection, the device is proved to have high accuracy, relatively low limit of detection (50 mg/L) and reasonably fast response time (100 sec). The fabrication of device is simple and low cost. The present work has provided some fundamental data for further system optimization to meet specific detection requirements.

  13. Negative differential resistance in a one-dimensional molecular wire ...

    Indian Academy of Sciences (India)

    differential resistance (NDR) at some critical bias, due to the degeneracy in the energies of the frontier molecular orbitals. The presence of ... Negative differential resistance in a one-dimensional molecular wire above Hamiltonian with the .... observed in many organic systems. Some of the explanations proposed in literature.

  14. Low prevalence of antibiotic-resistant gram-negative bacteria ...

    African Journals Online (AJOL)

    The objective of this study was to determine antibiotic resistance patterns and specific resistance genes in Gram-negative enteric bacteria recovered from 42 different drinking water sources servicing 2 rural villages in south-western Uganda. These water sites were prone to contamination by both human and cattle activity.

  15. SU(8) family unification with boson-fermion balance

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    Grand unification has been intensively investigated for over forty years, and many different approaches have been tried. In this talk I propose a model that involves three ingredients that do not appear in the usual constructions: (1) boson--fermion balance without full supersymmetry, (2) canceling the spin 1/2 fermion gauge anomalies against the anomaly from a gauged spin 3/2 gravitino, and (3) using a scalar field representation with non-zero U(1) generator to break the SU(8) gauge symmetry through a ground state which, before dynamical symmetry breaking, has a periodic U(1) generator structure. The model has a number of promising features: (1) natural incorporation of three families, (2) incorporation of the experimentally viable flipped SU(5) model, (3) a symmetry breaking pathway to the standard model using the scalar field required by boson-fermion balance, together with a stage of most attractive channel dynamical symmetry breaking, without postulating additional Higgs fields, (4) vanishing of bare Yuk...

  16. Cloning SU8 silicon masters using epoxy resins to increase feature replicability and production for cell culture devices

    Science.gov (United States)

    Kamande, J. W.; Wang, Y.; Taylor, A. M.

    2015-01-01

    In recent years, there has been a dramatic increase in the use of poly(dimethylsiloxane) (PDMS) devices for cell-based studies. Commonly, the negative tone photoresist, SU8, is used to pattern features onto silicon wafers to create masters (SU8-Si) for PDMS replica molding. However, the complexity in the fabrication process, low feature reproducibility (master-to-master variability), silane toxicity, and short life span of these masters have been deterrents for using SU8-Si masters for the production of cell culture based PDMS microfluidic devices. While other techniques have demonstrated the ability to generate multiple devices from a single master, they often do not match the high feature resolution (∼0.1 μm) and low surface roughness that soft lithography masters offer. In this work, we developed a method to fabricate epoxy-based masters that allows for the replication of features with high fidelity directly from SU8-Si masters via their PDMS replicas. By this method, we show that we could obtain many epoxy based masters with equivalent features to a single SU8-Si master with a low feature variance of 1.54%. Favorable feature transfer resolutions were also obtained by using an appropriate Tg epoxy based system to ensure minimal shrinkage of features ranging in size from ∼100 μm to epoxy masters with Cr/Au lead to effective demolding and yield PDMS chambers that are suitable for long-term culturing of sensitive primary hippocampal neurons. Finally, we incorporated pillars within the Au-epoxy masters to eliminate the process of punching media reservoirs and thereby reducing substantial artefacts and wastage. PMID:26180572

  17. Cloning SU8 silicon masters using epoxy resins to increase feature replicability and production for cell culture devices.

    Science.gov (United States)

    Kamande, J W; Wang, Y; Taylor, A M

    2015-05-01

    In recent years, there has been a dramatic increase in the use of poly(dimethylsiloxane) (PDMS) devices for cell-based studies. Commonly, the negative tone photoresist, SU8, is used to pattern features onto silicon wafers to create masters (SU8-Si) for PDMS replica molding. However, the complexity in the fabrication process, low feature reproducibility (master-to-master variability), silane toxicity, and short life span of these masters have been deterrents for using SU8-Si masters for the production of cell culture based PDMS microfluidic devices. While other techniques have demonstrated the ability to generate multiple devices from a single master, they often do not match the high feature resolution (∼0.1 μm) and low surface roughness that soft lithography masters offer. In this work, we developed a method to fabricate epoxy-based masters that allows for the replication of features with high fidelity directly from SU8-Si masters via their PDMS replicas. By this method, we show that we could obtain many epoxy based masters with equivalent features to a single SU8-Si master with a low feature variance of 1.54%. Favorable feature transfer resolutions were also obtained by using an appropriate Tg epoxy based system to ensure minimal shrinkage of features ranging in size from ∼100 μm to epoxy masters with Cr/Au lead to effective demolding and yield PDMS chambers that are suitable for long-term culturing of sensitive primary hippocampal neurons. Finally, we incorporated pillars within the Au-epoxy masters to eliminate the process of punching media reservoirs and thereby reducing substantial artefacts and wastage.

  18. Fabrication of micropressure sensor using SU-8/silver as piezoresistor and overhead projector transparency as substrate

    Science.gov (United States)

    Wong, Wah Seng; Azid, Ishak Abdul; Ibrahim, Kamarulazizi; Devarajan, Mutharasu

    2014-10-01

    This paper proposes a low-cost SU-8 pressure sensor fabricated using a piezoresistive material, SU-8/silver composite (SU-8/Ag), and a substrate material, overhead projector (OHP) transparency. SU-8/Ag has higher gauge factor (26.3) but shows a lower stiffness (2 GPa) compared with doped silicon. The OHP transparency substrate is cheap, easily forms the desired shape, is transparent to light (allows backside exposure), and allows for the dry release method through OHP transparency. Fabrication and characterization in this study were carried out using a typical semiconductor lab setup. The fabricated sensor showed high sensitivity (21.5 μV/Pa), low linearity error (Pearson's correlation coefficient=0.994937), and no apparent hysteresis response. The fabricated sensor with SU-8/Ag as the piezoresistive material exhibited 41 times higher sensitivity compared to that found in a previous study based on SU-8 and doped polysilicon.

  19. Fabrication of three-dimensional SU-8 microchannels by proton beam writing for microfluidics applications: Fluid flow characterisation

    Energy Technology Data Exchange (ETDEWEB)

    Al-Shehri, S., E-mail: s.al-shehri@surrey.ac.uk; Palitsin, V.; Webb, R.P.; Grime, G.W.

    2015-04-01

    The proton beam writing (PBW) technique was used to fabricate microfluidic structures in SU-8 resist. A network of the buried channels was fabricated as part of a project to develop functional microfluidic device for neuronal studies and self-powered microfluidics. Protons with energies between 2.5 MeV and 0.75 MeV were used to fabricate the buried channels with a minimum feature size of around 1 μm and depths of 40–55 μm. Roughness of channels sidewalls was around 2.5 nm rms. Exposure regime and examples of functional networks fabricated using PBW are described. COMSOL Multiphysics® software was used to model the flow characteristics of fluid in the SU-8 microchannels structured by PBW. The results obtained using PBW are compared with the structures fabricated by UV-lithography.

  20. A Simple Hydrophilic Treatment of SU-8 Surfaces for Cell Culturing and Cell Patterning

    DEFF Research Database (Denmark)

    Wang, Zhenyu; Stangegaard, Michael; Dufva, Hans Martin

    2005-01-01

    SU-8, an epoxy-based photoresist, widely used in constitution different mTAS systems, is incompatible with mammalian cell adhesion and culture in its native form. Here, we demonstrate a simple, cheap and robust two-step method to render a SU-8 surface hydrophilic and compatible with cell culture........ The contact angle of SU-8 surface was significantly reduced from 90° to 25° after the surface modification. The treated SU-8 surfaces provided a cell culture environment that was comparable with cell culture flask surface in terms of generation time and morphology....

  1. Negative differential resistance of TEMPO molecules on Si(111)

    NARCIS (Netherlands)

    Hallbäck, A.S.V.M.; Poelsema, Bene; Zandvliet, Henricus J.W.

    2007-01-01

    Negative differential resistance (NDR) has been observed for individual 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) molecules on Si(1 1 1) in ultra high vacuum (UHV) scanning tunneling microscopy (STM) and spectroscopy (STS) measurements at room temperature. NDR effects were observed exclusively at

  2. On Negative Resistance Oscillators as Modified Multi-vibrators

    DEFF Research Database (Denmark)

    Lindberg, Erik; Murali, K.; Tamasevicius, Arunas

    2015-01-01

    A tutorial discussion of negative resistance oscillators based on simple RLC circuits is presented. Two cases are based on parallel RLC circuits and two cases are based on series RLC circuits. Distortion is minimized by introducing symmetry in the movement of the complex pole-pair of the small...

  3. Single-mode waveguides with SU-8 polymer core and cladding for MOEMS applications

    DEFF Research Database (Denmark)

    Nordström, Maria; Zauner, Dan; Boisen, Anja

    2007-01-01

    Fabrication and optical characterization of singlemode polymeric embedded waveguides are performed. A specific material combination (SU-8 2005 as core and the modified SU-8 mr-L 6050XP as cladding) is chosen in order to obtain a small refractive index difference for single-mode propagation combin...

  4. Considerations on using SU-8 as a construction material for high aspect ratio structures

    NARCIS (Netherlands)

    Melai, J.; Salm, Cora; Smits, Sander M.; Blanco Carballo, V.M.; Schmitz, Jurriaan; Hageluken, Ben

    2007-01-01

    This paper discusses two material aspects of SU-8 that have up till now been insufficiently documented. We present initial results on the outgassing behavior and a study on the dielectric properties of SU-8 at high bias voltage. The dielectric strength is determined to be at least 2 MV/cm. These

  5. A Simple Hydrophilic Treatment of SU-8 Surfaces for Cell Culturing and Cell Patterning

    DEFF Research Database (Denmark)

    Wang, Zhenyu; Stangegaard, Michael; Dufva, Hans Martin

    2005-01-01

    SU-8, an epoxy-based photoresist, widely used in constitution different mTAS systems, is incompatible with mammalian cell adhesion and culture in its native form. Here, we demonstrate a simple, cheap and robust two-step method to render a SU-8 surface hydrophilic and compatible with cell culture...

  6. Negative-tone resist system using vinyl cyclic acetal crosslinker

    Science.gov (United States)

    Huang, Wu-Song; Lee, Kim Y.; Chen, K. Rex; Schepis, Dominic

    1996-06-01

    Most high performance negative tone resists are chemically amplified systems. The chemistry involves a creation of acid during photo-exposure and subsequent crosslinking of the polymer matrix during post-exposure bake. The commonly used crosslinkers are epoxies, melamines, benzyl alcohol and benzyl acetates. In light of the high reactivity of vinyl group on vinyl ether type compounds, literature has suggested that photochemical addition reaction of a polymer- bearing pendant vinyl ether with various thiol compounds can potentially be highly sensitive negative-type photoresists. Recently, bis-dihydropyrane derivative has been used for the first time to develop high performance negative tone resists for DUV, E-beam and x-ray applications. A cyclic acetal system based on acetal blocked aromatic aldehyde has also been demonstrated to be a good crosslinker for negative DUV resist. In order to take advantage of the above chemistries, we have investigated a crosslinker, 3,9-divinylspirobi(M-dioxane) (DVSDO), which contains both cyclic acetal groups and vinyl groups. Different loadings of DVSDO from 8% to 17% were formulated in combination with triphenyl sulfonyl triflate and N-sulfonyl triflate derivatives in polyhydroxystyrene matrix. One composition contains 8% N- sulfonyloxy derivative, 12% DVSDO in 20% solid of polyhydroxystyrene has shown resolution to 0.35 micrometer from Canon 0.37 NA DUV stepper. It also shows promising resolution in E-beam lithography. Varying the post apply bake (PAB) temperatures and post exposure bake temperatures (PEB) demonstrate a great dependency of sensitivity to baking temperature. The sensitivity increases with decreasing PAB, while decreases with decreasing PEB. Insufficient baking time (less than 4 - 5 minutes) at lower PEB temperature 90 degrees Celsius causes significant film loss after development in 0.14N TMAH for 60 - 75s. On the other hand, when the PEB temperature is too high (greater than 120 degrees Celsius), the resist

  7. Will new antimicrobials overcome resistance among Gram-negatives?

    Science.gov (United States)

    Bassetti, Matteo; Ginocchio, Francesca; Mikulska, Małgorzata; Taramasso, Lucia; Giacobbe, Daniele Roberto

    2011-10-01

    The spread of resistance among Gram-positive and Gram-negative bacteria represents a growing challenge for the development of new antimicrobials. The pace of antibiotic drug development has slowed during the last decade and, especially for Gram-negatives, clinicians are facing a dramatic shortage in the availability of therapeutic options to face the emergency of the resistance problem throughout the world. In this alarming scenario, although there is a shortage of compounds reaching the market in the near future, antibiotic discovery remains one of the keys to successfully stem and maybe overcome the tide of resistance. Analogs of already known compounds and new agents belonging to completely new classes of antimicrobials are in early stages of development. Novel and promising anti-Gram-negative antimicrobials belong both to old (cephalosporins, carbapenems, β-lactamase inhibitors, monobactams, aminoglycosides, polymyxin analogues and tetracycline) and completely new antibacterial classes (boron-containing antibacterial protein synthesis inhibitors, bis-indoles, outer membrane synthesis inhibitors, antibiotics targeting novel sites of the 50S ribosomal subunit and antimicrobial peptides). However, all of these compounds are still far from being introduced into clinical practice. Therefore, infection control policies and optimization in the use of already existing molecules are still the most effective approaches to reduce the spread of resistance and preserve the activity of antimicrobials.

  8. Emergence of a negative resistance in noisy coupled linear oscillators

    Science.gov (United States)

    Quiroz-Juárez, M. A.; Aragón, J. L.; León-Montiel, R. de J.; Vázquez-Medina, R.; Domínguez-Juárez, J. L.; Quintero-Torres, R.

    2016-12-01

    We report on the experimental observation of an emerging negative resistance in a system of coupled linear electronic RLC harmonic oscillators under the influence of multiplicative noise with long correlation time. When two oscillators are coupled by a noisy inductor, an analysis in the Fourier space of the electrical variables unveils the presence of an effective negative resistance, which acts as an energy transport facilitator. This might constitute a simple explanation of the now fashionable problem of energy transport assisted by noise in classical systems. The experimental setup is based on the working principle of an analog computer and by itself constitutes a versatile platform for studying energy transport in noisy systems by means of coupled electrical oscillator systems.

  9. Reduction of surface leakage current in InAs/GaSb strained layer long wavelength superlattice detectors using SU-8 passivation

    Science.gov (United States)

    Kim, H. S.; Plis, E.; Gautam, N.; Myers, S.; Sharma, Y.; Dawson, L. R.; Krishna, S.

    2010-10-01

    We report on SU-8 passivation for reducing surface leakage current in type-II InAs/GaSb strained layer superlattice detectors (λ100% cut-off˜12 μm). The electrical behavior of SU-8 passivated and unpassivated devices was compared for devices with variable mesa sizes. Dark current was reduced by more than one order of magnitude for the small area (50 μm×50 μm) passivated diode at 77 K. The surface resistivity, the responsivity and specific detectivity were measured for SU-8 passivated devices and are equal to 204 Ω cm, 0.58 A/W and 3.49×109 Jones, respectively (77 K).

  10. Submicron Optical Lithography Utilizing A Negative Deep UV Resist MRS

    Science.gov (United States)

    Tomioka, Hideki

    1985-04-01

    A negative deep UV resist MRS is successfully applied to 1:1 projection printings. The MRS has high resolution capability due to the absence of swelling in the developer, and resolves 1 μm patterns. Because of its intense absorption characteristics, the MRS is insensitive to variation in underlayer reflectivity, so the linewidth of the surface part of the MRS is well controlled. A further consequence is image profile variation depending on development 'conditions and resist thickness over steps. Anisotropic etching with high selectivity to resist may mitigate this effect. We are currently applying the MRS to obtain 1 pm-thick Al-Cu-Si metallization patterns realizing 1.5 μm spaces over 0.7 μm stepped substrates by the use of reactive ion etching. The MRS is reliable enough to apply to a single-layer resist process for production of 1.0 μm - 1.5 μm feature size devices. It is found that, using the MRS as a top layer for a tri-layer resist structure, 0.7 μm line and space patterns can be obtained with 1:1 deep UV projection printing. In our tri-layer resist process, the surface part of the MRS acts as a mask to etch the second thin SiO layer, which becomes the final mask pattern of the polymer bottom layer. The MRS tri-layer resist process has excellent resolution and controllability of linewidth compared with that of conventional positive resists.

  11. A facile micropatterning method for a highly flexible PEDOT:PSS on SU-8

    KAUST Repository

    Cho, Nam Chul

    2016-04-17

    We report the micropatterning of conducting polymer on the epoxy-based photoresist to demonstrate fully organic, conducting and flexible electrodes. We show that polystyrene sulfonic acid can be covalently linked to the surface of the photoresist (SU-8) by forming sulfonyl ester at the interfaces. We also present an application of the patterned PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate)/SU-8 to the electroplating of metal electrodes. © 2016 Elsevier B.V.

  12. Microfabrication of PDMS microchannels using SU-8/PMMA moldings and their sealing to polystyrene substrates

    Science.gov (United States)

    Bubendorfer, Andrea; Liu, Xianming; Ellis, Amanda V.

    2007-04-01

    In this paper we show increased interfacial bonding of a photoresist (SU-8) deposited onto highly polished poly(methyl methacrylate) (PMMA) substrates containing a UV absorber. We also demonstrate the facile sealing/covalent bonding of 100 µm × 20 µm PDMS replica microchannels, made from these PMMA/SU-8 moldings, onto thermally polymerized styrene. Sealing was achieved through radio-frequency plasma discharge (RFPD) oxygen plasma treatment.

  13. UV-LIGA Microfabrication of 220 GHz Sheet Beam Amplifier Gratings with SU-8 Photoresists

    Science.gov (United States)

    2010-01-01

    etching (DRIE) is not effective on copper substrates, but was used to fabricate metalized silicon test pieces [11]. This paper begins with a detailed...figure 9(b)). After an ultrasonic bath in Microclean 90 R© and water, only half of a dozen blackened bits of SU-8 remained. The remaining SU-8 residue... metallization Master of Science Thesis Dept of Chem. Eng., Case Western Reserve University [22] Pasquale M A, Gassa L M and Arvia A J 2008 Copper

  14. Frequency of negative differential resistance electrochemical oscillators: theory and experiments.

    Science.gov (United States)

    Kiss, István Z; Pelster, Lindsey N; Wickramasinghe, Mahesh; Yablonsky, Gregory S

    2009-07-21

    An approximate formula for the frequency of oscillations is theoretically derived for skeleton models for electrochemical systems exhibiting negative differential resistance (NDR) under conditions close to supercritical Hopf bifurcation points. The theoretically predicted omega infinity (k/R)1/2 relationship (where R is the series resistance of the cell and k is the rate constant of the charge transfer process) was confirmed in experiments with copper and nickel electrodissolution. The experimentally observed Arrhenius-type dependence of frequency on temperature can also be explained with the frequency equation. The experimental validity of the frequency equation indicates that 'apparent' rate constants can be extracted from frequency measurements of electrochemical oscillations; such method can aid future modeling of complex responses of electrochemical cells.

  15. Investigation on the mechanism of nitrogen plasma modified PDMS bonding with SU-8

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chengxin; Yuan, Yong J., E-mail: yongyuan@swjtu.edu.cn

    2016-02-28

    Graphical abstract: - Highlights: • Different nitrogen plasma processes modified PDMS bonding with SU-8 had been studied. • The effect of nitrogen plasma modification would produce the best result and the recovery of PDMS hydrophobicity could be delayed. - Abstract: Polydimethylsiloxane (PDMS) and SU-8 are both widely used for microfluidic system. However, it is difficult to permanently seal SU-8 microfluidic channels using PDMS with conventional methods. Previous efforts of combining these two materials mainly employed oxygen plasma modified PDMS. The nitrogen plasma modification of PDMS bonding with SU-8 is rarely studied in recent years. In this work, the mechanism of nitrogen plasma modified PDMS bonding with SU-8 was investigated. The fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle of a water droplet were used to analyze the nitrogen plasma modified surface and the hydrophilic stability of PDMS samples. Pull-off tests were used for estimating the bonding effect of interface between nitrogen plasma modified PDMS and SU-8.

  16. Antibiotic resistance: What is so special about multidrug-resistant Gram-negative bacteria?

    Science.gov (United States)

    Exner, Martin; Bhattacharya, Sanjay; Christiansen, Bärbel; Gebel, Jürgen; Goroncy-Bermes, Peter; Hartemann, Philippe; Heeg, Peter; Ilschner, Carola; Kramer, Axel; Larson, Elaine; Merkens, Wolfgang; Mielke, Martin; Oltmanns, Peter; Ross, Birgit; Rotter, Manfred; Schmithausen, Ricarda Maria; Sonntag, Hans-Günther; Trautmann, Matthias

    2017-01-01

    In the past years infections caused by multidrug-resistant Gram-negative bacteria have dramatically increased in all parts of the world. This consensus paper is based on presentations, subsequent discussions and an appraisal of current literature by a panel of international experts invited by the Rudolf Schülke Stiftung, Hamburg. It deals with the epidemiology and the inherent properties of Gram-negative bacteria, elucidating the patterns of the spread of antibiotic resistance, highlighting reservoirs as well as transmission pathways and risk factors for infection, mortality, treatment and prevention options as well as the consequences of their prevalence in livestock. Following a global, One Health approach and based on the evaluation of the existing knowledge about these pathogens, this paper gives recommendations for prevention and infection control measures as well as proposals for various target groups to tackle the threats posed by Gram-negative bacteria and prevent the spread and emergence of new antibiotic resistances. PMID:28451516

  17. Distribution of Gram Negative Bacteria and Evaluation of Resistance Profiles

    Directory of Open Access Journals (Sweden)

    Serap Pamukcuoglu

    2014-03-01

    Full Text Available Aim: In this study, we aimed to examine the distributon of Gram negative bacteria isolated from urine cultures of out-patients in Afyonkarahisar State Hospital and evaluate the antimicrobial resistance rates of these pathogens. Material and Method: Urine samples of out-patients which were sent to microbiology laboratory between 2012-2013 were retrospectively evaluated. The isolates were identified using conventional methods and/or automated Vitec 2.0 system. Antibiogram sensitivities were determined by Kirby-Bauer disc diffusion method or automated system and interpreted on the basis of Clinical and Laboratory Standards Institute (CSI criteria. Double disc sinergy test (DDST or Vitec 2.0 system was used to detect extended spectrum beta-lactamase (ESBL.When conventional methods could%u2019t be clarified according to their colony morphologies, gram staining patterns, biochemical test; automated system has been used. Results: A total of 671 isolates acquired from urine samples were studied. 427 Escherichia coli (63.6 %, 165 Klebsiella spp. (24.6 %, 22 Pseudomonas spp. (3.3 %, nine Acinetobacter spp. (1.3 %, 41 Proteus spp. (6.1 % and seven Serratia (1.0 % strains were identified among isolates. 97 E.coli (22.8 % and 41 Klebsiella (24.8 % isolates were ESBL positive. Most common bacteria were E.coli, 31.1 % of which were resistant to trimethoprim-sulfamethoxazole, 16 % to ciprofloxacin and 3.6 % to nitrofurantoin. Among Enterobacteriaceae, no resistance aganist carbapenems were detected. Moreover, aminoglicoside sensitivity rate was significantly high in this group. Discussion: Microorganisms that have progressively increasing antimicrobial resistance should be considered in the treatment of urinary tract infections. It is also important to use the most appropriate antibiotics to avoid unnecessary usage of these drugs in order to decrease drug resistance rates and ESBL production which may effect the success of the treatment.

  18. Combating multidrug-resistant Gram-negative bacterial infections.

    Science.gov (United States)

    Xu, Ze-Qi; Flavin, Michael T; Flavin, John

    2014-02-01

    Multidrug-resistant (MDR) bacterial infections, especially those caused by Gram-negative pathogens, have emerged as one of the world's greatest health threats. The development of novel antibiotics to treat MDR Gram-negative bacteria has, however, stagnated over the last half century. This review provides an overview of recent R&D activities in the search for novel antibiotics against MDR Gram-negatives. It provides emphasis in three key areas. First, the article looks at new analogs of existing antibiotic molecules such as β-lactams, tetracyclines, and aminoglycoside as well as agents against novel bacterial targets such as aminoacyl-tRNA synthetase and peptide deformylase. Second, it also examines alternative strategies to conventional approaches including cationic antimicrobial peptides, siderophores, efflux pump inhibitors, therapeutic antibodies, and renewed interest in abandoned treatments or those with limited indications. Third, the authors aim to provide an update on the current clinical development status for each drug candidate. The traditional analog approach is insufficient to meet the formidable challenge brought forth by MDR superbugs. With the disappointing results of the genomics approach for delivering novel targets and drug candidates, alternative strategies to permeate the bacterial cell membrane, enhance influx, disrupt efflux, and target specific pathogens via therapeutic antibodies are attractive and promising. Coupled with incentivized business models, governmental policies, and a clarified regulatory pathway, it is hoped that the antibiotic pipeline will be filled with an effective armamentarium to safeguard global health.

  19. Strain-induced negative differential resistance in ultrasmall carbon nanotube

    Science.gov (United States)

    Fang, Hui; Zhang, Fei-Peng; Ruan, Xing-Xiang; Huang, Can-Sheng; Jiang, Zhi-Nian; Peng, Jin-Yun; Wang, Ru-Zhi

    2017-08-01

    The transport properties in ultrasmall single-wall carbon nanotubes (SWCNTs) under tensile strain have been theoretically investigated. The regular negative differential resistance (NDR) induced by the strain undergoes a process from enhancement to weakening in the zigzag (3,0) SWCNT. The NDR achieves maximum with applying 4% tensile strain. Compared to the case of (3,0) SWCNT, that NDR cannot be manipulated by applying strain clearly in (4,0) and (5,0) ultrasmall SWCNTs with tensile strain lower than 10%. It proposes this strain-induced NDR effect to demonstrate the possibility of finding potential applications in SWCNT-based NDR nanodevices such as in memory devices, oscillators and fast switching devices.

  20. Novel SU-8/Ionic Liquid Composite for Tribological Coatings and MEMS

    Directory of Open Access Journals (Sweden)

    Leili Batooli

    2015-05-01

    Full Text Available Tribology of SU-8 polymer is increasingly relevant due to bursting use of this material in a variety of applications. This study is directed towards introduction and investigation of a novel self-lubricating composite of an ionic liquid (IL in SU-8. The new material can be utilized for fabrication of lubricating polymer coating with tunable surface properties or SU8-made elements for microelectromechanical systems (MEMS with enhanced tribological performance. It is shown that addition of IL drastically alters water affinity of the composite while UV patternability remains unmodified. A lower coefficient of friction and wear has been obtained for two investigated compositions with 4 and 10 wt % ionic liquid.

  1. A tapered hollow metallic microneedle array using backside exposure of SU-8

    Science.gov (United States)

    Kim, Kabseog; Park, Daniel S.; Lu, Hong M.; Che, Wooseong; Kim, Kyunghwan; Lee, Jeong-Bong; Ahn, Chong H.

    2004-04-01

    This paper presents a novel fabrication process for a tapered hollow metallic microneedle array using backside exposure of SU-8, and analytic solutions of critical buckling of a tapered hollow microneedle. An SU-8 mesa was formed on a Pyrex glass substrate and another SU-8 layer, which was spun on top of the SU-8 mesa, was exposed through the backside of the glass substrate. An array of SU-8 tapered pillar structures, with angles in the range of 3.1°-5°, was formed on top of the SU-8 mesa. Conformal electrodeposition of metal was carried out followed by a mechanical polishing using a planarizing polymeric layer. All organic layers were then removed to create a metallic hollow microneedle array with a fluidic reservoir on the backside. Both 200 µm and 400 µm tall, 10 by 10 arrays of metallic microneedles with inner diameters of the tip in the range of 33.6-101 µm and wall thickness of 10-20 µm were fabricated. Analytic solutions of the critical buckling of arbitrary-angled truncated cone-shaped columns are also presented. It was found that a single 400 µm tall hollow cylindrical microneedle made of electroplated nickel with a wall thickness of 20 µm, a tapered angle of 3.08° and a tip inner diameter of 33.6 µm has a critical buckling force of 1.8 N. This analytic solution can be used for square or rectangular cross-sectioned column structures with proper modifications.

  2. A high aspect ratio SU-8 fabrication technique for hollow microneedles for transdermal drug delivery and blood extraction

    Science.gov (United States)

    Chaudhri, Buddhadev Paul; Ceyssens, Frederik; De Moor, Piet; Van Hoof, Chris; Puers, Robert

    2010-06-01

    Protein drugs, e.g. hormonal drugs, cannot be delivered orally to a patient as they get digested in the gastro-intestinal (GI) tract. Thus, it is imperative that these kinds of drugs are delivered transdermally through the skin. To provide for real-time feedback as well as to test independently for various substances in the blood, we also need a blood sampling system. Microneedles can perform both these functions. Further, microneedles made of silicon or metal have the risk of breaking inside the skin thereby leading to complications. SU-8, being approved of as being biocompatible by the Food and Drug Agency (FDA) of the United States, is an attractive alternative because firstly it is a polymer material, thereby reducing the chances of breakages inside the skin, and secondly it is a negative photoresist, thereby leading to ease of fabrication. Thus, here we present very tall (around 1600 µm) SU-8 polymer-based hollow microneedles fabricated by a simple and repeatable process, which are a very good candidate for transdermal drug delivery as well as blood extraction. The paper elaborates on the details that allow the fabrication of such extreme aspect ratios (>100).

  3. Potential strategies for the eradication of multi-drug resistant Gram-negative bacterial infections

    OpenAIRE

    Huwaitat, Rawan; McCloskey, Alice P.; Gilmore, Brendan F.; Laverty, Garry

    2016-01-01

    Antimicrobial resistance is one of the leading threats to society. The increasing burden of multidrug-resistant Gram-negative infection is particularly concerning as such bacteria are demonstrating resistance to nearly all currently licensed therapies. Various strategies have been hypothesized to treat multidrug-resistant Gram-negative infections including: targeting the Gram-negative outer membrane; neutralization of lipopolysaccharide; inhibition of bacterial efflux pumps and prevention of ...

  4. Humidity influence on the adhesion of SU-8 polymer from MEMS applications

    Directory of Open Access Journals (Sweden)

    Birleanu Corina

    2017-01-01

    Full Text Available In this paper, the adhesion behaviors of SU-8 polymer thin film from MEMS application were investigated as a function of relative humidity. The adhesion test between the AFM tip and SU-8 polymer have been extensively studied using the atomic force microscope (AFM, for a relative humidity (RH varying between 20 and 90%. The samples for tests are SU-8 polymers hard baked at different temperatures. The hard bake temperature changes the tribo-mechanical properties of polymers. The paper reports the measurements and the modeling of adhesion forces versus humidity in controlled ranges between 20 to 90%RH. To investigate the effect of relative humidity on adhesion for SU-8 polymer hard baked we used an analytical method which encompasses the effect of capillarity as well as the solid-to-solid interaction. While the capillary force expression is considered to be the sum of the superficial tension and the Laplace force for the solid-solid interaction is expressed by the Derjagin, Muller and Toropov (DMT model of solids adhesion. The analytical results obtained are in accordance with those obtained experimentally.

  5. Improved performance of InAs/GaSb strained layer superlattice detectors with SU-8 passivation

    Science.gov (United States)

    Kim, H. S.; Plis, E.; Myers, S.; Khoshakhlagh, A.; Gautam, N.; Kutty, M. N.; Sharma, Y. D.; Dawson, L. R.; Krishna, S.

    2009-08-01

    We report on surface passivation using SU-8 for type-II InAs/GaSb strained layers superlattice (SLS) detectors with a PIN design operating in mid-wave infrared (MWIR) spectral region (λ50% cut-off ~ 4.4 μm). Material growth and characterization, single pixel device fabrication and testing, as well as focal plane array (FPA) processing are described. High quality strain-balanced SLS material with FWHM of 1st SLS satellite peak of 36 arcsec is demonstrated. The electrical and optical performance of devices passivated with SU-8 are reported and compared with those of unpassivated devices. The dark current density of a single pixel device with SU-8 passivation showed four orders of magnitude reduction compared to the device without any passivation. At 77K, the zero-bias responsivity and detectivity are equal to 1.1 A/W and 4 x 1012 Jones at 4μm, respectively, for the SU-8 passivated test pixel on the focal plane array.

  6. Nanochannels in SU-8 with floor and ceiling metal electrodes and integrated microchannels

    NARCIS (Netherlands)

    Nichols, K.P.F.; Eijkel, Jan C.T.; Gardeniers, Johannes G.E.

    2008-01-01

    Sacrificially etched 2-D nanofluidic channels and nanospaces with integrated floor and ceiling electrodes and arbitrary channel geometries have been demonstrated with channel heights from 20 nm to 400 nm, widths from 800 nm to 40 mm, and lengths up to 3 mm, using SU-8 as the channel structural

  7. Investigation of the bond strength between the photo-sensitive polymer SU-8 and gold

    DEFF Research Database (Denmark)

    Nordström, Maria; Johansson, Alicia; Sánchez Noguerón, E.

    2005-01-01

    We present the results from a thorough investigation of the bond strength between the photo-polymer SU-8 and Au. The data were obtained by pull-test experiments, below the glass transition temperature of the polymer. The different aspects that we investigated were:(i)the effect of using different...

  8. Dense vertical SU-8 microneedles drawn from a heated mold with precisely controlled volume

    Science.gov (United States)

    Xiang, Zhuolin; Wang, Hao; Kanna Murugappan, Suresh; Yen, Shih-Cheng; Pastorin, Giorgia; Lee, Chengkuo

    2015-02-01

    Drawing lithography technology has recently become a popular technique to fabricate (3D) microneedles. The conventional drawing process shows some limitations in fabricating dense, scale-up and small microneedles. In this study, we demonstrate a new drawing lithography process from a self-loading mold which is able to overcome these challenges. Different from the conventional molds which have difficult alignment and loading issues, a released SU-8 membrane is attached onto a SU-8 coated wafer to generate an innovative self-loading mold. The physically distinct SU-8 colloid in this mold successfully avoids the merging of the microneedle tips in the drawing process. Meanwhile, the same SU-8 colloid in mold can provide microneedles with uniform lengths on a large surface area. Furthermore, a low temperature drawing process with this improved technique prevents sharp tips from bending during the solidification stage. Remarkably, this new drawing lithography technology can fabricate microneedles with various lengths and they are strong enough to penetrate the outermost skin layer, namely the stratum corneum. The spacing between two adjacent microneedles is optimized to maximize the penetration rate through the skin. Histology images and drug diffusion testing demonstrate that microchannels are successfully created and the drugs can permeate the tissue under the skin. The fabricated microneedles are demonstrated to deliver insulin in vivo and lower blood glucose levels, suggesting future possible applications for minimally invasive transdermal delivery of macromolecules.

  9. Integrated SU-8 photonic gas sensors based on PANI polymer devices: Comparison between metrological parameters

    Science.gov (United States)

    Airoudj, A.; Bêche, B.; Debarnot, D.; Gaviot, E.; Poncin-Epaillard, F.

    2009-10-01

    In this work, we have designed and developed three families of integrated photonic sensors for ammonia detection. These photonic sensors are integrated onto single-mode TE 0-TM 0 SU-8 polymer planar waveguides and based on a polyaniline (PANI) sensitive polymer material. The first family relies on the deposit of a PANI-polymethyl methacrylate (PMMA) composite sensitive layer on a given SU-8 waveguide. The second family relies on a PMMA passive layer deposited on the SU-8 waveguide before applying the PANI sensitive layer on the PMMA passive layer. The third family takes advantage of a PANI layer deposited by plasma technique directly onto the SU-8 waveguide. The working principle of such sensors is based on the optical intensity modulation induced within the single-mode waveguide owing to the interaction between the evanescent field and the sensitive layer. The sensing proprieties of these integrated photonic sensors to ammonia gas at room temperature were characterized and the comparison between these different families of photonic sensors is presented. Experimental results show that the sensor based on new plasma-PANI as sensitive layer has the better metrological parameters.

  10. Drift study of SU8 cantilevers in liquid and gaseous environments

    DEFF Research Database (Denmark)

    Tenje, Maria; Keller, Stephan Sylvest; Dohn, Søren

    2010-01-01

    We present a study of the drift, in terms of cantilever deflections without probe/target interactions, of polymeric SU8 cantilevers. The drift is measured in PBS buffer (pH 7.4) and under vacuum (1 mbar) conditions. We see that the cantilevers display a large drift in both environments. We believ...

  11. FABRICATION OF A RETINAL PROSTHETIC TEST DEVICE USING ELECTRODEPOSITED SILICON OVER POLYPYRROLE PATTERNED WITH SU-8 PHOTORESIST.

    Science.gov (United States)

    Miller, Eric; Ellis, Daniel; Charles, Duran; McKenzie, Jason

    2015-01-01

    A materials fabrication study of a photodiode array for possible application of retina prosthesis was undertaken. A test device was fabricated using a glassy carbon electrode patterned with SU-8 photoresist. In the openings, p-type polypyrrole was first electrodeposited using 1-butyl-1-methylpyridinium bis(trifluoromethylsulfonyl)imide ionic liquid. The polypyrrole was self-doped with imide ion at ~1.5 mole %, was verified as p-type, and had a resistivity of ~20 Ωcm. N-type Silicon was then electrodeposited over this layer using silicon tetrachloride / phosphorus trichloride in acetonitrile and passivated in a second electrodeposition using trimethylchlorosilane. Electron microscopy revealed the successful electrodeposition of silicon over patterned polypyrrole. Rudimentary photodiode behavior was observed. The passivation improved but did not completely protect the electrodeposited silicon from oxidation by air.

  12. Antibiotic Resistance Patterns of Common Gram-negative ...

    African Journals Online (AJOL)

    Background: The resistance of bacteria causing urinary tract infection (UTI) to commonly prescribed antibiotics is increasing both in developing and developed countries. Resistance has emerged even to more potent antimicrobial agents. This study was undertaken to determine the current antibiotic resistance pattern ...

  13. Study on Negative Resistance Mechanism and Elimination Method of Network Simplification

    Science.gov (United States)

    Zhu, Lin; Fu, Dong; Sheng, Qiliang; Wang, Bei; Hu, Xinge

    2017-05-01

    The key of the further development of power system dynamic equivalence study is that correct understanding of negative resistance mechanism in network simplification and how to get rid of negative resistance. This paper analyzes the network simplification of power system, and it thoroughly studies the mechanism of equivalent branches with negative resistance. This paper also leads the definition of the constant impedance load and studies the property and the size of constant impedance load to further explain the mechanism of negative resistance production. This paper proposes a network transformation method which is based on power flow calculation results. This method transforms series branches which include negative resistance into PI-type branches. Finally the validity of this method is verified in sample cases from the China Southern Power Grid and IEEE 39 bus system. This method also solves the problem that some simulation software can’t model the branches with negative resistance.

  14. Negative differential resistance and resistive switching in SnO2/ZnO interface

    Science.gov (United States)

    Pant, Rohit; Patel, Nagabhushan; Nanda, K. K.; Krupanidhi, S. B.

    2017-09-01

    We report a very stable negative differential resistance (NDR) and resistive switching (RS) behavior of highly transparent thin films of the SnO2/ZnO bilayer, deposited by magnetron sputtering. When this bilayer of SnO2/ZnO was annealed at temperatures above 400 °C, ZnO diffuses into SnO2 at the threading dislocations and gaps between the grain boundaries, leading to the formation of a ZnO nanostructure surrounded by SnO2. Such a configuration forms a resonant tunneling type structure with SnO2/ZnO/SnO2…….ZnO/SnO2 interface formation. Interestingly, the heterostructure exhibits a Gunn diode-like behavior and shows NDR and RS irrespective of the voltage sweep direction, which is the characteristic of unipolar devices. A threshold voltage of ˜1.68 V and a peak-to-valley ratio of current ˜2.5 are observed for an electrode separation of 2 mm, when the bias is swept from -5 V to +5 V. It was also observed that the threshold voltage can be tuned with changing distance between the electrodes. The device shows a very stable RS with a uniform ratio of about 3.4 between the high resistive state and the low resistive state. Overall, the results demonstrate the application of SnO2/ZnO bilayer thin films in transparent electronics.

  15. Multidrug resistant gram-negative bacteria in clinical isolates from Karachi

    National Research Council Canada - National Science Library

    Saeed, Asma; Khatoon, Hajra; Ansari, Fasihuddin Ahmed

    2009-01-01

    A total of 54 gram-negative bacteria obtained from various pathological labs and hospitals of Karachi were screened for their resistance to ampicillin, chloramphenicol, gentamycin, kanamycin, neomycin...

  16. Appraising contemporary strategies to combat multidrug resistant gram-negative bacterial infections--proceedings and data from the Gram-Negative Resistance Summit.

    Science.gov (United States)

    Kollef, Marin H; Golan, Yoav; Micek, Scott T; Shorr, Andrew F; Restrepo, Marcos I

    2011-09-01

    The emerging problem of antibiotic resistance, especially among Gram-negative bacteria (GNB), has become a serious threat to global public health. Very few new antibacterial classes with activity against antibiotic-resistant GNB have been brought to market. Renewed and growing attention to the development of novel compounds targeting antibiotic-resistant GNB, as well as a better understanding of strategies aimed at preventing the spread of resistant bacterial strains and preserving the efficacy of existing antibiotic agents, has occurred. The Gram-Negative Resistance Summit convened national opinion leaders for the purpose of analyzing current literature, epidemiologic trends, clinical trial data, therapeutic options, and treatment guidelines related to the management of antibiotic-resistant GNB infections. After an in-depth analysis, the Summit investigators were surveyed with regard to 4 clinical practice statements. The results then were compared with the same survey completed by 138 infectious disease and critical care physicians and are the basis of this article.

  17. Preservation of Acquired Colistin Resistance in Gram-Negative Bacteria

    OpenAIRE

    Lee, Ji-Young; Choi, Myung-Jin; Choi, Hyeon Jin; Ko, Kwan Soo

    2015-01-01

    Colistin-resistant mutants were obtained from 17 colistin-susceptible strains of Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli. The stability of colistin resistance in these mutants was investigated. Three of four colistin-resistant P. aeruginosa mutants recovered colistin susceptibility in colistin-free medium; however, colistin-susceptible revertants were obtained from only one strain each of A. baumannii and E. coli. No susceptible revertants ...

  18. SU-8 passivation of type-II InAs/GaSb strained layer superlattice detectors

    Science.gov (United States)

    Kim, H. S.; Plis, E.; Gautam, N.; Khoshakhlagh, A.; Myers, S.; Kutty, M. N.; Sharma, Y.; Dawson, L. R.; Krishna, S.

    2010-04-01

    We report on surface passivation studies for type-II InAs/GaSb superlattice (SL) PIN detectors designed to operate in the mid-wave infrared (MWIR) region and the long wavelength infrared (LWIR) spectrum. The two SL structures were grown by molecular beam epitaxy and processed into mesa diodes using standard lithography. A simple spin on photoresist, SU-8, was used to passivate the sample after a wet etch. Optical and electrical measurements were then undertaken on the two devices. The dark current density of a single pixel device with SU-8 passivation is reduced by four orders of magnitude and by a factor of eight compared to devices without any passivation for the MWIR and LWIR pin detectors, respectively, at 77K.

  19. Towards a compact SU-8 micro-direct methanol fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, J.P.; Santander, J.; Cane, C.; Sabate, N. [Instituto de Microelectronica de Barcelona, IMB-CNM (CSIC), Campus UAB, 08193 Bellaterra, Barcelona (Spain); Senn, T.; Loergen, M.; Loechel, B. [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Application Centre for Microengineering, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Hernandez-Fernandez, P. [Dpto. Quimica-Fisica Aplicada, Facultad de Ciencias, Universidad Autonoma de Madrid (UAM), C/Francisco Tomas y Valiente 7, 28049 Madrid (Spain); Rojas, S. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, 28049 Madrid (Spain)

    2010-12-15

    This paper presents an all-polymer micro-direct methanol fuel cell (microDMFC) fabricated with SU-8 photoresist. The present development exploits the capability of SU-8 components to bond to each other by a hot-pressing process and obtain a compact device. The device is formed by a membrane electrode assembly (MEA) sandwiched between two current collectors. The MEA consists of a porous SU-8 membrane filled with a proton exchange polymer and covered by a thin layer of carbon-based electrodes with a low catalyst loading (1.0 mg cm{sup -2}). The current collectors consist of two metalized SU-8 plates provided with a grid of through-holes that allow delivering the reactants to the MEA by diffusion. Fuel cell characterization was performed by measuring the polarization curves under different methanol concentrations and temperatures. The components were first tested using an external casing. A maximum power density of 4.15 mW cm{sup -2} was measured with this assembly working with a 4 M methanol concentration and at a temperature of 40 C. The components were then bonded to obtain a compact micro-direct methanol fuel cell that yielded a power density of 0.65 mW cm{sup -2} under the same conditions. Despite this decrease in power density after bonding, the drastic reduction of the device dimensions resulted in an increase of more than 50 times the previous volumetric power density. The results obtained validate this novel approach to an all-polymer micro-fuel cell. (author)

  20. SU-8 Electrothermal Actuators: Optimization of Fabrication and Excitation for Long-Term Use

    Directory of Open Access Journals (Sweden)

    Thomas Winterstein

    2014-12-01

    Full Text Available In this paper we examine the suitability of SU-8 2000 as a construction material for electrothermal actuators and the actuator stability for long-term operation. The fabrication of SU-8 was optimized for mechanical and thermal stability. Samples with different softbake duration, exposure dose and postbake temperature were evaluated using Fourier-Transform IR-spectroscopy and dynamic-mechanical analysis. The exposure dose and postbake temperature proved to have a strong influence on the cross-linking and the glass transition temperature. A final hardbake levels the effects of the process history. A high degree of crosslinking, a low drop of the dynamic modulus over temperature (30% up to the glass transition temperature 100–140 °C were achieved for SU-8 with an exposure dose of 1500 mJ/cm², a postbake temperature of 95 °C and hardbake of 240 °C. Electrothermal actuators proved to be stable until the end of the experiment after 2400 duty cycles. Actuator deflections up to 55 μm were measured (actuator length: 4 mm for input powers up to 160 mW and a maximum operating temperature of 120 °C. Higher temperatures led to permanent deformations and failure. An offset drift of up to 20% occurs during actuation, but converges after a burn-in phase of about two hours.

  1. Design and fabricate multi channel microfluidic mold on top of glass slide using SU-8

    Science.gov (United States)

    Azman, N. A. N.; Rajapaksha, R. D. A. A.; Uda, M. N. A.; Hashim, U.

    2017-09-01

    Microfluidic is the study of fluid in microscale. Microfluidics provides miniaturized fluidic networks for processing and analyzing liquids in the nanoliter to milliliter range. Microfluidic device comprises of some essential segments or structure that are micromixer, microchannel and microchamber. The SU-8 mold is known as the most used technique in microfluidic fabrication due to the characteristic of very gooey polymer that can be spread over a thickness. In this study, in order to reduce the fabrication cost, the development and fabrication of SU-8 mold is replace by using a glass plate instead of silicon wafer which is used in the previous research. We designed a microfluidic chip for use with an IDE sensors to conduct multiplex detection of multiple channels. The microfluidic chip was designed to include multiplex detection for pathogen that consists of multiple channels of simultaneous results. The multi-channel microfluidic chip was designed, including the fluid outlet and inlet. A multi-channel microfluidic chip was used for pathogen detection. This paper sum up the fabrication of lab SU-8 mold using glass slide.

  2. SU-8 based microdevices to study self-induced chemotaxis in 3D microenvironments

    Directory of Open Access Journals (Sweden)

    Jose Maria Ayuso

    2015-05-01

    Full Text Available Tissues are complex three-dimensional structures in which cell behaviour is frequently guided by chemotactic signals. Although starvation and nutrient restriction induce many different chemotactic processes, the recreation of such conditions in vitro remains difficult when using standard cell culture equipment. Recently, microfluidic techniques have arisen as powerful tools to mimic such physiological conditions. In this context, microfluidic three-dimensional cell culture systems require precise control of cell/hydrogel location because samples need to be placed within a microchamber without obstruction of surrounding elements. In this article, SU-8 is studied as structural material for the fabrication of complex cell culture devices due to its good mechanical properties, low gas permeability and sensor integration capacity. In particular, this manuscript presents a SU-8 based microdevice designed to create self-induced medium starvation, based on the combination of nutrient restriction and natural cell metabolism. Results show a natural migratory response towards nutrient source, showing how cells adapt to their own microenvironment modifications. The presented results demonstrate the SU-8 potential for microdevice fabrication applied to cell culture.

  3. SU-8 as Hydrophobic and Dielectric Thin Film in Electrowetting-on-Dielectric Based Microfluidics Device

    Directory of Open Access Journals (Sweden)

    Vijay Kumar

    2012-01-01

    Full Text Available Electrowetting-on-dielectric (EWOD based droplet actuation in microfluidic chip is designed and fabricated. EWOD is used as on-chip micro-pumping scheme for moving fluid digitally in Lab-on-a-chip devices. For enabling this scheme, stacked deposition of thin dielectric and hydrophobic layer in that order between microchannel and electrodes is done. The present paper investigates the potential use of SU-8 as hydrophobic layer in conjunction of acting as dielectric in the device. The objective for the investigation is to lower the cost and a thin simplification in fabrication process of EWOD-based devices. We have done design and optimization of dimensions of electrode array including gap between arrays for EWOD micropump. Design and optimization are carried out in CoventorWare. The designing is followed by fabrication of device and analysis for droplet motion. The fabrication of the device includes array of electrodes over the silicon surface and embedding them in hydrophobic SU-8 layer. Water droplet movement in the order of microliter of spherical shape is demonstrated. It has been shown that an SU-8 microchannel in the current design allows microfluidic flow at tens of voltages comparable with costlier and more complicated to fabricate designs reported in the literature.

  4. PMMA to SU-8 Bonding for Polymer Based Lab-on -a-chip Systems with Integrated Optics

    DEFF Research Database (Denmark)

    Clausen, Bjarne

    2003-01-01

    An adhesive bonding technique for wafer-level sealing of SU-8 based lab-on-a-chip microsystems with integrated optical components is presented. Microfluidic channels and optical components, e.g. waveguides, are fabricated in cross-linked SU-8 and sealed with a Pyrex glass substrate by means...

  5. PMMA to SU-8 bonding for polymer based lab-on-a-chip systems with integrated optics

    DEFF Research Database (Denmark)

    Olsen, Brian Bilenberg; Nielsen, Theodor; Clausen, Bjarne Hans

    2004-01-01

    We present an adhesive bonding technique developed for SU-8 based "lab-on-a-chip"- systems with integrated optical components. Microfluidic channels and optical components (e.g. wave-guides) are defined in SU-8 photoresist on a Pyrex glass substrate. The microfluidic channels are sealed by a second...

  6. SU-8 cantilevers for bio/chemical sensing; Fabrication, characterisation and development of novel read-out methods

    DEFF Research Database (Denmark)

    Nordström, M.; Keller, Stephan Urs; Lillemose, Michael

    2008-01-01

    Here, we present the activities within our research group over the last five years with cantilevers fabricated in the polymer SU-8. We believe that SU-8 is an interesting polymer for fabrication of cantilevers for bio/chemical sensing due to its simple processing and low Young's modulus. We show...

  7. Simulation and experimental validation of a SU-8 based PCR thermocycler chip with integrated heaters and temperature sensor

    DEFF Research Database (Denmark)

    El-Ali, Jamil; Perch-Nielsen, Ivan R.; Poulsen, Claus Riber

    2004-01-01

    C/s, respectively, the performance of the chip is comparable with the best silicon micromachined PCR chips presented in the literature. The SU-8 chamber surface was found to be PCR compatible by amplification of yeast gene ribosomal protein S3 and Campylobacter gene cadF. The PCR compatibility of the chamber......We present a SU-8 based polymerase chain reaction (PCR) chip with integrated platinum thin film heaters and temperature sensor. The device is fabricated in SU-8 on a glass substrate. The use of SU-8 provides a simple microfabrication process for the PCR chamber, controllable surface properties...... and can allow on chip integration to other SU-8 based functional elements. Finite element modeling (FEM) and experiments show that the temperature distribution in the PCR chamber is homogeneous and that the chip is capable of fast thermal cycling. With heating and cooling rates of up to 50 and 30 degrees...

  8. Arabidopsis MAP kinase 4 negatively regulates systemic acquired resistance

    DEFF Research Database (Denmark)

    Petersen, M.; Brodersen, P.; Naested, H.

    2000-01-01

    Transposon inactivation of Arabidopsis MAP kinase 4 produced the mpk4 mutant exhibiting constitutive systemic acquired resistance (SAR) including elevated salicylic acid (SA) revels, increased resistance to virulent pathogens, and constitutive pathogenesis-related gene expression shown by Northern...... of NPR1. PDF1.2 and THI2.1 gene induction by jasmonate was blocked in mpk4 expressing NahG, suggesting that MPK4 is required for jasmonic acid-responsive gene expression....

  9. Low prevalence of antibiotic-resistant gram-negative bacteria ...

    African Journals Online (AJOL)

    2009-01-13

    Jan 13, 2009 ... detection of tetracycline resistance genes [tet(A), tet(B), tet(C), tet(D), tet(E), tet(G) and tet(M)]; macrolide or combinations of. TABLE 1. List of oligonucleotide primers used in this study. Resistance. Primer. Sequence (5′ → 3′). Amplicon. Reference gene name size (bp) ere(A). ereA-fw. TCA CTG GCT AGA ...

  10. Potential strategies for the eradication of multidrug-resistant Gram-negative bacterial infections.

    Science.gov (United States)

    Huwaitat, Rawan; McCloskey, Alice P; Gilmore, Brendan F; Laverty, Garry

    2016-07-01

    Antimicrobial resistance is one of the leading threats to society. The increasing burden of multidrug-resistant Gram-negative infection is particularly concerning as such bacteria are demonstrating resistance to nearly all currently licensed therapies. Various strategies have been hypothesized to treat multidrug-resistant Gram-negative infections including: targeting the Gram-negative outer membrane; neutralization of lipopolysaccharide; inhibition of bacterial efflux pumps and prevention of protein folding. Silver and silver nanoparticles, fusogenic liposomes and nanotubes are potential strategies for extending the activity of licensed, Gram-positive selective, antibiotics to Gram-negatives. This may serve as a strategy to fill the current void in pharmaceutical development in the short term. This review outlines the most promising strategies that could be implemented to solve the threat of multidrug-resistant Gram-negative infections.

  11. Plasmids in Gram negatives: molecular typing of resistance plasmids.

    Science.gov (United States)

    Carattoli, Alessandra

    2011-12-01

    A plasmid is defined as a double stranded, circular DNA molecule capable of autonomous replication. By definition, plasmids do not carry genes essential for the growth of host cells under non-stressed conditions but they have systems which guarantee their autonomous replication also controlling the copy number and ensuring stable inheritance during cell division. Most of the plasmids confer positively selectable phenotypes by the presence of antimicrobial resistance genes. Plasmids evolve as an integral part of the bacterial genome, providing resistance genes that can be easily exchanged among bacteria of different origin and source by conjugation. A multidisciplinary approach is currently applied to study the acquisition and spread of antimicrobial resistance in clinically relevant bacterial pathogens and the established surveillance can be implemented by replicon typing of plasmids. Particular plasmid families are more frequently detected among Enterobacteriaceae and play a major role in the diffusion of specific resistance genes. For instance, IncFII, IncA/C, IncL/M, IncN and IncI1 plasmids carrying extended-spectrum beta-lactamase genes and acquired AmpC genes are currently considered to be "epidemic resistance plasmids", being worldwide detected in Enterobacteriaceae of different origin and sources. The recognition of successful plasmids is an essential first step to design intervention strategies preventing their spread. Copyright © 2011 Elsevier GmbH. All rights reserved.

  12. Fabrication of thin SU-8 cantilevers: initial bending, release and time stability

    DEFF Research Database (Denmark)

    Keller, Stephan Urs; Haefliger, D.; Boisen, Anja

    2010-01-01

    development of the thin SU-8 film resulted in reduced cantilever bending due to removal of residual stress gradients. Further, improved time-stability of the devices was achieved due to the enhanced cross-linking of the polymer. A post-exposure bake at a temperature T-PEB = 50 degrees C followed by a hard...... bake at T-HB = 90 degrees C proved to be optimal to ensure low cantilever bending and low rotational deformation due to excellent device release and low change of these properties with time. With the optimized process, the reproducible fabrication of arrays with 2 mu m thick cantilevers with a length...

  13. Development of vertical SU-8 microneedles for transdermal drug delivery by double drawing lithography technology.

    Science.gov (United States)

    Xiang, Zhuolin; Wang, Hao; Pant, Aakanksha; Pastorin, Giorgia; Lee, Chengkuo

    2013-01-01

    Polymer-based microneedles have drawn much attention in transdermal drug delivery resulting from their flexibility and biocompatibility. Traditional fabrication approaches are usually time-consuming and expensive. In this study, we developed a new double drawing lithography technology to make biocompatible SU-8 microneedles for transdermal drug delivery applications. These microneedles are strong enough to stand force from both vertical direction and planar direction during penetration. They can be used to penetrate into the skin easily and deliver drugs to the tissues under it. By controlling the delivery speed lower than 2 μl/min per single microneedle, the delivery rate can be as high as 71%.

  14. Quinolones resistance and R-plasmids of some gram negative ...

    African Journals Online (AJOL)

    Out of the two hundred and sixty bacteria isolates from clinical specimens obtained from different body sites at the University College Hospital Ibadan, 166 belonged to the family of Enterobacteriaceae and Pseudomonaceae. The isolated gram-negative enteric bacilli consist of Escherichia coli (22), Klebsiella species (65), ...

  15. The power to resist: the relationship between power, stigma, and negative symptoms in schizophrenia.

    Science.gov (United States)

    Campellone, Timothy R; Caponigro, Janelle M; Kring, Ann M

    2014-02-28

    Stigmatizing beliefs about mental illness can be a daily struggle for people with schizophrenia. While investigations into the impact of internalizing stigma on negative symptoms have yielded mixed results, resistance to stigmatizing beliefs has received little attention. In this study, we examined the linkage between internalized stigma, stigma resistance, negative symptoms, and social power, or perceived ability to influence others during social interactions among people with schizophrenia. Further, we sought to determine whether resistance to stigma would be bolstered by social power, with greater power in relationships with other possibly buffering against motivation/pleasure negative symptoms. Fifty-one people with schizophrenia or schizoaffective disorder completed measures of social power, internalized stigma, and stigma resistance. Negative symptoms were assessed using the Clinical Assessment Interview for Negative Symptoms (CAINS). Greater social power was associated with less internalized stigma and negative symptoms as well as more stigma resistance. Further, the relationship between social power and negative symptoms was partially mediated by stigma resistance. These findings provide evidence for the role of stigma resistance as a viable target for psychosocial interventions aimed at improving motivation and social power in people with schizophrenia. © 2013 Published by Elsevier Ireland Ltd.

  16. [Resistant gram-negative bacteria. Therapeutic approach and risk factors].

    Science.gov (United States)

    Salgado, P; Gilsanz, F; Maseda, E

    2016-09-01

    The rapid spread of multidrug-resistant bacteria has become a serious threat, especially in critical care units, thereby prolonging the hospital stay. Enterobacteriaceae have a high capacity to adapt to any environment. Plasmids are the reason behind their expansion. The choice of empiric therapy for intra-abdominal or urinary infections requires knowledge of the intrinsic microbiological variability of each hospital or critical care unit, as well as the source of infection, safety or antibiotic toxicity, interaction with other drugs, the dosage regimen and the presence of risk factors. Carbapenems are the drug of choice in the case of suspected infection by ESBL-producing Enterobacteriaceae. The new ceftazidime/avibactam and ceftolozane/tazobactam drugs are opening up promising new horizons in the treatment of multidrug-resistant Enterobacteriaceae.

  17. Reversing Anoikis Resistance in Triple-Negative Breast Cancer

    Science.gov (United States)

    2015-10-01

    hepatocellular carcinoma after curative resection. Cancer. 2012;118:2708-17. Epub 2011/10/13. 38. Liu JJ, Shen R, Chen L, et al. Piwil2 is expressed ...200c suppresses translation of these transcripts inappropriately expressed by carcinomas to facilitate anoikis resistance AND alters splicing events...induces apoptosis by shuttling proteins to the nucleus. The full-length transcript encodes a tumor suppressor motor protein whose loss of expression has

  18. [Relatedness of methicillin-resistant coagulase-negative staphylococci].

    Science.gov (United States)

    Bogiel, Tomasz; Mikucka, Agnieszka; Deptuła, Aleksander; Gospodarek, Eugenia

    2009-01-01

    Many identification and relatedness studies methods had been commonly used for epidemiological studies in microbiological laboratories. Apart from phenotypic methods, genotypic are also often used. The aim of this study was to compare, obtained by PFGE chromosomal DNA patterns of methicillin-resistant S. epidermidis strains isolated from clinical material. 46 methicillin-resistant S. epidermidis strains were included in this study. Most of them were isolated from wound swabs (65.2%) and catheters (19.6%) from different surgical clinics (76.1%). To identify strains and receive biochemical profiles, ID 32 Staph tests and GPI cards of Vitek 1 system were used. Pulsed-field gel electrophoresis and Tenover et al. interpretation were used to compare chromosomal DNA patterns of examined strains. 44 and 42 PFGE patterns of chromosomal DNA were received, using visual interpretation classifying two pairs of strains as the same, two pairs as closely related and three pairs as probably related. Strains classified as identical and similar in visual evaluation were indistinguishable in Molecular Analyst DST interpretation, probably due to tolerance in bands location pattern. Strains probably related in visual interpretation represent at least 96% similarity in Molecular Analyst DST but different susceptibility and biochemical profiles obtained by ID 32 Staph and Vitek 1. PFGE analysis had foremost capacity to distinguish methicillin-resistant S. epidermidis strains using visual interpretation and Molecular Analyst DST (Bio-Rad) program and seems to be useful method in epidemiological studies. Strains with the same PFGE pattern, had different susceptibility and biochemical profiles.

  19. Inkjet Printing of High Aspect Ratio Superparamagnetic SU-8 Microstructures with Preferential Magnetic Directions

    Directory of Open Access Journals (Sweden)

    Loïc Jacot-Descombes

    2014-08-01

    Full Text Available Structuring SU-8 based superparamagnetic polymer composite (SPMPC containing Fe3O4 nanoparticles by photolithography is limited in thickness due to light absorption by the nanoparticles. Hence, obtaining thicker structures requires alternative processing techniques. This paper presents a method based on inkjet printing and thermal curing for the fabrication of much thicker hemispherical microstructures of SPMPC. The microstructures are fabricated by inkjet printing the nanoparticle-doped SU-8 onto flat substrates functionalized to reduce the surface energy and thus the wetting. The thickness and the aspect ratio of the printed structures are further increased by printing the composite onto substrates with confinement pedestals. Fully crosslinked microstructures with a thickness up to 88.8 μm and edge angle of 112° ± 4° are obtained. Manipulation of the microstructures by an external field is enabled by creating lines of densely aggregated nanoparticles inside the composite. To this end, the printed microstructures are placed within an external magnetic field directly before crosslinking inducing the aggregation of dense Fe3O4 nanoparticle lines with in-plane and out-of-plane directions.

  20. Development of vertical SU-8 microtubes integrated with dissolvable tips for transdermal drug delivery.

    Science.gov (United States)

    Xiang, Zhuolin; Wang, Hao; Pant, Aakanksha; Pastorin, Giorgia; Lee, Chengkuo

    2013-01-01

    Polymer-based microneedles have drawn much attention in the transdermal drug delivery resulting from their flexibility and biocompatibility. Traditional fabrication approach deploys various kinds of molds to create sharp tips at the end of needles for the penetration purpose. This approach is usually time-consuming and expensive. In this study, we developed an innovative fabrication process to make biocompatible SU-8 microtubes integrated with biodissolvable maltose tips as novel microneedles for the transdermal drug delivery applications. These microneedles can easily penetrate the skin's outer barrier represented by the stratum corneum (SC) layer. The drug delivery device of mironeedles array with 1000 μm spacing between adjacent microneedles is proven to be able to penetrate porcine cadaver skins successfully. The maximum loading force on the individual microneedle can be as large as 7.36 ± 0.48N. After 9 min of the penetration, all the maltose tips are dissolved in the tissue. Drugs can be further delivered via these open biocompatible SU-8 microtubes in a continuous flow manner. The permeation patterns caused by the solution containing Rhodamine 110 at different depths from skin surface were characterized via a confocal microscope. It shows successful implementation of the microneedle function for fabricated devices.

  1. Dielectric properties of ligand-modified gold nanoparticle/SU-8 photopolymer based nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Toor, Anju, E-mail: atoor@berkeley.edu [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); So, Hongyun, E-mail: hyso@berkeley.edu [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); Pisano, Albert P. [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093 (United States)

    2017-08-31

    Highlights: • Ligand-modified gold NP/SU-8 nanocomposites were synthesized and demonstrated. • Particle agglomeration and dispersion were characterized with different NPs concentration. • Nanocomposites showed higher average dielectric permittivity compared to SU-8 only. • Relatively lower dielectric loss (average 0.09 at 1 kHz) was achieved with 10 % w/w NPs. - Abstract: This article reports the enhanced dielectric properties of a photodefinable polymer nanocomposite material containing sub–10 nm coated metal nanoparticles (NPs). The surface morphology of the synthesized dodecanethiol-functionalized gold NPs was characterized using the transmission electron microscopy (TEM). We investigated the particle agglomeration and dispersion during the various stages of the nanocomposite synthesis using TEM. Physical properties such as dielectric permittivity and dielectric loss were measured experimentally. The dependence of the dielectric permittivity and loss tangent on the particle concentration, and frequency was studied. Nanocomposite films showed an approximately three times enhancement in average dielectric constant over the polymer base value and an average dielectric loss of 0.09 at 1 kHz, at a filler loading of 10% w/w.

  2. Antibiotic-resistant gram-negative bacilli in the sewage of the City of Concepcion, Chile.

    Science.gov (United States)

    Martínez, M; Mondaca, M A; Zemelman, R

    1994-01-01

    Counts of total and of antibiotic-resistant heterotrophic Gram-negative bacteria were performed in samples collected from the main sewage effluent of the city of Concepcion, Chile, during an eleven month period in 1991-1992. Antibiotic resistance patterns (ARP) were determined and antibiotic resistance indexes (ARI) were calculated for some fermenting and nonfermenting strains of resistant bacteria. Ampicillin-resistant strains were the most frequent among fermenting bacteria, whereas those cephalothin-resistant were the most frequent among nonfermenting bacilli. These results correlate with the frequency of clinical use of both antibiotics in the community of Concepción. Higher values of ARI for nonfermenting bacilli are probably due to the natural intrinsic resistance of these microorganisms to several beta-lactam compounds. Since plasmid-coded resistance is frequent among enteric bacilli, the large number of resistant bacilli in sewage may be important in the natural dis-

  3. Widespread Fosfomycin Resistance in Gram-Negative Bacteria Attributable to the Chromosomal fosA Gene

    Directory of Open Access Journals (Sweden)

    Ryota Ito

    2017-08-01

    Full Text Available Fosfomycin is a decades-old antibiotic which is being revisited because of its perceived activity against many extensively drug-resistant Gram-negative pathogens. FosA proteins are Mn2+ and K+-dependent glutathione S-transferases which confer fosfomycin resistance in Gram-negative bacteria by conjugation of glutathione to the antibiotic. Plasmid-borne fosA variants have been reported in fosfomycin-resistant Escherichia coli strains. However, the prevalence and distribution of fosA in other Gram-negative bacteria are not known. We systematically surveyed the presence of fosA in Gram-negative bacteria in over 18,000 published genomes from 18 Gram-negative species and investigated their contribution to fosfomycin resistance. We show that FosA homologues are present in the majority of genomes in some species (e.g., Klebsiella spp., Enterobacter spp., Serratia marcescens, and Pseudomonas aeruginosa, whereas they are largely absent in others (e.g., E. coli, Acinetobacter baumannii, and Burkholderia cepacia. FosA proteins in different bacterial pathogens are highly divergent, but key amino acid residues in the active site are conserved. Chromosomal fosA genes conferred high-level fosfomycin resistance when expressed in E. coli, and deletion of chromosomal fosA in S. marcescens eliminated fosfomycin resistance. Our results indicate that FosA is encoded by clinically relevant Gram-negative species and contributes to intrinsic fosfomycin resistance.

  4. Outcome of infections due to pandrug-resistant (PDR Gram-negative bacteria

    Directory of Open Access Journals (Sweden)

    Bliziotis Ioannis A

    2005-04-01

    Full Text Available Abstract Background The increasing problem of infections due to multidrug-resistant Gram-negative bacteria has led to re-use of polymyxins in several countries. However, there are already clinical isolates of Gram-negative bacteria that are resistant to all available antibiotics, including polymyxins. Methods We present a case series of patients with infections due to pathogens resistant to all antimicrobial agents tested, including polymyxins. An isolate was defined as pandrug-resistant (PDR if it exhibited resistance to all 7 anti-pseudomonal antimicrobial agents, i.e. antipseudomonal penicillins, cephalosporins, carbapenems, monobactams, quinolones, aminoglycosides, and polymyxins. Results Clinical cure of the infection due to pandrug-resistant (PDR Gram-negative bacteria, namely Pseudomonas aeruginosa or Klebsiella pneumoniae was observed in 4 out of 6 patients with combination of colistin and beta lactam antibiotics. Conclusion Colistin, in combination with beta lactam antibiotics, may be a useful agent for the management of pandrug-resistant Gram-negative bacterial infections. The re-use of polymyxins, an old class of antibiotics, should be done with caution in an attempt to delay the rate of development of pandrug-resistant Gram-negative bacterial infections.

  5. Infections Caused by Resistant Gram-Negative Bacteria: Epidemiology and Management.

    Science.gov (United States)

    Kaye, Keith S; Pogue, Jason M

    2015-10-01

    Infections caused by resistant gram-negative bacteria are becoming increasingly prevalent and now constitute a serious threat to public health worldwide because they are difficult to treat and are associated with high morbidity and mortality rates. In the United States, there has been a steady increase since 2000 in rates of extended-spectrum β-lactamase-producing Enterobacteriaceae, carbapenem-resistant Enterobacteriaceae, and multidrug-resistant strains of Pseudomonas aeruginosa and Acinetobacter baumannii, particularly among hospitalized patients with intraabdominal infections, urinary tract infections, ventilator-associated pneumonia, and bacteremia. Colonization with resistant gram-negative bacteria is common among residents in long-term care facilities (particularly those residents with an indwelling device), and these facilities are considered important originating sources of such strains for hospitals. Antibiotic resistance is associated with a substantial clinical and economic burden, including increased mortality, greater hospital and antibiotic costs, and longer stays in hospitals and intensive care units. Control of resistant gram-negative infections requires a comprehensive approach, including strategies for risk factor identification, detection and identification of resistant organisms, and implementation of infection-control and prevention strategies. In treating resistant gram-negative infections, a review of surveillance data and hospital-specific antibiograms, including resistance patterns within local institutions, and consideration of patient characteristics are helpful in guiding the choice of empiric therapy. Although only a few agents are available with activity against resistant gram-negative organisms, two recently released β-lactam/β-lactamase inhibitor combinations - ceftolozane/tazobactam and ceftazidime/avibactam - have promising activity against these organisms. In this article, we review the epidemiology, risk factors, and

  6. Antibiotic-resistant gram negative bacilli in meals delivered at a general hospital, Italy.

    Science.gov (United States)

    Plano, Maria Rosa Anna; Di Noto, Anna Maria; Firenze, Alberto; Sciortino, Sonia; Mammina, Caterina

    2009-01-01

    This study aimed at detecting the presence of antibiotic-resistant Gram-negatives in samples of meals delivered at the University General Hospital of Palermo, Italy. Antibiotic resistant Gram negatives were isolated in July-September 2007 ffrom cold dishes and food contact surfaces and utensils. Bacterial strains were submitted to susceptibility test and subtyped by random amplification of polymorphic DNA (RAPD). Forty-six of 55 (83.6%) food samples and 14 of 17 (82.3%) environmental swabs were culture positive for Gram negative bacilli resistant to at least one group of antibacterial drugs. A total of 134 antibiotic resistant strains, 51 fermenters and 83 non-fermenters, were recovered. Fermenters and non-fermenters showed frequencies as high as 97.8% of resistance to two or more groups of antibiotics and non fermenters were 28.9% resistant to more than three groups. Molecular typing detected 34 different profiles among the fermenters and 68 among the non-fermenters. Antibiotic resistance was very common among both fermenters and non-fermenters. However, the wide heterogeneity of RAPD patterns seems to support a prominent role of cross-contamination rather than a clonal expansion of a few resistant isolates. A contribution of commensal Gram negatives colonizing foods to a common bacterial resistance pool should not been overlooked.

  7. Antibiotic-Resistant Gram Negative Bacilli in Meals Delivered at a General Hospital, Italy

    Directory of Open Access Journals (Sweden)

    Maria Rosa Anna Plano

    2009-01-01

    Full Text Available This study aimed at detecting the presence of antibiotic-resistant Gram-negatives in samples of meals delivered at the University General Hospital of Palermo, Italy. Antibiotic resistant Gram negatives were isolated in July—September 2007 ffrom cold dishes and food contact surfaces and utensils. Bacterial strains were submitted to susceptibility test and subtyped by random amplification of polymorphic DNA (RAPD. Forty-six of 55 (83.6% food samples and 14 of 17 (82.3% environmental swabs were culture positive for Gram negative bacilli resistant to at least one group of antibacterial drugs. A total of 134 antibiotic resistant strains, 51 fermenters and 83 non-fermenters, were recovered. Fermenters and non-fermenters showed frequencies as high as 97.8% of resistance to two or more groups of antibiotics and non fermenters were 28.9% resistant to more than three groups. Molecular typing detected 34 different profiles among the fermenters and 68 among the non-fermenters. Antibiotic resistance was very common among both fermenters and non-fermenters. However, the wide heterogeneity of RAPD patterns seems to support a prominent role of cross-contamination rather than a clonal expansion of a few resistant isolates. A contribution of commensal Gram negatives colonizing foods to a common bacterial resistance pool should not been overlooked.

  8. [Antimicrobial therapy in severe infections with multidrug-resistant Gram-negative bacterias].

    Science.gov (United States)

    Duszyńska, Wiesława

    2010-01-01

    Multidrug-resistant Gram-negative bacteria pose a serious and rapidly emerging threat to patients in healthcare settings, and are especially prevalent and problematic in intensive therapy units. Recently, the emergence of pandrug-resistance in Gram-negative bacteria poses additional concerns. This review examines the clinical impact and epidemiology of multidrug-resistant Gram-negative bacteria as a cause of increased morbidity and mortality among ITU patients. Beta-lactamases, cephalosporinases and carbapenemases play the most important role in resistance to antibiotics. Despite the tendency to increased resistance, carbapenems administered by continuous infusion remain the most effective drugs in severe sepsis. Drug concentration monitoring, albeit rarely used in practice, is necessary to ensure an effective therapeutic effect.

  9. A two-step sealing-and-reinforcement SU8 bonding paradigm for the fabrication of shallow microchannels

    Science.gov (United States)

    Mehboudi, Aryan; Yeom, Junghoon

    2018-03-01

    Adhesive bonding is a key technique to create microfluidic devices when two separate substrates are used to form microchannels. Among many adhesives explored in microchannel fabrication, SU8 has been widely used as an adhesive layer for sealing the microchannel sidewalls. The majority of the available SU8-based bonding methods, however, suffer from the difficulties associated with sealing of two important types of the microchannel architecture: (1) shallow microchannels with small patterns on a large area, and (2) microchannels with ultra-low aspect ratios (e.g. 6 mm in width and 2~μ m in height). In this paper, a new bonding paradigm based upon the low-temperature and low-pressure SU8 bonding, consisting of two steps of sealing using a thin-SU8-coated PET film and bonding reinforcement using a SU8-coated glass slide, is proposed to resolve the aforementioned difficulties. Since it does not need complicated instruments such as a wafer bonding machine and a lamination device, the developed bonding paradigm is convenient and economical. We successfully demonstrate the compatibility of the proposed bonding paradigm with the two microchannel fabrication approaches based on the glass wet etching and the SU8 photo-lithography, where small microchannels with the innermost surfaces fully made of SU8 are obtained. A theoretical model is employed to better investigate the flow characteristics and the structural behavior of the microchannel including the PET film deformation, strain and von Mises stress distributions, bonding strength, etc. Moreover, we demonstrate the fabrication of the multi-height deep–shallow microchannel sidewalls and their sealing using the SU8-coated PET film. Finally, as a proof-of-concept device, a microfluidic filter consisting of the double-height deep–shallow microchannel is fabricated for separation of 3 µm and 10 µm particles.

  10. Antimicrobial resistance in coagulase-negative staphylococci from Nigerian traditional fermented foods.

    Science.gov (United States)

    Fowoyo, P T; Ogunbanwo, S T

    2017-01-31

    Coagulase-negative staphylococci have become increasingly recognized as the etiological agent of some infections. A significant characteristic of coagulase-negative staphylococci especially strains isolated from animals and clinical samples is their resistance to routinely used antibiotics although, resistant strains isolated from fermented foods have not been fully reported. A total of two hundred and fifty-five CoNS isolates were subjected to antimicrobial susceptibility test using the disc diffusion technique. The minimum inhibitory concentration of the isolates to the tested antibiotics was determined using the microbroth dilution method. Methicillin resistant strains were confirmed by detection of methicillin resistant genes (mecA) and also employing cefoxitin screening test. The isolates were confirmed to be methicillin resistant by the detection of mecA genes and the cefoxitin screening test. The isolates demonstrated appreciable resistance to ampicillin (86.7%), sulfomethoxazole-trimethoprim (74.9%), amoxicillin-clavulanic acid (52.5%) and oxacillin (35.7%). Methicillin resistance was exhibited by 13 out of the 255 isolates although no mecA gene was detected. It was also observed that the methicillin resistant isolates were prevalent in these traditional foods; iru, kindirmo, nono and wara. This study has ameliorated the incidence of multiple antibiotic resistant coagulase-negative staphylococci in Nigerian fermented foods and if not tackled adequately might lead to horizontal transfer of antibiotic resistance from food to man.

  11. Epidemiology and molecular characterization of multidrug-resistant Gram-negative bacteria in Southeast Asia

    OpenAIRE

    Nuntra Suwantarat; Karen C Carroll

    2016-01-01

    Abstract Background Multidrug-resistant Gram-negative bacteria (MDRGN), including extended-spectrum β-lactamases (ESBLs) and multidrug-resistant glucose-nonfermenting Gram-negative bacilli (nonfermenters), have emerged and spread throughout Southeast Asia. Methods We reviewed and summarized current critical knowledge on the epidemiology and molecular characterization of MDRGN in Southeast Asia by PubMed searches for publications prior to 10 March 2016 with the term related to “MDRGN definitio...

  12. Antibiotic-Resistant Gram Negative Bacilli in Meals Delivered at a General Hospital, Italy

    OpenAIRE

    Maria Rosa Anna Plano; Anna Maria Di Noto; Alberto Firenze; Sonia Sciortino; Caterina Mammina

    2009-01-01

    This study aimed at detecting the presence of antibiotic-resistant Gram-negatives in samples of meals delivered at the University General Hospital of Palermo, Italy. Antibiotic resistant Gram negatives were isolated in July—September 2007 ffrom cold dishes and food contact surfaces and utensils. Bacterial strains were submitted to susceptibility test and subtyped by random amplification of polymorphic DNA (RAPD). Forty-six of 55 (83.6%) food samples and 14 of 17 (82.3%) environmental swabs ...

  13. Antibiotic Resistance in Staphylococcus aureus and Coagulase Negative Staphylococci Isolated from Goats with Subclinical Mastitis

    Directory of Open Access Journals (Sweden)

    Salvatore Virdis

    2010-01-01

    Full Text Available Antimicrobial resistance patterns and gene coding for methicillin resistance (mecA were determined in 25 S. aureus and 75 Coagulase Negative Staphylococci (CNS strains isolates from half-udder milk samples collected from goats with subclinical mastitis. Fourteen (56.0% S. aureus and thirty-one (41.3% CNS isolates were resistant to one or more antimicrobial agents. S. aureus showed the highest resistance rate against kanamycin (28.0%, oxytetracycline (16.0%, and ampicillin (12.0%. The CNS tested were more frequently resistant to ampicillin (36.0% and kanamycin (6.7%. Multiple antimicrobial resistance was observed in eight isolates, and one Staphylococcus epidermidis was found to be resistant to six antibiotics. The mecA gene was not found in any of the tested isolates. Single resistance against β-lactamics or aminoglicosides is the most common trait observed while multiresistance is less frequent.

  14. Applications of SU-8 in the development of a Single Ion Hit Facility

    Energy Technology Data Exchange (ETDEWEB)

    Arteaga-Marrero, N. [Division of Nuclear Physics, Department of Physics, Lund University, Professorsgatan 1, Box 118, SE-22100 Lund (Sweden)], E-mail: natalia.arteaga@nuclear.lu.se; Astromskas, G. [Division of Solid State Physics, Department of Physics, Lund University, Professorsgatan 1, Box 118, SE-22100 Lund (Sweden); Olsson, M.G. [Department of Infection Medicine, Lund University, Soelvegatan 19, B14, SE-22184 Lund (Sweden); Elfman, M.; Kristiansson, P.; Nilsson, E.J.C.; Nilsson, C.; Pallon, J. [Division of Nuclear Physics, Department of Physics, Lund University, Professorsgatan 1, Box 118, SE-22100 Lund (Sweden)

    2009-06-15

    The Lund Nuclear Microprobe (LNM) has been adapted to be used as a Single Ion Hit Facility (SIHF) for proton cell irradiation experiments at low dose. In order to test the capabilities of the system, Ni dot arrays and artificial cells have been fabricated with the photopolymer SU-8 and common lithographic techniques. The primary purpose of the Ni dot arrays was to determine the targeting accuracy of the beam in vacuum and in air. Additionally, this sample was employed to evaluate the system performance during cell target irradiation experiments. The Ni dot arrays were also used for beam characterization. The artificial cells were originally fabricated to test the software for cell recognition and localization, developed and implemented at the LNM. However, this sample became very functional to make small adjustments at the irradiation chamber for cell irradiation experiments. A description of the samples, fabrication procedure and applications are presented in this paper.

  15. A superhydrophobic chip based on SU-8 photoresist pillars suspended on a silicon nitride membrane

    KAUST Repository

    Marinaro, Giovanni

    2014-07-28

    We developed a new generation of superhydrophobic chips optimized for probing ultrasmall sample quantities by X-ray scattering and fluorescence techniques. The chips are based on thin Si3N4 membranes with a tailored pattern of SU-8 photoresist pillars. Indeed, aqueous solution droplets can be evaporated and concentrated at predefined positions using a non-periodic pillar pattern. We demonstrated quantitatively the deposition and aggregation of gold glyconanoparticles from the evaporation of a nanomolar droplet in a small spot by raster X-ray nanofluorescence. Further, raster nanocrystallography of biological objects such as rod-like tobacco mosaic virus nanoparticles reveals crystalline macro-domain formation composed of highly oriented nanorods. © 2014 the Partner Organisations.

  16. Simulation of a low frequency Z-axis SU-8 accelerometer in coventorware and MEMS+

    KAUST Repository

    Carreno, Armando Arpys Arevalo

    2013-04-01

    This paper presents the simulation of a z-axis SU-8 capacitive accelerometer. The study consists of a modal analysis of the modeled accelerometer, a study relating capacitance to acceleration, capacitance to deflection, an effective spring constant calculation, and a comparison of results achieved using CoventorWare® ANALYZER™ and MEMS+®. A fabricated energy harvester design from [1] was used for modeling and simulation in this study, with a four spring attachment of a 650μm×650μm; ×110μm proof mass of 4.542×10-8 kg. At rest, the spacing between electrodes is 4μm along the z-axis, and at 1.5g acceleration, there is 1.9μm spacing between electrodes, at which point pull in occurs for a 1V voltage. © 2013 IEEE.

  17. Resistance to Methicillin in Coagulase-negative Staphylococci and Its Detection

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    Milan Kolář

    2010-01-01

    Full Text Available Resistance of staphylococci to methicillin is important especially in the case of Staphylococcus aureus isolates. Its impact in veterinary medicine is not exactly specified in coagulase-negative staphylococci; however, these staphylococci may represent an important reservoir of resistance genes. The study aimed at detecting resistance to methicillin in coagulase-negative staphylococci from raw materials and foodstuffs of animal origin and assessing the tests frequently used to determine this resistance. Coagulase-negative staphylococci (198 isolates of 12 species were tested. Resistance to methicillin was determined by the disk diffusion method using oxacillin and cefoxitin disks, microdilution method, detection of PBP2a and the mecA gene. Of the tested isolates, 109 (55.1% were classified as resistant by the diffusion test with oxacillin, 32 isolates (16.2% by the test with cefoxitin and 50 isolates (25.3% on the basis of oxacillin minimum inhibitory concentration (MIC. No resistant isolates were incorrectly identified as susceptible when using the disk diffusion method with oxacillin (sensitivity of 100%. However, apart from 22 correctly classified resistant isolates, another 87 isolates were incorrectly identified as resistant as well (specificity of 50.6%. The test with cefoxitin showed the lowest (45.5% sensitivity in determination of resistant isolates. By contrast, this test was the most precise in classification of resistant isolates (specificity of 87.5%. When using the microdilution method, resistant strains were identified with the sensitivity and specificity of 68.2% and 80.1%, respectively. The results revealed substantial variability of methicillin-resistant isolates ranging from 16.2% to 55.1%, depending on the phenotyping methods and recommended interpretation criteria used. Therefore, it is advisable to reconsider the current interpretation criteria in the case of coagulasenegative staphylococci of animal origin (with the

  18. Widespread Fosfomycin Resistance in Gram-Negative Bacteria Attributable to the Chromosomal fosA Gene.

    Science.gov (United States)

    Ito, Ryota; Mustapha, Mustapha M; Tomich, Adam D; Callaghan, Jake D; McElheny, Christi L; Mettus, Roberta T; Shanks, Robert M Q; Sluis-Cremer, Nicolas; Doi, Yohei

    2017-08-29

    Fosfomycin is a decades-old antibiotic which is being revisited because of its perceived activity against many extensively drug-resistant Gram-negative pathogens. FosA proteins are Mn2+ and K+-dependent glutathione S-transferases which confer fosfomycin resistance in Gram-negative bacteria by conjugation of glutathione to the antibiotic. Plasmid-borne fosA variants have been reported in fosfomycin-resistant Escherichia coli strains. However, the prevalence and distribution of fosA in other Gram-negative bacteria are not known. We systematically surveyed the presence of fosA in Gram-negative bacteria in over 18,000 published genomes from 18 Gram-negative species and investigated their contribution to fosfomycin resistance. We show that FosA homologues are present in the majority of genomes in some species (e.g., Klebsiella spp., Enterobacter spp., Serratia marcescens, and Pseudomonas aeruginosa), whereas they are largely absent in others (e.g., E. coli, Acinetobacter baumannii, and Burkholderia cepacia). FosA proteins in different bacterial pathogens are highly divergent, but key amino acid residues in the active site are conserved. Chromosomal fosA genes conferred high-level fosfomycin resistance when expressed in E. coli, and deletion of chromosomal fosA in S. marcescens eliminated fosfomycin resistance. Our results indicate that FosA is encoded by clinically relevant Gram-negative species and contributes to intrinsic fosfomycin resistance.IMPORTANCE There is a critical need to identify alternate approaches to treat infections caused by extensively drug-resistant (XDR) Gram-negative bacteria. Fosfomycin is an old antibiotic which is routinely used for the treatment of urinary tract infections, although there is substantial interest in expanding its use to systemic infections caused by XDR Gram-negative bacteria. In this study, we show that fosA genes, which encode dimeric Mn2+- and K+-dependent glutathione S-transferase, are widely distributed in the genomes of

  19. Beta-lactam resistance in the gram negatives: increasing complexity of conditional, composite and multiply resistant phenotypes.

    Science.gov (United States)

    Iredell, Jon; Thomas, Lee; Espedido, Björn

    2006-12-01

    The greatest impact of microbiology data on clinical care is in the critically ill. Unfortunately, this is also the area in which microbiology laboratories are most often non-contributive. Attempts to move to rapid, culture-independent diagnostics are driven by the need to expedite urgent results. This is difficult in Gram-negative infection because of the complexity of the antibiotic resistance phenotype. Here, we discuss resistance to modern beta-lactams as a case in point. Recent outbreaks of transmissible carbapenem resistance among Gram-negative enteric pathogens in Sydney and Melbourne serve to illustrate the pitfalls of traditional phenotypical approaches. A better understanding of the epidemiology and mosaic nature of antibiotic resistance elements in the microflora is needed for us to move forward.

  20. SU-8 Based MEMS Process with Two Metal Layers using α-Si as a Sacrificial Material

    KAUST Repository

    Ramadan, Khaled S.

    2012-04-01

    Polymer based microelectromechanical systems (MEMS) micromachining is finding more interest in research and applications. This is due to its low cost and less time processing compared with silicon MEMS. SU-8 is a photo-patternable polymer that is used as a structural layer for MEMS and microfluidic devices. In addition to being processed with low cost, it is a biocompatible material with good mechanical properties. Also, amorphous silicon (α-Si) has found use as a sacrificial layer in silicon MEMS applications. α-Si can be deposited at large thicknesses for MEMS applications and also can be released in a dry method using XeF2 which can solve stiction problems related to MEMS applications. In this thesis, an SU-8 MEMS process is developed using amorphous silicon (α-Si) as a sacrificial layer. Electrostatic actuation and sensing is used in many MEMS applications. SU-8 is a dielectric material which limits its direct use in electrostatic actuation. This thesis provides a MEMS process with two conductive metal electrodes that can be used for out-of-plane electrostatic applications like MEMS switches and variable capacitors. The process provides the fabrication of dimples that can be conductive or non-conductive to facilitate more flexibility for MEMS designers. This SU-8 process can fabricate SU-8 MEMS structures of a single layer of two different thicknesses. Process parameters were tuned for two sets of thicknesses which are thin (5-10μm) and thick (130μm). Chevron bent-beam structures and different suspended beams (cantilevers and bridges) were fabricated to characterize the SU-8 process through extracting the density, Young’s Modulus and the Coefficient of Thermal Expansion (CTE) of SU-8. Also, the process was tested and used as an educational tool through which different MEMS structures were fabricated including MEMS switches, variable capacitors and thermal actuators.

  1. Study of antibiotic resistance of staph aureus and coagulase negative staphylococci isolated from patient samples

    Directory of Open Access Journals (Sweden)

    M Anvary

    2006-04-01

    Full Text Available Introduction: Drug resistant Staphylococci are the most important agents of nosocomial infections. In this survey, effect of different antibiotics on these bacteria and their drug resistance was investigated. Methods: The study included 500 strains of Staphylococci. Minimum Inhibitory Concentrations of all antibiotics was determined by the broth macro dilution technique and standard methods from the National Committee for Clinical Laboratory Standards. Result : Oxacillin resistance of S. aureus was 14.2% and that of coagulase-negative staphylococci was 53.4%. The activity of different antibiotics is presented in detail. Conclusion: Surveillance of strains resistant to methicillin is necessary.

  2. Development of an SU-8 MEMS process with two metal electrodes using amorphous silicon as a sacrificial material

    KAUST Repository

    Ramadan, Khaled S.

    2013-02-08

    This work presents an SU-8 surface micromachining process using amorphous silicon as a sacrificial material, which also incorporates two metal layers for electrical excitation. SU-8 is a photo-patternable polymer that is used as a structural layer for MEMS and microfluidic applications due to its mechanical properties, biocompatibility and low cost. Amorphous silicon is used as a sacrificial layer in MEMS applications because it can be deposited in large thicknesses, and can be released in a dry method using XeF2, which alleviates release-based stiction problems related to MEMS applications. In this work, an SU-8 MEMS process was developed using ;-Si as a sacrificial layer. Two conductive metal electrodes were integrated in this process to allow out-of-plane electrostatic actuation for applications like MEMS switches and variable capacitors. In order to facilitate more flexibility for MEMS designers, the process can fabricate dimples that can be conductive or nonconductive. Additionally, this SU-8 process can fabricate SU-8 MEMS structures of a single layer of two different thicknesses. Process parameters were optimized for two sets of thicknesses: thin (5-10 m) and thick (130 m). The process was tested fabricating MEMS switches, capacitors and thermal actuators. © 2013 IOP Publishing Ltd.

  3. Multidrug-resistant Gram-negative bacteria in solid organ transplant recipients with bacteremias.

    Science.gov (United States)

    Wan, Q Q; Ye, Q F; Yuan, H

    2015-03-01

    Bloodstream infections (BSIs) remain as life-threatening complications and are associated with significant morbidity and mortality among solid organ transplant (SOT) recipients. Multidrug-resistant (MDR) Gram-negative bacteria can cause serious bacteremias in these recipients. Reviews have aimed to investigate MDR Gram-negative bacteremias; however, they were lacking in SOT recipients in the past. To better understand the characteristics of bacteremias due to MDR Gram-negative bacteria, optimize preventive and therapeutic strategies, and improve the outcomes of SOT recipients, this review summarize the epidemiology, clinical and laboratory characteristics, and explores the mechanisms, prevention, and treatment of MDR Gram-negative bacteria.

  4. Risk factors for nosocomial bloodstream infection caused by multidrug resistant gram-negative bacilli in pediatrics

    Directory of Open Access Journals (Sweden)

    Mariana V. Arnoni

    Full Text Available The aim of this study was to identify the risk factors for nosocomial bloodstream infections by multidrug resistant Gram-negative bacilli. From November 2001 to December 2003, in the Pediatric Department of the Santa Casa de São Paulo, a retrospective case-control study was developed concerning patients who had nosocomial bloodstream infection caused by Gram-negative bacilli. Patients with multidrug resistant infections were designated as case patients, and control patients were those with an infection that did not meet the criteria for multidrug resistance. Previous use of central venous catheter and previous use of vancomycin plus third generation cephalosporins were associated to a higher chance of infections by multidrug resistant Gram-negative bacilli (Odds ratio - 5.8 and 5.2, respectively. Regarding sensitivity of the isolated agents, 47.8% were multidrug resistant, 54.2% were Klebsiella spp. ESBL producers and 36.4% were imipenem resistant Pseudomonas aeruginosa. The lethality rate was 36.9% in the studied cases and this rate was significantly higher in the group of patients with multidrug resistant infections (p=0.013. Risk factor identification as well as the knowledge of the susceptibility of the nosocomial infectious agents gave us the possibility to perform preventive and control strategies to reduce the costs and mortality related to these infections.

  5. Risk factors for nosocomial bloodstream infection caused by multidrug resistant gram-negative bacilli in pediatrics.

    Science.gov (United States)

    Arnoni, Mariana V; Berezin, Eitan N; Martino, Marinês D V

    2007-04-01

    The aim of this study was to identify the risk factors for nosocomial bloodstream infections by multidrug resistant Gram-negative bacilli. From November 2001 to December 2003, in the Pediatric Department of the Santa Casa de São Paulo, a retrospective case-control study was developed concerning patients who had nosocomial bloodstream infection caused by Gram-negative bacilli. Patients with multidrug resistant infections were designated as case patients, and control patients were those with an infection that did not meet the criteria for multidrug resistance. Previous use of central venous catheter and previous use of vancomycin plus third generation cephalosporins were associated to a higher chance of infections by multidrug resistant Gram-negative bacilli (Odds ratio--5.8 and 5.2, respectively). Regarding sensitivity of the isolated agents, 47.8% were multidrug resistant, 54.2% were Klebsiella spp. ESBL producers and 36.4% were imipenem resistant Pseudomonas aeruginosa. The lethality rate was 36.9% in the studied cases and this rate was significantly higher in the group of patients with multidrug resistant infections (p=0.013). Risk factor identification as well as the knowledge of the susceptibility of the nosocomial infectious agents gave us the possibility to perform preventive and control strategies to reduce the costs and mortality related to these infections.

  6. CXC Chemokines Exhibit Bactericidal Activity against Multidrug-Resistant Gram-Negative Pathogens

    Directory of Open Access Journals (Sweden)

    Matthew A. Crawford

    2017-11-01

    Full Text Available The continued rise and spread of antimicrobial resistance among bacterial pathogens pose a serious challenge to global health. Countering antimicrobial-resistant pathogens requires a multifaceted effort that includes the discovery of novel therapeutic approaches. Here, we establish the capacity of the human CXC chemokines CXCL9 and CXCL10 to kill multidrug-resistant Gram-negative bacteria, including New Delhi metallo-beta-lactamase-1-producing Klebsiella pneumoniae and colistin-resistant members of the family Enterobacteriaceae that harbor the mobile colistin resistance protein MCR-1 and thus possess phosphoethanolamine-modified lipid A. Colistin-resistant K. pneumoniae isolates affected by genetic mutation of the PmrA/PmrB two-component system, a chromosomally encoded regulator of lipopolysaccharide modification, and containing 4-amino-4-deoxy-l-arabinose-modified lipid A were also found to be susceptible to chemokine-mediated antimicrobial activity. However, loss of PhoP/PhoQ autoregulatory control, caused by disruption of the gene encoding the negative regulator MgrB, limited the bactericidal effects of CXCL9 and CXCL10 in a variable, strain-specific manner. Cumulatively, these findings provide mechanistic insight into chemokine-mediated antimicrobial activity, highlight disparities amongst determinants of colistin resistance, and suggest that chemokine-mediated bactericidal effects merit additional investigation as a therapeutic avenue for treating infections caused by multidrug-resistant pathogens.

  7. Trojan Horse Antibiotics-A Novel Way to Circumvent Gram-Negative Bacterial Resistance?

    Science.gov (United States)

    Tillotson, Glenn S

    2016-01-01

    Antibiotic resistance has been emerged as a major global health problem. In particular, gram-negative species pose a significant clinical challenge as bacteria develop or acquire more resistance mechanisms. Often, these bacteria possess multiple resistance mechanisms, thus nullifying most of the major classes of drugs. Novel approaches to this issue are urgently required. However, the challenges of developing new agents are immense. Introducing novel agents is fraught with hurdles, thus adapting known antibiotic classes by altering their chemical structure could be a way forward. A chemical addition to existing antibiotics known as a siderophore could be a solution to the gram-negative resistance issue. Siderophore molecules rely on the bacterial innate need for iron ions and thus can utilize a Trojan Horse approach to gain access to the bacterial cell. The current approaches to using this potential method are reviewed.

  8. Incidence of carbapenem-resistant gram negatives in Italian transplant recipients: a nationwide surveillance study.

    Directory of Open Access Journals (Sweden)

    Simone Lanini

    Full Text Available Bacterial infections remain a challenge to solid organ transplantation. Due to the alarming spread of carbapenem-resistant gram negative bacteria, these organisms have been frequently recognized as cause of severe infections in solid organ transplant recipients.Between 15 May and 30 September 2012 we enrolled 887 solid organ transplant recipients in Italy with the aim to describe the epidemiology of gram negative bacteria spreading, to explore potential risk factors and to assess the effect of early isolation of gram negative bacteria on recipients' mortality during the first 90 days after transplantation. During the study period 185 clinical isolates of gram negative bacteria were reported, for an incidence of 2.39 per 1000 recipient-days. Positive cultures for gram negative bacteria occurred early after transplantation (median time 26 days; incidence rate 4.33, 1.67 and 1.14 per 1,000 recipient-days in the first, second and third month after SOT, respectively. Forty-nine of these clinical isolates were due to carbapenem-resistant gram negative bacteria (26.5%; incidence 0.63 per 1000 recipient-days. Carbapenems resistance was particularly frequent among Klebsiella spp. isolates (49.1%. Recipients with longer hospital stay and those who received either heart or lung graft were at the highest risk of testing positive for any gram negative bacteria. Moreover recipients with longer hospital stay, lung recipients and those admitted to hospital for more than 48h before transplantation had the highest probability to have culture(s positive for carbapenem-resistant gram negative bacteria. Forty-four organ recipients died (0.57 per 1000 recipient-days during the study period. Recipients with at least one positive culture for carbapenem-resistant gram negative bacteria had a 10.23-fold higher mortality rate than those who did not.The isolation of gram-negative bacteria is most frequent among recipient with hospital stays >48 hours prior to transplant

  9. Incidence of carbapenem-resistant gram negatives in Italian transplant recipients: a nationwide surveillance study.

    Science.gov (United States)

    Lanini, Simone; Costa, Alessandro Nanni; Puro, Vincenzo; Procaccio, Francesco; Grossi, Paolo Antonio; Vespasiano, Francesca; Ricci, Andrea; Vesconi, Sergio; Ison, Michael G; Carmeli, Yehuda; Ippolito, Giuseppe

    2015-01-01

    Bacterial infections remain a challenge to solid organ transplantation. Due to the alarming spread of carbapenem-resistant gram negative bacteria, these organisms have been frequently recognized as cause of severe infections in solid organ transplant recipients. Between 15 May and 30 September 2012 we enrolled 887 solid organ transplant recipients in Italy with the aim to describe the epidemiology of gram negative bacteria spreading, to explore potential risk factors and to assess the effect of early isolation of gram negative bacteria on recipients' mortality during the first 90 days after transplantation. During the study period 185 clinical isolates of gram negative bacteria were reported, for an incidence of 2.39 per 1000 recipient-days. Positive cultures for gram negative bacteria occurred early after transplantation (median time 26 days; incidence rate 4.33, 1.67 and 1.14 per 1,000 recipient-days in the first, second and third month after SOT, respectively). Forty-nine of these clinical isolates were due to carbapenem-resistant gram negative bacteria (26.5%; incidence 0.63 per 1000 recipient-days). Carbapenems resistance was particularly frequent among Klebsiella spp. isolates (49.1%). Recipients with longer hospital stay and those who received either heart or lung graft were at the highest risk of testing positive for any gram negative bacteria. Moreover recipients with longer hospital stay, lung recipients and those admitted to hospital for more than 48h before transplantation had the highest probability to have culture(s) positive for carbapenem-resistant gram negative bacteria. Forty-four organ recipients died (0.57 per 1000 recipient-days) during the study period. Recipients with at least one positive culture for carbapenem-resistant gram negative bacteria had a 10.23-fold higher mortality rate than those who did not. The isolation of gram-negative bacteria is most frequent among recipient with hospital stays >48 hours prior to transplant and in those

  10. A highly integrated vertical SU8 valve for stepwise in-series reactions

    Science.gov (United States)

    Calvo, V.; Ezkerra, A.; Elizalde, J.; Fernández, L. J.; Berganzo, J.; Mayora, K.; Ruano-López, J. M.

    2011-06-01

    Stepwise performance of reactions demands highly integrated microfluidic control. The vertical valve presented in this work allows performing reactions in cascade with reduced control requirements, by controlling the rupture of an SU8 wall that separates a chamber from an adjacent evacuation channel. Owing to its vertical construction, the valve can be readily integrated into any geometry with a low increase in footprint. Two valve approaches are presented, which differ in the location of the rupture region, the breaking pressures and the size of the fluidic path open. Breaking the wall about its upper end has proven to be more limited in terms of geometry and resulting gap size, whereas breaking the wall about its root opens a wider fluidic path that allows smooth filling of downstream chambers. Following these conclusions, a sequence of two reactions has been demonstrated, using a wall-valve-regulated double-chamber device. The chosen protocol, DNA concentration, elution and transport, has been successfully accomplished, as evidenced by positive on-chip polymerase chain reaction in a second double-chamber device.

  11. MEMS flexible artificial basilar membrane fabricated from piezoelectric aluminum nitride on an SU-8 substrate

    Science.gov (United States)

    Jang, Jongmoon; Jang, Jeong Hun; Choi, Hongsoo

    2017-07-01

    In this paper, we present a flexible artificial basilar membrane (FABM) that mimics the passive mechanical frequency selectivity of the basilar membrane. The FABM is composed of a cantilever array made of piezoelectric aluminum nitride (AlN) on an SU-8 substrate. We analyzed the orientations of the AlN crystals using scanning electron microscopy and x-ray diffraction. The AIN crystals are oriented in the c-axis (0 0 2) plane and effective piezoelectric coefficient was measured as 3.52 pm V-1. To characterize the frequency selectivity of the FABM, mechanical displacements were measured using a scanning laser Doppler vibrometer. When electrical and acoustic stimuli were applied, the measured resonance frequencies were in the ranges of 663.0-2369 Hz and 659.4-2375 Hz, respectively. These results demonstrate that the mechanical frequency selectivity of this piezoelectric FABM is close to the human communication frequency range (300-3000 Hz), which is a vital feature of potential auditory prostheses.

  12. Study of functional viability of SU-8-based microneedles for neural applications

    Science.gov (United States)

    Fernández, Luis J.; Altuna, Ane; Tijero, Maria; Gabriel, Gemma; Villa, Rosa; Rodríguez, Manuel J.; Batlle, Montse; Vilares, Roman; Berganzo, Javier; Blanco, F. J.

    2009-02-01

    This paper presents the design, fabrication, packaging and first test results of SU-8-based microneedles for neural applications. By the use of photolithography, sputtering and bonding techniques, polymer needles with integrated microchannels and electrodes have been successfully fabricated. The use of photolithography for the patterning of the fluidic channel integrated in the needle allows the design of multiple outlet ports at the needle tip, minimizing the possibility of being blocked by the tissue. Furthermore, the flexibility of the polymer reduces the risk of fracture and tissue damage once the needle is inserted, while it is still rigid enough to allow a perfect insertion into the neural tissue. Fluidic and electric characterization of the microneedles has shown their viability for drug delivery and monitoring in neural applications. First drug delivery tests in ex vivo tissue demonstrated the functional viability of the needle to deliver drugs to precise points. Furthermore, in vivo experiments have demonstrated lower associated damages during insertion than those by stereotaxic standard needles.

  13. Necessity of resist model in source mask optimization for negative tone development process

    Science.gov (United States)

    Zhao, Lijun; Dong, Lisong; Chen, Wenhui; Wei, Yayi; Ye, Tianchun; Yue, Liwan; Jiang, Yuntao; Wu, Qiang

    2017-07-01

    As the semiconductor technology node comes to 14 nm and below, using bright-field exposure with negative tone development (NTD) has been a dominant lithographic solution for metal and contact layers, which has benefits of larger process windows and higher image contrasts than positive tone development (PTD). For PTD, a resist model is usually optional in source mask optimization (SMO) because optical models with aerial image blur can predict resist behaviors in most cases. However, NTD has much stronger resist effects, such as resist shrinkage and two-dimensional-effect-induced local stress. It has been suggested that the calibrated resist model is strongly required in the SMO of NTD process. We clarify this issue-the necessity of resist model in SMO for NTD process. First, we analyze the mismatch between simulation and experimental data when the aerial image blur is only used to simulate resist effects. Second, we present the calibration flow of resist model. Finally, we use the calibrated resist model to check the test pattern and run the SMO. The result demonstrates that the simulation data have the same tendency with experimental data, and the model has a good prediction on NTD resist behaviors under different conditions.

  14. [Bile-resistant Gram-negative bacteria effect of different kinds of root decoction pieces].

    Science.gov (United States)

    Deng, Yan; Wang, Ya-Ke; Han, Xiao-Yu; Wang, Ya-Qi; Jiang, Zhen-Yu; Yu, Zhi-Jun; Deng, Hai-Ying

    2017-11-01

    To investigate the microbial contamination in Chinese herbal decoction pieces with different functional types by studying the total aerobic microbial count (TAMC), and total yeast and mould count (TYMC) in 40 samples of 8 types of root decoction pieces; further evaluate the contamination load of bile-resistant Gram-negative bacteria, and identify the Gram-negative bacteria by using biochemical identification system for Gram-negative bacteria. Our results showed that the TAMC value was more than 1 000 CFU•g⁻¹ in 85% (34/40) samples, and was more than 100 CFU•g⁻¹ in 30% (12/40) samples; the contamination of bile-resistant Gram-negative bacteria was detected in 45% (18/40) of the samples. The bile-resistant Gram-negative bacteria load of seven batches of samples was N>1 000 MPN•g⁻¹. Sixteen bacterium strains including Serratia plymouthensis, Cedecea neteri, Escherichia vulneris, Klebsiella oxytoca, Enterobacter amnigenus, E. cloacae, E. sakazakii, Proteus penneri and E. gergoviae were obtained and identified. E. cloacae was the predominant bacterium that was isolated from Salviae Miltiorrhizae Radix et Rhizoma, while E. amnigenus, Yersinia pseudotuberculosis was the typical bacterium of Ophiopogonis Radix and Codonopsis Radix, respectively. All these suggested that the contamination of bile-resistant Gram-negative bacteria was severe for the root decoction pieces in Wuhan city. Microbial species have certain selection specificity for medicinal ingredients, so the type and limit of control bacteria for detection should be formulated according to the pollution type and quantity of bile-resistant Gram-negative bacteria. Copyright© by the Chinese Pharmaceutical Association.

  15. Emergence of Pan-drug resistance amongst gram negative bacteria! The First case series from India

    Directory of Open Access Journals (Sweden)

    Abdul Ghafur

    2014-09-01

    Full Text Available Objective: Increasing prevalence of carbapenem resistant Gram negative bacteria is a serious clinical and public health challenge. Bacteria resistant to all available antibiotics (Pan Drug Resistance herald the onset of post antibiotics era. We hereby report clinical profile of 13 patients with pan drug resistant gram negative isolates. Methods:Retrospective analysis of 13 patients with pan drug resistant gram negative isolates over the last 18 months was done by medical records review. Identification of the isolates and susceptibility testing was done using VITEK auto analyzer in concordance with the corresponding CLSI guidelines. Results:Out of four patients with bacteremic isolates, three patients received colistin based combination therapy. Though two of these patients had microbiologic clearance, all the three died. Out of the 9 patients with non bacteremic isolates, 4 had infection and 5 had colonization. Three (out of four were treated with combination therapy including colistin and one patient received colistin monotherapy. All four patients had microbiological clearance. Three patients had clinical cure and were discharged. One patient later developed bacteremia and died. Conclusion:Infections, particularly blood stream with pan drug resistant organisms has a higher mortality. Urgent studies to reevaluate existing therapeutic options and research into new antibiotic molecules are the need of the hour. J Microbiol Infect Dis 2014; 4(3: 86-91

  16. Mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swab specimens in Brazil

    OpenAIRE

    dos Santos, Danielle Caldeira Martins; da Costa, Thaina Miranda; Rabello, Renata Fernandes; Alves, F?bio Aguiar; de Mondino, Silvia Susana Bona

    2015-01-01

    The isolation of mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swabs is reported. Among the 59 isolates, 9 (15%) isolates were mannitol-negative; all of these isolates were categorized as staphylococcal cassette chromosome mec (SCCmec) type IVa. This report emphasizes that mannitol fermentation on mannitol salt agar should not be used as the sole criterion when screening nasal swab specimens for S. aureus.

  17. Mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swab specimens in Brazil

    Directory of Open Access Journals (Sweden)

    Danielle Caldeira Martins dos Santos

    2015-06-01

    Full Text Available The isolation of mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swabs is reported. Among the 59 isolates, 9 (15% isolates were mannitol-negative; all of these isolates were categorized as staphylococcal cassette chromosome mec (SCCmec type IVa. This report emphasizes that mannitol fermentation on mannitol salt agar should not be used as the sole criterion when screening nasal swab specimens for S. aureus.

  18. Mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swab specimens in Brazil.

    Science.gov (United States)

    dos Santos, Danielle Caldeira Martins; da Costa, Thaina Miranda; Rabello, Renata Fernandes; Alves, Fábio Aguiar; de Mondino, Silvia Susana Bona

    2015-06-01

    The isolation of mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swabs is reported. Among the 59 isolates, 9 (15%) isolates were mannitol-negative; all of these isolates were categorized as staphylococcal cassette chromosome mec (SCCmec) type IVa. This report emphasizes that mannitol fermentation on mannitol salt agar should not be used as the sole criterion when screening nasal swab specimens for S. aureus.

  19. Incidence of Carbapenem-Resistant Gram Negatives in Italian Transplant Recipients: A Nationwide Surveillance Study

    OpenAIRE

    Simone Lanini; Alessandro Nanni Costa; Vincenzo Puro; Francesco Procaccio; Paolo Antonio Grossi; Francesca Vespasiano; Andrea Ricci; Sergio Vesconi; Ison, Michael G.; Yehuda Carmeli; Giuseppe Ippolito

    2015-01-01

    Background Bacterial infections remain a challenge to solid organ transplantation. Due to the alarming spread of carbapenem-resistant gram negative bacteria, these organisms have been frequently recognized as cause of severe infections in solid organ transplant recipients. Methods and Findings Between 15 May and 30 September 2012 we enrolled 887 solid organ transplant recipients in Italy with the aim to describe the epidemiology of gram negative bacteria spreading, to explore potential risk f...

  20. The Changing Role of the Clinical Microbiology Laboratory in Defining Resistance in Gram-negatives.

    Science.gov (United States)

    Endimiani, Andrea; Jacobs, Michael R

    2016-06-01

    The evolution of resistance in Gram-negatives has challenged the clinical microbiology laboratory to implement new methods for their detection. Multidrug-resistant strains present major challenges to conventional and new detection methods. More rapid pathogen identification and antimicrobial susceptibility testing have been developed for use directly on specimens, including fluorescence in situ hybridization tests, automated polymerase chain reaction systems, microarrays, mass spectroscopy, next-generation sequencing, and microfluidics. Review of these methods shows the advances that have been made in rapid detection of resistance in cultures, but limited progress in direct detection from specimens. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Methicillin-resistant coagulase-negative staphylococci from healthy dogs in Nsukka, Nigeria

    Directory of Open Access Journals (Sweden)

    Kennedy F. Chah

    2014-01-01

    Full Text Available The occurrence, resistance phenotype and molecular mechanisms of resistance of methicillin-resistant staphylococci from groin swabs of 109 clinically healthy dogs in Nsukka, Nigeria were investigated. The groin swab samples were cultured on mannitol salt agar supplemented with 10 µgof cloxacillin. Sixteen methicillin-resistant coagulase negative staphylococci (MRCoNS, all harbouring the mecA gene were isolated from 14 (12.8% of the 109 dogs studied. The MRCoNS isolated were: S. sciuri subspecies rodentium, S. lentus, S. haemolyticus, and S. simulans with S. sciuri subspecies rodentium (62.5% being the predominant species. Thirteen (81.3% of the MRCoNS were resistant to tetracycline while 12 (75% and 10 (62.5% were resistant to kanamycin and trimthoprim-sulphamethoxazole respectively. None of the isolates was resistant to fusidic acid, linezolid and vancomycin. Thirteen (81.3% of the MRCoNS were multi-drug resistance (MDR. Other antimicrobial genes detected were: blaZ, tet(K, tet(M, tet(L, erm(B, lnu(A, aacA-aphD, aphA3, str, dfr(G, cat pC221,and cat pC223. Methicillin-resistant staphylococci are common colonizers of healthy dogs in Nigeria with a major species detected being S. sciuri subsp. rodentium.

  2. Phenotypical and Genotypical Antimicrobial Resistance of Coagulase-negative staphylococci Isolated from Cow Mastitis.

    Science.gov (United States)

    Klimiene, I; Virgailis, M; Pavilonis, A; Siugzdiniene, R; Mockeliunas, R; Ruzauskas, M

    2016-09-01

    The objectives of this study were to determine the prevalence and antimicrobial resistance of coagulase-negative staphylococci (CNS) isolated from dairy cows with subclinical mastitis. Antimicrobial resistance in staphylococci were evaluated by breakpoint values specific to the species (EU-CAST). The presence of resistance-encoding genes was detected by multiplex PCR. A total of 191 CNS isolates were obtained. The CNS isolates were typically resistant to penicillin (67.4%), tetracyc-line (18.9%), and erythromycin (13.7%). CNS isolates (78.0%) were resistant to at least one antimicrobial compound, and 22.0% were multiresistant. The multiresistant isolates were predominantly Staphylococcus chromogenes (28.6%), Staphylococcus warneri (19%) and Staphylococcus haemolyticus (14.3%). According to MIC pattern data, multiresistant isolates showed the highest resistance (p<0.05) rates to penicillin (85.7%), tetracycline (66.7%), and erythromycin (48.2%), but all of them were sensitive to daptomycin, oxacillin, qiunupristin/dalfopristin, and vancomycin. S. chromogenes (9.5%), S. haemolyticus (4.8%), and S. capitis ss capitis (2.4%) strains were resistant to methicillin; their resistance to oxacillin and penicillin was more than 8 mg/l. A high rate of resistance to penicillin was linked to a blaZ gene found in 66.6% of the isolated multiresistant CNS strains. Resistance to tetracycline via the tetK (38.1%) gene and penicillin via the mecA (23.8%) gene were detected less frequently. Gene msrAB was responsible for macrolides and lincosamides resistance and detected in 28.6% of the CNS isolates. Antimicrobial resistance genes were identified more frequently in S. epidermidis, S. chromogenes, and S. warneri.

  3. Antimicrobial Resistance in Gram-Negative Rods Causing Bacteremia in Hematopoietic Stem Cell Transplant Recipients

    DEFF Research Database (Denmark)

    Averbuch, Diana; Tridello, Gloria; Hoek, Jennifer

    2017-01-01

    Background: This intercontinental study aimed to study gram-negative rod (GNR) resistance in hematopoietic stem cell transplantation (HSCT). Methods: GNR bacteremias occurring during 6 months post-HSCT (February 2014-May 2015) were prospectively collected, and analyzed for rates and risk factors ...

  4. Colonization and resistance dynamics of gram-negative bacteria in patients during and after hospitalization.

    NARCIS (Netherlands)

    P.M.G. Filius (Margreet); I.C. Gyssens (Inge); I.M. Kershof (Irma); P.J. Roovers (Patty); A. Ott (Alewijn); A.G. Vulto (Arnold); H.A. Verbrugh (Henri); H.P. Endtz (Hubert)

    2005-01-01

    textabstractThe colonization and resistance dynamics of aerobic gram-negative bacteria in the intestinal and oropharyngeal microfloras of patients admitted to intensive care units (ICU) and general wards were investigated during and after hospitalization. A total of 3,316 specimens were obtained

  5. Negative e-beam resists using for nano-imprint lithography and silicone mold fabrication

    Science.gov (United States)

    Shy, S. L.; T. V., Anil Kumar; Sheu, Gene; Yang, Shao-Ming; Chen, M. C.; Hong, C. S.

    2015-03-01

    Nano-imprinting technology, as one of the most promising fabrication technologies, has been demonstrated to be a powerful tool for large-area replication up to wafer-level, with features down to nanometer scale. This study aims to develop capabilities in patterning nano structure using thermal nano-imprint lithography (NIL). 30nm Si molds are patterned by electron-beam lithography (EBL) using NEB22 A2 negative e-beam resist. The NEB22 A2 negative e-beam resist possess a variety of characteristics desirable for NIL, such as low viscosity, low bulk-volumetric shrinkage, high Young's modulus, high thermal stability, and excellent dry-etch resistance. The excellent oxygenetch resistance of the barrier material enables a final transfer pattern that is about three times higher than that of the original NIL mold. Based on these imprint on negative electron beam resist approach is used for pattern transfer into silicon substrates. The result is a high-resolution pattern with feature sizes in the range of nanometer to several microns.

  6. Simplified phase noise model for negative-resistance oscillators and a comparison with feedback oscillator models.

    Science.gov (United States)

    Everard, Jeremy; Xu, Min; Bale, Simon

    2012-03-01

    This paper describes a greatly simplified model for the prediction of phase noise in oscillators which use a negative resistance as the active element. It is based on a simple circuit consisting of the parallel addition of a noise current, a negative admittance/resistance, and a parallel (Qlimited) resonant circuit. The transfer function is calculated as a forward trans-resistance (VOUT/IIN) and then converted to power. The effect of limiting is incorporated by assuming that the phase noise element of the noise floor is kT/2, i.e., -177 dBm/Hz at room temperature. The result is the same as more complex analyses, but enables a simple, clear insight into the operation of oscillators. The phase noise for a given power in the resonator appears to be lower than in feedback oscillators. The reasons for this are explained. Simulation and experimental results are included.

  7. Antibiotic-non-antibiotic combinations for combating extremely drug-resistant Gram-negative 'superbugs'.

    Science.gov (United States)

    Schneider, Elena K; Reyes-Ortega, Felisa; Velkov, Tony; Li, Jian

    2017-02-28

    The emergence of antimicrobial resistance of Gram-negative pathogens has become a worldwide crisis. The status quo for combating resistance is to employ synergistic combinations of antibiotics. Faced with this fast-approaching post-antibiotic era, it is critical that we devise strategies to prolong and maximize the clinical efficacy of existing antibiotics. Unfortunately, reports of extremely drug-resistant (XDR) Gram-negative pathogens have become more common. Combining antibiotics such as polymyxin B or the broad-spectrum tetracycline and minocycline with various FDA-approved non-antibiotic drugs have emerged as a novel combination strategy against otherwise untreatable XDR pathogens. This review surveys the available literature on the potential benefits of employing antibiotic-non-antibiotic drug combination therapy. The apex of this review highlights the clinical utility of this novel therapeutic strategy for combating infections caused by 'superbugs'. © 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  8. Changes of Antimicrobial Resistance among Coagulase-Negative Staphylococci Isolated in 8 Consecutive Years in the First Bethune Hospital

    Science.gov (United States)

    Xu, Jiancheng; Yan, Chaoying; Wang, Liqiang; Zhou, Qi

    This study was to investigate the antimicrobial resistance of coagulase-negative Staphylococci isolated in 8 consecutive years in the First Bethune Hospital. Disk diffusion test was used to study the antimicrobial resistance. The data were analyzed by WHONET 5 software according to Clinical and Laboratory Standards Institute (CLSI). Most of 2484 strains of coagulase-negative Staphylococci were collected from blood 925 (37.2%), secretions 652 (26.2%) and urine 323 (13.0%) during the past 8 years. The rates of methicillin-resistant coagulase-negative Staphylococci (MRCNS) were between 79.4% and 81.5% during the past 8 years, respectively. In recent 8 years, the antimicrobial resistance of coagulase-negative Staphylococci had increased. Monitoring the antimicrobial resistance to coagulase-negatives Staphylococci should be strengthened. The change of the antimicrobial resistance should be investigated in order to direct rational drug usage in the clinic and prevent bacterial strain of drug resistance from being transmitted.

  9. [News of antibiotic resistance among Gram-negative bacilli in Algeria].

    Science.gov (United States)

    Baba Ahmed-Kazi Tani, Z; Arlet, G

    2014-06-01

    Antibiotic resistance has become a major public health problem in Algeria. Indeed the past decade, we have seen a significant increase in resistance to antibiotics especially in Gram-negative bacilli. Resistance to β-lactams in enterobacteria is dominated by the production of ESBL CTX-M-3 and CTX-M-15. The strains producing these enzymes are often the cause of potentially serious infections in both hospital and community settings. Identified plasmid cephalosporinases are CMY-2, CMY-12 and DHA-1. The isolation of strains of Enterobacteriaceae and Pseudomonas aeruginosa producing carbapenemases is rare in Algeria. Some Enterobacteriaceae producing OXA-48 or VIM-19 have been reported; so far, only VIM-2 has been identified in P. aeruginosa. However, the situation regarding the strains of Acinetobacter baumannii resistant to carbapenemases seems to be more disturbing. The carbapenemase OXA-23 is the most common and seems to be endemic in the north. The carbapenemase NDM-1 has also been identified. Resistance to aminoglycosides is marked by the identification armA gene associated with blaCTX-M genes in strains of Salmonella sp. Several other resistance genes have been identified sporadically in strains of Enterobacteriaceae, P. aeruginosa and A. baumannii. Resistance genes to fluoroquinolones are more recent identification in Algeria. The most common are the Qnr determinants followed by the bifunctional enzyme AAC[6']-Ib-cr. Resistance to sulfonamides and trimethoprim was also reported in Enterobacteriaceae strains in the west of the country. Copyright © 2014. Published by Elsevier SAS.

  10. Serum acylated ghrelin is negatively correlated with the insulin resistance in the CODING study.

    Directory of Open Access Journals (Sweden)

    Peyvand Amini

    Full Text Available Ghrelin is a 28-amino acid orexigenic peptide synthesized mainly in the stomach. Acute administration of ghrelin has been found to decrease insulin secretion. However, little data is available regarding whether ghrelin contributes to the long-term regulation of insulin resistance at the population level. The aim of this study is to investigate the association between circulating ghrelin and insulin resistance in a large population based study.A total of 2082 CODING study (Complex Diseases in the Newfoundland population: Environment and Genetics subjects were assessed. Subjects were of at least third generation Newfoundland descent, between the ages of 20 and 79 years, and had no serious metabolic, cardiovascular, or endocrine diseases. Ghrelin was measured with an Enzyme Immunoassay method. Insulin and fasting glucose were measured by Immulite 2500 autoanalyzer and Lx20 clinical chemistry analyzer, respectively. Homeostatic Model Assessment of β cell function (HOMA-β and Insulin Resistance (HOMA-IR and Quantitative Insulin-sensitivity Check Index (QUICKI were used for measurement of insulin resistance.Partial correlation analyses showed a significant negative correlation between circulating ghrelin and insulin level and insulin resistance in the entire cohort and also in men and women separately. The aforementioned correlation was independent of age, percentage of trunk fat and HDL-cholesterol. According to menopausal status, only pre-menopausal women revealed negative correlations.Our results suggest that except for postmenopausal women, high circulating ghrelin level is associated with lower insulin resistance in the general population.

  11. Plasmid-Mediated Antibiotic Resistance and Virulence in Gram-negatives: the Klebsiella pneumoniae Paradigm.

    Science.gov (United States)

    Ramirez, Maria S; Traglia, German M; Lin, David L; Tran, Tung; Tolmasky, Marcelo E

    Plasmids harbor genes coding for specific functions including virulence factors and antibiotic resistance that permit bacteria to survive the hostile environment found in the host and resist treatment. Together with other genetic elements such as integrons and transposons, and using a variety of mechanisms, plasmids participate in the dissemination of these traits resulting in the virtual elimination of barriers among different kinds of bacteria. In this article we review the current information about physiology and role in virulence and antibiotic resistance of plasmids from the gram-negative opportunistic pathogen Klebsiella pneumoniae. This bacterium has acquired multidrug resistance and is the causative agent of serious communityand hospital-acquired infections. It is also included in the recently defined ESKAPE group of bacteria that cause most of US hospital infections.

  12. Plasmid-Mediated Antibiotic Resistance and Virulence in Gram-Negatives: the Klebsiella pneumoniae Paradigm.

    Science.gov (United States)

    Ramirez, Maria S; Traglia, German M; Lin, David L; Tran, Tung; Tolmasky, Marcelo E

    2014-10-01

    Plasmids harbor genes coding for specific functions including virulence factors and antibiotic resistance that permit bacteria to survive the hostile environment found in the host and resist treatment. Together with other genetic elements such as integrons and transposons, and using a variety of mechanisms, plasmids participate in the dissemination of these traits, resulting in the virtual elimination of barriers among different kinds of bacteria. In this article we review the current information about the physiology of plasmids and their role in virulence and antibiotic resistance from the Gram-negative opportunistic pathogen Klebsiella pneumoniae. This bacterium has acquired multidrug resistance and is the causative agent of serious community- and hospital-acquired infections. It is also included in the recently defined ESKAPE group of bacteria that cause most U.S. hospital infections.

  13. Phenotypic and Genotypic Detection of Metallo-beta-lactamases among Imipenem-Resistant Gram Negative Isolates

    Directory of Open Access Journals (Sweden)

    Mohammad Mohammadzadeh

    2016-08-01

    Full Text Available Background:   Imipenem-resistant gram negative bacteria, resulting from metallo-beta-lactamase (MBLs-producing strains have been reported to be among the important causes of nosocomial infections and of serious therapeutic problem worldwide. Because of their broad range, potent carbapenemase activity and resistance to inhibitors, these enzymes can confer resistance to almost all beta-lactams. The prevalence of metallo-beta-lactamase among imipenem-resistant Acinetobacter spp., Pseudomonas spp. and Enerobacteriaceae isolates is determined.Methods:   In this descriptive study 864 clinical isolates of Acinetobacter spp., Pseudomonas spp. and Enterobacteriaceae, were initially tested for imipenem susceptibility. The metallo-beta-lactamase production was detected using combined disk diffusion, double disk synergy test, and Hodge test. Then all imipenem resistant isolates were tested by PCR for imp, vim and ndm genes. Results:   Among 864 isolates, 62 (7.17 % were imipenem-resistant. Positive phonetypic test for metallo-beta-lactamase was 40 (64.5%, of which 24 (17.1% and 16 (9.2% isolates were Acinetobacter spp. and Pseudomonas spp., respectively. By PCR method 30 (48.4% of imipenem resistant Acinetobacter, and Pseudomonas isolates were positive for MBL-producing genes. None of the Enterobacteriaceae isolates were positive for metallo-beta-lactamase activity. Conclusion:   The results of this study are indicative of the growing number of nosocomial infections associated with multidrug-resistant gram negative bacteria in this region leading to difficulties in antibiotic therapy. Thereby, using of phenotypic methods can be helpful for management of this problem.

  14. Membrane permeabilization of colistin toward pan-drug resistant Gram-negative isolates.

    Science.gov (United States)

    Mohamed, Yasmine Fathy; Abou-Shleib, Hamida Moustafa; Khalil, Amal Mohamed; El-Guink, Nadia Mohamed; El-Nakeeb, Moustafa Ahmed

    2016-01-01

    Pan-drug resistant Gram-negative bacteria, being resistant to most available antibiotics, represent a huge threat to the medical community. Colistin is considered the last therapeutic option for patients in hospital settings. Thus, we were concerned in this study to demonstrate the membrane permeabilizing activity of colistin focusing on investigating its efficiency toward those pan-drug resistant isolates which represent a critical situation. We determined the killing dynamics of colistin against pan-drug resistant isolates. The permeability alteration was confirmed by different techniques as: leakage, electron microscopy and construction of an artificial membrane model; liposomes. Moreover, selectivity of colistin against microbial cells was also elucidated. Colistin was proved to be rapid bactericidal against pan-drug resistant isolates. It interacts with the outer bacterial membrane leading to deformation of its outline, pore formation, leakage of internal contents, cell lysis and finally death. Furthermore, variations in membrane composition of eukaryotic and microbial cells provide a key for colistin selectivity toward bacterial cells. Colistin selectively alters membrane permeability of pan-drug resistant isolates which leads to cell lysis. Colistin was proved to be an efficient last line treatment for pan-drug resistant infections which are hard to treat. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

  15. Optimization of processing parameters and metrology for novel NCA negative resists for NGL

    Science.gov (United States)

    Singh, Vikram; Satyanarayana, V. S. V.; Kessler, Felipe; Scheffer, Francine R.; Weibel, Daniel E.; Sharma, Satinder K.; Ghosh, Subrata; Gonsalves, Kenneth E.

    2014-04-01

    It is expected that EUV resists must simultaneously pattern 20-nm half-pitch and below, with an LWR of <1.8 nm, and a sensitivity of 5-20 mJ/cm2. In order to make a resist perform optimally, new resist chemistry is required. One such approach being investigated by us is the development of polymeric non-CAR negative photo resists for sub 16 nm technology which is directly sensitive to radiation without utilizing the concept of chemical amplification (CARs). These resist designs are accomplished by homopolymers which are prepared from monomers containing sulfonium groups. We have achieved 20 nm patterns by e-beam lithography using this system. Here we will discuss in detail process parameters such as: spinning conditions for film thicknesses <50 nm and resulting surface topographies, baking regimes, exposure conditions and protocols on sensitivity, contrast, resolution and LER/LWR. Etch resistance data on these thin films will also be provided. Our results are aimed to provide a clear understanding of how these critical steps in the lithographic imaging process will affect extendibility of the non-CAR resist concept to sub 20 nanoscale features. Photodynamics and EUV exposure data will be covered.

  16. Colonization with antibiotic-resistant gram-negative organisms in a pediatric intensive care unit.

    Science.gov (United States)

    Toltzis, P; Yamashita, T; Vilt, L; Blumer, J L

    1997-03-01

    To measure the prevalence of colonization with antibiotic-resistant Gram-negative organisms and its association with potential risk factors, including antibiotic exposure, in a pediatric intensive care unit (ICU). Prospective, observational study. A 16-bed tertiary care pediatric ICU. All children admitted to the pediatric ICU for > 24 hrs over a 5-month period. Two hundred ninety-six patients, approximately half of all patients admitted to the ICU, were enrolled in the study; 236 patients had sufficient data collected for analysis and were prospectively examined for nasopharyngeal and gastrointestinal colonization by antibiotic-resistant Gram-negative organisms (ceftazidime minimal inhibitory concentration of > 16 micrograms/mL, or tobramycin minimal inhibitory concentration > 8 micrograms/mL). Association between colonization and potential predisposing factors including demographics, diagnosis, Pediatric Risk of Mortality (PRISM) score, invasive instrumentation, and prior ICU antibiotic exposure was assessed. More than 20% of patients were found to be colonized with an antibiotic-resistant Gram-negative organism. Examination of the timing of colonization indicated that more than half were identified within 72 hrs of admision. Colonization was associated by unadjusted analysis to prior ICU antibiotic exposure, as well as by factors associated with the severity of illness (PRISM score and invasive instrumentation) and young age. However, when the independence of these factors was tested by logistic regression, prior antibiotic exposure was no longer associated with resistant organism colonization. These data suggest that antibiotic-resistant Gram-negative organisms are a significant risk to intensively III children and that in many instances, they are imported into the unit or rapidly acquired from environmental reservoirs. Since risk factors for colonization are multiple, policies confined to antibiotic utilization within the ICU may have fixed, and possibly

  17. Antimicrobial resistance of coagulase-negative staphylococci and lactic acid bacteria from industrially produced dairy products

    Directory of Open Access Journals (Sweden)

    Nevijo Zdolec

    2013-03-01

    Full Text Available In this research, the susceptibility to clindamycin, tetracycline, amikacin, amoxicillin + clavulanic acid, enrofloxacine, vancomycin, trimethoprim + sulphametoxazol, tobramycin, chloramphenicol, ciprofloxacin, erythromycin, penicillin and trimethoprim was tested in coagulase-negative staphylococci (n=78 and lactic acid bacteria (n=30 by means of disk diffusion test and E-test. The isolates were collected from soft and hard cheeses, butter and brine. All isolates of coagulase-negative staphylococci were susceptible to clindamycin, amikacin, amoxicillin + clavulanic acid, enrofloxacine, vancomycin, chloramphenicol and ciprofloxacin according to CLSI breakpoints. A total of 30 staphylococci isolates (38.46 % were resistant to erythromycin, 18 to penicillin (23.07 %, 4 to tetracycline (5.12 %, and one isolate to trimethoprim, tobramicin and trimethoprim + sulphametoxazol (1.28 %. Among 78 tested staphylococci, 35 of them were resistant to at least one antimicrobial substance (44.87 %. The rate of resistant isolates of different soft cheese types ranged from 22 to 70 %, while resistant staphylococci were absent in hard cheese and brine. The growth of lactic acid bacteria was not influenced by trimethoprim + sulphametoxazol (n=29, vancomycin (n=29, trimethoprim (n=28, amikacin (n=10 and tobramycin (n=10. The results show that significant part of apathogenic microbiota in different dairy products is phenotypically resistant to antimicrobial agents.

  18. Multiple antimicrobial resistance in gram negative bacilli isolated from clinical specimens, Jimma Hospital, southwest Ethiopia.

    Science.gov (United States)

    Tenssaie, Z W

    2001-10-01

    A total of 413 clinical specimens (pus, blood, urine, and stool) collected from patients admitted to Jimma Hospital were cultured for isolation and identification of aerobic bacteria and antimicrobial susceptibility testing. Out of these, 124 specimens yielded one or more Gram-negative bacilli strains. Frequent Gram negative bacterial isolates were Proteus species 34(27%), Klebsiella species 26(21%), Enterobacter species 24(19%), and E. coli 24(19%). Antimicrobial susceptibility test results showed that all E. coli, Klebsiella, and Enterobacter species were resistant to ampicillin. Ninety-two percent of Enterbacter sp., 85% of Klebisiella and 79% of E. coli were resistant to tetracycline. Almost all the isolates were found to be multi-resistant to the commonly used antimicrobials, ampicillin, tetracycline, chloramphenicol, and trimethoprim-sulphamethoxazole. Antimicrobial resistant strains of bacteria are increasing and may contribute to spread of serious infectious diseases in Jimma Hospital and elsewhere in the country. Therefore, if we are to prevent and control infections by emerging antimicrobial resistant bacterial strains, measures such as strengthening clinical microbiology laboratory, increased emphasis on effective infection control, emphasis on hygienic practices in hospital, and prudent use of existing antimicrobial agents is recommended.

  19. [Enzymatic mechanisms of resistance to aminoglycoside antibiotics in gram negative bacilli from Chilean hospitals].

    Science.gov (United States)

    Del Solar, E; García, A; Bello, H; Domínguez, M; González, G; Zemelman, R

    1995-03-01

    The presence of aminoglycoside modifying enzymes (AMEs) has been investigated, by an agar diffusion method, in 344 strains of aminoglycoside-resistant Gram negative bacilli isolated in different Chilean hospitals. Most of the strains exhibited a combination of enzymatic mechanism of resistance, but two acetylating (AAC(3)II and AAC(6')I) and one phosphorylating (APH(3')I) enzymes were the main mechanism detected in the strains. A significant increase in the frequency of strains producing AAC(6')I, possible due to wide use of amikacin, has been found when results were compared with those of a report published in 1985.

  20. Characterization of carbapenem-resistant Gram-negative bacteria from Tamil Nadu.

    Science.gov (United States)

    Nachimuthu, Ramesh; Subramani, Ramkumar; Maray, Suresh; Gothandam, K M; Sivamangala, Karthikeyan; Manohar, Prasanth; Bozdogan, Bülent

    2016-10-01

    Carbapenem resistance is disseminating worldwide among Gram-negative bacteria. The aim of this study was to identify carbapenem-resistance level and to determine the mechanism of carbapenem resistance among clinical isolates from two centres in Tamil Nadu. In the present study, a total of 93 Gram-negative isolates, which is found to be resistant to carbapenem by disk diffusion test in two centres, were included. All isolates are identified at species level by 16S rRNA sequencing. Minimal inhibitory concentrations (MICs) of isolates for Meropenem were tested by agar dilution method. Presence of blaOXA, blaNDM, blaVIM, blaIMP and blaKPC genes was tested by PCR in all isolates. Amplicons were sequenced for confirmation of the genes. Among 93 isolates, 48 (%52) were Escherichia coli, 10 (%11) Klebsiella pneumoniae, nine (%10) Pseudomonas aeruginosa. Minimal inhibitory concentration results showed that of 93 suspected carbapenem-resistant isolates, 27 had meropenem MICs ≥ 2 μg/ml. The MIC range, MIC50 and MIC90 were 128 μg/ml, 0.12 and 16 μg/ml, respectively. Fig. 1 . Among meropenem-resistant isolates, E. coli were the most common (9/48, 22%), followed by K. pneumoniae (7/9, 77%), P. aeruginosa (6/10, 60%), Acinetobacter baumannii (2/2, 100%), Enterobacter hormaechei (2/3, 67%) and one Providencia rettgeri (1/1, 100%). PCR results showed that 16 of 93 carried blaNDM, three oxa181, and one imp4. Among blaNDM carriers, nine were E. coli, four Klebsiella pneumoniae, two E. hormaechei and one P. rettgeri. Three K. pneumoniae were OXA-181 carriers. The only imp4 carrier was P. aeruginosa. A total of seven carbapenem-resistant isolates were negatives by PCR for the genes studied. All carbapenem-resistance gene-positive isolates had meropenem MICs >2 μg/ml. Our results confirm the dissemination of NDM and emergence of OXA-181 beta-lactamase among Gram-negative bacteria in South India. This study showed the emergence of NDM producer in clinical isolates of E

  1. Epidemiology and molecular characterization of multidrug-resistant Gram-negative bacteria in Southeast Asia

    Directory of Open Access Journals (Sweden)

    Nuntra Suwantarat

    2016-05-01

    Full Text Available Abstract Background Multidrug-resistant Gram-negative bacteria (MDRGN, including extended-spectrum β-lactamases (ESBLs and multidrug-resistant glucose-nonfermenting Gram-negative bacilli (nonfermenters, have emerged and spread throughout Southeast Asia. Methods We reviewed and summarized current critical knowledge on the epidemiology and molecular characterization of MDRGN in Southeast Asia by PubMed searches for publications prior to 10 March 2016 with the term related to “MDRGN definition” combined with specific Southeast Asian country names (Thailand, Singapore, Malaysia, Vietnam, Indonesia, Philippines, Laos, Cambodia, Myanmar, Brunei. Results There were a total of 175 publications from the following countries: Thailand (77, Singapore (35, Malaysia (32, Vietnam (23, Indonesia (6, Philippines (1, Laos (1, and Brunei (1. We did not find any publications on MDRGN from Myanmar and Cambodia. We did not include publications related to Shigella spp., Salmonella spp., and Vibrio spp. and non-human related studies in our review. English language articles and abstracts were included for analysis. After the abstracts were reviewed, data on MDRGN in Southeast Asia from 54 publications were further reviewed and included in this study. Conclusions MDRGNs are a major contributor of antimicrobial-resistant bacteria in Southeast Asia. The high prevalence of ESBLs has been a major problem since 2005 and is possibly related to the development of carbapenem resistant organisms in this region due to the overuse of carbapenem therapy. Carbapenem–resistant Acinetobacter baumannii is the most common pathogen associated with nosocomial infections in this region followed by carbapenem-resistant Pseudomonas aeruginosa. Although Southeast Asia is not an endemic area for carbapenem-resistant Enterobacteriaceae (CRE, recently, the rate of CRE detection has been increasing. Limited infection control measures, lack of antimicrobial control, such as the presence of

  2. Epidemiology and molecular characterization of multidrug-resistant Gram-negative bacteria in Southeast Asia.

    Science.gov (United States)

    Suwantarat, Nuntra; Carroll, Karen C

    2016-01-01

    Multidrug-resistant Gram-negative bacteria (MDRGN), including extended-spectrum β-lactamases (ESBLs) and multidrug-resistant glucose-nonfermenting Gram-negative bacilli (nonfermenters), have emerged and spread throughout Southeast Asia. We reviewed and summarized current critical knowledge on the epidemiology and molecular characterization of MDRGN in Southeast Asia by PubMed searches for publications prior to 10 March 2016 with the term related to "MDRGN definition" combined with specific Southeast Asian country names (Thailand, Singapore, Malaysia, Vietnam, Indonesia, Philippines, Laos, Cambodia, Myanmar, Brunei). There were a total of 175 publications from the following countries: Thailand (77), Singapore (35), Malaysia (32), Vietnam (23), Indonesia (6), Philippines (1), Laos (1), and Brunei (1). We did not find any publications on MDRGN from Myanmar and Cambodia. We did not include publications related to Shigella spp., Salmonella spp., and Vibrio spp. and non-human related studies in our review. English language articles and abstracts were included for analysis. After the abstracts were reviewed, data on MDRGN in Southeast Asia from 54 publications were further reviewed and included in this study. MDRGNs are a major contributor of antimicrobial-resistant bacteria in Southeast Asia. The high prevalence of ESBLs has been a major problem since 2005 and is possibly related to the development of carbapenem resistant organisms in this region due to the overuse of carbapenem therapy. Carbapenem-resistant Acinetobacter baumannii is the most common pathogen associated with nosocomial infections in this region followed by carbapenem-resistant Pseudomonas aeruginosa. Although Southeast Asia is not an endemic area for carbapenem-resistant Enterobacteriaceae (CRE), recently, the rate of CRE detection has been increasing. Limited infection control measures, lack of antimicrobial control, such as the presence of active antimicrobial stewardship teams in the hospital, and

  3. Resistance to antibiotics in Gram-negative bacteria isolated from broiler carcasses

    Directory of Open Access Journals (Sweden)

    Moreira M.A.S.

    2002-01-01

    Full Text Available One hundred and ninety-seven isolates of Gram-negative bacteria, comprising 10 genera, were isolated from poultry carcasses at a processing plant in order to investigate resistance to low levels of antibiotics. The samples were taken just after evisceration and before inspection. Most of the isolates were of Samonella and Escherichia. Other genera present were Enterobacter, Serratia, Klebsiella, Kluyvera, Erwinia, Citrobacter, Pseudomonas and Aeromonas. Distinct profiles of antibiotic resistance were detected. Resistance to more than two antibiotics predominated and spanned several classes of antibiotics. Salmonellae and escherichiae were mainly resistant to the aminoglycosides, followed by tetracycline, nitrofuran, sulpha, macrolide, chloramphenicol, quinolones and beta-lactams. Most isolates were sensitive to 30mug/ml olaquindox, the growth promoter in use at the time of sampling. However, many were resistant to a level of 10mug/ml and 13mug/ml olaquindox, levels present in the gut due to the dilution in the feed. The results suggest a possible role of low level administration of antibiotics to broilers in selecting multi-resistant bacteria in vivo.

  4. The Challenge of Efflux-Mediated Antibiotic Resistance in Gram-Negative Bacteria

    Science.gov (United States)

    Plésiat, Patrick

    2015-01-01

    SUMMARY The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps. PMID:25788514

  5. Negative-resistance voltage-current characteristics of superconductor contact junctions for macro-scale applications

    CERN Document Server

    Takayasu, M; Minervini, J V; 10.1109/TASC.2003.812854

    2003-01-01

    Voltage-current characteristics of mechanical pressure contact junctions between superconducting wires are investigated using a voltage-driving method. It is found that the switching regions at low voltages result from negative resistance of the contact junction. The current transport of the contact junctions is discussed from the perspective of two existing models: the multiple Andreev reflections at the two SN interfaces of a SNS (Superconductor/Normal metal /Superconductor) junction and the inhomogeneous multiple Josephson weak-link array. (13 refs).

  6. [Linezolid resistant coagulase-negative Staphylococcus: phenotypical and genotypical characteristics and sensitivity to antibiotic combinations].

    Science.gov (United States)

    López-Fabal, Fátima; Román Alonso, Federico; Almagro Moltó, María; Sanz Rodríguez, Nuria; Gómez-Garcés, José Luis

    2013-01-01

    We recovered 22 coagulase-negative staphylococci isolates in our hospital to study their identity, susceptibility, epidemiological profile, linezolid resistance mechanisms, and the possibilities of different antibiotic combinations. Isolate identification was performed using mass spectrometry (Vitek-MS, bioMérieux). Susceptibility testing was carried out with the Vitek-2 system and the broth microdilution method according to CLSI guidelines. Pulsed-field gel electrophoresis (PFGE) was performed to analyze the genetic relationship between isolates. Linezolid resistance mechanisms were evaluated by PCR/sequencing: presence of cfr gene, point mutations in domain V of 23S ribosomal RNA and additional ribosomal mutations (in the rplC, rplD and rplV genes). The in vitro activity of linezolid was investigated alone and in combination with another three antibiotics acting on different cellular targets, using E-test strips. Twenty isolates were identified as Staphylococcus epidermidis, and 2 as Staphylococcus hominis. PFGE showed that isolates belonged to diverse clones, 21 of them presented mutations in the domain V region of 23S rRNA and the cfr gene was found in 54.5%. Prior administration of linezolid was documented in most of cases. Linezolid in combination with gentamicin showed a synergistic activity in 45.5% of isolates. Staphylococcus epidermidis was the most prevalent linezolid-resistant coagulase-negative staphylococci. All isolates showed increased MIC values compared to other anti-staphylococcal drugs and several linezolid resistance mechanisms. Our data suggest that linezolid plus gentamicin could be a synergistic combination against linezolid-resistant coagulase-negative staphylococci. Copyright © 2012 Elsevier España, S.L. All rights reserved.

  7. Colistin and tigecycline resistance in carbapenemase-producing Gram-negative bacteria: emerging resistance mechanisms and detection methods.

    Science.gov (United States)

    Osei Sekyere, J; Govinden, U; Bester, L A; Essack, S Y

    2016-09-01

    A literature review was undertaken to ascertain the molecular basis for tigecycline and colistin resistance mechanisms and the experimental basis for the detection and delineation of this resistance particularly in carbapenemase-producing Gram-negative bacteria. Pubmed, Google Scholar and Science Direct were searched with the keywords colistin, tigecycline, resistance mechanisms and detection methods. Trans-complementation and comparative MIC studies, mass spectrometry, chromatography, spectrofluorometry, PCR, qRT-PCR and whole genome sequencing (WGS) were commonly used to determine tigecycline and colistin resistance mechanisms, specifically modifications in the structural and regulatory efflux (acrAB, OqxAB, kpgABC adeABC-FGH-IJK, mexAB-XY-oprJM and soxS, rarA robA, ramRAB marRABC, adeLRS, mexRZ and nfxb) and lipid A (pmrHFIJFKLM, lpxA, lpxC lpxD and mgrB, pmrAB, phoPQ,) genes respectively. Mutations in the ribosomal 16S rRNA operon rrnBC, also yielded resistance to tigecycline through target site modifications. The mcr-1 gene conferring resistance to colistin was identified via WGS, trans-complementation and a murine thigh infection model studies. Common detection methods are mainly antibiotic sensitivity testing with broth microdilution while molecular identification tools are mostly PCR and WGS. Spectrofluorometry, MALDI-TOF MS, micro-array and real-time multiplex PCR hold much promise for the future as new detection tools. © 2016 The Society for Applied Microbiology.

  8. Negative Resistance Effect and Charge Transfer Mechanisms in the lon Beam Deposited Diamond Like Carbon Superlattices

    Directory of Open Access Journals (Sweden)

    Andrius VASILIAUSKAS

    2011-03-01

    Full Text Available In the present study DLC:SiOx/DLC/DLC:SiOx/nSi and DLC:SiOx/DLC/DLC:SiOx/pSi structures were fabricated by ion beam deposition using a closed drift ion source. Current-voltage (I-V characteristics of the multilayer samples were measured at room temperature. The main charge transfer mechanisms were considered. Unstable negative resistance effect was observed for some DLC:SiOx/DLC/DLC:SiOx/nSi and DLC:SiOx/DLC/DLC:SiOx/pSi structures. In the case of the diamond like carbon superlattices fabricated on nSi it was observed only during the first measurement. In the case of the some DLC:SiOx/DLC/DLC:SiOx/pSi negative resistance "withstood" several measurements. Changes of the charge carrier mechanisms were observed along with the dissapear of the negative resistance peaks. It seems, that in such a case influence of the bulk related charge transfer mechanisms such as Poole-Frenkel emission increased, while the influence of the contact limited charge transfer mechanisms such as Schottky emission decreased. Observed results were be explained by current flow through the local microconducting channels and subsequent destruction of the localized current pathways as a result of the heating by flowing electric current.http://dx.doi.org/10.5755/j01.ms.17.1.240

  9. Negative differential resistance and characteristic nonlinear electromagnetic response of a Topological Insulator

    Science.gov (United States)

    Lee, Ching Hua; Zhang, Xiao; Guan, Bochen

    2015-12-01

    Materials exhibiting negative differential resistance have important applications in technologies involving microwave generation, which range from motion sensing to radio astronomy. Despite their usefulness, there has been few physical mechanisms giving rise to materials with such properties, i.e. GaAs employed in the Gunn diode. In this work, we show that negative differential resistance also generically arise in Dirac ring systems, an example of which has been experimentally observed in the surface states of Topological Insulators. This novel realization of negative differential resistance is based on a completely different physical mechanism from that of the Gunn effect, relying on the characteristic non-monotonicity of the response curve that remains robust in the presence of nonzero temperature, chemical potential, mass gap and impurity scattering. As such, it opens up new possibilities for engineering applications, such as frequency upconversion devices which are highly sought for terahertz signal generation. Our results may be tested with thin films of Bi2Se3 Topological Insulators, and are expected to hold qualitatively even in the absence of a strictly linear Dirac dispersion, as will be the case in more generic samples of Bi2Se3 and other materials with topologically nontrivial Fermi sea regions.

  10. Increased resistance of gram-negative urinary pathogens after kidney transplantation.

    Science.gov (United States)

    Korth, Johannes; Kukalla, Julia; Rath, Peter-Michael; Dolff, Sebastian; Krull, Marco; Guberina, Hana; Bienholz, Anja; Wilde, Benjamin; Becker, Stefan; Ross, Birgit; Anastasiou, Olympia Evdoxia; Kribben, Andreas; Witzke, Oliver

    2017-05-19

    Urinary tract infection is the most common complication after kidney transplantation. It can cause severe sepsis and transplant loss. Emergence of drug resistance among gram-negative urinary pathogens is the current challenge for urinary tract infection treatment after kidney transplantation. This study analyzes the antimicrobial susceptibility of gram-negative urinary pathogens after kidney transplantation from 2009 to 2012 at the Transplant Outpatient Clinic of the University Hospital Essen, Germany. Kidney transplant patients at the University Hospital Essen receive regular follow up examinations after transplantation. Midstream urines were examined for bacteriuria at each follow up visit. From 2009 to 2012 15.741 urine samples were obtained from 859 patients. In 2985 (19%) samples bacterial growth was detected. The most frequently detected gram-negative bacteria were E.coli 1109 (37%), Klebsiella spp. 242 (8%) and Pseudomonas aeruginosa 136 (4.5%). Klebsiella spp. showed a significant increase of resistance to trimethoprim-sulfamethoxazole by 19% (p = 0.02), ciprofloxacin by 15% (p = 0.01) and ceftazidime by 17% (p = 0.004). E.coli and P. aeruginosa isolates presented no significant differences of antimicrobial susceptibility to the analyzed antibiotics. Antimicrobial resistance of Klebsiella spp. increased significant to trimethoprim-sulfamethoxazole, ciprofloxacin and ceftazidime from 2009 to 2012.

  11. The Growing Threat of Multidrug-Resistant Gram-Negative Infections in Patients with Hematologic Malignancies

    Science.gov (United States)

    Baker, Thomas M.; Satlin, Michael J.

    2016-01-01

    Prolonged neutropenia and chemotherapy-induced mucositis render patients with hematologic malignancies highly vulnerable to Gram-negative bacteremia. Unfortunately, multidrug-resistant (MDR) Gram-negative bacteria are increasingly encountered globally, and current guidelines for empirical antibiotic coverage in these patients may not adequately treat these bacteria. This expansion of resistance, coupled with traditional culturing techniques requiring 2-4 days for bacterial identification and antimicrobial susceptibility results, have grave implications for these immunocompromised hosts. This review characterizes the epidemiology, risk factors, resistance mechanisms, recommended treatments, and outcomes of the MDR Gram-negative bacteria that commonly cause infections in patients with hematologic malignancies. We also examine infection prevention strategies in hematology patients, such as infection control practices, antimicrobial stewardship, and targeted decolonization. Finally, we assess strategies to improve outcomes of infected patients, including gastrointestinal screening to guide empirical antibiotic therapy, new rapid diagnostic tools for expeditious identification of MDR pathogens, and use of two new antimicrobial agents, ceftolozane/tazobactam and ceftazidime/avibactam. PMID:27339405

  12. Resisting Negative Images and Stereotypes: One Latina Prospective Teacher’s Story

    Directory of Open Access Journals (Sweden)

    Terri L. Rodriguez

    2010-06-01

    Full Text Available This article focuses on one Latina prospective teacher’s act of resisting negative stereotypes regarding attire imposed upon her by a white female principal. The event is embedded within a larger life history study that explores the experiences of bilingual Latino prospective teachers in the elementary education program of a large Midwestern university. The selected narrative is contextualized in relation to resistance narratives. Patricia Morales tells about her experiences in U.S. schools. It explores how Patricia’s life history is marked by experiences of discrimination, yet how her constructions of these events represent “counterstories” (Delgado, 2000; Solorzano & Yosso, 2002 through which she “talks back” (hooks, 1989 to distorted images and stereotypes. Patricia’s narratives are shown to constitute creative acts of resistance through which she negotiates a positive and affirming identity (Suarez-Orozco & Suarez-Orozco, 2001 as a Latina prospective teacher.

  13. Capillary electrophoresis for fast detection of heterogeneous population in colistin-resistant Gram-negative bacteria.

    Science.gov (United States)

    Sautrey, Guillaume; Duval, Raphaël E; Chevalley, Alicia; Fontanay, Stéphane; Clarot, Igor

    2015-10-01

    It has been shown that diverse strains of bacteria can be separated according to their characteristic surface properties by means of CE. We employed here this analytical technique to the study of colistin-resistance in Gram-negative bacteria, which involves the selection of mutants with modified outer membrane composition resulting in changes of surface cell properties. In the same way as with molecular entities, we performed firstly the validation of an ITP-based CE method for three common pathogenic Gram-negative bacteria namely Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Secondly, we compared the electrophoretic profiles of bacterial samples from a colistin-susceptible clinical isolate of K. pneumoniae and from the corresponding colistin-resistant derivative. By a simple CE run taking a few minutes, the coexistence of several bacterial subpopulations in the colistin-resistant derivative was clearly evidenced. This work encourages further research that would allow applications of CE in clinical laboratory for a daily monitoring of bacterial population in cared patients when "last-chance" colistin treatment is initiated against multidrug-resistant bacteria. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Antibiotic resistance profiles of coagulase-negative staphylococci in livestock environments.

    Science.gov (United States)

    Schoenfelder, Sonja M K; Dong, Ying; Feßler, Andrea T; Schwarz, Stefan; Schoen, Christoph; Köck, Robin; Ziebuhr, Wilma

    2017-02-01

    Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) have globally emerged in animal husbandry. In addition to methicillin resistance, LA-MRSA may carry a variety of novel and uncommon antimicrobial resistance genes. Occurrence of the same resistance genes in coagulase-negative staphylococci (CoNS) and S. aureus suggests an ongoing genetic exchange between LA-MRSA and other staphylococci whose driving forces in the ecological niche of the farm environment are, however, still poorly understood. To assess the potential of CoNS as putative reservoirs for antibiotic resistance genes, we analysed the antimicrobial susceptibility of CoNS from dust and manure samples obtained in 41 pig farms in Germany, most of them (36 of 41) with a proven LA-MRSA/MSSA history. Among the 344 isolates analysed, 18 different CoNS species were identified and S. sciuri represented the most prevalent species (46%). High resistance rates were detected for tetracycline (71%), penicillin (65%) and oxacillin (64%) as well as fusidic acid (50%), which was mainly due to reduced susceptibility among S. sciuri isolates. S. sciuri exhibited pronounced multiresistance, and many isolates were characterised by the carriage of a number of uncommon (multi)resistance genes (e.g. cfr, apmA, fexA) and decreased susceptibility towards last resort antibiotics such as linezolid and daptomycin. The combined data suggest that S. sciuri harbours a significant resistance gene pool that requires further attention. We hypothesise that members of this species, due to their flexible lifestyle, might contribute to the spread of such genes in livestock environments. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Elaboration of Approaches to Internet Negative Impact Resistance for University Students

    Directory of Open Access Journals (Sweden)

    Natalya Nikolaevna Zerkina

    2016-11-01

    Full Text Available In the information society Internet technologies provide not only positive information and psychological impact but negative and destructive one either. The lack of attention to the problems of prevention and correction of destructive information impact on young students in higher education institutions negatively affects the development of intellectual abilities of students, their professional socialization and it leads to the spiritual and moral degradation, economic and legal nihilism, which finally leads to a decrease the quality of training of future specialists. The research summarizes and arranges theoretical and empirical studies on the problem of forming resistance to negative effects of Internet resources on university students and young adults. A set of resistance-forming and preventing Internet negative effects recommendations is elaborated and can be applied for the process of teaching. Complex methodology is used for elaboration of methodical positions and practical recommendations. The proposed concept enriches pedagogical theory, brings to the new level of research problems of information-psychological security of students online activity. The developed suggestions are theoretical contribution to the content and technology development of educational support safe and efficient use of information resources in the preparation of future specialists at the university.

  16. Engineered endolysin-based "Artilysins" to combat multidrug-resistant gram-negative pathogens.

    Science.gov (United States)

    Briers, Yves; Walmagh, Maarten; Van Puyenbroeck, Victor; Cornelissen, Anneleen; Cenens, William; Aertsen, Abram; Oliveira, Hugo; Azeredo, Joana; Verween, Gunther; Pirnay, Jean-Paul; Miller, Stefan; Volckaert, Guido; Lavigne, Rob

    2014-07-01

    The global threat to public health posed by emerging multidrug-resistant bacteria in the past few years necessitates the development of novel approaches to combat bacterial infections. Endolysins encoded by bacterial viruses (or phages) represent one promising avenue of investigation. These enzyme-based antibacterials efficiently kill Gram-positive bacteria upon contact by specific cell wall hydrolysis. However, a major hurdle in their exploitation as antibacterials against Gram-negative pathogens is the impermeable lipopolysaccharide layer surrounding their cell wall. Therefore, we developed and optimized an approach to engineer these enzymes as outer membrane-penetrating endolysins (Artilysins), rendering them highly bactericidal against Gram-negative pathogens, including Pseudomonas aeruginosa and Acinetobacter baumannii. Artilysins combining a polycationic nonapeptide and a modular endolysin are able to kill these (multidrug-resistant) strains in vitro with a 4 to 5 log reduction within 30 min. We show that the activity of Artilysins can be further enhanced by the presence of a linker of increasing length between the peptide and endolysin or by a combination of both polycationic and hydrophobic/amphipathic peptides. Time-lapse microscopy confirmed the mode of action of polycationic Artilysins, showing that they pass the outer membrane to degrade the peptidoglycan with subsequent cell lysis. Artilysins are effective in vitro (human keratinocytes) and in vivo (Caenorhabditis elegans). Importance: Bacterial resistance to most commonly used antibiotics is a major challenge of the 21st century. Infections that cannot be treated by first-line antibiotics lead to increasing morbidity and mortality, while millions of dollars are spent each year by health care systems in trying to control antibiotic-resistant bacteria and to prevent cross-transmission of resistance. Endolysins--enzymes derived from bacterial viruses--represent a completely novel, promising class of

  17. Multi-drug resistant gram-negative enteric bacteria isolated from flies at Chengdu Airport, China.

    Science.gov (United States)

    Liu, Yang; Yang, Yu; Zhao, Feng; Fan, Xuejun; Zhong, Wei; Qiao, Dairong; Cao, Yi

    2013-11-01

    We collected flies from Chengdu Shuangliu International Airport to examine for the presence of bacteria and to determine the sensitivity patterns of those bacteria. A total of 1,228 flies were collected from 6 sites around Chengdu Shuangliu International Airport from April to September 2011. The predominant species was Chrysomya megacephala (n=276, 22.5%). Antimicrobial-resistant gram-negative enteric bacteria (n=48) were isolated from flies using MacConkey agar supplemented with cephalothin (20 microg/ml). These were identified as Escherichia coli (n=37), Klebsiella pneumoniae (n=6), Pseudomonas aeruginosa (n=3) and Aeromonas hydrophila (n=2). All isolated bacteria were tested for resistance to 21 commonly used antimicrobials: amoxicillin (100%), ticarcillin (100%), cephalothin (100%), cefuroxime (100%), ceftazidime 1 (93.8%), piperacillin (93.8%), cefotaxime (89.6%), ticarcillin-clavulanate (81.3%), trimethoprim-sulfamethoxazole (62.5%), ciprofloxacin (54.2%), gentamicin (45.8%), cefepime (39.6%), tobramycin (39.6%), ceftazidime (22.9%), cefoxitin (16.7%), amikacin (16.7%), netilmicin (14.6%), amoxicillin-clavulanate (6.3%) and piperacillin-tazobactam (2.1%). No resistance to meropenem or imipenem was observed. Antibiotic resistance genes among the isolated bacteria were analyzed for by polymerase chain reaction. Thirty of the 48 bacteria with resistance (62.5%) possessed the blaTEM gene.

  18. Mechanisms of resistance of chemotherapy in early-stage triple negative breast cancer (TNBC).

    Science.gov (United States)

    Wein, Lironne; Loi, Sherene

    2017-08-01

    Triple negative breast cancer (TNBC) a clinically aggressive subtype of breast cancer with poor outcomes. Chromosomal instability is a hallmark of many TNBCs, and likely underlies its ability to adapt and rapidly become resistant to chemotherapy. A study of residual disease after neoadjuvant chemotherapy have identified biological mechanisms driving this resistance to chemotherapy. Copy number amplifications such as MCL1, MYC and JAK2, as well as PTEN deletions or mutations have all been identified at a higher frequency in residual disease, suggesting they may play a role in de novo or acquired chemotherapy resistance. Increased copy number and expression of the PIM1 proto-oncogene in TNBC has also been identified as a new target of chemotherapy resistance. However, given the genomic instability and subclonal nature of driver mutations in TNBC, single agent targeted therapy is unlikely to be effective. Lately immune evasion has also been identified as another key characteristic of poor prognostic and chemo-resistant primary TNBCs. Combinations of checkpoint inhibition with targeted therapy and/or chemotherapy are currently being investigated. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Multidrug-resistant Gram-negative bacteria: a product of globalization.

    Science.gov (United States)

    Hawkey, P M

    2015-04-01

    Global trade and mobility of people has increased rapidly over the last 20 years. This has had profound consequences for the evolution and the movement of antibiotic resistance genes. There is increasing exposure of populations all around the world to resistant bacteria arising in the emerging economies. Arguably the most important development of the last two decades in the field of antibiotic resistance is the emergence and spread of extended-spectrum β-lactamases (ESBLs) of the CTX-M group. A consequence of the very high rates of ESBL production among Enterobacteriaceae in Asian countries is that there is a substantial use of carbapenem antibiotics, resulting in the emergence of plasmid-mediated resistance to carbapenems. This article reviews the emergence and spread of multidrug-resistant Gram-negative bacteria, focuses on three particular carbapenemases--imipenem carbapenemases, Klebsiella pneumoniae carbapenemase, and New Delhi metallo-β-lactamase--and highlights the importance of control of antibiotic use. Copyright © 2015. Published by Elsevier Ltd.

  20. Structure and Dimerization of IreB, a Negative Regulator of Cephalosporin Resistance in Enterococcus faecalis.

    Science.gov (United States)

    Hall, Cherisse L; Lytle, Betsy L; Jensen, Davin; Hoff, Jessica S; Peterson, Francis C; Volkman, Brian F; Kristich, Christopher J

    2017-07-21

    Enterococcus faecalis, a leading cause of hospital-acquired infections, exhibits intrinsic resistance to most cephalosporins, which are antibiotics in the beta-lactam family that target cell-wall biosynthesis. A comprehensive understanding of the underlying genetic and biochemical mechanisms of cephalosporin resistance in E. faecalis is lacking. We previously determined that a transmembrane serine/threonine kinase (IreK) and its cognate phosphatase (IreP) reciprocally regulate cephalosporin resistance in E. faecalis, dependent on the kinase activity of IreK. Other than IreK itself, thus far the only known substrate for reversible phosphorylation by IreK and IreP is IreB, a small protein of unknown function that is well conserved in low-GC Gram-positive bacteria. We previously showed that IreB acts as a negative regulator of cephalosporin resistance in E. faecalis. However, the biochemical mechanism by which IreB modulates cephalosporin resistance remains unknown. As a next step toward an understanding of the mechanism by which IreB regulates resistance, we initiated a structure-function study on IreB. The NMR solution structure of IreB was determined, revealing that IreB adopts a unique fold and forms a dimer in vitro. Dimerization of IreB was confirmed in vivo. Substitutions at the dimer interface impaired IreB function and stability in vivo, indicating that dimerization is functionally important for the biological activity of IreB. Hence, these studies provide new insights into the structure and function of a widely conserved protein of unknown function that is an important regulator of antimicrobial resistance in E. faecalis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Prevalence of faecal carriage of colistin-resistant Gram-negative rods in a university hospital in western France, 2016.

    Science.gov (United States)

    Saly, Marion; Jayol, Aurelie; Poirel, Laurent; Megraud, Francis; Nordmann, Patrice; Dubois, Veronique

    2017-06-01

    Plasmid-mediated and chromosomally-encoded colistin resistance is increasingly being reported worldwide. We aimed to determine the prevalence of faecal carriage of colistin-resistant Gram-negative rod isolates in a university hospital in western France. From February to May 2016, rectal swabs from 653 patients hospitalized in various clinical settings were recovered and subsequently screened for colistin resistance using the SuperPolymyxin medium. Antimicrobial susceptibilities were determined according to EUCAST guidelines. Genetic detection of plasmid-mediated colistin resistance was performed by PCR. The faecal carriage with intrinsic colistin-resistant isolates was high (23 %), while the faecal carriage with Gram-negative rods showing acquired resistance was low (1.4 %). No isolate carried the plasmid-mediated mcr-1/mcr-2 genes. It was noteworthy that none of the patients carrying isolates with acquired colistin resistance had previously received a colistin-based treatment, while these isolates were not multidrug resistant.

  2. Multi-Drug-Resistant Gram-Negative Infections in Deployment-Related Trauma Patients.

    Science.gov (United States)

    Campbell, Wesley R; Li, Ping; Whitman, Timothy J; Blyth, Dana M; Schnaubelt, Elizabeth R; Mende, Katrin; Tribble, David R

    2017-04-01

    The contribution of multi-drug-resistant gram-negative bacilli infections (MDRGN-I) in patients with trauma is not well described. We present characteristics of MDRGN-Is among military personnel with deployment-related trauma (2009-2014). Data from the Trauma Infectious Disease Outcomes Study were assessed for infectious outcomes and microbial recovery. Infections were classified using standardized definitions. Gram-negative bacilli were defined as multi-drug-resistant if they showed resistance to ≥3 antibiotic classes or were producers of extended-spectrum β-lactamase or carbapenemases. Among 2,699 patients admitted to participating U.S. hospitals, 913 (33.8%) experienced ≥1 infection event, of which 245 (26.8%) had a MDRGN-I. There were 543 MDRGN-I events (24.6% of unique 2,210 infections) with Escherichia coli (48.3%), Acinetobacter spp. (38.6%), and Klebsiella pneumoniae (8.4%) as the most common MDRGN isolates. Incidence of MDRGN-I was 9.1% (95% confidence interval [CI]: 8.0-10.2). Median time to MDRGN-I event was seven days with 75% occurring within 13 days post-trauma. Patients with MDRGN-Is had a greater proportion of blast injuries (84.1% vs. 62.5%; p trauma patient population.

  3. Design and verification of a negative resistance electromagnetic shunt damper for spacecraft micro-vibration

    Science.gov (United States)

    Stabile, Alessandro; Aglietti, Guglielmo S.; Richardson, Guy; Smet, Geert

    2017-01-01

    Active control techniques are often required to mitigate the micro-vibration environment existing on board spacecraft. However, reliability issues and high power consumption are major drawbacks of active isolation systems that have limited their use for space applications. In the present study, an electromagnetic shunt damper (EMSD) connected to a negative-resistance circuit is designed, modelled and analysed. The negative resistance produces an overall reduction of the circuit resistance that results in an increase of the induced current in the closed circuit and thus the damping performance. This damper can be classified as a semi-active damper since the shunt does not require any control algorithm to operate. Additionally, the proposed EMSD is characterised by low required power, simplified electronics and small device mass, allowing it to be comfortably integrated on a satellite. This work demonstrates, both analytically and experimentally, that this technology is capable of effectively isolating typical satellite micro-vibration sources over the whole temperature range of interest.

  4. Spread of resistant gram negatives in a Sri Lankan intensive care unit.

    Science.gov (United States)

    Tissera, Kavinda; Liyanapathirana, Veranja; Dissanayake, Nilanthi; Pinto, Vasanthi; Ekanayake, Asela; Tennakoon, Manjula; Adasooriya, Dinuka; Nanayakkara, Dulmini

    2017-07-11

    Infections with multi drug resistant (MDR) organisms are a major problem in intensive care units (ICUs). Proper infection control procedures are mandatory to combat the spread of resistant organisms within ICUs. Well stablished surveillance programmes will enhance the adherence of the staff to infection control protocols. The study was conducted to assess the feasibility of using basic molecular typing methods and routine hospital data for laboratory surveillance of resistance organisms in resource limited settings. A retrospective study was conducted using consecutive Gram negative isolates obtained from an ICU over a six month period. Antibiotic sensitivity patterns and random amplified polymorphic DNA (RAPD) based typing was performed on the given isolates. Of the seventy isolates included in the study, seven were E.coli. All E.coli were MDRs and Extended Spectrum β lactamse (ESBL) producers carrying bla CTX-M. Fourteen isolates were K.pneumoniae, and all were MDRs and ESBL producers. All K.pneumoniae harboured bla SHV while 13 harboured bla CTX-M. The MDR rate among P.aeruginosa was 13% (n=15) while all acinetobacters (n=30) were MDRs. Predominant clusters were identified within all four types of Gram negatives using RAPD and the ICU stay of patients overlapped temporally. We propose that simple surveillance methods like RAPD based typing and basic hospital data can be used to convince hospital staff to adhere to infection control protocols more effectively, in low and middle income countries.

  5. PBP-2 Negative Methicillin Resistant Staphylococcus schleiferi Bacteremia from a Prostate Abscess: An Unusual Occurrence

    Directory of Open Access Journals (Sweden)

    Chandni Merchant

    2016-01-01

    Full Text Available Staphylococcus schleiferi subsp. schleiferi is a coagulase-negative Staphylococcus which has been described as a pathogen responsible for various nosocomial infections including bacteremia, brain abscess, and infection of intravenous pacemakers. Recently, such bacteria have been described to be found typically on skin and mucosal surfaces. It is also believed to be a part of the preaxillary human flora and more frequently found in men. It is very similar in its pathogenicity with Staphylococcus aureus group and expresses a fibronectin binding protein. Literature on this pathogen reveals that it commonly causes otitis among dogs because of its location in the auditory meatus of canines. Also, it has strong association with pyoderma in dogs. The prime concern with this organism is the antibiotic resistance and relapse even after appropriate treatment. Very rarely, if any, cases have been reported about prostatic abscess (PA with this microbe. Our patient had a history of recurrent UTIs and subsequent PA resulting in S. schleiferi bacteremia in contrast to gram negative bacteremia commonly associated with UTI. This organism was found to be resistant to methicillin, in spite of being negative for PBP2, which is a rare phenomenon and needs further studies.

  6. Molecular Epidemiology and Colistin Resistant Mechanism of mcr-Positive and mcr-Negative Clinical Isolated Escherichia coli

    Directory of Open Access Journals (Sweden)

    Qixia Luo

    2017-11-01

    Full Text Available Transmissible colistin resistance mediated by the mcr gene has been reported worldwide, but clinical isolates of mcr-negative colistin-resistant Escherichia coli are rarely reported. The aim of this study was to evaluate the mechanism of colistin resistance among mcr-positive and mcr-negative E. coli clinical isolates by performing a molecular epidemiological surveillance. For the first time ever, we show nearly the same isolation ratio for mcr-negative and mcr-positive colistin-resistant clinical isolates (47.5 and 52.5%, respectively, with no demonstrable nosocomial transmission. We provide evidence for the prevalence of the mcr-positive IncX4 plasmid and its high potential for horizontal transfer, with no obvious sequence type (ST preference. In addition, the minimal inhibitory concentrations (MICs of colistin of the mcr-negative E. coli isolates were obviously higher than those of mcr-positive isolates. Apart from the usually detected genes, i.e., pmrAB, phoPQ, and mgrB, other genes may be associated with the colistin resistance in mcr-negative E. coli. To the best of our knowledge, this is the first paper to report the molecular epidemiological surveillance and the proper mechanism of colistin resistance in mcr-negative E. coli clinical isolates. Together, the results show that colistin resistance was prevalent not only in the mcr-positive clinical E. coli isolates but also in the mcr-negative isolates.

  7. Distribution of multi-resistant Gram-negative versus Gram-positive bacteria in the hospital inanimate environment.

    Science.gov (United States)

    Lemmen, S W; Häfner, H; Zolldann, D; Stanzel, S; Lütticken, R

    2004-03-01

    We prospectively studied the difference in detection rates of multi-resistant Gram-positive and multi-resistant Gram-negative bacteria in the inanimate environment of patients harbouring these organisms. Up to 20 different locations around 190 patients were surveyed. Fifty-four patients were infected or colonized with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE) and 136 with multi-resistant Gram-negative bacteria. The environmental detection rate for MRSA or VRE was 24.7% (174/705 samples) compared with 4.9% (89/1827 samples) for multi-resistant Gram-negative bacteria (PGram-positive bacteria were isolated more frequently than Gram-negatives from the hands of patients (PGram-positive and Gram-negative isolates. Our results suggest that the inanimate environment serves as a secondary source for MRSA and VRE, but less so for Gram-negative bacteria. Thus, strict contact isolation in a single room with complete barrier precautions is recommended for MRSA or VRE; however, for multi-resistant Gram-negative bacteria, contact isolation with barrier precautions for close contact but without a single room seems sufficient. This benefits not only the patients, but also the hospital by removing some of the strain placed on already over-stretched resources.

  8. Prediction of Fluoroquinolone Resistance in Gram-Negative Bacteria Causing Bloodstream Infections.

    Science.gov (United States)

    Dan, Seejil; Shah, Ansal; Justo, Julie Ann; Bookstaver, P Brandon; Kohn, Joseph; Albrecht, Helmut; Al-Hasan, Majdi N

    2016-04-01

    Increasing rates of fluoroquinolone resistance (FQ-R) have limited empirical treatment options for Gram-negative infections, particularly in patients with severe beta-lactam allergy. This case-control study aims to develop a clinical risk score to predict the probability of FQ-R in Gram-negative bloodstream isolates. Adult patients with Gram-negative bloodstream infections (BSI) hospitalized at Palmetto Health System in Columbia, South Carolina, from 2010 to 2013 were identified. Multivariate logistic regression was used to identify independent risk factors for FQ-R. Point allocation in the fluoroquinolone resistance score (FQRS) was based on regression coefficients. Model discrimination was assessed by the area under receiver operating characteristic curve (AUC). Among 824 patients with Gram-negative BSI, 143 (17%) had BSI due to fluoroquinolone-nonsusceptible Gram-negative bacilli. Independent risk factors for FQ-R and point allocation in FQRS included male sex (adjusted odds ratio [aOR], 1.97; 95% confidence intervals [CI], 1.36 to 2.98; 1 point), diabetes mellitus (aOR, 1.54; 95% CI, 1.03 to 2.28; 1 point), residence at a skilled nursing facility (aOR, 2.28; 95% CI, 1.42 to 3.63; 2 points), outpatient procedure within 30 days (aOR, 3.68; 95% CI, 1.96 to 6.78; 3 points), prior fluoroquinolone use within 90 days (aOR, 7.87; 95% CI, 4.53 to 13.74; 5 points), or prior fluoroquinolone use within 91 to 180 days of BSI (aOR, 2.77; 95% CI, 1.17 to 6.16; 3 points). The AUC for both final logistic regression and FQRS models was 0.73. Patients with an FQRS of 0, 3, 5, or 8 had predicted probabilities of FQ-R of 6%, 22%, 39%, or 69%, respectively. The estimation of patient-specific risk of antimicrobial resistance using FQRS may improve empirical antimicrobial therapy and fluoroquinolone utilization in Gram-negative BSI. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  9. HER2 in Breast Cancer Stemness: A Negative Feedback Loop towards Trastuzumab Resistance

    Directory of Open Access Journals (Sweden)

    Babak Nami

    2017-04-01

    Full Text Available HER2 receptor tyrosine kinase that is overexpressed in approximately 20% of all breast cancers (BCs is a poor prognosis factor and a precious target for BC therapy. Trastuzumab is approved by FDA to specifically target HER2 for treating HER2+ BC. However, about 60% of patients with HER2+ breast tumor develop de novo resistance to trastuzumab, partially due to the loss of expression of HER2 extracellular domain on their tumor cells. This is due to shedding/cleavage of HER2 by metalloproteinases (ADAMs and MMPs. HER2 shedding results in the accumulation of intracellular carboxyl-terminal HER2 (p95HER2, which is a common phenomenon in trastuzumab-resistant tumors and is suggested as a predictive marker for trastuzumab resistance. Up-regulation of the metalloproteinases is a poor prognosis factor and is commonly seen in mesenchymal-like cancer stem cells that are risen during epithelial to mesenchymal transition (EMT of tumor cells. HER2 cleavage during EMT can explain why secondary metastatic tumors with high percentage of mesenchymal-like cancer stem cells are mostly resistant to trastuzumab but still sensitive to lapatinib. Importantly, many studies report HER2 interaction with oncogenic/stemness signaling pathways including TGF-β/Smad, Wnt/β-catenin, Notch, JAK/STAT and Hedgehog. HER2 overexpression promotes EMT and the emergence of cancer stem cell properties in BC. Increased expression and activation of metalloproteinases during EMT leads to proteolytic cleavage and shedding of HER2 receptor, which downregulates HER2 extracellular domain and eventually increases trastuzumab resistance. Here, we review the hypothesis that a negative feedback loop between HER2 and stemness signaling drives resistance of BC to trastuzumab.

  10. Emergence of Imipenem-Resistant Gram-Negative Bacilli in Intestinal Flora of Intensive Care Patients

    Science.gov (United States)

    Angebault, Cécile; Barbier, François; Hamelet, Emilie; Defrance, Gilles; Ruppé, Etienne; Bronchard, Régis; Lepeule, Raphaël; Lucet, Jean-Christophe; El Mniai, Assiya; Wolff, Michel; Montravers, Philippe; Plésiat, Patrick; Andremont, Antoine

    2013-01-01

    Intestinal flora contains a reservoir of Gram-negative bacilli (GNB) resistant to cephalosporins, which are potentially pathogenic for intensive care unit (ICU) patients; this has led to increasing use of carbapenems. The emergence of carbapenem resistance is a major concern for ICUs. Therefore, in this study, we aimed to assess the intestinal carriage of imipenem-resistant GNB (IR-GNB) in intensive care patients. For 6 months, 523 consecutive ICU patients were screened for rectal IR-GNB colonization upon admission and weekly thereafter. The phenotypes and genotypes of all isolates were determined, and a case control study was performed to identify risk factors for colonization. The IR-GNB colonization rate increased regularly from 5.6% after 1 week to 58.6% after 6 weeks in the ICU. In all, 56 IR-GNB strains were collected from 50 patients: 36 Pseudomonas aeruginosa strains, 12 Stenotrophomonas maltophilia strains, 6 Enterobacteriaceae strains, and 2 Acinetobacter baumannii strains. In P. aeruginosa, imipenem resistance was due to chromosomally encoded resistance (32 strains) or carbapenemase production (4 strains). In the Enterobacteriaceae strains, resistance was due to AmpC cephalosporinase and/or extended-spectrum β-lactamase production with porin loss. Genomic comparison showed that the strains were highly diverse, with 8 exceptions (4 VIM-2 carbapenemase-producing P. aeruginosa strains, 2 Klebsiella pneumoniae strains, and 2 S. maltophilia strains). The main risk factor for IR-GNB colonization was prior imipenem exposure. The odds ratio for colonization was already as high as 5.9 (95% confidence interval [95% CI], 1.5 to 25.7) after 1 to 3 days of exposure and increased to 7.8 (95% CI, 2.4 to 29.8) thereafter. In conclusion, even brief exposure to imipenem is a major risk factor for IR-GNB carriage. PMID:23318796

  11. Trends of 9,416 multidrug-resistant Gram-negative bacteria

    Directory of Open Access Journals (Sweden)

    Viviane Decicera Colombo Oliveira

    2015-06-01

    Full Text Available Summary Objective: a resistance of hospital-acquired bacteria to multiple antibiotics is a major concern worldwide. The objective of this study was to investigate multidrugresistant (MDR bacteria, clinical specimens, origin of specimen and trends, and correlate these with bacterial sensitivity and consumption of antimicrobials. Methods: 9,416 bacteria of nosocomial origin were evaluated in a tertiary hospital, from 1999 to 2008. MDR was defined for Gram-negative bacteria (GNB as resistance to two or more classes/groups of antibiotics. Results: GNB MDR increased by 3.7 times over the study period (p<0.001. Acinetobacter baumannii was the most prevalent (36.2%. Over the study period, there were significant 4.8-fold and 14.6-fold increases for A. baumannii and K. pneumoniae (p<0.001, respectively. Sixty-seven percent of isolates of MDR GNB were isolated in intensive care units. The resistance of A. baumannii to carbapenems increased from 7.4 to 57.5% during the study period and concomitant with an increased consumption. Conclusion: that decade showed prevalence of GNB and a gradual increase in MDR GNB. There was an increase in carbapenem resistance of 50.1% during the study.

  12. Trends of 9,416 multidrug-resistant Gram-negative bacteria.

    Science.gov (United States)

    Oliveira, Viviane Decicera Colombo; Rubio, Fernando Góngora; Almeida, Margarete Teresa Gottardo; Nogueira, Mara Corrêa Lelles; Pignatari, Antonio Carlos Campos

    2015-01-01

    a resistance of hospital-acquired bacteria to multiple antibiotics is a major concern worldwide. The objective of this study was to investigate multidrugresistant (MDR) bacteria, clinical specimens, origin of specimen and trends, and correlate these with bacterial sensitivity and consumption of antimicrobials. 9,416 bacteria of nosocomial origin were evaluated in a tertiary hospital, from 1999 to 2008. MDR was defined for Gram-negative bacteria (GNB) as resistance to two or more classes/groups of antibiotics. GNB MDR increased by 3.7 times over the study period (p<0.001). Acinetobacter baumannii was the most prevalent (36.2%). Over the study period, there were significant 4.8-fold and 14.6-fold increases for A. baumannii and K. pneumoniae (p<0.001), respectively. Sixty-seven percent of isolates of MDR GNB were isolated in intensive care units. The resistance of A. baumannii to carbapenems increased from 7.4 to 57.5% during the study period and concomitant with an increased consumption. that decade showed prevalence of GNB and a gradual increase in MDR GNB. There was an increase in carbapenem resistance of 50.1% during the study.

  13. Heavy-metal resistance in Gram-negative bacteria isolated from Kongsfjord, Arctic.

    Science.gov (United States)

    Neethu, C S; Mujeeb Rahiman, K M; Saramma, A V; Mohamed Hatha, A A

    2015-06-01

    Isolation and characterization of heterotrophic Gram-negative bacteria was carried out from the sediment and water samples collected from Kongsfjord, Arctic. In this study, the potential of Arctic bacteria to tolerate heavy metals that are of ecological significance to the Arctic (selenium (Se), mercury (Hg), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn)) was investigated. Quantitative assay of 130 isolates by means of plate diffusion and tube dilution methods was carried out by incorporation of different concentrations of metals. Growth in Se and Pb at a concentration of 3000 μg/L was significantly lower (P≤0.0001) than at 2000 μg/L. The minimum inhibitory concentration for Cd and Hg was 50 μg/L (P≤0.0001, F=264.23 and P≤0.0001, F=291.08, respectively) even though in the tube dilution test, Hg-containing tubes showed much less growth, revealing its superior toxicity to Cd. Thus, the level of toxicity of heavy metals was found to be in the order of Hg>Cd>Cu>Zn>Pb>Se. Multiple-metal-resistant isolates were investigated for their resistance against antibiotics, and a positive correlation was observed between antibiotic and metal resistance for all the isolates tested. The resistant organisms thus observed might influence the organic and inorganic cycles in the Arctic and affect the ecosystem.

  14. Coagulase-negative staphylococci strains resistant to oxacillin isolated from neonatal blood cultures

    Directory of Open Access Journals (Sweden)

    Valeria Cataneli Pereira

    2013-11-01

    Full Text Available Coagulase-negative staphylococci (CoNS are the microorganisms most frequently isolated from clinical samples and are commonly found in neonatal blood cultures. Oxacillin is an alternative treatment of choice for CoNS infections; however, resistance to oxacillin can have a substantial impact on healthcare by adversely affecting morbidity and mortality. The objective of this study was to detect and characterise oxacillin-resistant CoNS strains in blood cultures of newborns hospitalised at the neonatal ward of the University Hospital of the Faculty of Medicine of Botucatu. One hundred CoNS strains were isolated and the mecA gene was detected in 69 of the CoNS strains, including 73.2% of Staphylococcus epidermidis strains, 85.7% of Staphylococcus haemolyticus strains, 28.6% of Staphylococcus hominis strains and 50% of Staphylococcus lugdunensis strains. Among these oxacillin-resistant CoNS strains, staphylococcal cassette chromosome mec (SCCmec type I was identified in 24.6%, type II in 4.3%, type III in 56.5% and type IV in 14.5% of the strains. The data revealed an increase in the percentage of CoNS strains isolated from blood cultures from 1991-2009. Furthermore, a predominant SCCmec profile of the oxacillin-resistant CoNS strains isolated from neonatal intensive care units was identified with a prevalence of SCCmec types found in hospital-acquired strains.

  15. Infections caused by carbapenem-resistant Gram-negative pathogens in hospitalized children.

    Science.gov (United States)

    Maltezou, Helena C; Kontopidou, Flora; Katerelos, Panos; Daikos, George; Roilides, Emmanuel; Theodoridou, Maria

    2013-04-01

    Carbapenem-resistant Gram-negative pathogens (CRPs) are emerging as major causes of nosocomial infections that increase morbidity, mortality and healthcare costs. Little is known about CRP infections in children. All newly detected infections caused by carbapenem-resistant Klebsiella spp, Pseudomonas spp or Acinetabocater spp in hospitalized patients are prospectively reported to the Hellenic Center for Disease Control and Prevention. All children history of hospitalization the previous 6 months; 42 (59.2%) and 36 (50.7%) infections occurred among patients who had received broad-spectrum antibiotics including carbapenems the previous 6 months, respectively. The crude mortality at 28 days after the first positive CRP culture was 21.1%. Infections caused by CRPs among children are associated with significant morbidity and mortality.

  16. Observation and Measurement of Negative Differential Resistance on PtSi Schottky Junctions on Porous Silicon

    Directory of Open Access Journals (Sweden)

    Mansor Mohtashamifar

    2010-01-01

    Full Text Available Nanosize porous Si is made by two step controlled etching of Si. The first etching step is carried on the Si surface and the second is performed after deposition of 75 Å of platinum on the formed surface. A platinum silicide structure with a size of less than 25 nm is formed on the porous Si surface, as measured with an Atomic Forced Microscope (AFM. Differential resistance curve as a function of voltage in 77 K and 100 K shows a negative differential resistance and indicates the effect of quantum tunneling. In general form, the ratio of maximum to minimum tunneling current (PVR and the number of peaks in I-V curves reduces by increasing the temperature. However, due to accumulation of carriers behind the potential barrier and superposition of several peaks, it is observed that the PVR increases at 100 K and the maximum PVR at 100 K is 189.6.

  17. Low antibiotic resistance among anaerobic Gram-negative bacteria in periodontitis 5 years following metronidazole therapy.

    Science.gov (United States)

    Dahlen, G; Preus, H R

    2017-02-01

    The objective of this study was to assess antibiotic susceptibility among predominant Gram-negative anaerobic bacteria isolated from periodontitis patients who 5 years prior had been subject to mechanical therapy with or without adjunctive metronidazole. One pooled sample was taken from the 5 deepest sites of each of 161 patients that completed the 5 year follow-up after therapy. The samples were analyzed by culture. A total number of 85 anaerobic strains were isolated from the predominant subgingival flora of 65/161 patient samples, identified, and tested for antibiotic susceptibility by MIC determination. E-tests against metronidazole, penicillin, amoxicillin, amoxicillin + clavulanic acid and clindamycin were employed. The 73/85 strains were Gram-negative rods (21 Porphyromonas spp., 22 Prevotella/Bacteroides spp., 23 Fusobacterium/Filifactor spp., 3 Campylobacter spp. and 4 Tannerella forsythia). These were all isolated from the treated patients irrespective of therapy procedures (+/-metronidazole) 5 years prior. Three strains (Bifidobacterium spp., Propionibacterium propionicum, Parvimonas micra) showed MIC values for metronidazole over the European Committee on Antimicrobial Susceptibility Testing break point of >4 μg/mL. All Porphyromonas and Tannerella strains were highly susceptible. Metronidazole resistant Gram-negative strains were not found, while a few showed resistance against beta-lactam antibiotics. In this population of 161 patients who had been subject to mechanical periodontal therapy with or without adjunct metronidazole 5 years prior, no cultivable antibiotic resistant anaerobes were found in the predominant subgingival microbiota. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Surveillance culture for multidrug-resistant gram-negative bacteria: Performance in liver transplant recipients.

    Science.gov (United States)

    Freire, Maristela Pinheiro; Villela Soares Oshiro, Isabel Cristina; Bonazzi, Patrícia Rodrigues; Pierrotti, Ligia Câmera; de Oliveira, Larissa Marques; Machado, Anna Silva; Van Der Heijdenn, Inneke Marie; Rossi, Flavia; Costa, Silvia Figueiredo; Carneiro D'Albuquerque, Luiz Augusto; Abdala, Edson

    2017-03-01

    The prevalence of infection with multidrug-resistant gram-negative bacteria (MDR-GNB) after solid-organ transplantation is increasing. Surveillance culture (SC) seems to be an important tool for MDR-GNB control. The goal of this study was to analyze the performance of SC for MDR-GNB among liver transplant (LT) recipients. This was a prospective cohort study involving patients who underwent LT between November 2009 and November 2011. We screened patients for extended spectrum β-lactamase-producing Escherichia coli, extended spectrum β-lactamase-producing Klebsiella pneumoniae, and carbapenem-resistant Enterobacteriaceae, carbapenem-resistant Pseudomonas aeruginosa (CRPA), and carbapenem-resistant Acinetobacter baumannii (CRAB). We collected SC samples immediately before LT and weekly thereafter, until hospital discharge. Samples were collected from the inguinal-rectal area, axilla, and throat. The performance of SC was evaluated through analysis of its sensitivity, negative predictive value, and accuracy. During the study period, 181 patients were evaluated and 4,110 SC samples were collected. The GNB most often identified was CRAB, in 45.9% of patients, followed by CRKP in 40.3%. For all microorganisms, the positivity rate was highest among the inguinal-rectal samples. If only samples collected from this area were considered, the SC would fail to identify 34.9% of the cases of CRAB colonization. The sensitivity of SC for CRKP was 92.5%. The performance of SC was poorest for CRAB (sensitivity, 80.6%). Our data indicate that SC is a sensitive tool to identify LT recipients colonized by MDR-GNB. Copyright © 2017 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  19. Single-band negative differential resistance in metallic armchair MoS2 nanoribbons

    Science.gov (United States)

    Chen, Cheng; Wang, Xue-Feng; Li, Yao-Sheng; Cheng, Xue-Mei; Yao, A.-Long

    2017-11-01

    Semiconductor armchair MoS2 nanoribbons can be converted into conductors by edge functionalization of H atoms or OH groups. Those metallic nanoribbons exhibit I–V characteristics of a single half-filled band with strong negative differential resistance (NDR) under a voltage bias less than 1 V. This originates from the spatial separation between electrons in the conduction and valence bands. The NDR becomes spin dependent if the H atoms or OH groups are not uniformly adsorbed on the edge. Furthermore, the spin polarization can be greatly enhanced in heterojunctions of H- and OH-passivated nanoribbons.

  20. Antibiotic resistance of Gram-negative benthic bacteria isolated from the sediments of Kardzhali Dam (Bulgaria)

    OpenAIRE

    Iliev, Ivan; Marhova, Mariana; Gochev, Velizar; Tsankova, Marinela; Trifonova, Sonya

    2015-01-01

    The aim of the present study was to carry out a preliminary assessment for the occurrence of bacterial strains resistant to frequently used antibiotics in the sediments beneath the sturgeon cage farm in Kardzhali Dam (Bulgaria). Samples were taken from the top 2 cm of sediments under a fish farm and from a control station in the aquatory of the reservoir in the period July?October 2011. Surveillance of bacterial susceptibility to 16 antimicrobial agents was performed for 160 Gram-negative str...

  1. Switchable Negative Differential Resistance Induced by Quantum Interference Effects in Porphyrin-based Molecular Junctions.

    Science.gov (United States)

    Nozaki, Daijiro; Lokamani; Santana-Bonilla, Alejandro; Dianat, Arezoo; Gutierrez, Rafael; Cuniberti, Gianaurelio

    2015-10-01

    Charge transport signatures of a carbon-based molecular switch consisting of different tautomers of metal-free porphyrin embedded between graphene nanoribbons is studied by combining electronic structure and nonequilibrium transport. Different low-energy and low-bias features are revealed, including negative differential resistance (NDR) and antiresonances, both mediated by subtle quantum interference effects. Moreover, the molecular junctions can display moderate rectifying or nonlinear behavior depending on the position of the hydrogen atoms within the porphyrin core. We rationalize the mechanism leading to NDR and antiresonances by providing a detailed analysis of transmission pathways and frontier molecular orbital distribution.

  2. Negative Differential Resistance due to Nonlinearities in Single and Stacked Josephson Junctions

    DEFF Research Database (Denmark)

    Filatrella, Giovanni; Pierro, Vincenzo; Pedersen, Niels Falsig

    2014-01-01

    of the fluxon system have demonstrated that a cavity induced NDR plays a crucial role for the emission of electromagnetic radiation. We consider the case of an NDR region in the McCumber curve itself of a single junction and found that it has an effect on the emission of electromagnetic radiation. Two different......Josephson junction systems with a negative differential resistance (NDR) play an essential role for applications. As a well-known example, long Josephson junctions of the BSCCO type have been considered as a source of terahertz radiation in recent experiments. Numerical results for the dynamics...

  3. Evaluation of a high-resolution negative-acting electron-beam resist GMC for photomask manufacturing

    Science.gov (United States)

    Chen, Wen-Chih; Novembre, Anthony E.

    1991-03-01

    As mask and reticle designs continue to evolve in complexity and resolution requirements, maskmakers are investigating what advantages negative acting electron beam resists may have in meeting these requirements. One candidate is Poly (glycidyl methacrylate-co-3- chlorostyrene), GMC, which is an advanced negative resist used for the purpose of photomask fabrication. In this paper, a statistically designed experiment will be described in which GMC resist was evaluated for use on the MEBES system. Variables explored included exposure dosage, chrome etch time, resist descum and strip time. The effects of these variables on defect density, critical dimension (CD) size and uniformity will be presented.

  4. Graphene nanoribbon based negative resistance device for ultra-low voltage digital logic applications

    Science.gov (United States)

    Khatami, Yasin; Kang, Jiahao; Banerjee, Kaustav

    2013-01-01

    Negative resistance devices offer opportunities in design of compact and fast analog and digital circuits. However, their implementation in logic applications has been limited due to their small ON current to OFF current ratios (peak to valley ratio). In this paper, a design for a 2-port negative resistance device based on arm-chair graphene nanoribbon is presented. The proposed structure takes advantage of electrostatic doping, and offers high ON current (˜700 μA/μm) as well as ON current to OFF current ratio of more than 105. The effects of several design parameters such as doping profile, gate workfunction, bandgap, and hetero-interface characteristics are investigated to improve the performance of the proposed devices. The proposed device offers high flexibility in terms of the design and optimization, and is suitable for digital logic applications. A complementary logic is developed based on the proposed device, which can be operated down to 200 mV of supply voltage. The complementary logic is used in design of an ultra-compact bi-stable switching static memory cell. Due to its compactness and high drive current, the proposed memory cell can outperform the conventional static random access memory cells in terms of switching speed and power consumption.

  5. Engineered Endolysin-Based “Artilysins” To Combat Multidrug-Resistant Gram-Negative Pathogens

    Science.gov (United States)

    Briers, Yves; Walmagh, Maarten; Van Puyenbroeck, Victor; Cornelissen, Anneleen; Cenens, William; Aertsen, Abram; Oliveira, Hugo; Azeredo, Joana; Verween, Gunther; Pirnay, Jean-Paul; Miller, Stefan; Volckaert, Guido

    2014-01-01

    ABSTRACT The global threat to public health posed by emerging multidrug-resistant bacteria in the past few years necessitates the development of novel approaches to combat bacterial infections. Endolysins encoded by bacterial viruses (or phages) represent one promising avenue of investigation. These enzyme-based antibacterials efficiently kill Gram-positive bacteria upon contact by specific cell wall hydrolysis. However, a major hurdle in their exploitation as antibacterials against Gram-negative pathogens is the impermeable lipopolysaccharide layer surrounding their cell wall. Therefore, we developed and optimized an approach to engineer these enzymes as outer membrane-penetrating endolysins (Artilysins), rendering them highly bactericidal against Gram-negative pathogens, including Pseudomonas aeruginosa and Acinetobacter baumannii. Artilysins combining a polycationic nonapeptide and a modular endolysin are able to kill these (multidrug-resistant) strains in vitro with a 4 to 5 log reduction within 30 min. We show that the activity of Artilysins can be further enhanced by the presence of a linker of increasing length between the peptide and endolysin or by a combination of both polycationic and hydrophobic/amphipathic peptides. Time-lapse microscopy confirmed the mode of action of polycationic Artilysins, showing that they pass the outer membrane to degrade the peptidoglycan with subsequent cell lysis. Artilysins are effective in vitro (human keratinocytes) and in vivo (Caenorhabditis elegans). PMID:24987094

  6. Tetracycline improved the efficiency of other antimicrobials against Gram-negative multidrug-resistant bacteria.

    Science.gov (United States)

    Mawabo, Isabelle K; Noumedem, Jaurès A K; Kuiate, Jules R; Kuete, Victor

    2015-01-01

    Treatment of infectious diseases with antimicrobials constituted a great achievement in the history of medicine. Unfortunately, the emergence of resistant strains of bacteria to all classes of antimicrobials limited their efficacy. The present study was aimed at evaluating the effect of combinations of antibiotics on multi-drug resistant Gram-negative (MDRGN) bacteria. A liquid micro-broth dilution method was used to evaluate the antibacterial activity of 10 different classes of antimicrobials on 20 bacterial strains belonging to six different species. The antimicrobials were associated with phenylalanine β-naphthylamide (PAβN), an efflux pump inhibitor, and with other antimicrobials at their sub-inhibitory concentrations. The effectiveness of each combination was monitored using the minimal inhibitory concentration (MIC) and the fractional inhibitory concentration (FIC). Most of the antimicrobials tested showed low antibacterial activity with a MIC value of 128 mg/L on a majority of the bacterial strains, justifying their multidrug-resistant (MDR) profile. Synergistic effects were mostly observed (FIC≤0.5) when ampicillin (AMP), cloxacillin (CLX), erythromycin (ERY), chloramphenicol (CHL), kanamycin (KAN) and streptomycin (STR) were combined with tetracycline (TET) at the sub-inhibitory concentration of MIC/5 or MIC/10. The results of the present work suggest that the association of several antimicrobials with TET could improve the fight against MDRGN bacterial species. Copyright © 2014 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

  7. Resisting Negative Images and Stereotypes: One Latina Prospective Teacher’s Story

    Directory of Open Access Journals (Sweden)

    Terri L. Rodriguez

    2010-01-01

    Full Text Available This article focuses on one Latina prospective teacher’s act of resisting negative stereotypes regarding attire imposed upon her by a white female principal.  The event is embedded within a larger life history study that explores the experiences of bilingual Latino prospective teachers in the elementary education program of a large Midwestern university.  The selected narrative is contextualized in relation to resistance narratives. Patricia Morales tells about her experiences in U.S. schools.  It explores how Patricia’s life history is marked by experiences of discrimination, yet how her constructions of these events represent “counterstories” (Delgado, 2000; Solorzano & Yosso, 2002 through which she “talks back” (hooks, 1989 to distorted images and stereotypes.  Patricia’s narratives are shown to constitute creative acts of resistance through which she negotiates a positive and affirming identity (Suarez-Orozco & Suarez-Orozco, 2001 as a Latina prospective teacher.   Keywords: preservice teachers; teacher education; Latino critical race theory; narrative inquiry

  8. Extended spectrum β-lactamases, carbapenemases and mobile genetic elements responsible for antibiotics resistance in Gram-negative bacteria.

    Science.gov (United States)

    El Salabi, Allaaeddin; Walsh, Timothey R; Chouchani, Chedly

    2013-05-01

    Infectious diseases due to Gram-negative bacteria are a leading cause of morbidity and mortality worldwide. Antimicrobial agents represent one major therapeutic tools implicated to treat these infections. The misuse of antimicrobial agents has resulted in the emergence of resistant strains of Gram-negatives in particular Enterobacteriaceae and non-fermenters; they have an effect not only on a human but on the public health when bacteria use the resistance mechanisms to spread in the hospital environment and to the community outside the hospitals by means of mobile genetic elements. Gram-negative bacteria have become increasingly resistant to antimicrobial agents. They have developed several mechanisms by which they can withstand to antimicrobials, these mechanisms include the production of Extended-spectrum β-lactamases (ESBLs) and carbapenemases, furthermore, Gram-negative bacteria are now capable of spreading such resistance between members of the family Enterobacteriaceae and non-fermenters using mobile genetic elements as vehicles for such resistance mechanisms rendering antibiotics useless. Therefore, addressing the issue of mechanisms of antimicrobial resistance is considered one of most urgent priorities. This review will help to illustrate different resistance mechanisms; ESBLs, carbapenemases encoded by genes carried by mobile genetic elements, which are used by Gram-negative bacteria to escape antimicrobial effect.

  9. Comparative study between the results of effective index based matrix method and characterization of fabricated SU-8 waveguide

    Science.gov (United States)

    Samanta, Swagata; Dey, Pradip Kumar; Banerji, Pallab; Ganguly, Pranabendu

    2017-01-01

    A study regarding the validity of effective-index based matrix method (EIMM) for the fabricated SU-8 channel waveguides is reported. The design method is extremely fast compared to other existing numerical techniques, such as, BPM and FDTD. In EIMM, the effective index method was applied in depth direction of the waveguide and the resulted lateral index profile was analyzed by a transfer matrix method. By EIMM one can compute the guided mode propagation constants and mode profiles for each mode for any dimensions of the waveguides. The technique may also be used to design single mode waveguide. SU-8 waveguide fabrication was carried out by continuous-wave direct laser writing process at 375 nm wavelength. The measured propagation losses of these wire waveguides having air and PDMS as superstrates were 0.51 dB/mm and 0.3 dB/mm respectively. The number of guided modes, obtained theoretically as well as experimentally, for air-cladded waveguide was much more than that of PDMS-cladded waveguide. We were able to excite the isolated fundamental mode for the later by precise fiber positioning, and mode image was recorded. The mode profiles, mode indices, and refractive index profiles were extracted from this mode image of the fundamental mode which matched remarkably well with the theoretical predictions.

  10. Epidemiological surveillance of multidrug-resistant gram-negative bacteria in a solid organ transplantation department.

    Science.gov (United States)

    Geladari, Anastasia; Karampatakis, Theodoros; Antachopoulos, Charalampos; Iosifidis, Elias; Tsiatsiou, Olga; Politi, Lida; Karyoti, Aggeliki; Papanikolaou, Vasilios; Tsakris, Athanassios; Roilides, Emmanuel

    2017-06-01

    We assessed the impact of intensified infection control measures (ICM) on colonization and infection caused by carbapenem-resistant (CR) Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii in a solid organ transplantation (SOT) department. A quasi-experimental methodology was followed. The study was divided into three periods: pre-intervention, intervention with implementation of an ICM bundle including active surveillance program (ASP) and gradually enhanced measures, and post-ASP without ASP. The bundle included active surveillance cultures, contact precautions, hand hygiene, education of health care workers (HCWs), monitoring of compliance, and environmental cleaning. Incidence of colonization and infection caused by CR gram-negative bacteria was recorded. Molecular analysis of CR bacteria was performed for a certain period. During the intervention, incidence of colonization reduced from 19% to 9% (Pbacteria increased from 2.8 to 6.9/1000 bed-days (Pgram-negative bacteria are endemic, colonization and infection rates by these bacteria are high among SOT recipients. Implementation of enhanced ICM in all related units of a hospital, although challenging, reduces colonization rates by CR gram-negative bacteria. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. Antibiotic resistance of gram-negative enteric bacteria from pigs in three herds with different histories of antibiotic exposure.

    OpenAIRE

    Gellin, G; Langlois, B E; Dawson, K A; Aaron, D K

    1989-01-01

    The antibiotic resistance patterns of gram-negative fecal bacteria from pigs in three herds with different histories of antibiotic exposure were examined. In general, smaller proportions of antibiotic-resistant or multiply resistant fecal isolates (P less than 0.05) were obtained from pigs in a herd not exposed to antimicrobial agents for 154 months than from pigs in a herd continuously exposed to antimicrobial agents at subtherapeutic doses or from pigs in a herd exposed only to therapeutic ...

  12. Genetic Diversity and Antibiotic Resistance Among Coagulase-Negative Staphylococci Recovered from Birds of Prey in Portugal

    OpenAIRE

    Sousa, Margarida; Silva, Nuno; Igrejas, Gilberto; Sargo, Roberto; Benito, Daniel; Gómez, Paula; Lozano, Carmen; Manageiro, Vera; Torres, Carmen; Caniça, Manuela; Poeta, Patrícia

    2016-01-01

    Wild animal populations in contact with antimicrobials and antimicrobial resistant bacteria that are daily released into the environment are able to become unintentional hosts of these resistant microorganisms. To clarify this issue, our study evaluated the presence of antibiotic resistance determinants on coagulase-negative staphylococci recovered from birds of prey and studied their genetic relatedness by pulsed-field gel electrophoresis (PFGE). The unusual vga(A) and erm(T) genes, which co...

  13. Screen Printing of SU-8 Layers for Microstructure Fabrication / Ar Sietspiedi Uzklātu SU-8 Pārklājumi Mikro-Struktūru Izgatavošanai

    Science.gov (United States)

    Klavins, J.; Mozolevskis, G.; Ozols A., A.; Nitiss, E.; Rutkis, M.

    2015-10-01

    We report on a screen printing fabrication process for large-area SU-8 layers utilised for the preparation of microstructures in display devices such as microelectronic, electrowetting or bistable devices. The screen printing method has been selected for its effectiveness and simplicity over traditionally used spin-coating ones. Layers and microstructures produced thereof have shown proper homogeneity. Relationships between screen parameters to coating thickness have been established. Coating on an ITO (indium tin oxide) hydrophobic surface is possible when surface has been treated by UV/Ozone to increase its aqueous ability. To this end, the hydrophilic microstructure grids have been successfully built on a hydrophobic layer by screen printing and traditional lithography processes. Compared to conventional spin-coating methods, the screen printing method offers the advantages of simple, cheap and fast fabrication, and is especially suitable for large-area display fabrication Rakstā aprakstīta sietspiedes metode liela izmēra SU-8 pārklājumu iegūšanai, lai izgatavotu mikrostruktūras mikroelektronikai, elektroslapināšanas un bistabilajiem ekrāniem. Sietspiede ir efektīvāka un vienkāršāka metode nekā tradicionāli izmantotā spin-coating metode. Šādiem pārklājumuiem un mikrostruktūrām ir pietiekoša homogenitāte. Tika atrasta sakarība starp sietu parametriem un pārklājumu biezumu. Pārklājumus var uzklāt uz hidrofobiskās ITO (indija alvas oksīds) virsmas, ja tā tiek apstrādāta ar UV/Ozonu, jo tas palielina ūdens slapināšanas īpašības. Tika izgatavoti hidrofīliskas mikrostruktūras režģi uz hidrofobiskas pamatnes ar sietspiedi un tradicionālo SU-8 litogrāfijas metodi. Salīdzinājumā ar tradicionālo spin-coating metodi, sietspiede ir vienkārša, lēta un ātra un ir labi piemērota liela izmēra ekrānu izgatavošanai.

  14. Study of Nitrogen terminated doped zigzag GNR FET exhibiting negative differential resistance

    Science.gov (United States)

    Gupta, Santosh Kumar; Jaiswal, Girija Nandan

    2015-10-01

    This paper presents the study of Gallium and Aluminum doped Nitrogen terminated zigzag Graphene Nano Ribbon (GNR) FET with high-k dielectric. The GNR FET structure has been designed and simulated using Quantumwise Atomistix Toolkit software package. The presented GNR FET with n-type (Nitrogen doped) electrodes and p-type (Gallium or Aluminum doped) scattering region are simulated and analyzed using Density Functional Theory combined with NEGF formalism and Device Density of States (DDOS). The device shows a negative differential resistance phenomenon which can be controlled by the gate of the zigzag GNR FET. It is found that doping of Gallium and Aluminum in scattering region provides higher drain current, higher ION/IOFF and IP/IV ratios as compared to that of Boron doped zigzag GNR FET. The potential applications of the device are in logical, high frequency, and memory devices.

  15. Bidirectional negative differential thermal resistance phenomenon and its physical mechanism in the Frenkel-Kontorova lattices

    Energy Technology Data Exchange (ETDEWEB)

    Jianqiang, Zhang; Linru, Nie, E-mail: lrnie@163.com; Chongyang, Chen; Xinyu, Zhang [Faculty of Science, Kunming University of Science and Technology, Kunming 650500 (China)

    2016-07-15

    Thermal conduction of the Frenkel-Kontorova (FK) lattices with interfacial coupling is investigated numerically. The results indicate that: (i) For appropriate lattice periods, as the system is symmetric, a bidirectional negative differential thermal resistance (NDTR) phenomenon will appear. If the system is asymmetric, the bidirectional NDTR is gradually converted into an unidirectional NDTR. (ii) The bidirectional NDTR phenomenon effect also depends on the period of the FK lattice as the other parameters remains unchanged. With the increment of the lattice period, the bidirectional NDTR will gradually disappear. (iii) From a stochastic dynamics point of view, thermal transport properties of the system are determined by the competition between the two types of thermal conduction: one comes from the collusion between atoms, the other is due to the elastic coupling between atoms. For the smaller lattice periods, the former type of thermal conduction occupies the dominating position and the NDTR effect will appear.

  16. Negative differential resistance and rectifying performance induced by doped graphene nanoribbons p-n device

    Science.gov (United States)

    Zhou, Yuhong; Qiu, Nianxiang; Li, Runwei; Guo, Zhansheng; Zhang, Jian; Fang, Junfeng; Huang, Aisheng; He, Jian; Zha, Xianhu; Luo, Kan; Yin, Jingshuo; Li, Qiuwu; Bai, Xiaojing; Huang, Qing; Du, Shiyu

    2016-03-01

    Employing nonequilibrium Green's Functions in combination with density functional theory, the electronic transport properties of armchair graphene nanoribbon (GNR) devices with various widths are investigated in this work. In the adopted model, two semi-infinite graphene electrodes are periodically doped with boron or nitrogen atoms. Our calculations reveal that these devices have a striking nonlinear feature and show notable negative differential resistance (NDR). The results also indicate the diode-like properties are reserved and the rectification ratios are high. It is found the electronic transport properties are strongly dependent on the width of doped nanoribbons and the positions of dopants and three distinct families are elucidated for the current armchair GNR devices. The NDR as well as rectifying properties can be well explained by the variation of transmission spectra and the relative shift of discrete energy states with applied bias voltage. These findings suggest that the doped armchair GNR is a promising candidate for the next generation nanoscale device.

  17. Motuporamine Derivatives as Antimicrobial Agents and Antibiotic Enhancers against Resistant Gram-Negative Bacteria.

    Science.gov (United States)

    Borselli, Diane; Blanchet, Marine; Bolla, Jean-Michel; Muth, Aaron; Skruber, Kristen; Phanstiel, Otto; Brunel, Jean Michel

    2017-02-01

    Dihydromotuporamine C and its derivatives were evaluated for their in vitro antimicrobial activities and antibiotic enhancement properties against Gram-negative bacteria and clinical isolates. The mechanism of action of one of these derivatives, MOTU-N44, was investigated against Enterobacter aerogenes by using fluorescent dyes to evaluate outer-membrane depolarization and permeabilization. Its efficiency correlated with inhibition of dye transport, thus suggesting that these molecules inhibit drug transporters by de-energization of the efflux pump rather than by direct interaction of the molecule with the pump. This suggests that depowering the efflux pump provides another strategy to address antibiotic resistance. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  18. Resonant transport and negative differential resistance in the graphene and graphyne quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ye; Xie, Yuee, E-mail: xieyech@xtu.edu.cn; Ouyang, Tao; Chen, Yuanping, E-mail: chenyp@xtu.edu.cn

    2014-07-15

    The electronic transport properties of graphene and graphyne quantum dots embedded in zigzag-edged graphene nanoribbons are studied. The results show that the quasi-bound states in the quantum dots induce resonant transmission around the Fermi level in the transmission spectrums. While the resonant peaks lead to robust negative differential resistance (NDR) behaviors. Moreover, the resonant transmission and NDR behavior are very sensitive to the size of the quantum dots. As the size of quantum dots increases, the number of resonant peaks increases and shift to the Fermi level, correspondingly the NDR phenomena shift to lower bias. Compared with graphene quantum dots, graphyne quantum dots show more amazing transport properties. These interesting findings could offer useful guidelines for the design of electronics associated with resonant and NDR phenomenon/.

  19. Novel five-state latch using double-peak negative differential resistance and standard ternary inverter

    Science.gov (United States)

    Shin, Sunhae; Rok Kim, Kyung

    2016-04-01

    We propose complement double-peak negative differential resistance (NDR) devices with ultrahigh peak-to-valley current ratio (PVCR) over 106 by combining tunnel diode with conventional CMOS and its compact five-state latch circuit by introducing standard ternary inverter (STI). At the “high”-state of STI, n-type NDR device (tunnel diode with nMOS) has 1st NDR characteristics with 1st peak and valley by band-to-band tunneling (BTBT) and trap-assisted tunneling (TAT), whereas p-type NDR device (tunnel diode with pMOS) has second NDR characteristics from the suppression of diode current by off-state MOSFET. The “intermediate”-state of STI permits double-peak NDR device to operate five-state latch with only four transistors, which has 33% area reduction compared with that of binary inverter and 57% bit-density reduction compared with binary latch.

  20. Different phenotypic and molecular mechanisms associated with multidrug resistance in Gram-negative clinical isolates from Egypt

    Directory of Open Access Journals (Sweden)

    Helmy OM

    2017-12-01

    Full Text Available Omneya M Helmy, Mona T Kashef Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, Egypt Objectives: We set out to investigate the prevalence, different mechanisms, and clonal relatedness of multidrug resistance (MDR among third-generation cephalosporin-resistant Gram-negative clinical isolates from Egypt.Materials and methods: A total of 118 third-generation cephalosporin-resistant Gram-negative clinical isolates were included in this study. Their antimicrobial susceptibility pattern was determined using Kirby–Bauer disk diffusion method. Efflux pump-mediated resistance was tested by the efflux-pump inhibitor-based microplate assay using chlorpromazine. Detection of different aminoglycoside-, β-lactam-, and quinolone-resistance genes was done using polymerase chain reaction. The genetic diversity of MDR isolates was investigated using random amplification of polymorphic DNA.Results: Most of the tested isolates exhibited MDR phenotypes (84.75%. The occurrence of efflux pump-mediated resistance in the different MDR species tested was 40%–66%. Acinetobacter baumannii isolates showed resistance to most of the tested antibiotics, including imipenem. The blaOXA-23-like gene was detected in 69% of the MDR A. baumannii isolates. The MDR phenotype was detected in 65% of Pseudomonas aeruginosa isolates, of which only 23% exhibited efflux pump-mediated resistance. On the contrary, efflux-mediated resistance to piperacillin and gentamicin was recorded in 47.5% of piperacillin-resistant and 25% of gentamicin-resistant MDR Enterobacteriaceae. Moreover, the plasmid-mediated quinolone-resistance genes (aac(6’-Ib-cr, qnrB, and qnrS were detected in 57.6% and 83.33% of quinolone-resistant MDR Escherichia coli and Klebsiella pneumoniae isolates, respectively. The β-lactamase-resistance gene blaSHV-31 was detected for the first time in one MDR K. pneumoniae isolate from an endotracheal tube specimen in Egypt

  1. Development of antibiotic resistance in Gram negative bacilli: An eye opener

    Directory of Open Access Journals (Sweden)

    Ravinder Pal Singh

    2014-01-01

    Full Text Available Context: Antibiotic resistance is a global problem. Organisms are showing resistance to not only the conventional antibiotics but also to the higher generation drugs. This enormous amount of resistance faced is a serious threat to mankind and this is further accentuated by the fact that the antibiotic pipeline is fast drying up. We are now left with only a handful of antibiotics to deal with all infections - serious or otherwise. The present paper highlights the current scenario of drug resistance especially in nosocomial settings. Aims and Objectives: To determine the distribution of bacterial pathogens causing nosocomial infections and their antibiogram, a surveillance data from January to December 2011 was collected in Mohan Dai Oswal Hospital. A total of 1800 samples were taken of which maximum samples were urine (766 followed by blood (428 and pus (216, and so on. Settings and Design: This observational study was conducted in the microbiology department of a multispeciality hospital during January-December 2011. Materials and Methods: A total of 1800 samples from different sources were included in the study like pus, blood, urine, sputum, etc., which were taken from patients admitted in the hospital for more than a week. Gram negative bacilli were isolated, identified, and subjected to antibiotic sensitivity test. Statistical Analysis Used: Descriptive statistics using percentages. Results: Out of the total 1800 samples included, maximum positivity was found in the pus samples (70%. Extended-spectrum beta-lactamase (ESBL positivity was also maximum in the pus samples (90%. These ESBL positive organisms were further subjected to antibiotic sensitivity tests and huge amounts of resistance was noted to the conventional drugs including the higher end agents like Carbapenems. In light of this, newer drugs like Tigecycline, Colistin, and Polymyxin B were also tested. Barring Tigecycline, none showed favorable results. A noteworthy finding was the

  2. The antibiotic pipeline for multi-drug resistant gram negative bacteria: what can we expect?

    Science.gov (United States)

    Falagas, Matthew E; Mavroudis, Andreas D; Vardakas, Konstantinos Z

    2016-08-01

    A real concern in the medical community is the increasing resistance of bacteria, especially that of Gram-negative types. New antibiotics are currently under clinical development, promising to tackle severe infections caused, especially, by multi-drug resistant (MDR) bacteria and broaden the armamentarium of clinicians. We searched PUBMED and GOOGLE databases. Combinations of already approved β-lactams or monobactams with new β-lactamase inhibitors [imipenem-cilastatin/MK-7655 (relebactam), meropenem/RPX7009 (vaborbactam), ceftaroline/avibactam, aztreonam/avibactam], new β-lactams (S-649266, BAL30072), aminoglycosides (plazomicin), quinolones (finafloxacin) and tetracyclines (eravacycline) were included in the review. Expert commentary: For the majority of the upcoming antibiotics the currently available data is limited to their microbiology and pharmacokinetics. Their effectiveness and safety against infections due to MDR bacteria remain to be proved. Significant issues are also the impact of these antibiotics on the human intestinal microbiota and their possible co-administration with already-known antimicrobial agents in difficult-to-treat-infections; further studies should be conducted for these objectives.

  3. Combined Phosphoproteomics and Bioinformatics Strategy in Deciphering Drug Resistant Related Pathways in Triple Negative Breast Cancer

    Directory of Open Access Journals (Sweden)

    Xinyu Deng

    2014-01-01

    Full Text Available Because of the absence of a clear therapeutic target for triple negative breast cancer (TNBC, conventional chemotherapy is the only available systemic treatment option for these patients. Despite chemotherapy treatment, TNBC patients still have worse prognosis when compared with other breast cancer patients. The study is to investigate unique phosphorylated proteins expressed in chemoresistant TNBC cell lines. In the current study, twelve TNBC cell lines were subjected to drug sensitivity assays against chemotherapy drugs docetaxel, doxorubicin, gemcitabine, and cisplatin. Based on their half maximal inhibitory concentrations, four resistant and two sensitive cell lines were selected for further analysis. The phosphopeptides from these cells were enriched with TiO2 beads and fractionated using strong cation exchange. 1,645 phosphoprotein groups and 9,585 unique phosphopeptides were identified by a high throughput LC-MS/MS system LTQ-Orbitrap. The phosphopeptides were further filtered with Ascore system and 1,340 phosphoprotein groups, 2,760 unique phosphopeptides, and 4,549 unique phosphosites were identified. Our study suggested that differentially phosphorylated Cdk5, PML, AP-1, and HSF-1 might work together to promote vimentin induced epithelial to mesenchymal transition (EMT in the drug resistant cells. EGFR and HGF were also shown to be involved in this process.

  4. RND efflux pump mediated antibiotic resistance in Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa: a major issue worldwide.

    Science.gov (United States)

    Puzari, Minakshi; Chetia, Pankaj

    2017-02-01

    Therapeutic failures against diseases due to resistant Gram-negative bacteria have become a major threat nowadays as confirmed by surveillance reports across the world. One of the methods of development of multidrug resistance in Escherichia coli and Pseudomonas aeruginosa is by means of RND efflux pumps. Inhibition of these pumps might help to combat the antibiotic resistance problem, for which the structure and regulation of the pumps have to be known. Moreover, judicious antibiotic use is needed to control the situation. This paper focuses on the issue of antibiotic resistance as well as the structure, regulation and inhibition of the efflux pumps present in Escherichia coli and Pseudomonas aeruginosa.

  5. The photodetected function of silicon photoelectronic lambda negative resistance transistor (PLBT)

    Science.gov (United States)

    Zhang, Shi-lin; Zhang, Bo; Guo, Wei-lian; Mao, Lu-hong; Zhang, Pei-ning

    2005-01-01

    In this paper, the photo-detected and controlled functions based on silicon photo-electronic Lambda transistor (PLBT) are reported. PLBT is composed of a npn vertical bipolar transistor as main device and a enhancement-mode MOSFET transistor as feedback device which connected in parallel across the base and collector terminals of bipolar transistor. Photo-electronic-lambda bipolar transistor (PLBT) is one important member of Si-photo electronic negative resistance devices. It has wide applications in photo-electronic coupler, light detector, light sensor and other photo-electronic circuit modules, which is significant for the further study of photo-electronic devices and circuits. When the Si-photo-electronic negative transistor device works as a load, it has two stable output states (bistability characteristics) with the change of the input light signals. Using the photo-bistable and self-locking characteristics of the PLBT, a photo-controlled Bistable Logic Circuit Element has been set up successfully. Through detail studying and analyzing to the operation feature and load feature of the photo-controlled bistable circuit, the nonlinear characteristic of the circuit is demonstrated. Furthermore the applications of this circuit element have been studied and verified.

  6. Antimicrobial-resistant Gram-negative bacteria in febrile neutropenic patients with cancer: current epidemiology and clinical impact.

    Science.gov (United States)

    Trecarichi, Enrico M; Tumbarello, Mario

    2014-04-01

    In the recent years, several studies involving cancer patients have demonstrated a clear trend in the epidemiology of bacterial infections showing a shift in the prevalence from Gram-positive to Gram-negative bacteria and the extensive emergence of antimicrobial-resistant strains among Gram-negatives isolated from the blood. The aim of this systematic review was to examine the recent trends in epidemiology and antimicrobial resistance in Gram-negatives recovered from neutropenic cancer patients, with particular emphasis on the impact of antimicrobial resistance on the clinical outcome of severe infections caused by such microorganisms. Overall, from 2007 to date, the rate of Gram-negative bacteria recovery ranged from 24.7 to 75.8% (mean 51.3%) in cancer patient cohorts. Escherichia coli represented the most common species (mean frequency of isolation 32.1%) among the Gram-negatives, followed by Pseudomonas aeruginosa (mean frequency of isolation 20.1%). An increasing frequency of Acinetobacter spp. and Stenotrophomonas maltophilia was also reported. Increased rates of multidrug-resistant Gram-negative strains have been highlighted among Enterobacteriaceae and nonfermenting Gram-negative rods, despite discontinuation of fluoroquinolone-based antibacterial prophylaxis for neutropenic patients. In addition, antimicrobial resistance and/or the inadequacy of empirical antibiotic treatment have been frequently linked to a worse outcome in cancer patients with bloodstream infections caused by Gram-negative isolates. Sound knowledge of the local distribution of pathogens and their susceptibility patterns and prompt initiation of effective antimicrobial treatment for severe infections caused by Gram-negative bacteria are essential in cancer patients.

  7. Multi-drug resistance and extended spectrum beta lactamase producing Gram negative bacteria from chicken meat in Bharatpur Metropolitan, Nepal.

    Science.gov (United States)

    Shrestha, Anil; Bajracharya, Anup Muni; Subedi, Hemraj; Turha, Raju Shah; Kafle, Sachin; Sharma, Saroj; Neupane, Sunil; Chaudhary, Dhiraj Kumar

    2017-11-07

    Multidrug resistance (MDR) and extended spectrum beta lactamase (ESBL) producer Gram negative bacteria are considered as a major health problem, globally. ESBL enzyme hydrolyses the beta lactam ring of third generation cephalosporins, which alters the structure of the antibiotic. Due to the modification in structure of the antibiotic, bacteria show resistance to these antibiotics. Resistant bacterial strains are transmitted to humans from animals through consumption of uncooked meat, through contact with uncooked meat and meat surfaces. This study aims to assess bacteriological profile and analyze the situation of antibiotic resistance, multidrug resistance, and ESBL producing Gram negative bacteria in chicken meat. A total of 38 chicken meat samples were studied in which 103 Gram negative bacteria were isolated. Species of Gram negative bacteria were identified as Citrobacter spp. (44.7%), Salmonella spp. (26.2%), Proteus spp. (18.4%), Escherichia coli (4.8%), Shigella spp. (3.9%), Pseudomonas spp. (1.9%), and Klebsiella spp. (1.0%). The prevalence of MDR isolates was found to be 79.6%. Total ESBL producer was 36.9% and ESBL producer among MDR was 34.9%. This concludes wide range of antibiotic resistance bacteria is prevalent in raw chicken meat.

  8. Antimicrobial resistance pattern of Gram –negative bacilli isolated of Vali-Asr Hospital wards in Arak

    Directory of Open Access Journals (Sweden)

    Farshid Didgar

    2014-11-01

    Full Text Available Background: Infectious diseases are of the most important causes of mortality all around the world particular in developing countries. Recently, the most important thing that has worried medical society is antibiotic resistance. Multi-resistant gram_negative rods are important pathogens in hospitals, causing high rate of mortality.The main goal of this study was to investigate the antimicrobial resistance patterns among common gram-negative bacilli isolated from patients of Vali-Asr Hospital. Material and Methods: This is a cross-sectional descriptive study conducted between the years 2010-2012 in Vali-Asr hospital in Arak. In this study 1120 specimen were examined. Bacterial strains were isolated by conventional methods from various clinical samples of patients including: blood, urine, wound, sputum, CSF, andetc.All isolates were examined for antimicrobial resistance using disc diffusion method. Results: In this study 737 specimen were positive cultures. A total of 332 isolates of Gram-negative bacilli were identified. The most frequent gram negative bacteria were isolated from urine, wound, blood, respiratory secretion and catheter. The most frequent pathogens were E.coli followed by k.pneumonia, entrobacter, p.oaeruginosa, Acinetobacter spp, citrobacter and proteus. High rate of resistance to third generation of cephalospoins & carbapenems observed amang isolates of Acintobacter spp.Prodution of extended spectrum beralactamases (ESBLS was found in 51.4% of all Gram negative bacteria. Conclusion: Antibiotic resistance, particularly multi-drug resistance is frequent among microorganisms of ValiAsr Hospital. Resistance in our country, like other countries have been shown to be increased, so it is highly recommended to prohibit unnecessary prescription of antibiotics.

  9. Predicting Multidrug-Resistant Gram-Negative Bacterial Colonization and Associated Infection on Hospital Admission.

    Science.gov (United States)

    Tseng, Wen-Pin; Chen, Yee-Chun; Yang, Bey-Jing; Chen, Shang-Yu; Lin, Jr-Jiun; Huang, Ya-Huei; Fu, Chia-Ming; Chang, Shan-Chwen; Chen, Shey-Ying

    2017-10-01

    OBJECTIVE Isolation of multidrug-resistant gram-negative bacteria (MDR-GNB) from patients in the community has been increasingly observed. A prediction model for MDR-GNB colonization and infection risk stratification on hospital admission is needed to improve patient care. METHODS A 2-stage, prospective study was performed with 995 and 998 emergency department patients enrolled, respectively. MDR-GNB colonization was defined as isolates resistant to 3 or more classes of antibiotics, identified in either the surveillance or early (≤48 hours) clinical cultures. RESULTS A score-assigned MDR-GNB colonization prediction model was developed and validated using clinical and microbiological data from 995 patients enrolled in the first stage of the study; 122 of these patients (12.3%) were MDR-GNB colonized. We identified 5 independent predictors: age>70 years (odds ratio [OR], 1.84 [95% confidence interval (CI), 1.06-3.17]; 1 point), assigned point value in the model), residence in a long-term-care facility (OR, 3.64 [95% CI, 1.57-8.43); 3 points), history of cerebrovascular accidents (OR, 2.23 [95% CI, 1.24-4.01]; 2 points), hospitalization within 1 month (OR, 2.63 [95% CI, 1.39-4.96]; 2 points), and recent antibiotic exposure (OR, 2.18 [95% CI, 1.16-4.11]; 2 points). The model displayed good discrimination in the derivation and validation sets (area under ROC curve, 0.75 and 0.80, respectively) with the best cutoffs ofhospitalization between low- and high-risk groups (probability, 0.02 vs 0.12, respectively; log-rank test, P<.001). CONCLUSION A model was developed to optimize both the decision to initiate antimicrobial therapy and the infection control interventions to mitigate threats from MDR-GNB. Infect Control Hosp Epidemiol 2017;38:1216-1225.

  10. Peripheral Immune Cell Populations Associated with Cognitive Deficits and Negative Symptoms of Treatment-Resistant Schizophrenia.

    Directory of Open Access Journals (Sweden)

    Emilio Fernandez-Egea

    Full Text Available Hypothetically, psychotic disorders could be caused or conditioned by immunological mechanisms. If so, one might expect there to be peripheral immune system phenotypes that are measurable in blood cells as biomarkers of psychotic states.We used multi-parameter flow cytometry of venous blood to quantify and determine the activation state of 73 immune cell subsets for 18 patients with chronic schizophrenia (17 treated with clozapine, and 18 healthy volunteers matched for age, sex, BMI and smoking. We used multivariate methods (partial least squares to reduce dimensionality and define populations of differentially co-expressed cell counts in the cases compared to controls.Schizophrenia cases had increased relative numbers of NK cells, naïve B cells, CXCR5+ memory T cells and classical monocytes; and decreased numbers of dendritic cells (DC, HLA-DR+ regulatory T-cells (Tregs, and CD4+ memory T cells. Likewise, within the patient group, more severe negative and cognitive symptoms were associated with decreased relative numbers of dendritic cells, HLA-DR+ Tregs, and CD4+ memory T cells. Motivated by the importance of central nervous system dopamine signalling for psychosis, we measured dopamine receptor gene expression in separated CD4+ cells. Expression of the dopamine D3 (DRD3 receptor was significantly increased in clozapine-treated schizophrenia and covaried significantly with differentiated T cell classes in the CD4+ lineage.Peripheral immune cell populations and dopaminergic signalling are disrupted in clozapine-treated schizophrenia. Immuno-phenotypes may provide peripherally accessible and mechanistically specific biomarkers of residual cognitive and negative symptoms in this treatment-resistant subgroup of patients.

  11. Negative mental imagery in public speaking anxiety: Forming cognitive resistance by taxing visuospatial working memory.

    Science.gov (United States)

    Homer, Sophie R; Deeprose, Catherine; Andrade, Jackie

    2016-03-01

    This study sought to reconcile two lines of research. Previous studies have identified a prevalent and causal role of negative imagery in social phobia and public speaking anxiety; others have demonstrated that lateral eye movements during visualisation of imagery reduce its vividness, most likely by loading the visuospatial sketchpad of working memory. It was hypothesised that using eye movements to reduce the intensity of negative imagery associated with public speaking may reduce anxiety resulting from imagining a public speaking scenario compared to an auditory control task. Forty undergraduate students scoring high in anxiety on the Personal Report of Confidence as a Speaker scale took part. A semi-structured interview established an image that represented the participant's public speaking anxiety, which was then visualised during an eye movement task or a matched auditory task. Reactions to imagining a hypothetical but realistic public speaking scenario were measured. As hypothesised, representative imagery was established and reduced in vividness more effectively by the eye movement task than the auditory task. The public speaking scenario was then visualised less vividly and generated less anxiety when imagined after performing the eye movement task than after the auditory task. Self-report measures and a hypothetical scenario rather than actual public speaking were used. Replication is required in larger as well as clinical samples. Visuospatial working memory tasks may preferentially reduce anxiety associated with personal images of feared events, and thus provide cognitive resistance which reduces emotional reactions to imagined, and potentially real-life future stressful experiences. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Clinical Effectiveness and Nephrotoxicity of Aerosolized Colistin Treatment in Multidrug-Resistant Gram-Negative Pneumonia

    Directory of Open Access Journals (Sweden)

    Seung Yong Park

    2016-08-01

    Full Text Available Background: Colistin (polymyxin E is active against multidrug-resistant Gram-negative bacteria (MDR-GNB. However, the effectiveness of inhaled colistin is unclear. This study was designed to assess the effectiveness and safety of aerosolized colistin for the treatment of ventilator-associated pneumonia (VAP caused by MDR-GNB. Methods: In this retrospective longitudinal study, we evaluated the medical records of 63 patients who received aerosolized colistin treatment for VAP caused by MDR-GNB in the medical intensive care unit (MICU from February 2012 to March 2014. Results: A total of 25 patients with VAP caused by MDR-GNB were included in this study. The negative conversion rate was 84.6% after treatment, and acute kidney injury (AKI occurred in 11 patients (44%, AKI group. The average length of MICU stay and colistin treatment-related factors, such as daily and total cumulative doses and administration period, were not significantly different between groups. In-hospital mortality tended to be higher in the AKI group (p = 0.07. Multivariate analysis showed that a body mass index less than 18 was an independent risk factor of mortality (odds ratio [OR] = 21.95, 95% confidence interval [CI] 1.59-302.23; p = 0.02. Notably, AKI occurrence was closely related to the administration of more than two nephrotoxic drugs combined with aerosolized colistin (OR = 15.03, 95% CI 1.40-161.76; p = 0.025 and septic shock (OR = 8.10, 95% CI 1.40-161.76; p = 0.04. Conclusions: The use of adjunctive aerosolized colistin treatment appears to be a relatively safe and effective option for the treatment of VAP caused by MDR-GNB. However, more research on the concomitant use of nephrotoxic drugs with aerosolized colistin will be necessary, as this can be an important risk factor of development of AKI.

  13. Antimicrobial resistance and virulence characterization of Staphylococcus aureus and coagulase-negative staphylococci from imported beef meat.

    Science.gov (United States)

    Osman, Kamelia; Alvarez-Ordóñez, Avelino; Ruiz, Lorena; Badr, Jihan; ElHofy, Fatma; Al-Maary, Khalid S; Moussa, Ihab M I; Hessain, Ashgan M; Orabi, Ahmed; Saad, Alaa; Elhadidy, Mohamed

    2017-05-10

    The objectives of this study were to characterize the diversity and magnitude of antimicrobial resistance among Staphylococcus species recovered from imported beef meat sold in the Egyptian market and the potential mechanisms underlying the antimicrobial resistance phenotypes including harboring of resistance genes (mecA, cfr, gyrA, gyrB, and grlA) and biofilm formation. The resistance gene mecA was detected in 50% of methicillin-resistant non-Staphylococcus aureus isolates (4/8). Interestingly, our results showed that: (i) resistance genes mecA, gyrA, gyrB, grlA, and cfr were absent in Staphylococcus hominis and Staphylococcus hemolyticus isolates, although S. hominis was phenotypically resistant to methicillin (MR-non-S. aureus) while S. hemolyticus was resistant to vancomycin only; (ii) S. aureus isolates did not carry the mecA gene (100%) and were phenotypically characterized as methicillin- susceptible S. aureus (MSS); and (iii) the resistance gene mecA was present in one isolate (1/3) of Staphylococcus lugdunensis that was phenotypically characterized as methicillin-susceptible non-S. aureus (MSNSA). Our findings highlight the potential risk for consumers, in the absence of actionable risk management information systems, of imported foods and advice a strict implementation of international standards by different venues such as CODEX to avoid the increase in prevalence of coagulase positive and coagulase negative Staphylococcus isolates and their antibiotic resistance genes in imported beef meat at the Egyptian market.

  14. Use of Triplex PCR for Rapid Detection of PVL and Differentiation of MRSA from Methicillin Resistant Coagulase Negative Staphylococci

    OpenAIRE

    Abimanyu, Nagarajan; Krishnan, Arunkumar; Murugesan, Saravanan; Subramanian G, Kaushik; Gurumurthy, Sivakumar; Krishnan, Padma

    2013-01-01

    Introduction: Methicillin-Resistant Staphylococcus aureus (MRSA) has become a major public health problem in both hospitals and communities. Panton – Valentine Leucocidin (PVL) has been reported to be an important marker for the highly pathogenic community acquired S. aureus infections. A rapid detection of these MRSA is very important for its treatment. The specific detection of MRSA is always a problem due to the prevalence of methicillin resistance among the coagulase negative Staphylococc...

  15. Development and transmission of antimicrobial resistance among Gram-negative bacteria in animals and their public health impact.

    Science.gov (United States)

    Mukerji, Shewli; O'Dea, Mark; Barton, Mary; Kirkwood, Roy; Lee, Terence; Abraham, Sam

    2017-02-28

    Gram-negative bacteria are known to cause severe infections in both humans and animals. Antimicrobial resistance (AMR) in Gram-negative bacteria is a major challenge in the treatment of clinical infections globally due to the propensity of these organisms to rapidly develop resistance against antimicrobials in use. In addition, Gram-negative bacteria possess highly efficient mechanisms through which the AMR can be disseminated between pathogenic and commensal bacteria of the same or different species. These unique traits of Gram-negative bacteria have resulted in evolution of Gram-negative bacterial strains demonstrating resistance to multiple classes of antimicrobials. The evergrowing resistance issue has not only resulted in limitation of treatment options but also led to increased treatment costs and mortality rates in humans and animals. With few or no new antimicrobials in production to combat severe life-threatening infections, AMR has been described as the one of the most severe, long-term threats to human health. Aside from overuse and misuse of antimicrobials in humans, another factor that has exacerbated the emergence of AMR in Gram-negative bacteria is the veterinary use of antimicrobials that belong to the same classes considered to be critically important for treating serious life-threatening infections in humans. Despite the fact that development of AMR dates back to before the introduction of antimicrobials, the recent surge in the resistance towards all available critically important antimicrobials has emerged as a major public health issue. This review thus focuses on discussing the development, transmission and public health impact of AMR in Gram-negative bacteria in animals. © 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  16. Immunogenomics for identification of disease resistance genes in pigs: a review focusing on Gram-negative bacilli

    Directory of Open Access Journals (Sweden)

    Zhao Shuhong

    2012-11-01

    Full Text Available Abstract Over the past years, infectious disease has caused enormous economic loss in pig industry. Among the pathogens, gram negative bacteria not only cause inflammation, but also cause different diseases and make the pigs more susceptible to virus infection. Vaccination, medication and elimination of sick pigs are major strategies of controlling disease. Genetic methods, such as selection of disease resistance in the pig, have not been widely used. Recently, the completion of the porcine whole genome sequencing has provided powerful tools to identify the genome regions that harboring genes controlling disease or immunity. Immunogenomics, which combines DNA variations, transcriptome, immune response, and QTL mapping data to illustrate the interactions between pathogen and host immune system, will be an effective genomics tool for identification of disease resistance genes in pigs. These genes will be potential targets for disease resistance in breeding programs. This paper reviewed the progress of disease resistance study in the pig focusing on Gram-negative bacilli. Major porcine Gram-negative bacilli and diseases, suggested candidate genes/pathways against porcine Gram-negative bacilli, and distributions of QTLs for immune capacity on pig chromosomes were summarized. Some tools for immunogenomics research were described. We conclude that integration of sequencing, whole genome associations, functional genomics studies, and immune response information is necessary to illustrate molecular mechanisms and key genes in disease resistance.

  17. Controversies in guidelines for the control of multidrug-resistant Gram-negative bacteria in EU countries.

    Science.gov (United States)

    Otter, J A; Mutters, N T; Tacconelli, E; Gikas, A; Holmes, A H

    2015-12-01

    The various guidelines that are available for multidrug-resistant Gram-negative bacteria are useful, and contain broad areas of agreement. However, there are also important areas of controversy between the guidelines in terms of the details of applying contact precautions, single-room isolation and active surveillance cultures, differences in the approach to environmental cleaning and disinfection, and whether or not to perform staff and patient cohorting, healthcare worker screening or patient decolonization. The evidence-base is extremely limited and further research is urgently required to inform an evidence-based approach to multidrug-resistant Gram-negative bacteria prevention and control. Copyright © 2015. Published by Elsevier Ltd.

  18. Enhancement of superconductivity in NbN nanowires by negative electron-beam lithography with positive resist

    Science.gov (United States)

    Charaev, I.; Silbernagel, T.; Bachowsky, B.; Kuzmin, A.; Doerner, S.; Ilin, K.; Semenov, A.; Roditchev, D.; Vodolazov, D. Yu.; Siegel, M.

    2017-08-01

    We performed comparative experimental investigation of superconducting NbN nanowires which were prepared by means of positive- and negative electron-beam lithography with the same positive tone Poly-methyl-methacrylate (PMMA) resist. We show that nanowires with a thickness 4.9 nm and widths less than 100 nm demonstrate at 4.2 K higher critical temperature and higher density of critical and retrapping currents when they are prepared by negative lithography. Also the ratio of the experimental critical current to the depairing critical current is larger for nanowires prepared by negative lithography. We associate the observed enhancement of superconducting properties with the difference in the degree of damage that nanowire edges sustain in the lithographic process. A whole range of advantages which is offered by the negative lithography with positive PMMA resist ensures high potential of this technology for improving the performance metrics of superconducting nanowire singe-photon detectors.

  19. New Formation Technology of Plasma Display Panel Barrier-Rib Structure Using Silicone Rubber Mold Transferred from SU-8 Master Structure

    Science.gov (United States)

    Son, Seung-Hyun; Park, Yong-Suk; Choi, Sie-Young

    2002-06-01

    A new formation technology for a plasma display panel (PDP) barrier-rib structure is presented to realize a barrier rib with a high aspect ratio and reduce the manufacturing cost. In this study, we used an SU-8 50 photoresist, which is sensitive to UV irradiation, instead of polymethylmethacrylate (PMMA) which is sensitive to X-ray irradiation, so that the silicone rubber mold could be applicable to a large-area PDP. The first step is to produce an SU-8 master structure using amorphous silicon as an adhesion layer between a glass substrate and SU-8 photoresist. Second, a precise soft mold is manufactured for mass replication of the PDP barrier-rib construction, by molding liquid silicone rubber onto the glass substrate with lithographically defined SU-8 master structures. Third, a PDP barrier-rib structure is formed using the pattern-transferring process with a reusable silicone rubber mold. This is a very simple and inexpensive process consisting with printing of barrier-rib paste, drying, pattern-transferring, and sintering. The pattern-transferring process with a soft mold also demonstrates that the disadvantages of the conventional mold pressing process with a hard mold can be overcome. Consequently, by using the pattern-transferring process with the silicone rubber mold transferred from the SU-8 master structure, the desired barrier-rib shapes can be realized with a high aspect ratio and various dimensions.

  20. First principles design of divacancy defected graphene nanoribbon based rectifying and negative differential resistance device

    Directory of Open Access Journals (Sweden)

    Soubhik Chakrabarty

    2015-08-01

    Full Text Available We have studied using density functional theory and non-equilibrium Green’s function based approach, the electronic structures of 555-777 divacancy (DV defected armchair edged graphene nanoribbons (AGNR as well as the transport properties of AGNR based two-terminal devices constructed with one defected electrode and one N doped electrode. Introduction of 555-777 DV defect into AGNR results in shifting of the π and π∗ bands towards the higher energy value indicating a downward shift of the Fermi level. Formation of a potential barrier, analogous to that of conventional p-n junction, has been observed across the junction of defected and N-doped AGNR. The two terminal devices show diode like property with high rectifying efficiency for a wide range of bias voltages. The devices also show robust negative differential resistance with very high peak-to-valley ratio. Shift of the electrode energy states and modification of the transmission function with applied bias have been analyzed, in order to gain an insight into the nonlinear and asymmetric behavior of the current-voltage characteristics. Variation of the transport properties on the width of the ribbons has also been discussed.

  1. Tunable negative differential resistance in planar graphene superlattice resonant tunneling diode

    Science.gov (United States)

    Sattari-Esfahlan, S. M.; Fouladi-Oskuei, J.; Shojaei, S.

    2017-04-01

    Here, we study the negative differential resistance (NDR) of Dirac electrons in biased planar graphene superlattice (PGSL) and investigate the transport characteristics by adopted transfer matrix method within Landauer-Buttiker formalism. Our model device is based on one-dimensional Kronig-Penney type electrostatic potential in monolayer graphene deposited on a substrate, where the bias voltage is applied by two electrodes in the left and right. At Low bias voltages, we found that NDR appears due to breaking of minibands to Wannier-Stark ladders (WSLs). At the critical bias voltage, delocalization appeared by WS states leads to tunneling peak current in current-voltage (I-V) characteristics. With increasing bias voltage, crossing of rungs from various WSL results in multi-peak NDR. The results demonstrate that the structure parameters like barrier/well thickness and barrier height have remarkable effect on I-V characteristics of PGSL. In addition, Dirac gap enhances peak to valley (PVR) value due to suppressing Klein tunneling. Our results show that the tunable PVR in PGSL resonant tunneling diode can be achievable by structure parameters engineering. NDR at ultra-low bias voltages, such as 100 mV, with giant PVR of 20 is obtained. In our device, the multiple same NDR peaks with ultra-low bias voltage provide promising prospect for multi-valued memories and the low power nanoelectronic tunneling devices.

  2. The negative-differential-resistance (NDR) mechanism of a hydroelastic microfluidic oscillator

    Science.gov (United States)

    Xia, H. M.; Wu, J. W.; Wang, Z. P.

    2017-07-01

    A microfluidic oscillator is of interest because it converts a stable laminar flow to oscillatory flow, especially in view of the fact that turbulence is typically absent in miniaturized fluidic devices. One important design approach is to utilize hydroelastic effect-induced autonomous oscillations to modify the flow, so to reduce the reliance on external controllers. However, as complex fluid-structure interactions are involved, the prediction of its mechanism is rather challenging. Here, we present a simple equivalent circuit model and investigate the negative-differential-resistance (NDR) mechanism of a hydroelastic microfluidic oscillator. We show that a variety of complex flow behaviors including the onset of oscillation, formation of different oscillation patterns, collapse of the channel, etc can be well explained by this model. It provides a generic approach for construction of microfluidic NDR oscillators, following which a new design is also proposed. Relevant findings give more insights into the hydroelastic instability problems in microfluidics, and enrich the study of microfluidic flow control devices based on the electric circuit theory.

  3. Investigation on nickel ferrite nanowire device exhibiting negative differential resistance — a first-principles investigation

    Directory of Open Access Journals (Sweden)

    V. Nagarajan

    2017-06-01

    Full Text Available The electronic property of NiFe_2O_4 nanowire device is investigated through nonequilibrium Green’s functions (NEGF in combination with density functional theory (DFT. The electronic transport properties of NiFe_2O_4 nanowire are studied in terms of density of states, transmission spectrum and I–V characteristics. The density of states gets modified with the applied bias voltage across NiFe_2O_4 nanowire device, the density of charge is observed both in the valence band and in the conduction band on increasing the bias voltage. The transmission spectrum of NiFe_2O_4 nanowire device gives the insights on the transition of electrons at different energy intervals. The findings of the present work suggest that NiFe_2O_4 nanowire device can be used as negative differential resistance (NDR device and its NDR property can be tuned with the bias voltage, which may be used in microwave device, memory devices and in fast switching devices.

  4. Room temperature negative differential resistance in terahertz quantum cascade laser structures

    Energy Technology Data Exchange (ETDEWEB)

    Albo, Asaf, E-mail: asafalbo@gmail.com; Hu, Qing [Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Reno, John L. [Center for Integrated Nanotechnologies, Sandia National Laboratories, MS 1303, Albuquerque, New Mexico 87185-1303 (United States)

    2016-08-22

    The mechanisms that limit the temperature performance of GaAs/Al{sub 0.15}GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding, we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. This result is a strong evidence for the effective suppression of the aforementioned leakage channel.

  5. Carbon-doping-induced negative differential resistance in armchair phosphorene nanoribbons

    Science.gov (United States)

    Guo, Caixia; Xia, Congxin; Wang, Tianxing; Liu, Yufang

    2017-03-01

    By using a combined method of density functional theory and non-equilibrium Green’s function formalism, we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons (APNRs). The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal. Meanwhile, obvious negative differential resistance (NDR) behaviors are obtained by tuning the doping position and concentration. In particular, with reducing doping concentration, NDR peak position can enter into mV bias range. These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs. Project supported by the National Natural Science Foundation of China (No. 11274096), the University Science and Technology Innovation Team Support Project of Henan Province (No. 13IRTSTHN016), the University key Science Research Project of Henan Province (No.16A140043). The calculation about this work was supported by the High Performance Computing Center of Henan Normal University.

  6. Bacteremia and resistant gram-negative pathogens among under-fives in Tanzania.

    Science.gov (United States)

    Christopher, Alexandra; Mshana, Stephen E; Kidenya, Benson R; Hokororo, Aldofineh; Morona, Domenica

    2013-05-08

    Antibiotic resistance is one of the most serious public health concerns worldwide and is increasing at an alarming rate, making daily treatment decisions more challenging. This study is aimed at identifying local bacterial isolates and their antimicrobial susceptibility patterns to avoid irrational antibiotic use, especially in settings where unguided management occurs and febrile illnesses are predominant. A hospital-based prospective cross-sectional study was conducted from September 2011 to February 2012. Febrile children were serially recruited and demographic and clinical data were collected using a standardized data collection tool. A blood culture was performed and identification of the isolates was undertaken using in-house biochemical tests. Susceptibility to common antibiotics was investigated using the disc diffusion methods. Of the 1081 children admitted during the study period, 317 (29.3%) met the inclusion criteria and were recruited, of whom 195 (61.5%) and 122 (38.5%) were male and female respectively. The median age was 18 months with an interquartile range of 9 to 36 months. Of the 317 children, 251 (79.2%) were below or equal to 36 months of age. The prevalence of bacteremia was 6.6%. A higher prevalence of bacteraemia was observed in children below 36 months than in those ≥ 36 months (7.5% vs. 3.0%, p = 0.001). Predictors of bacteraemia were an axillary temperature of >38.5 °C (OR =7, 95% CI = 2.2 - 14.8, p-value = 0.0001), a positive malaria slide (OR =5, 95% CI = 3.0 - 21.2, p-value = 0.0001) and a high neutrophils' count (OR =21 95% CI = 5.6 - 84, p-value = 0.0001). Escherichia coli and Klebsiella pneumoniae accounted for 7 (33.3%) and 6 (28.6%) of all the isolates respectively. Others gram-negatives bacteria were Citrobacter spp 2 (9.5%), Enterobacter spp 1 (4.25%), Pseudomonas spp 2 (9.5%), Proteus spp 1 (4.25%) and Salmonella spp 1 (4.25%). These isolates were highly resistant to ampicillin (95%), co

  7. Genetic Diversity and Antibiotic Resistance Among Coagulase-Negative Staphylococci Recovered from Birds of Prey in Portugal.

    Science.gov (United States)

    Sousa, Margarida; Silva, Nuno; Igrejas, Gilberto; Sargo, Roberto; Benito, Daniel; Gómez, Paula; Lozano, Carmen; Manageiro, Vera; Torres, Carmen; Caniça, Manuela; Poeta, Patrícia

    2016-12-01

    Wild animal populations in contact with antimicrobials and antimicrobial resistant bacteria that are daily released into the environment are able to become unintentional hosts of these resistant microorganisms. To clarify this issue, our study evaluated the presence of antibiotic resistance determinants on coagulase-negative staphylococci recovered from birds of prey and studied their genetic relatedness by pulsed-field gel electrophoresis (PFGE). The unusual vga(A) and erm(T) genes, which confer resistance to clindamycin and erythromycin, respectively, were detected in Staphylococcus sciuri or Staphylococcus xylosus strains and the tet(K) gene in Staphylococcus kloosii. The PFGE patterns showed that three S. xylosus (isolated of Strix aluco and Otus scops) and two S. sciuri (recovered from Strix aluco and Milvus migrans) were clonally indistinguishable. These animals could be a source of unusual antimicrobial resistance determinants for highly used antibiotics in veterinary clinical practice.

  8. Phenotypic and Molecular Antibiotic Resistance Determination of Airborne Coagulase Negative Staphylococcus spp. Strains from Healthcare Facilities in Southern Poland.

    Science.gov (United States)

    Lenart-Boroń, Anna; Wolny-Koładka, Katarzyna; Stec, Joanna; Kasprowic, Andrzej

    2016-10-01

    This study assessed the antimicrobial resistance of airborne Staphylococcus spp. strains isolated from healthcare facilities in southern Poland. A total of 55 isolates, belonging to 10 coagulase-negative staphylococci (CoNS) species, isolated from 10 healthcare facilities (including hospitals and outpatient units) were included in the analysis. The most frequently identified species were Staphylococcus saprophyticus and Staphylococcus warneri, which belong to normal human skin flora, but can also be the cause of common and even severe nosocomial infections. Disk diffusion tests showed that the bacterial strains were most frequently resistant to erythromycin and tetracycline and only 18% of strains were susceptible to all tested antimicrobials. Polymerase chain reaction amplification of specific gene regions was used to determine the presence of the Macrolide-Lincosamide-Streptogramin resistance mechanisms in CoNS. The molecular analysis, conducted using specific primer pairs, identified the msrA1 gene, encoding active efflux pumps in bacterial cells, as the most frequent resistance gene. As many as seven antibiotic resistance genes were found in one isolate, whereas the most common number of resistance genes per isolate was five (n = 17). It may be concluded that drug resistance was widely spread among the tested strains, but the resulting antimicrobial resistance profile indicates that in the case of infection, the use of antibiotics from the basic antibiogram group will be effective in therapy. However, before administering treatment, determination of the specific antimicrobial resistance should be conducted, particularly in the case of hospitalized patients.

  9. Organic and conventional fruits and vegetables contain equivalent counts of Gram-negative bacteria expressing resistance to antibacterial agents.

    Science.gov (United States)

    Ruimy, Raymond; Brisabois, Anne; Bernede, Claire; Skurnik, David; Barnat, Saïda; Arlet, Guillaume; Momcilovic, Sonia; Elbaz, Sandrine; Moury, Frédérique; Vibet, Marie-Anne; Courvalin, Patrice; Guillemot, Didier; Andremont, Antoine

    2010-03-01

    Resistance to antibiotics is a major public health problem which might culminate in outbreaks caused by pathogenic bacteria untreatable by known antibiotics. Most of the genes conferring resistance are acquired horizontally from already resistant commensal or environmental bacteria. Food contamination by resistant bacteria might be a significant source of resistance genes for human bacteria but has never been precisely assessed, nor is it known whether organic products differ in this respect from conventionally produced products. We showed here, on a large year-long constructed sample set containing 399 products that, irrespective of their mode of production, raw fruits and vegetables are heavily contaminated by Gram-negative bacteria (GNB) resistant to multiple antibiotics. Most of these bacteria originate in the soil and environment. We focused on non-oxidative GNB resistant to third-generation cephalosporins, because of their potential impact on human health. Among them, species potentially pathogenic for immunocompetent hosts were rare. Of the products tested, 13% carried bacteria producing extended-spectrum beta-lactamases, all identified as Rahnella sp. which grouped into two phylotypes and all carrying the bla(RAHN) gene. Thus, both organic and conventional fruits and vegetables may constitute significant sources of resistant bacteria and of resistance genes.

  10. Epidemiology of multi-resistance Gram negative pathogen circulating in Liguria and molecular characterization of different carbapenemases

    Directory of Open Access Journals (Sweden)

    Erika Coppo

    2011-06-01

    Full Text Available This study was conducted during January-April 2010 with the collaboration of 7 clinical microbiology laboratories evenly distributed across the Ligurian area to identify the most frequent Gram negative species and to evaluate their antibiotic susceptibility patterns Overall, 110 consecutive multi-resistant non duplicate Gram negative isolates,were collected and sent to the coordinating laboratory (Sezione di Microbiologia del DISC, University of Genoa, Italy together with susceptibility data obtained by routine methods. In addition, strains resistant to carbapenems were characterized by PCR. A total of 110 Gram negative multi-resistance strains were found, including 74 and 36 isolated from healthcare or nosocomial settings and community acquired infections, respectively. The most represented pathogens were: A. baumannii (38, 34.5%, E. coli (30, 27.2%, P. aeruginosa (29, 26.3%, K. pneumoniae (9, 8.2% and P. mirabilis (4, 3.6%. A. baumannii were more frequently collected from healthcare settings or nosocomial samples, while the other strains were generally equally isolated from in- and out-patients. Amikacin was the most active molecule against E. coli and P. mirabilis (96,7% and 100% of susceptible stains respectively. Colistin was the only active molecule agains A. baumanii and P. aeruginosa (100% of susceptible strains. Against K. pneumoniae tigecycline and colistin were the most active molecules (100% of susceptible strains. Imipenem was the most active compound against E. coli and P. mirabilis (100% of susceptible strains. A large number (97.4% of A. baumannii was resistant to imipenem. K. pneumoniae and P. aeruginosa showed rates of resistance of 88% and 34.4% respectively. A. baumannii, K. pneumoniae and P. aeruginosa isolates resistant to Imipenem, carried OXA-23, KPC and VIM carbapenemases.These data shown a significant spread of multidrug-resistant Gram negative bacteria in hospitals and in communities.The production of carbapenemase in

  11. Aminoglycoside resistance rates, phenotypes, and mechanisms of Gram-negative bacteria from infected patients in upper Egypt.

    Directory of Open Access Journals (Sweden)

    Gamal F Gad

    Full Text Available With the re-emergence of older antibiotics as valuable choices for treatment of serious infections, we studied the aminoglycoside resistance of Gram-negative bacteria isolated from patients with ear, urinary tract, skin, and gastrointestinal tract infections at Minia university hospital in Egypt. Escherichia coli (mainly from urinary tract and gastrointestinal tract infections was the most prevalent isolate (28.57%, followed by Pseudomonas aeruginosa (25.7% (mainly from ear discharge and skin infections. Isolates exhibited maximal resistance against streptomycin (83.4%, and minimal resistance against amikacin (17.7% and intermediate degrees of resistance against neomycin, kanamycin, gentamicin, and tobramycin. Resistance to older aminoglycosides was higher than newer aminoglycosides. The most common aminoglycoside resistance phenotype was that of streptomycin resistance, present as a single phenotype or in combination, followed by kanamycin-neomycin as determined by interpretative reading. The resistant Pseudomonas aeruginosa strains were capable of producing aminoglycoside-modifying enzymes and using efflux as mechanisms of resistance. Using checkerboard titration method, the most frequently-observed outcome in combinations of aminoglycosides with β-lactams or quinolones was synergism. The most effective combination was amikacin with ciprofloxacin (100% Synergism, whereas the least effective combination was gentamicin with amoxicillin (53.3% Synergistic, 26.7% additive, and 20% indifferent FIC indices. Whereas the studied combinations were additive and indifferent against few of the tested strains, antagonism was never observed. The high resistance rates to aminoglycosides exhibited by Gram-negative bacteria in this study could be attributed to the selective pressure of aminoglycoside usage which could be controlled by successful implementation of infection control measures.

  12. Performance improvement of InAs/GaSb strained layer superlattice detectors by reducing surface leakage currents with SU-8 passivation

    Science.gov (United States)

    Kim, H. S.; Plis, E.; Khoshakhlagh, A.; Myers, S.; Gautam, N.; Sharma, Y. D.; Dawson, L. R.; Krishna, S.; Lee, S. J.; Noh, S. K.

    2010-01-01

    We report on SU-8 passivation for performance improvement of type-II InAs/GaSb strained layer superlattice detectors (λcut-off˜4.6 μm). Optical and electrical behavior of SU-8 passivated and unpassivated devices was compared. The dark current density was improved by four orders of magnitude for passivated single diodes at 77 K. The zero bias responsivity and detectivity at 77 K was equal to 0.9 A/W and 3.5×1012 Jones for SU-8 passivated single pixel diodes. FPA size diodes (24×24 μm2) were also fabricated and they showed responsivity and detectivity of 1.3 A/W and 3.5×1012 Jones, respectively at 77 K.

  13. Antimicrobial Resistance and Molecular Investigation of H2S-Negative Salmonella enterica subsp. enterica serovar Choleraesuis Isolates in China.

    Directory of Open Access Journals (Sweden)

    Jing Xie

    Full Text Available Salmonella enterica subsp. enterica serovar Choleraesuis is a highly invasive pathogen of swine that frequently causes serious outbreaks, in particular in Asia, and can also cause severe invasive disease in humans. In this study, 21 S. Choleraesuis isolates, detected from 21 patients with diarrhea in China between 2010 and 2011, were found to include 19 H2S-negative S. Choleraesuis isolates and two H2S-positive isolates. This is the first report of H2S-negative S. Choleraesuis isolated from humans. The majority of H2S-negative isolates exhibited high resistance to ampicillin, chloramphenicol, gentamicin, tetracycline, ticarcillin, and trimethoprim-sulfamethoxazole, but only six isolates were resistant to norfloxacin. In contrast, all of the isolates were sensitive to cephalosporins. Fifteen isolates were found to be multidrug resistant. In norfloxacin-resistant isolates, we detected mutations in the gyrA and parC genes and identified two new mutations in the parC gene. Pulsed-field gel electrophoresis (PFGE, multilocus sequence typing (MLST, and clustered regularly interspaced short palindromic repeat (CRISPR analysis were employed to investigate the genetic relatedness of H2S-negative and H2S-positive S. Choleraesuis isolates. PFGE revealed two groups, with all 19 H2S-negative S. Choleraesuis isolates belonging to Group I and H2S-positive isolates belonging to Group II. By MLST analysis, the H2S-negative isolates were all found to belong to ST68 and H2S-positive isolates belong to ST145. By CRISPR analysis, no significant differences in CRISPR 1 were detected; however, one H2S-negative isolate was found to contain three new spacers in CRISPR 2. All 19 H2S-negative isolates also possessed a frame-shift mutation at position 760 of phsA gene compared with H2S-positive isolates, which may be responsible for the H2S-negative phenotype. Moreover, the 19 H2S-negative isolates have similar PFGE patterns and same mutation site in the phsA gene, these

  14. High resistance rate against 15 different antibiotics in aerobic gram-negative bacteria isolates of cardiology intensive care unit patients

    Directory of Open Access Journals (Sweden)

    Küçükates E

    2002-01-01

    Full Text Available Aerobic gram negative bacteria were isolated and examined microbiologically from various clinical samples of 602 patients hospitalized between January 1997 and December 2000 in surgical and coronary intensive care units (ICUs. A total of 827 isolates were obtained from 602 patients. The majority of microorganisms were isolated from the respiratory tract (50.3% and blood (39.9%. Pseudomonas spp. were the most frequently isolated gram negative species (32.7%, followed by Acinetobacter spp. (24.0% and Klebsiella pneumoniae (19.4%. High resistance rates to all antibiotics studied were observed. Imipenem and meropenem were the most effective antibiotics against gram negatives.

  15. Design, numerical simulation and experimental investigation of an SU-8 microgripper based on the cascaded V-shaped electrothermal actuators

    Science.gov (United States)

    Voicu, Rodica-Cristina

    2016-10-01

    This paper presents the numerical simulation results and the experimental investigations of a polymeric microgripper designed using the cascaded V-shaped electrothermal actuators. The microgripper was simulated using electro-thermo-mechanical finite element method (FEM) based on Coventorware 2014 software in order to check the performance of the gripper. As structural material of the microgripper, the SU-8 biocompatible polymer was used during the fabrication process. The metallic micro-heaters were encapsulated in the polymeric actuation structures of the microgrippers to reduce the undesirable out-of-plane displacement of the gripper tips, to reduce the mechanical stress and to improve the thermal efficiency. Experimental testing has been performed to determine the openings of the microgripper tips as function of electrical current. A displacement of the tips of more than 50 pm can be obtained at an electrical current of around 25-26 mA. Over 27-28 mA the heaters are still working but a softening and a damaging status in the polymer were observed.

  16. Potential role of non-antibiotics (helper compounds) in the treatment of multidrug-resistant Gram-negative infections

    DEFF Research Database (Denmark)

    Martins, Marta; Dastidar, Sujata G; Fanning, Seamus

    2008-01-01

    Multidrug resistance in Gram-negative bacteria is now known to be primarily caused by overexpression of efflux pumps that extrude unrelated antibiotics from the periplasm or cytoplasm of the bacterium prior to their reaching their intended target. This review focuses on a variety of agents...

  17. New structures simultaneously harboring class 1 integron and ISCR1-linked resistance genes in multidrug-resistant Gram-negative bacteria.

    Science.gov (United States)

    Cheng, Cancan; Sun, Jingjing; Zheng, Fen; Lu, Wenting; Yang, Qiu; Rui, Yongyu

    2016-04-21

    The connection structure of class 1 integron and insertion sequence common region 1 (ISCR1) is called "complex class 1 integrons" or "complex sul1-type integrons", which is also known to be associated with many resistance genes. This structure is a powerful gene-capturing tool kit that can mobilize antibiotic resistance genes. In order to look for and study the structure among clinical multidrug-resistant (MDR) Gram-negative isolates, 63 isolates simultaneously harbored class 1 integron and ISCR1-linked resistance genes were isolated from 2309 clinical non-redundant MDR Gram-negative isolates in Nanfang Hospital in 2008-2013. The connecting regions between the class 1 integrons and ISCR1 were examined using PCR and DNA sequencing to determine the structures in these isolates. The two elements (the variable regions of the class 1 integron structures and the ISCR1-linked resistance genes) are connected in series among 63 isolates according to long-extension PCR and DNA sequencing. According to the kinds and permutations of resistance genes in the structure, 12 distinct types were identified, including 8 types that have never been described in any species. Several types of these structures are similar with the structures of other reports, but not entirely same. This study is the first to determine the structure simultaneously harboring class 1 integron and ISCR1-linked resistance genes by detecting the region connecting class 1 integrons and ISCR1 in a large number of MDR bacteria. These structures carrying various resistance genes were closely associated with multidrug resistance bacteria in Southern China.

  18. [Antimicrobial resistance in gram negative bacteria isolated from intensive care units of Colombian hospitals, WHONET 2003, 2004 and 2005].

    Science.gov (United States)

    Miranda, María Consuelo; Pérez, Federico; Zuluaga, Tania; Olivera, María del Rosario; Correa, Adriana; Reyes, Sandra Lorena; Villegas, Maria Virginia

    2006-09-01

    Surveillance systems play a key role in the detection and control of bacterial resistance. It is necessary to constantly collect information from all institutions because the mechanisms of bacterial resistance can operate in different ways between countries, cities and even in hospitals in the same area. Therefore local information is important in order to learn about bacterial behaviour and design appropriate interventions for each institution. Between January 2003 and December 2004, the Centro Internacional de Entrenamiento e Investigaciones Médicas (CIDEIM) developed a surveillance project in 10 tertiary hospitals in 6 cities of Colombia. Describe the trends of antibiotic resistance among the isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomona aeruginosa, Acinetobacter baumannii and Enterobacter cloacae, five of the most prevalent nosocomial Gram negative pathogens. The susceptibility tests were performed by automated methods in 9 hospitals and by Kirby Bauer in 1 hospital. Antibiotics with known activity against Gram negatives, according to the Clinical Laboratory Standards Institute guidelines, were selected. The laboratories performed internal and external quality controls. During the study period, the information was downloaded monthly from the databases of each microbiology laboratory and sent to CIDEIM where it was centralized in a database using the system WHONET 5.3. The high resistance rates reported especially for A. baumannii, evidenced the presence of multidrug resistant bacteria in both ICUs and wards at every studied institution. The creation of a national surveillance network to improve our capabilities to detect, follow up, and control the antibiotic resistance in Colombia is urgently needed.

  19. Exposure parameters in proton beam writing for KMPR and EPO Core negative tone photoresists

    Energy Technology Data Exchange (ETDEWEB)

    Ynsa, M.D., E-mail: m.ynsa@uam.es [Centro de Micro-Analisis de Materiales (CMAM), Universidad Autonoma de Madrid, Campus de Cantoblanco Edif. 22, Faraday 3, E-28049 Madrid (Spain); Departamento de Fisica Aplicada C-12, Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Shao, P.; Kulkarni, S.R.; Liu, N.N.; Kan, J.A. van [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore ,117542 Singapore (Singapore)

    2011-10-15

    In spite of its recent establishment, proton beam writing (PBW) has already demonstrated to be a highly competitive lithographic technique. PBW is a fast direct-write technique capable of producing high-aspect-ratio micro- and nano-structures in resist material. Typical applications can be found in nanoimprinting, biomedical research, photonics, and optics, among other fields. The progress of PBW is linked to the successful introduction of new resist materials. In this paper, KMPR and EPO Core, negative tone photoresists are tested on their compatibility with PBW. KMPR resist has similar chemical and process properties compared to SU-8. Employing UV lithography on KMPR resist, details of 30 {mu}m have been obtained in Ni, indicating a possible advantage compared to SU-8 for optical lithography . In this study, the sensitivity to MeV proton exposure and sub-micron feature sizes are presented in KMPR. PBW has been also combined with Ni electroplating in order to determine the suitability of KMPR and EPO Core resist to fabricate 3D metallic moulds and stamps.

  20. Emergence of integron borne PER-1 mediated extended spectrum cephalosporin resistance among nosocomial isolates of Gram-negative bacilli

    Directory of Open Access Journals (Sweden)

    Anand Prakash Maurya

    2015-01-01

    Full Text Available Background & objectives: Pseudomonas extended resistant (PER enzymes are rare type of extended-spectrum beta lactamases (ESBLs that confer third generation cephalosporin resistance. These are often integron borne and laterally transmitted. The aim of the present study was to investigate the emergence of integron borne cephalosporin resistant PER-1 gene in diverse incompatibility (Inc group plasmids among Gram-negative bacteria. Methods: A total of 613 consecutive, non-duplicate, Gram-negative bacteria of Enterobacteriaceae family and non-fermenting Gram-negative bacteria were isolated from different clinical specimens during a period of 18 months. For amplification and detection of blaPER, multiplex PCR was done. For understanding the genetic environment of blaPER-1, integrase gene PCR and cassette PCR (59 be was performed. Gene transferability experiment was carried out and PCR based replicon typing was performed for incompatibility group typing of plasmids using 18 pairs of primers. An inhibitor based method was used for phenotypic detection of intrinsic resistance. Results: Multiplex PCR and sequencing confirmed that 45 isolates were harbouring blaPER-1. Both class 1 and class 2 integrons were observed among them. Integrase and cassette PCR (59 be PCR results confirmed that the resistant determinant was located within class 1 integron. Transformation and conjugation experiments revealed that PER-1 was laterally transferable and disseminated through diverse Inc plasmid type. Efflux pump mediated carbapenem resistance was observed in all isolates. All isolates belonged to heterogenous groups. Interpretation & conclusions: This study demonstrates the dissemination of cephalosporins resistant, integron borne blaPER-1 in hospital setting in this part of the country and emphasizes on the rational use of third generation cephalosporins to slow down the expansion of this rare type of ESBL gene.

  1. Emergence of integron borne PER-1 mediated extended spectrum cephalosporin resistance among nosocomial isolates of Gram-negative bacilli

    Science.gov (United States)

    Maurya, Anand Prakash; Choudhury, Debarati; Talukdar, Anupam Das; Dhar (Chanda), Debadatta; Chakravarty, Atanu; Bhattacharjee, Amitabha

    2015-01-01

    Background & objectives: Pseudomonas extended resistant (PER) enzymes are rare type of extended-spectrum beta lactamases (ESBLs) that confer third generation cephalosporin resistance. These are often integron borne and laterally transmitted. The aim of the present study was to investigate the emergence of integron borne cephalosporin resistant PER-1 gene in diverse incompatibility (Inc) group plasmids among Gram-negative bacteria. Methods: A total of 613 consecutive, non-duplicate, Gram-negative bacteria of Enterobacteriaceae family and non-fermenting Gram-negative bacteria were isolated from different clinical specimens during a period of 18 months. For amplification and detection of blaPER, multiplex PCR was done. For understanding the genetic environment of blaPER-1, integrase gene PCR and cassette PCR (59 be) was performed. Gene transferability experiment was carried out and PCR based replicon typing was performed for incompatibility group typing of plasmids using 18 pairs of primers. An inhibitor based method was used for phenotypic detection of intrinsic resistance. Results: Multiplex PCR and sequencing confirmed that 45 isolates were harbouring blaPER-1. Both class 1 and class 2 integrons were observed among them. Integrase and cassette PCR (59 be) PCR results confirmed that the resistant determinant was located within class 1 integron. Transformation and conjugation experiments revealed that PER-1 was laterally transferable and disseminated through diverse Inc plasmid type. Efflux pump mediated carbapenem resistance was observed in all isolates. All isolates belonged to heterogenous groups. Interpretation & conclusions: This study demonstrates the dissemination of cephalosporins resistant, integron borne blaPER-1 in hospital setting in this part of the country and emphasizes on the rational use of third generation cephalosporins to slow down the expansion of this rare type of ESBL gene. PMID:26205025

  2. Development of a miniaturised microarray-based assay for the rapid identification of antimicrobial resistance genes in Gram-negative bacteria

    DEFF Research Database (Denmark)

    Batchelor, Miranda; Hopkins, Katie L; Liebana, Ernesto

    2008-01-01

    We describe the development of a miniaturised microarray for the detection of antimicrobial resistance genes in Gram-negative bacteria. Included on the array are genes encoding resistance to aminoglycosides, trimethoprim, sulphonamides, tetracyclines and beta-lactams, including extended-spectrum ......We describe the development of a miniaturised microarray for the detection of antimicrobial resistance genes in Gram-negative bacteria. Included on the array are genes encoding resistance to aminoglycosides, trimethoprim, sulphonamides, tetracyclines and beta-lactams, including extended...

  3. Fabrication of Al/MgO/C and C/MgO/InSe/C tunneling barriers for tunable negative resistance and negative capacitance applications

    Energy Technology Data Exchange (ETDEWEB)

    Qasrawi, A.F., E-mail: aqasrawi@aauj.edu [Group of Physics, Faculty of Engineering, Atilim University, 06836 Ankara (Turkey); Department of Physics, Arab-American University, Jenin, West Bank, Palestine (Country Unknown)

    2013-07-01

    Highlights: • Aluminum and indium selenide thin films are used to design MgO tunneling diodes. • The Al/MgO/C and C/MgO/InSe/C tunneling diode structures are characterized. • The C/MgO/InSe/C device exhibited a peak to valley current ratio of 135. • It reflected negative resistance effect in the voltage range of 0.94–2.24. • A resonance peak located at 39 MHz was observed. -- Abstract: In this work, the design and characterization of magnesium oxide based tunneling diodes which are produced on Al and InSe films as rectifying substrates are investigated. It was found that when Al thin films are used, the device exhibit tunneling diode behavior of sharp valley at 0.15 V and peak to valley current ratio (PVCR) of 11.4. In addition, the capacitance spectra of the Al/MgO/C device show a resonance peak of negative capacitance (NC) values at 44.7 MHz. The capacitance and resistance–voltage characteristics handled at an ac signal frequency of 100 MHz reflected a build in voltage (V{sub bi}) of 1.29 V and a negative resistance (NR) effect above 2.05 V. This device quality factor (Q)–voltage response is ∼10{sup 4}. When the Al substrate is replaced by InSe thin film, the tunneling diode valley appeared at 1.1 V. In addition, the PVCR, NR range, NC resonance peak, Q and V{sub bi} are found to be 135, 0.94–2.24 and 39.0 MHz, ∼10{sup 5} and 1.34 V, respectively. Due to the wide differential negative resistance and capacitance voltage ranges and due to the response of the C/MgO/InSe/C device at 1.0 GHz, these devices appear to be suitable for applications as frequency mixers, amplifiers, and monostable–bistable circuit elements (MOBILE)

  4. The distribution of carbapenem- and colistin-resistance in Gram-negative bacteria from the Tamil Nadu region in India.

    Science.gov (United States)

    Manohar, Prasanth; Shanthini, Thamaraiselvan; Ayyanar, Ramankannan; Bozdogan, Bulent; Wilson, Aruni; Tamhankar, Ashok J; Nachimuthu, Ramesh; Lopes, Bruno S

    2017-07-01

    The occurrence of carbapenem- and colistin-resistance among Gram-negative bacteria is increasing worldwide. The aim of this study was to understand the distribution of carbapenem- and colistin-resistance in two areas in Tamil Nadu, India. The clinical isolates (n=89) used in this study were collected from two diagnostic centres in Tamil Nadu, India. The bacterial isolates were screened for meropenem- and colistin-resistance. Further, resistance genes blaNDM-1, blaOXA-48-like, blaIMP, blaVIM, blaKPC, mcr-1 and mcr-2 and integrons were studied. The synergistic effect of meropenem in combination with colistin was assessed. A total of 89 bacterial isolates were studied which included Escherichia coli (n=43), Klebsiella pneumoniae (n=18), Pseudomonas aeruginosa (n=10), Enterobacter cloacae (n=6), Acinetobacter baumannii (n=5), Klebsiella oxytoca (n=4), Proteus mirabilis (n=2) and Salmonella paratyphi (n=1). MIC testing showed that 58/89 (65 %) and 29/89 (32 %) isolates were resistant to meropenem and colistin, respectively, whereas 27/89 (30 %) isolates were resistant to both antibiotics. Escherichia coli, K. pneumoniae, K. oxytoca, Pseudomonas aeruginosa, and Enterobacter cloacae isolates were blaNDM-1-positive (n=20). Some strains of Escherichia coli, K. pneumoniae and K. oxytoca were blaOXA-181-positive (n=4). Class 1, 2 and 3 integrons were found in 24, 20 and 3 isolates, respectively. Nine NDM-1-positive Escherichia coli strains could transfer carbapenem resistance via plasmids to susceptible Escherichia coli AB1157. Meropenem and colistin showed synergy in 10/20 (50 %) isolates by 24 h time-kill studies. Our results highlight the distribution of carbapenem- and colistin-resistance in Gram-negative bacteria isolated from the Tamil Nadu region in South India.

  5. Compact silicon-based optrode with integrated laser diode chips, SU-8 waveguides and platinum electrodes for optogenetic applications

    Science.gov (United States)

    Schwaerzle, M.; Paul, O.; Ruther, P.

    2017-06-01

    We report on a compact optrode, i.e. a MEMS-based, invasive, bidirectional neural interface allowing to control neural activity using light while neural signals are recorded nearby. The optrode consists of a silicon (Si) base carrying two pairs of bare laser diodes (LDs) emitting at 650 nm and of two 8 mm-long, 250 µm-wide and down to 50 µm-thick shanks extending from the base. Each LD is efficiently coupled to one of four 15 or 20 µm-wide and 13 µm-high SU-8 waveguides (WGs) running in pairs along the shanks. In addition, each shank comprises four 20 µm-diameter platinum electrodes for neural recording near the WG end facets. After encapsulation of the LDs with a Si cover chip blocking stray light and protecting the LDs from the harsh environment to which the probe is destined, the compact base measures only 4  ×  4  ×  0.43 mm3. The time averaged radiant emittance at the WG end facet is 96.9 mW mm-2 for an LD current of 35 mA at a duty cycle of 5%. The absolute electrode impedance at 1 kHz is 1.54  ±  0.06 MΩ. Using infrared thermography, the temperature increase of the probe during LD operation was determined to be about 1 K under neuroscientifically relevant operating conditions.

  6. Antibiotic Resistance of Gram Negatives isolates from loggerhead sea turtles (Caretta caretta) in the central Mediterranean Sea.

    Science.gov (United States)

    Foti, M; Giacopello, C; Bottari, Teresa; Fisichella, V; Rinaldo, D; Mammina, C

    2009-09-01

    Previous studies on fish and marine mammals support the hypothesis that marine species harbor antibiotic resistance and therefore may serve as reservoirs for antibiotic-resistance genetic determinants. The aim of this study was to assess the resistance to antimicrobial agents of Gram negative strains isolated from loggerhead sea turtles (Carettacaretta). Oral and cloacal swabs from 19 live-stranded loggerhead sea turtles, with hooks fixed into the gut, were analyzed. The antimicrobial resistance of the isolates to 31 antibiotics was assessed using the disk-diffusion method. Conventional biochemical tests identified Citrobacter spp., Proteus spp., Enterobacter spp., Escherichia spp., Providencia spp., Morganella spp., Pantoea spp., Pseudomonas spp. and Shewanella spp. Highest prevalences of resistance was detected to carbenicillin (100%), cephalothin (92.6%), oxytetracycline (81.3%) and amoxicillin (77.8%). The isolates showing resistance to the widest range of antibiotics were identified as Citrobacterfreundii, Proteusvulgaris, Providenciarettgeri and Pseudomonasaeruginosa. In this study, antibiotic resistant bacteria reflect marine contamination by polluted effluents and C.caretta is considered a bioindicator which can be used as a monitor for pollution.

  7. Integrating rapid diagnostics and antimicrobial stewardship improves outcomes in patients with antibiotic-resistant Gram-negative bacteremia.

    Science.gov (United States)

    Perez, Katherine K; Olsen, Randall J; Musick, William L; Cernoch, Patricia L; Davis, James R; Peterson, Leif E; Musser, James M

    2014-09-01

    An intervention for Gram-negative bloodstream infections that integrated mass spectrometry technology for rapid diagnosis with antimicrobial stewardship oversight significantly improved patient outcomes and reduced hospital costs. As antibiotic resistance rates continue to grow at an alarming speed, the current study was undertaken to assess the impact of this intervention in a challenging patient population with bloodstream infections caused by antibiotic-resistant Gram-negative bacteria. A total of 153 patients with antibiotic-resistant Gram-negative bacteremia hospitalized prior to the study intervention were compared to 112 patients treated post-implementation. Outcomes assessed included time to optimal antibiotic therapy, time to active treatment when inactive, hospital and intensive care unit length of stay, all-cause 30-day mortality, and total hospital expenditures. Integrating rapid diagnostics with antimicrobial stewardship improved time to optimal antibiotic therapy (80.9 h in the pre-intervention period versus 23.2 h in the intervention period, P Gram-negatives. The intervention decreased hospital and intensive care unit length of stay, total hospital costs, and reduced all-cause 30-day mortality. Copyright © 2014. Published by Elsevier Ltd.

  8. Magnetic field-induced bipolar resistive switching and negative differential resistance in (110)SrTiO3:Nb/ZnO heterojunctions

    Science.gov (United States)

    Fang, Yinglong; Li, Jiachen; Chen, Yonghai; Zhang, Weifeng; Jia, Caihong

    2017-09-01

    (110)SrTiO3:Nb (NSTO)/ZnO heterojunctions were fabricated by magnetron sputtering. The NSTO/ZnO heterojunctions exhibit a typical rectification characteristic, and two attendant behaviors of bipolar resistive switching and negative differential resistance appear after applying a magnetic field. The ideality factor (n) increases from 3.0 to 8.8 and the density of interface state Nss increases from 8.4×1013 to 1.8×1014 eV-1·cm-2 after applying a magnetic field. The variance of interface state density can be used to qualitatively understand the above results.

  9. Low-Resistance Dual-Purpose Air Filter Releasing Negative Ions and Effectively Capturing PM2.5.

    Science.gov (United States)

    Zhao, Xinglei; Li, Yuyao; Hua, Ting; Jiang, Pan; Yin, Xia; Yu, Jianyong; Ding, Bin

    2017-04-05

    The fatal danger of pollution due to particulate matter (PM) calls for both high-efficiency and low-resistance air purification materials, which also provide healthcare. This is however still a challenge. Herein, a low-resistance air filter capable of releasing negative ions (NIs) and efficiently capturing PM2.5 was prepared by electrospinning polyvinylidene fluoride (PVDF) fibers doped with negative ions powder (NIPs). The air-resistance of fibrous membranes decreased from 9.5 to 6 Pa (decrease of 36%) on decreasing the average fiber diameter from 1.16 to 0.41 μm. Moreover, the lower rising rate of air-resistance with reduction in pore size, for fibrous membranes with thinner fiber diameter was verified. In addition, a single PVDF/NIPs fiber was provided with strong surface potentials, due to high fluorine electronegativity, and tested using atomic force microscopy. This strong surface potential resulted in higher releasing amounts of NIs (RANIs). Interestingly, reduction of fiber diameter favored the alleviation of the shielding effects on electric field around fibers and promoted the RANIs from 798 to 1711 ions cc(-1). Moreover, by regulating the doping contents of NIPs, the RANIs increased from 1711 to 2818 ions cc(-1). The resultant fibrous membranes showed low air resistance of 40.5 Pa. Field-tests conducted in Shanghai showed stable PM2.5 purification efficiency of 99.99% at high RANIs, in the event of haze.

  10. Gram-Negative Bacterial Infections: Research Priorities, Accomplishments, and Future Directions of the Antibacterial Resistance Leadership Group.

    Science.gov (United States)

    Doi, Yohei; Bonomo, Robert A; Hooper, David C; Kaye, Keith S; Johnson, James R; Clancy, Cornelius J; Thaden, Joshua T; Stryjewski, Martin E; van Duin, David

    2017-03-15

    Antimicrobial resistance in pathogenic gram-negative bacteria is one of the most pressing challenges in the field of infectious diseases and is one of 4 key areas of unmet medical need identified by the Antibacterial Resistance Leadership Group (ARLG). The mission of the Gram-Negative Committee is to advance our knowledge of these challenging infections and implement studies to improve patient outcomes. Studies have fallen primarily into 2 broad categories: prospective cohort studies and interventional trials. Among the observational studies, CRACKLE (Consortium on Resistance Against Carbapenems in Klebsiella pneumoniae and Other Enterobacteriaceae) has contributed seminal multicenter data describing risk factors and clinical outcomes of carbapenem-resistant Enterobacteriaceae (CRE) in sentinel US hospitals. Building on this success, CRACKLE II will expand the network to hospitals across the United States and Colombia. Similar protocols have been proposed to include Acinetobacter baumannii and Pseudomonas aeruginosa (SNAP and POP studies). In addition, the CREST study (Carbapenem-Resistant Enterobacteriaceae in Solid Organ Transplant Patients) has provided pivotal data on extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and CRE carriage among solid organ transplant recipients to inform management of this vulnerable patient population. Two clinical trials to define novel ways of using an existing antibiotic, fosfomycin, to treat ESBL-producing Enterobacteriaceae (one that has completed enrollment and the other in late protocol development) will determine the clinical efficacy of fosfomycin as step-down oral therapy to treat complicated urinary tract infections. Additional clinical studies and trials using immunotherapeutic or newly approved agents are also in the planning stage, with the main goals of generating actionable data that will inform clinical decision making and facilitate development of new treatment options for highly resistant gram-negative

  11. Susceptibility trends including emergence of linezolid resistance among coagulase-negative staphylococci and meticillin-resistant Staphylococcus aureus from invasive infections.

    Science.gov (United States)

    Decousser, Jean-Winoc; Desroches, Marine; Bourgeois-Nicolaos, Nadège; Potier, Julien; Jehl, François; Lina, Gérard; Cattoir, Vincent; Vandenesh, François; Doucet-Populaire, Florence

    2015-12-01

    Multiresistance in staphylococci constitutes a major challenge for the antimicrobial chemotherapy of invasive infections such as bacteraemia or bone and joint infections (BJIs). A nationwide prospective study was performed to detect antimicrobial resistance trends among staphylococci causing invasive infections. Between October 2011 and February 2012, 367 meticillin-resistant Staphylococcus aureus (MRSA) and 695 coagulase-negative staphylococci (CoNS) were collected from 37 French hospitals, mainly from bacteraemia (59.9%) and osteoarticular infections (29.0%). Minimum inhibitory concentrations (MICs) were determined by broth microdilution, and specific screening and confirmation tests were performed to detect heterogeneous vancomycin-intermediate S. aureus (hVISA). Staphylococcal isolates exhibiting a linezolid MIC>4 mg/L were further characterised to determinate their clonal relationships and the mechanism of resistance. MRSA exhibited additional resistances, including levofloxacin (82% associated resistance), gentamicin (13.6%), fusidic acid (13.6%) and rifampicin (6.5%), compromising oral step-down therapy in BJIs. Only two hVISA strains (0.5%) were identified. Among the CoNS, mainly Staphylococcus epidermidis (506/695; 72.8%), resistance to first- and second-line agents was more common. Linezolid resistance was identified in 10 CoNS (1.4%). The most frequent linezolid resistance mechanism was the G2576T mutation in 23S rDNA (9/10). For the first time in France, the cfr gene was found in five related sequence type 2 (ST2) S. epidermidis from two different hospitals, in association with ribosomal RNA and L3 ribosomal protein mutations. These national data must be considered when selecting empirical treatment for invasive staphylococcal infections. Moreover, the emergence and spread of linezolid-resistant CoNS carrying the cfr gene is of concern. Copyright © 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

  12. Prevalence of the Antibiotic Resistance Genes in Coagulase-Positive-and Negative-Staphylococcus in Chicken Meat Retailed to Consumers

    Science.gov (United States)

    Osman, Kamelia; Badr, Jihan; Al-Maary, Khalid S.; Moussa, Ihab M. I.; Hessain, Ashgan M.; Girah, Zeinab M. S. Amin; Abo-shama, Usama H.; Orabi, Ahmed; Saad, Aalaa

    2016-01-01

    The use of antibiotics in farm management (growing crops and raising animals) has become a major area of concern. Its implications is the consequent emergence of antibiotic resistant bacteria (ARB) and accordingly their access into the human food chain with passage of antibiotic resistance genes (ARG) to the normal human intestinal microbiota and hence to other pathogenic bacteria causative human disease. Therefore, we pursued in this study to unravel the frequency and the quinolone resistance determining region, mecA and cfr genes of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), methicillin-resistant coagulase-negative staphylococci (MRCNS) and methicillin-susceptible coagulase-negative staphylococci (MSCNS) isolated from the retail trade of ready-to-eat raw chicken meat samples collected during 1 year and sold across the Great Cairo area. The 50 Staphylococcus isolated from retail raw chicken meat were analyzed for their antibiotic resistance phenotypic profile on 12 antibiotics (penicillin, oxacillin, methicillin, ampicillin-sulbactam, erythromycin, tetracycline, clindamycin, gentamicin, ciprofloxacin, chloramphenicol, sulfamethoxazole-trimethoprim, and vancomycin) and their endorsement of the quinolone resistance determining region, mecA and cfr genes. The isolation results revealed 50 isolates, CPS (14) and CNS (36), representing ten species (S. aureus, S. hyicus, S. epidermedius, S. lugdunensis, S. haemolyticus, S. hominus, S. schleiferi, S. cohnii, S. intermedius, and S. lentus). Twenty seven isolates were methicillin-resistant. Out of the characterized 50 staphylococcal isolates, three were MRSA but only 2/3 carried the mecA gene. The ARG that bestows resistance to quinolones, β-lactams, macrolides, lincosamides, and streptogramin B [MLS(B)] in MRSA and MR-CNS were perceived. According to the available literature, the present investigation was a unique endeavor into the identification of the quinolone-resistance

  13. Prevalence of the antibiotic resistance genes in coagulase-positive- and negative-Staphylococcus in chicken meat retailed to consumers

    Directory of Open Access Journals (Sweden)

    Kamelia Mahmoud Osman

    2016-11-01

    Full Text Available The use of antibiotics in farm management (growing crops and raising animals has become a major area of concern. Its implications is the consequent emergence of antibiotic resistant bacteria (ARB and accordingly their access into the human food chain with passage of antibiotic resistance genes (ARG to the normal human intestinal microbiota and hence to other pathogenic bacteria causative human disease. Therefore, we pursued in this study to unravel the frequency and the quinolone resistance determining region, mecA and cfr genes of methicillin-susceptible Staphylococcus aureus (MSSA, methicillin-resistant S. aureus (MRSA, methicillin-resistant coagulase-negative staphylococci (MRCNS and methicillin-susceptible coagulase-negative staphylococci (MSCNS isolated from the retail trade of ready-to-eat raw chicken meat samples collected during one year and sold across the Great Cairo area. The 50 Staphylococcus isolated from retail raw chicken meat were analyzed for their antibiotic resistance phenotypic profile on 12 antibiotics (penicillin, oxacillin, methicillin, ampicillin-sulbactam, erythromycin, tetracycline, clindamycin, gentamicin, ciprofloxacin, chloramphenicol, sulfamethoxazole-trimethoprim and vancomycin and their endorsement of the quinolone resistance determining region, mecA and cfr genes. The isolation results revealed 50 isolates, CPS (14 and CNS (36, representing ten species (S. aureus, S. hyicus, S. epidermedius, S. lugdunensis, S. haemolyticus, S. hominus, S. schleiferi, S. cohnii, S. intermedius and S. lentus. Twenty seven isolates were methicillin-resistant. Out of the characterized 50 staphylococcal isolates, three were MRSA but only 2/3 carried the mecA gene. The ARG that bestows resistance to quinolones, β-lactams, macrolides, lincosamides and streptogramin B (MLS(B in MRSA and MR-CNS were perceived. According to the available literature, the present investigation was a unique endeavor into the identification of the quinolone-resistance

  14. Prevalence of the Antibiotic Resistance Genes in Coagulase-Positive-and Negative-Staphylococcus in Chicken Meat Retailed to Consumers.

    Science.gov (United States)

    Osman, Kamelia; Badr, Jihan; Al-Maary, Khalid S; Moussa, Ihab M I; Hessain, Ashgan M; Girah, Zeinab M S Amin; Abo-Shama, Usama H; Orabi, Ahmed; Saad, Aalaa

    2016-01-01

    The use of antibiotics in farm management (growing crops and raising animals) has become a major area of concern. Its implications is the consequent emergence of antibiotic resistant bacteria (ARB) and accordingly their access into the human food chain with passage of antibiotic resistance genes (ARG) to the normal human intestinal microbiota and hence to other pathogenic bacteria causative human disease. Therefore, we pursued in this study to unravel the frequency and the quinolone resistance determining region, mecA and cfr genes of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), methicillin-resistant coagulase-negative staphylococci (MRCNS) and methicillin-susceptible coagulase-negative staphylococci (MSCNS) isolated from the retail trade of ready-to-eat raw chicken meat samples collected during 1 year and sold across the Great Cairo area. The 50 Staphylococcus isolated from retail raw chicken meat were analyzed for their antibiotic resistance phenotypic profile on 12 antibiotics (penicillin, oxacillin, methicillin, ampicillin-sulbactam, erythromycin, tetracycline, clindamycin, gentamicin, ciprofloxacin, chloramphenicol, sulfamethoxazole-trimethoprim, and vancomycin) and their endorsement of the quinolone resistance determining region, mecA and cfr genes. The isolation results revealed 50 isolates, CPS (14) and CNS (36), representing ten species (S. aureus, S. hyicus, S. epidermedius, S. lugdunensis, S. haemolyticus, S. hominus, S. schleiferi, S. cohnii, S. intermedius, and S. lentus). Twenty seven isolates were methicillin-resistant. Out of the characterized 50 staphylococcal isolates, three were MRSA but only 2/3 carried the mecA gene. The ARG that bestows resistance to quinolones, β-lactams, macrolides, lincosamides, and streptogramin B [MLS(B)] in MRSA and MR-CNS were perceived. According to the available literature, the present investigation was a unique endeavor into the identification of the quinolone-resistance

  15. Resistance to oral antibiotics in 4569 Gram-negative rods isolated from urinary tract infection in children.

    Science.gov (United States)

    Calzi, Anna; Grignolo, Sara; Caviglia, Ilaria; Calevo, Maria Grazia; Losurdo, Giuseppe; Piaggio, Giorgio; Bandettini, Roberto; Castagnola, Elio

    2016-09-01

    To investigate antibiotic resistance among pathogens isolated from urines in a tertiary care children's hospital in Italy. Retrospective analysis of prospectively collected data on antibiotic susceptibility of Gram-negatives isolated from urines at the Istituto Giannina Gaslini, Genoa - Italy from 2007 to 2014. Antibiotic susceptibility was evaluated. By means of CLSI criteria from 2007 to 2010, while from 2011 EUCAST criteria were adopted. Data on susceptibility to amoxicillin-clavulanate, co-trimoxazole, cefuroxime, nitrofurantoin, fosfomycin and ciprofloxacin were evaluated for Escherichia coli, while for other Enterobacteriaceae data were collected for amoxicillin-clavulanate, co-trimoxazole and ciprofloxacin and for ciprofloxacin against Pseudomonas aeruginosa. Univariate and multivariable analyses were performed for risk factors associated with resistance. A total of 4596 Gram-negative strains were observed in 3364 patients. A significant increase in the proportion of resistant strains was observed for E.coli against amoxicillin-clavulanate, cefuroxime and ciprofloxacin and for others Enterobacteriaceae against co-trimoxazole and ciprofloxacin. Resistance to nitrofurantoin and fosfomycin was very infrequent in E.coli. Logistic regression analysis showed that repeated episode of urinary tract infections was a risk factor for E.coli resistance to amoxicillin-clavulanate, co-trimoxazole and cefuroxime, while admission in one of the Units usually managing children with urinary tract malformations was significantly associated to resistance to amoxicillin-clavulanate and cefuroxime. In conclusion the present study shows an increase in antibiotic resistance in pediatric bacteria isolated from urines in children, especially in presence of repeated episodes and/or urinary tract malformations. This resistance is worrisome for beta-lactams and cotrimoxazole, and start to increase also for fluoroquinolones while nitrofurantoin and fosfomycin still could represent useful

  16. High-level and novel mechanisms of carbapenem resistance in Gram-negative bacteria from tertiary hospitals in Nigeria.

    Science.gov (United States)

    Ogbolu, D O; Webber, M A

    2014-05-01

    To determine the occurrence and molecular basis of carbapenem resistance in Gram-negative bacteria from tertiary hospitals in Nigeria, 182 non-duplicate Gram-negative bacterial isolates were investigated for antimicrobial susceptibility, presence of carbapenemases (tested phenotypically and genotypically), random amplified polymorphic DNA (RAPD) typing, plasmid sizing and replicon typing. Minimum inhibitory concentrations of carbapenems showed a high degree of resistance, with 67 isolates (36.8%) being resistant to all carbapenems, of which 40 (59.7%) produced enzymes able to hydrolyse imipenem. PCR and sequencing identified only 10 isolates (5.5%) carrying known carbapenemase genes, including bla(NDM), bla(VIM) and bla(GES). The majority of phenotypically carbapenem-resistant and carbapenemase-producing isolates did not carry a known carbapenemase gene. Transconjugant or transformant plasmid sizes were estimated to be 115 kb for bla(NDM)- and 93 kb for bla(VIM)-carrying plasmids. These plasmids were untypeable for replicon/incompatibility and transferred various other genes including plasmid-mediated quinolone resistance (PMQR) genes and bla(CTX-M-15). Typing showed that the isolates in this study were not clonally related. There is a high level of carbapenem resistance in Nigeria. As well as the globally relevant carbapenemases (bla(NDM), bla(VIM) and bla(GES)), there are other unknown gene(s) or variant(s) in circulation able to hydrolyse carbapenems and confer high-level resistance. Copyright © 2014 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

  17. Antibiotic Resistance Patterns of Gram-Negative Psychrotrophic Bacteria from Bulk Tank Milk.

    Science.gov (United States)

    Decimo, Marilù; Silvetti, Tiziana; Brasca, Milena

    2016-04-01

    Bacterial resistance to antibiotics is a major global health problem and resistance of Pseudomonadaceae and Enterobacteriaceae is a serious concern. We investigated the prevalence of drug-resistance in a total of 80 psychrotrophic strains from bulk milk belonging to Pseudomonas genus (n. 63) and Enterobacteriaceae group (n. 17). All the strains were tested against 16 antibiotics. Pseudomonas were further investigated for their sensitivity against 12 additional antibiotics. Pseudomonas showed a high susceptibility toward fluoroquinolones, aminoglycosides, and piperacillin and, to a lesser extent, to imipenem, ceftazidime, cefepime. Thirty-five out of 63 Pseudomonas strains were susceptible to meropenem, while among antibiotics for which recommended breakpoints are not yet available, 55% of Pseudomonas strains had no inhibition halo in presence of nitrofurantoin, highlighting a resistance toward this drug. The results obtained in this study indicate a high efficiency of fluoroquinolones, chloramphenicol (94%), and kanamycin (76%) for Enterobacteriaceae while a high prevalence of resistant strains was found to ampicillin (13/17). Serratia marcescens is highly susceptible to fluoroquinolones, chloramphenicol, and kanamycin. Moreover, mupirocin seems to be the new antibiotic with the less efficacy for Enterobacteriaceae, with 41% of strains without halo, pointing out an important resistance. Further knowledge on resistance to known and new antibiotics among Pseudomonas species and Enterobacteriaceae of milk origin was acquired. © 2016 Institute of Food Technologists®

  18. Jasmonic acid negatively regulates resistance to Tobacco mosaic virus in tobacco.

    Science.gov (United States)

    Oka, Kumiko; Kobayashi, Michie; Mitsuhara, Ichiro; Seo, Shigemi

    2013-12-01

    Nicotiana tabacum (tobacco) cultivars possessing the N resistance gene to Tobacco mosaic virus (TMV) induce a hypersensitive response, which is accompanied by the production of phytohormones such as salicylic acid (SA) and jasmonic acid (JA), to enclose the invaded virus at the initial site of infection, which inhibits viral multiplication and spread. SA functions as a positive regulator of TMV resistance. However, the role of JA in TMV resistance has not been fully elucidated. Exogenously applied methyl jasmonate, a methyl ester of JA, reduced local resistance to TMV and permitted systemic viral movement. Furthermore, in contrast to a previous finding, we demonstrated that silencing of CORONATINE-INSENSITIVE 1 (COI1), a JA receptor, reduced viral accumulation in a tobacco cultivar possessing the N gene, as did that of allene oxide synthase, a JA biosynthetic enzyme. The reduction in viral accumulation in COI1-silenced tobacco plants was correlated with an increase in SA, and lowering SA levels by introducing an SA hydroxylase gene attenuated this reduction. Viral susceptibility did not change in a COI1-silenced tobacco cultivar lacking the N gene. These results suggest that JA signaling is not directly responsible for susceptibility to TMV, but is indirectly responsible for viral resistance through the partial inhibition of SA-mediated resistance conferred by the N gene, and that a balance between endogenous JA and SA levels is important for determining the degree of resistance.

  19. Multidrug-Resistant Gram-Negative Bacterial and Carbapenem-Resistant Enterobacteriaceae Infections in the Department of the Navy: Annual Report 2013

    Science.gov (United States)

    2015-03-19

    prevalent in the region and a frequent cause of travelers’ diarrhea. 12 In 2001, Jones et al. reported that nosocomial infections accounted for more... nosocomial infections and continue to be a concern, gram-negative organisms have been emerging with resistance at troubling rates. 13 In intensive...associated infections : nosocomial pneumonia, urinary tract infections (UTIs), surgical site infections (SSIs), and blood stream infections (BSIs). 14

  20. Extra-pulmonary primary multidrug-resistant tubercular lymphadenitis in an HIV negative patient

    Science.gov (United States)

    Kant, Surya; Saheer, S; Hassan, Ghulam; Parengal, Jabeed

    2012-01-01

    A 28-year-old woman without any history of prior antituberculosis treatment presented with cervical lymphadenopathy and a cold abscess near medial end of clavicle of 5 months duration. Pus culture and sensitivity revealed Mycobacterium tuberculosis resistant to rifampicin and isoniazid. Thus she was diagnosed as a case of primary multidrug-resistant tuberculosis and treated with second line drugs according to culture susceptibility pattern. On completion of therapy, patent showed good clinical response. This case highlights the observation that even extra-pulmonary primary multidrug-resistant tuberculosis can be successfully treated with currently available second line drugs. PMID:22605844

  1. When Bad Things Happen to a Protagonist Like You: The Role of Self in Resistance to Negatively Framed Health Narratives.

    Science.gov (United States)

    Kim, Hye Kyung; Shapiro, Michael A

    2016-12-01

    This study examines when and how shared risk-relevant experience (autobiographic similarity) influences resistance to negatively framed health narratives. We conducted a 2 (narrative perspective: 1st vs. 3rd person) × 2 (processing motive: experiential vs. analytical) randomized experiment with a short narrative depicting the negative effects of an illicitly used study drug. For those autobiographically similar to the study drug user, a 1st-person narration (vs. 3rd-person) produced greater transportation only when participants processed to understand the story (experiential condition), whereas the reverse was found when participants processed for the persuasive message (analytical condition). Transportation was a significant mediator that transferred these interactive effects onto greater perceived risk only among those with autobiographic similarity. This study highlights the active role played by the audience's self-concept in narrative persuasion and addresses boundary conditions for overcoming defensive resistance.

  2. Some methods to regulate low-bias negative differential resistance in σ barrier separating nanoscale molecular transport systems

    Science.gov (United States)

    Shen, Ji-Mei; Liu, Jing; Min, Yi; Zhou, Li-Ping

    2016-12-01

    Using the first-principles method which combines the nonequilibrium Green’s function (NEGF) with density functional theory (DFT), the role of defect, dopant, barrier length and geometric deformation for low-bias negative differential resistance (NDR) in two capped armchair carbon nanotubes (CNTs) sandwiching σ barrier are systematically analyzed. We found that this method can regulate the negative differential resistance (NDR) effects such as current peak and peak position. The adjusting mechanism may originate from orbital interaction and orbital reconstruction. Our calculations try to manipulate the transport characteristics in energy space by simply manipulating the structure in real space, which may promise the potential applications in nanomolecular-electronics in the future.

  3. Transition Frequencies and Negative Resistance of Inductively Terminated CMOS Buffer Cell and Application in MMW LC VCO

    Directory of Open Access Journals (Sweden)

    S. M. Rezaul Hasan

    2010-01-01

    looking into the source of the buffer cell changes sign. Possible limiting frequencies of oscillation are determined based on resonators formed by a grounded gate inductor and a parasitic capacitance at the gate of the negative resistance buffer cell. The range of frequencies of oscillation of this negative resistance buffer cell for variations in the different circuit parameters/elements is explored. Following this, a millimeter wave (MMW oscillator is simulated using the IBM 130 nm CMOS process technology which can operate at 70 GHz. High-frequency MOSFET model was used for these simulations. The cell had an extremely low power dissipation of under 3 mW. Extensive Monte Carlo simulations were carried out for manufacturability analysis considering up to 50% variation in process and geometrical parameters, supply voltage, and ambient temperature. Noise analysis and a simulated estimate of the phase noise in an MMW LC VCO application is also reported.

  4. Enhanced autophagy reveals vulnerability of P-gp mediated epirubicin resistance in triple negative breast cancer cells.

    Science.gov (United States)

    Zhang, Li-han; Yang, Ai-jun; Wang, Min; Liu, Wei; Wang, Chen-yu; Xie, Xiao-feng; Chen, Xu; Dong, Jing-fei; Li, Min

    2016-04-01

    Epirubicin (EPI) is widely used for triple negative breast cancer (TNBC), but a substantial number of patients develop EPI resistance that is associated with poor outcome. The underlying mechanism for EPI resistance remains poorly understood. We have developed and characterized an EPI-resistant (EPI-R) cell line from parental MDA-MB-231 cells. These EPI-R cells reached stable growth in the medium containing 8 μg/ml of EPI. They overexpressed P-glycoprotein (P-gp) and contained numerous autophagic vacuoles. The suppression of P-gp overexpression and/or autophagy restored the sensitivity of these EPI-R cells to EPI. We further show that autophagy conferred resistance to EPI on MDA cells by blocking the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-mediated pro-apoptotic signals. Together, these results reveal a synergistic role of P-gp, autophagy, and NF-κB pathways in the development of EPI resistance in TNBC cells. They also suggest that blocking the P-gp overexpression and autophagy may be an effective means of reducing EPI resistance.

  5. [Activity of vancomycin, teicoplanin and linezolid in methicillin resistant coagulase-negative Staphylococci isolates from paediatric blood cultures].

    Science.gov (United States)

    Fajardo Olivares, Miguel; Hidalgo Orozco, Rocío; Rodríguez Garrido, Saray; Gaona Álvarez, Cristina; Sánchez Silos, Rosa María; Hernández Rastrollo, Ramón; Martínez Tallo, Emilia; Cordero Carrasco, Juan Luis

    2012-03-01

    Coagulase-negative-Staphylococci (CNS) are the major cause of bacteraemia and sepsis in newborns. CNS methicillin resistance and its loss of sensitivity to glycopeptide antibiotics, make treatment significantly more difficult in positive cocci infections. To study MIC vancomycin, teicoplanin and linezolid in different species of CNS methicillin resistant isolates from blood cultures from paediatric patients. Clinically relevant CNS methicillin resistant isolates from paediatric blood cultures from different hospitalization wards were tested. The isolates were identified by biochemical tests by means in the Combo panels 31 of MicroScan (Dade Behring, Siemens). Resistance to oxacillin and susceptibility to vancomycin, teicoplanin and linezolid were tested by microdilution panels as cited above. We also tested teicoplanin and linezolid sensitivity using Etest. 50 methicillin resistant strains were isolated: 37 (74%)S. epidermidis, 7 (14%) S. hominis, 4 (8%) S. haemolyticus and 2 (4%) Staphylococcus spp. 26 strains were observed with reduced susceptibility to vancomycin MIC = 2 mg/L, (22 S. epidermidis, 2 S. haemolyticus and 2 Staphylococcus spp.) and 21 strains with loss of susceptibility to teicoplanin, MIC = 4-16 mg/L (20 S. epidermidis and 1 S. haemolyticus). No CNS linezolid resistant was found. There is a linear correlation between increased vancomycin MIC and teicoplanin MIC. There is a statistically significant difference (p teicoplanin in the vancomycin group = 2 mg/L with respect to the vancomycin group ≤ 1 mg/L. We also observed very low levels of linezolid MIC for all strains.

  6. Elaboration of Approaches to Internet Negative Impact Resistance for University Students

    Science.gov (United States)

    Chusavitina, Galina Nikolaevna; Zerkina, Natalya Nikolaevna; ?hernova, Elena Vladimirovna; Kolobova, Olga Leonidovna; Nazarova, Olga Borisovna

    2016-01-01

    In the information society Internet technologies provide not only positive information and psychological impact but negative and destructive one either. The lack of attention to the problems of prevention and correction of destructive information impact on young students in higher education institutions negatively affects the development of…

  7. Antibacterial and antibiotic-resistance modifying activity of the extracts and compounds from Nauclea pobeguinii against Gram-negative multi-drug resistant phenotypes.

    Science.gov (United States)

    Seukep, Jackson A; Sandjo, Louis P; Ngadjui, Bonaventure T; Kuete, Victor

    2016-07-07

    Multi-drug resistance of Gram-negative bacteria constitutes a major obstacle in the antibacterial fight worldwide. The discovery of new and effective antimicrobials and/or resistance modulators is necessary to combat the spread of resistance or to reverse the multi-drug resistance. In this study, we investigated the antibacterial and antibiotic-resistance modifying activities against 29 Gram-negative bacteria including multi-drug resistant (MDR) phenotypes of the methanol extracts from Nauclea pobeguiinii leaves (NPL), Nauclea pobeguiinii bark (NPB) and six compounds from the bark extract, identified as 3-acetoxy-11-oxo-urs-12-ene (1), p-coumaric acid (2), citric acid trimethyl ester (3), resveratrol (4), resveratrol β- D -glucopyranoside (5) and strictosamide (6). The broth microdilution method was used to determine the minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) of crude extracts and compounds as well as the antibiotic-resistance modifying effects of MPB and 4. MIC determinations indicate values ranging from 32-1024 μg/mL for NPB and NPL on 89.7 % and 69.0 % of the tested bacterial strains respectively. MIC values below 100 μg/mL were obtained with NPB against Escherichia coli ATCC10536, AG100 and Enterobacter aerogenes CM64 strains. The lowest MIC value for crude extracts of 32 μg/mL was obtained with NPB against E. coli ATCC10536. Compound 4 was active all tested bacteria, whilst 1, 3 and 6 displayed weak and selective inhibitory effects. The corresponding MIC value (16 μg/mL) was obtained with 4 against Klebsiella pneumoniae KP55 strain. Synergistic effects of the combination of NPB with chloramphenicol (CHL), kanamycin (KAN) as well as that of compound 4 with streptomycin (STR) and ciprofloxacin (CIP) were observed. The present study provides information on the possible use of Nauclea pobeguinii and compound 4 in the control of Gram-negative bacterial infections including MDR phenotypes. It also indicates

  8. Distribution of plasmid-mediated quinolone resistance in Gram-negative bacteria from a tertiary hospital in Nigeria.

    Science.gov (United States)

    Ogbolu, David Olusoga; Alli, Armstrong Oyebode; Anorue, Michael C; Daini, Oluwole Adebayo; Oluwadun, Afolabi

    2016-01-01

    Until recently, mechanisms of resistance to quinolones in Gram-negative bacteria were believed to be only chromosome encoded. However, emergence of plasmid-mediated quinolone resistance (PMQR) has been reported worldwide. This study investigated distribution of PMQR in Gram-negative bacteria from a tertiary hospital in eastern part of Nigeria. Seventy-one nonduplicate Gram-negative bacterial isolates of eight species were analyzed for antimicrobial susceptibility, genotypic detection of various PMQRs, typed by random amplified polymorphic DNA (RAPD) and analysis of plasmids present, including replicon typing. The minimum inhibitory concentrations showed MIC90values as high as 256 μg/ml for fluoroquinolones. Carriage of PMQR was found to be 35.2%. Twenty (28.2%) isolates carried various qnr genes, of which seven (9.9%) qnrA1; four (5.6%) qnrB1; eight (11.3%) qnrS1 while one (1.4%) encoded qnrD1. Eighteen (25.4%) isolates were positive for aac(6')-Ib-cr while carriage of multiple genes exists in some strains. Similarly, 13 isolates (18.7%) were found to carry PMQR efflux pump gene, qepA. Conjugation experiments revealed that the plasmids once transferred coded for fluoroquinolone resistance. The transconjugant strains carried a common plasmid estimated to be 65 kb. These plasmids were untypable for replicon/incompatibility. Typing revealed high diversity among all species tested with no identical RAPD pattern seen. This study further confirms high level resistance to many antimicrobials in different species of Gram-negative bacteria including fluoroquinolones and spread of PMQR genes in Southern Nigeria.

  9. Adjunctive aerosolized colistin for multi-drug resistant gram-negative pneumonia in the critically ill: a retrospective study

    OpenAIRE

    Doshi, Neha M; Cook, Charles H; Mount, Kari L; Stawicki, Stanislaw P; Frazee, Erin N; Personett, Heather A; Schramm, Garrett E; Arnold, Heather M; Murphy, Claire V

    2013-01-01

    Background The incidence of multi-drug resistant (MDR) gram-negative (GN) organisms including Pseudomonas and Acinetobacter spp has increased in the last decade, prompting re-evaluation of colistin for the management of these infections. Aerosolized colistin as an adjunct to intravenous therapy is a current option for the management of MDR-GN pneumonia, although data supporting this practice is limited. This study evaluates the efficacy of adjunctive aerosolized colistin in combination with i...

  10. Antimicrobial resistance patterns among Gram-negative bacilli isolated from patients with nosocomial infections: Disk diffusion versus E-test

    Directory of Open Access Journals (Sweden)

    Hadadi A

    2007-08-01

    Full Text Available Background: The object of this study was to investigate the antimicrobial resistance pattern among common nosocomial Gram-negative bacilli isolated from patients with nosocomial infections. Methods: From June 2004 to December 2005, 380 isolates of common Gram-negative bacilli (Klebsiella, Pseudomonas, Acinetobacter and E. coli from 270 patients with nosocomial infections in Sina and Imam Hospitals, Tehran, Iran, were evaluated for susceptibility to Imipenem, Cefepime, Ciprofloxacine, Ceftriaxone and Ceftazidime by Disc diffusion and E-test methods. Results: The most frequent pathogens isolated were Klebsiella spp. (40%, followed by Pseudomonas (28%, Acinetobacter spp. (20% and E. coli (12%. The most active antibiotic was imipenem (84%. 26% of all isolates were sensitive to Cefepime, 26% to Ciprofloxacin, 20% to Ceftazidime and 10% to Ceftrixone. The susceptibility rates of Klebsiella to Imipenem, cefepime, ciprofloxacin, Ceftazidime and Ceftriaxone were 91, 25, 21, 13 and 7 percent, respectively and 91, 19, 17, 21 and 21 percent, respectively, for E. coli. Among Acineto- bacter spp., the susceptibility rate was 77% for Imipenem and 21% for Ciprofloxacin. Among Pseudomonas spp., 75% of isolates were susceptible to Imipenem and 39% to Ciprofloxacin. The comparison of the resistance status of microorganisms by both Disc diffusion and E-test methods showed a clinically noticeable agreement between these two tests. Conclusions: Since antibiotic resistance among Gram-negative bacilli has increased, enforcement of policy regarding proper antibiotic use is urgently needed in order to delay the development of resistance. Although it is widely accepted that E-test is more accurate in determining the resistance of microorganisms, our study showed that the Disc diffusion test will give the same results in most occasions and is therefore still considered useful in clinical practice.

  11. The emergence of pan-resistant Gram-negative pathogens merits a rapid global political response.

    Science.gov (United States)

    Walsh, Timothy R; Toleman, Mark A

    2012-01-01

    Recent media coverage of New Delhi metallo-β-lactamase (NDM-1) put antibiotic resistance back on the political map if only for the wrong reasons, mainly the reaction to the naming of NDM-1 and the incorrect assumption that medical tourism was being deliberately targeted. However, work on NDM-1 has most certainly highlighted the rapid dissemination of new antibiotic resistance mechanisms via economic globalization. The example of NDM-1 has also magnified the desperate need for a publicly funded global antibiotic surveillance system rather than just national or regional systems. Furthermore, there is a pressing need to establish a global task force to enforce international transparency and accountability on antibiotic stewardship and the implementation of measures to curb antibiotic resistance. An international antibiotic stewardship index should be established that is related to each country's gross domestic product (GDP) and assesses how much of their GDP is committed to publically funded health initiatives aimed at controlling antibiotic resistance.

  12. Use of Triplex PCR for Rapid Detection of PVL and Differentiation of MRSA from Methicillin Resistant Coagulase Negative Staphylococci

    Science.gov (United States)

    Abimanyu, Nagarajan; Krishnan, Arunkumar; Murugesan, Saravanan; Subramanian G, Kaushik; Gurumurthy, Sivakumar; Krishnan, Padma

    2013-01-01

    Introduction: Methicillin-Resistant Staphylococcus aureus (MRSA) has become a major public health problem in both hospitals and communities. Panton – Valentine Leucocidin (PVL) has been reported to be an important marker for the highly pathogenic community acquired S. aureus infections. A rapid detection of these MRSA is very important for its treatment. The specific detection of MRSA is always a problem due to the prevalence of methicillin resistance among the coagulase negative Staphylococci. Hence, this study was done to develop a rapid triplex PCR for the detection of PVL positive MRSA and for the simultaneous differentiation of MRSA from Coagulase Negative Staphylococci (CoNS). Materials and Methods: We developed a triplex PCR for the specific detection of PVL positive Community Acquired (CA) – MRSA and for its simultaneous differentiation from the coagulase negative Staphylococci. We used PCR for targeting the fem A gene which is specific for S. aureus, mecA which is specific for methicillin-resistance and luk - PV which is specific for the PVL toxin. The method was evaluated with a total of 100 clinical isolates of Staphylococcus spp. Results: The triplex PCR was successfully standardized by using the reference strains and it was evaluated by using clinical strains. The method was found to be rapid, highly sensitive (100%), specific (99%) and cost effective. Conclusion: Triplex PCR can be used as a diagnostic tool for the detection of the highly pathogenic strains of CA-MRSA. PMID:23542876

  13. Comparison of Two PCR Methods in determining the Methicillin-Resistant Gene in Coagulase-Negative Staphylococci

    Directory of Open Access Journals (Sweden)

    M. Bokaeian

    2016-09-01

    Full Text Available Aims: It is very important to detect the coagulase-negative Staphylococci, which produce the hospital infections. Being one of the most expensive and time-consuming stages before the polymerase chain reaction (PCR, DNA extraction is one of the primary stages of PCR. Then, it should be noticed that the elimination of the stage might save time and costs. The aim of this study was to compare two PCR methods including the method with the utilization of the extracted DNA with the extraction kit and the direct PCR method in the detection of the methicillin-resistant genes in the coagulase-negative Staphylococci. Materials & Methods: In the descriptive cross-sectional study, 135 Staphylococcus epidermidis and 88 Staphylococcus saprophyticus samples were studied, separated from blood, wounds, urinary catheter, and urine samples of patients hospitalized in the treatment centers of Zahedan. The direct PCR was done on the Staphylococcus saprophyticus and Staphylococcus epidermidis colonies. PCR with the extracted DNA was done for mecA and 16srDNA genes using the extraction kit, and the results were compared. Findings: In both methods, mecA and 16srDNA genes were successfully amplified in 310bp and 420bp related to Staphylococcus bacteria identifying gene and methicillin resistant gene, respectively. In addition, there were approximately the same band qualities. Conclusion: In order to save time and costs, the direct PCR method can be used to detect methicillin-resistant coagulase-negative Staphylococci.

  14. E-cadherin expression is correlated with focal adhesion kinase inhibitor resistance in Merlin-negative malignant mesothelioma cells.

    Science.gov (United States)

    Kato, T; Sato, T; Yokoi, K; Sekido, Y

    2017-09-28

    Malignant mesothelioma (MM) is an aggressive tumor commonly caused by asbestos exposure after a long latency. Focal adhesion kinase (FAK) inhibitors inhibit the cell growth of Merlin-deficient MM cells; however, their clinical efficacy has not been clearly determined. The aim of this study was to evaluate the growth inhibitory effect of the FAK inhibitor VS-4718 on MM cell lines and identify biomarkers for its efficacy. Although most Merlin-deficient cell lines were sensitive to VS-4718 compared with control MeT-5A cells, a subset of these cell lines exhibited resistance to this drug. Microarray and qRT-PCR analyses using RNA isolated from Merlin-deficient MM cell lines revealed a significant correlation between E-cadherin mRNA levels and VS-4718 resistance. Merlin- and E-cadherin-negative Y-MESO-22 cells underwent apoptosis upon treatment with a low concentration of VS-4718, whereas Merlin-negative, E-cadherin-positive Y-MESO-9 cells did not undergo VS-4718-induced apoptosis. Furthermore, E-cadherin knockdown in Merlin-negative MM cells significantly sensitized cells to VS-4718 and induced apoptotic cell death upon VS-4718 treatment. Together, our results suggest that E-cadherin serves as a predictive biomarker for molecular target therapy with FAK inhibitors for patients with mesothelioma and that its expression endows MM cells with resistance to FAK inhibitors.

  15. Morning glory resin glycosides as modulators of antibiotic activity in multidrug-resistant gram-negative bacteria.

    Science.gov (United States)

    Corona-Castañeda, Berenice; Pereda-Miranda, Rogelio

    2012-01-01

    Twenty-six microbiologically inactive (MIC > 512 µg/mL) convolvulaceous resin glycosides ( 1- 26) were tested for resistance modulatory activity in vitro against Escherichia coli Rosetta-gami and two nosocomial pathogens, Salmonella typhi and Shigella flexneri. These compounds exerted a potentiation effect of the clinically useful antibiotics tetracycline, kanamycin, and chloramphenicol against the tested gram-negative bacteria by increasing antibiotic susceptibility up to 32-fold at concentrations of 25 µg/mL. Therefore, the oligosaccharides from the morning glory family (Convolvulaceae) represent metabolites that reverse microbial resistance mechanisms, favoring an increase in the strength and effectiveness of current antibiotics that are not effective in the treatment of refractive infections caused by multidrug-resistant strains. © Georg Thieme Verlag KG Stuttgart · New York.

  16. High excess costs of infections caused by carbapenem-resistant gram-negative bacilli in an endemic region.

    Science.gov (United States)

    Vargas-Alzate, Carlos Andrés; Higuita-Gutiérrez, Luis Felipe; López López, Lucelly; Cienfuegos Gallet, Astrid Vanessa; Jiménez Quiceno, Judy Natalia

    2017-12-22

    The financial burden of antibiotic resistance is a serious concern worldwide. The aim of this study is to describe the excess costs associated with pneumonia, bacteremia, surgical site infections and intra-abdominal infections caused by carbapenem-resistant gram-negative bacilli in Medellín, Colombia, an endemic region for carbapenem resistance. A cohort study was conducted in a third level hospital from 2014 to 2015. All patients with carbapenem-resistant and carbapenem-susceptible gram-negative bacteria infections were included. Pharmaceutical, medical and surgical direct costs were described from the health system perspective. The excess costs were estimated from generalized linear models using a gamma distribution and adjusted for variables that could affect the cost difference. A total of 218 patients were enrolled, 22% of whom were infected with carbapenem-resistant bacteria. Intra-abdominal infections were the most frequent. The adjusted total excess costs was USD $3,966 (95%CI, 1,684-6,249) with a significantly higher cost for antibiotics, followed by hospital stays, laboratory tests and inter-consultation. The highest excess cost was attributed mainly to the use of broad-spectrum antibiotics (USD $1,827, 95%CI, 1,005-2,648) and followed by length of hospital stay (USD $1,015, 95%CI, 163-1867). The results of this study highlight the importance of designing antimicrobial stewardship programs and infection control strategies in endemic regions to reduce the financial threat of antimicrobial resistance to health systems. Copyright © 2017 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

  17. Activity of cefiderocol (S-649266) against carbapenem-resistant Gram-negative bacteria collected from inpatients in Greek hospitals.

    Science.gov (United States)

    Falagas, Matthew E; Skalidis, Tilemachos; Vardakas, Konstantinos Z; Legakis, Nicholas J

    2017-06-01

    Cefiderocol (S-649266), a siderophore cephalosporin, utilizes a novel mechanism of entry into the periplasmic space of Gram-negative bacteria and is broadly stable to ESBLs and carbapenemases. A collection of carbapenem-resistant Gram-negative bacteria isolated from clinical specimens in 18 Greek hospitals was tested for susceptibility to cefiderocol, meropenem, ceftazidime, cefepime, ceftazidime/avibactam, ceftolozane/tazobactam, aztreonam, amikacin, ciprofloxacin, colistin and tigecycline. Broth microdilution plates were used to determine MICs. In total 189 non-fermentative Gram-negative bacteria (107 Acinetobacter baumannii and 82 Pseudomonas aeruginosa ) and 282 Enterobacteriaceae (including 244 Klebsiella pneumoniae , 14 Enterobacter cloacae and 11 Providencia stuartii ) were studied. For both A. baumannii and P. aeruginosa the MIC 90 of cefiderocol was 0.5 mg/L. For K. pneumoniae , E. cloacae and P. stuartii the MIC 90 of cefiderocol was 1, 1 and 0.5 mg/L, respectively. Tigecycline was the second most active antibiotic, followed by colistin. Cefiderocol exhibited greater antimicrobial activity in vitro against carbapenem-resistant Gram-negative bacteria than comparator antibiotics.

  18. Antibacterial activities of selected edible plants extracts against multidrug-resistant Gram-negative bacteria

    National Research Council Canada - National Science Library

    Djeussi, Doriane E; Noumedem, Jaurès A K; Seukep, Jackson A; Fankam, Aimé G; Voukeng, Igor K; Tankeo, Simplice B; Nkuete, Antoine H L; Kuete, Victor

    2013-01-01

    ...). The phytochemical screening of the studied extracts was performed using described methods whilst the liquid broth micro dilution was used for all antimicrobial assays against 27 Gram-negative bacteria...

  19. The pathogenicity and antibiotic resistance of coagulase-negative Staphylococci isolated from the maxillary and ethmoid sinuses.

    Science.gov (United States)

    Aral, Murat; Keleş, Erol; Okur, Erdoğan; Alpay, H Cengiz; Yilmaz, Mustafa

    2004-09-01

    To investigate the pathogenicity and antibiotic resistance of coagulase-negative staphylococci (CNS) isolated from the maxillary and ethmoid sinuses of patients undergoing endoscopic sinus surgery for chronic sinusitis. Ninety-three patients (63 males, 30 females) aged between 19 - 68 years, who had undergone functional endoscopic sinus surgery (FESS) for chronic sinusitis, were included in the study. Nasal mucosa, skin and adjacent structures were cleansed with povidone-iodine solution before surgery to prevent a probable contamination. In all patients, nasal swabs were taken before and after the application of povidone-iodine solution. Colonies isolated and identified as Staphylococci in cultures were further investigated for pathogenicity and antibiotic susceptibility. Slime test was used to determine the pathogenicity of CNS. The relationship between antibiotic resistance of pathogenic and non-pathogenic CNS was compared by chi2 analysis. While bacterial growth rate was 62.3% in nasal swab cultures taken before the application of povidone-iodine solution, it decreased to 12.9% after the application of solution. Microorganisms were isolated in 95.6% of cultures taken from maxillary sinuses and in 91.3% of cultures obtained from ethmoid sinuses during the FESS. The most frequently isolated microorganism in each of the sinuses was CNS. Slime test was carried out in 30 CNS isolated. Twelve of these were slime positive and 18 were slime negative. While 83.3% of CNS isolated was resistant to penicilin, all of CNS were sensitive to vancomycin and teikoplanine. The difference between slime positive and slime negative CNS for gentamicin and ciprofloxacin resistance was statistically significant (p<0.05). We consider that the pathogenicity tests like slime production and antimicrobial susceptibilities of CNS frequently isolated from the patients with chronic sinusitis should be investigated and also these microorganisms should be kept in mind in the selection of empiric

  20. In vitro activity of potential old and new drugs against multidrug-resistant gram-negatives.

    Science.gov (United States)

    Rizek, Camila; Ferraz, Juliana Rosa; van der Heijden, Inneke Marie; Giudice, Mauro; Mostachio, Anna Karina; Paez, Jorge; Carrilho, Claudia; Levin, Anna Sara; Costa, Silvia F

    2015-02-01

    The aim of this study was to evaluate the in vitro susceptibility of MDR gram-negatives bacteria to old drugs such as polymyxin B, minocycline and fosfomycin and new drugs such as tigecycline. One hundred and fifty-three isolates from 4 Brazilian hospitals were evaluated. Forty-seven Acinetobacter baumannii resistant to carbapenens harboring adeB, blaOxA23, blaOxA51, blaOxA143 and blaIMP genes, 48 Stenotrophomonas maltophilia including isolates resistant to levofloxacin and/or trimethoprim-sulfamethoxazole harboring sul-1, sul-2 and qnrMR and 8 Serratia marcescens and 50 Klebsiella pneumoniae resistant to carbapenens harboring blaKPC-2 were tested to determine their minimum inhibitory concentrations (MICs) by microdilution to the following drugs: minocycline, ampicillin-sulbactam, tigecycline, and polymyxin B and by agar dilution to fosfomycin according with breakpoint criteria of CLSI and EUCAST (fosfomycin). In addition, EUCAST fosfomycin breakpoint for Pseudomonas spp. was applied for Acinetobacter spp and S. maltophilia, the FDA criteria for tigecycline was used for Acinetobacter spp and S. maltophilia and the Pseudomonas spp polymyxin B CLSI criterion was used for S. maltophilia. Tigecycline showed the best in vitro activity against the MDR gram-negative evaluated, followed by polymyxin B and fosfomycin. Polymyxin B resistance among K. pneumoniae was detected in 6 isolates, using the breakpoint of MIC > 8 ug/mL. Two of these isolates were resistant to tigecycline. Minocycline was tested only against S. maltophilia and A. baumannii and showed excellent activity against both. Fosfomycin seems to not be an option to treat infections due to the A. baumannii and S. maltophilia isolates according with EUCAST breakpoint, on the other hand, showed excellent activity against S. marcescens and K. pneumoniae. Copyright © 2014 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

  1. Colistin resistance in gram-negative bacteria during prophylactic topical colistin use in intensive care units

    NARCIS (Netherlands)

    Oostdijk, Evelien A. N.; Smits, Loek; de Smet, Anne Marie G. A.; Leverstein-van Hall, Maurine A.; Kesecioglu, Jozef; Bonten, Marc J. M.

    Topical use of colistin as part of selective digestive decontamination (SDD) and selective oropharyngeal decontamination (SOD) has been associated with improved patient outcome in intensive care units (ICU), yet little is known about the risks of colistin resistance. We quantified effects of

  2. Rapid emergence of resistant coagulase-negative staphylococci on the skin after antibiotic prophylaxis

    NARCIS (Netherlands)

    Terpstra, S; Noordhoek, GT; Voesten, HGJ; Degener, JE

    One approach for prosthetic vascular surgery is to continue antimicrobial prophylaxis while intravascular lines and catheters are in place. However this may give rise to antimicrobial resistance in the colonizing bacterial flora. We studied 37 patients undergoing vascular surgery, who received

  3. Activity of siderophores against drug-resistant Gram-positive and Gram-negative bacteria

    Directory of Open Access Journals (Sweden)

    Gokarn K

    2018-01-01

    Full Text Available Karuna Gokarn,1,2 Ramprasad B Pal1 1Department of Microbiology, Sir Hurkisondas Nurrotumdas Medical Research Society, 2Caius Research Laboratory, St Xavier’s College, Mumbai, India Abstract: Infections by drug-resistant bacteria are life-threatening. As iron is a vital element for the growth of bacteria, iron-chelating agents (siderophores can be used to arrest their multiplication. Exogenous siderophores – exochelin-MS and deferoxamine-B – were evaluated for their inhibitory activity against methicillin-resistant Staphylococcus aureus and metallo-β-lactamase producers – Pseudomonas aeruginosa and Acinetobacter baumannii – by disc diffusion, micro-broth dilution, and turbidimetric growth assays. The drug-resistant isolates were inhibited by the synergistic activity of siderophores and antibiotics. Minimum inhibitory concentration of exochelin-MS+ampicillin for different isolates was between 0.05 and 0.5 mg/mL. Minimum inhibitory concentration of deferoxamine-B+ampicillin was 1.0 mg/mL and greater. Iron-chelation therapy could provide a complementary approach to overcome drug resistance in pathogenic bacteria. Keywords: iron-chelation, xenosiderophores, exochelin MS, deferoxamine B

  4. A Simple and Reliable PDMS and SU-8 Irreversible Bonding Method and Its Application on a Microfluidic-MEA Device for Neuroscience Research

    Directory of Open Access Journals (Sweden)

    Yufei Ren

    2015-12-01

    Full Text Available Polydimethylsiloxane (PDMS and SU-8 are currently two very commonly used polymeric materials in the microfluidics field for biological applications. However; there is a pressing need to find a simple, reliable, irreversible bonding method between these two materials for their combined use in innovative integrated microsystems. In this paper, we attempt to investigate the aminosilane-mediated irreversible bonding method for PDMS and SU-8 with X-Ray Photoelectron Spectroscopy (XPS surface analysis and bonding strength tests. Additionally, the selected bonding method was applied in fabricating a microelectrode array (MEA device, including microfluidic features, which allows electrophysiological observations on compartmentalized neuronal cultures. As there is a growing trend towards microfluidic devices for neuroscience research, this type of integrated microdevice, which can observe functional alterations on compartmentalized neuronal culture, can potentially be used for neurodegenerative disease research and pharmaceutical development.

  5. Is colistin effective in the treatment of infections caused by multidrug-resistant (MDR) or extremely drug-resistant (XDR) gram-negative microorganisms in children?

    Science.gov (United States)

    Ozsurekci, Yasemin; Aykac, Kubra; Cengiz, Ali Bulent; Bayhan, Cihangul; Sancak, Banu; Karadag Oncel, Eda; Kara, Ates; Ceyhan, Mehmet

    2016-06-01

    The increasing incidence of infections caused by multidrug-resistant (MDR) or extremely drug-resistant (XDR) gram-negative organisms has led to the reemergence of colistin use. Clinical and demographic data were collected on 94 pediatric patients diagnosed with MDR or XDR gram-negative infections and treated with either a colistin-containing regimen (colistin group) or at least one antimicrobial agent other than colistin (noncolistin group). The overall clinical response rates were 65.8% in the colistin group and 70.0% in the noncolistin group (P = 0.33). The infection-related mortality rates were 11% in the colistin group and 13.3% in the noncolistin group (P = 0.74). There was no statistically significant difference in nephrotoxicity in the colistin and noncolistin groups. Colistin therapy was at least as effective and as safe as beta-lactam antibiotics or quinolones, with or without aminoglycosides, in the treatment of infections caused by gram-negative organisms and may be a therapeutic option in children. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Prevalence and antibiotic resistance of coagulase-negative Staphylococci isolated from poultry farms in three regions of Ghana

    Directory of Open Access Journals (Sweden)

    Boamah VE

    2017-06-01

    Full Text Available Vivian Etsiapa Boamah,1 Christian Agyare,1 Hayford Odoi,1 Francis Adu,1 Stephen Yao Gbedema,1 Anders Dalsgaard2 1Microbiology Section, Department of Pharmaceutics, Faculty of Pharmacy and Pharmaceutical Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana; 2Section of Food Safety and Zoonoses, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederisksberg, Denmark Abstract: The use of antibiotics in animal production has been associated with the development and spread of antibiotic-resistant organisms including commensals. Coagulase-negative Staphylococcus (CoNS species, which were until recently considered non-pathogenic, have been associated with opportunistic infections and high resistance to several antibiotics. This study sought to determine the prevalence, identity, and phenotypic resistance of coagulase-negative Staphylococcus spp. isolated from some selected poultry farms and farm workers in the Ashanti, Brong Ahafo, and Greater Accra regions of Ghana. Poultry litter samples and oral swabs of poultry farm workers were collected, from which bacterial species were isolated, identified, and analyzed. Various selective media were used for the presumptive identification of the different species. Confirmation of bacterial identity was done using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF mass spectrometry. Antibiotic susceptibility testing of the isolates was performed using the Kirby-Bauer disk diffusion method. Zones of growth inhibition were interpreted based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST guidelines. Two hundred and fifty-six coagulase-negative Staphylococcus spp., comprising S. sciuri (42.97%, S. lentus (35.94%, S. gallinarum (6.64%, S. xylosus (4.30%, S. haemolyticus (3.91%, S. saprophyticus (1.95%, and S. cohnii (0.39% were confirmed by MALDI-TOF. CoNS were isolated from samples

  7. Negative Resistance Circuit for Damping an Array of Coupled FitzHugh-Nagumo Oscillators

    DEFF Research Database (Denmark)

    Tamaševičius, Arūnas; Adomaitienė, Elena; Bumelienė, Skaidra

    2015-01-01

    An analog circuit, based on a negative impedance converter and a capacitor, for damping oscillations in an array of mean-field coupled neuronal FitzHugh–Nagumo (FHN) type oscillators is described. The circuit is essentially a two-terminal feedback controller. When coupled to an array of the FHN o...

  8. Characterization of methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative Staphylococcus spp. isolated from US West Coast public marine beaches.

    Science.gov (United States)

    Soge, Olusegun O; Meschke, John S; No, David B; Roberts, Marilyn C

    2009-12-01

    The aim of this study was to isolate and characterize methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus spp. (MRCoNS) from marine water and intertidal beach sand from public beaches in Washington State, USA. Fifty-one staphylococci from Washington State beaches were characterized using antimicrobial susceptibility testing, carriage of acquired tetracycline and/or macrolide resistance genes, staphylococcal cassette chromosome mec (SCCmec) typing, the BBL Crystal Gram-Positive ID System and/or 16S rRNA sequencing, coagulase test and multilocus sequence typing (MLST) for MRSA. Five multidrug-resistant MRSA SCCmec type I, of which three were MLST type ST45, one ST59 and one a new MLST type, ST1405, plus one susceptible non-typeable (NT) MRSA ST30 were characterized. Thirty-three MRCoNS isolates, representing 21 strains from 9 Staphylococcus spp., carried a range of SCCmec types [I (2), II (6), III (3), V (2), I/II (1) and NT (7)] and varied in their antibiotic susceptibility to other antibiotic classes and carriage of acquired tetracycline/macrolide resistance gene(s). MRSA and MRCoNS donors co-transferred tet(M) and erm(A) genes to an Enterococcus faecalis recipient at a frequency of 10(-8). This is the first report of MRSA and MRCoNS isolated from marine water and intertidal beach sand. The MLST types and antibiotic carriage of five MRSA isolates were similar to hospital MRSA isolates rather than US community-acquired MRSA isolates. Our results suggest that public marine beaches may be a reservoir for transmission of MRSA to beach visitors as well as an ecosystem for exchange of antibiotic resistance genes among staphylococci and related genera.

  9. Antibacterial and antibiotic resistance modulatory activities of leaves and bark extracts of Recinodindron heudelotii (Euphorbiaceae) against multidrug-resistant Gram-negative bacteria.

    Science.gov (United States)

    Fankam, Aimé Gabriel; Kuiate, Jules-Roger; Kuete, Victor

    2017-03-24

    Recinodindron heudelotii (Euphorbiaceae) is a plant used in Africa, particularly in Cameroon to treat various ailments including bacterial infections. In this study, we evaluated the extracts of the leaves (RHL) and bark (RHB) of R. heudelotii for their antibacterial and antibiotic resistance modulating activities against 29 Gram-negative bacteria, including multidrug-resistant (MDR) phenotypes. The broth micro-dilution assay was used to evaluate the antibacterial activity, and the antibiotic resistance modulating effects of the plant extracts. RHL displayed the most important spectrum of activity with minimal inhibitory concentrations (MICs) values ranging from 256 to 1024 μg/mL against 75.86% of the 29 tested bacteria strains while RHB was not active. RHL also showed killing effects with minimal bactericidal concentrations (MBCs) ranging from 256 to 1024 μg/mL. The activities of tetracycline and kanamycin associated with RHL were improved on 88.89% and 77.78% of the tested MDR bacteria, at MIC/2 at MIC/4 respectively, with 2 to 16-folds decreasing of MIC. This suggests the antibiotic resistance modulating effects of these antibiotics. The present study provides data indicating a possible use of the leaves extract of Recinodindron heudelotii alone or in association with common antibiotics in the fight against bacterial infections including those involving MDR bacteria.

  10. Resistance in gram-negative bacilli in a cardiac intensive care unit in India: Risk factors and outcome

    Directory of Open Access Journals (Sweden)

    Pawar Mandakini

    2008-01-01

    Full Text Available The objective of this study was to compare the risk factors and outcome of patients with preexisting resistant gram-negative bacilli (GNB with those who develop sensitive GNB in the cardiac intensive care unit (ICU. Of the 3161 patients ( n = 3,161 admitted to the ICU during the study period, 130 (4.11% developed health care-associated infections (HAIs with GNB and were included in the cohort study. Pseudomonas aeruginosa (37.8% was the most common organism isolated followed by Klebsiella species (24.2%, E. coli (22.0%, Enterobacter species (6.1%, Stenotrophomonas maltophilia (5.7%, Acinetobacter species (1.3%, Serratia marcescens (0.8%, Weeksella virosa (0.4% and Burkholderia cepacia (0.4%. Univariate analysis revealed that the following variables were significantly associated with the antibiotic-resistant GNB: females ( P = 0.018, re-exploration ( P = 0.004, valve surgery ( P = 0.003, duration of central venous catheter ( P < 0.001, duration of mechanical ventilation ( P < 0.001, duration of intra-aortic balloon counter-pulsation ( P = 0.018, duration of urinary catheter ( P < 0.001, total number of antibiotic exposures prior to the development of resistance ( P < 0.001, duration of antibiotic use prior to the development of resistance ( P = 0.014, acute physiology and age chronic health evaluation score (APACHE II, receipt of anti-pseudomonal penicillins (piperacillin-tazobactam ( P = 0.002 and carbapenems ( P < 0.001. On multivariate analysis, valve surgery (adjusted OR = 2.033; 95% CI = 1.052-3.928; P = 0.035, duration of mechanical ventilation (adjusted OR = 1.265; 95% CI = 1.055-1.517; P = 0.011 and total number of antibiotic exposure prior to the development of resistance (adjusted OR = 1.381; 95% CI = 1.030-1.853; P = 0.031 were identified as independent risk factors for HAIs in resistant GNB. The mortality rate in patients with resistant GNB was significantly higher than those with sensitive GNB (13.9% vs. 1.8%; P = 0.03. HAI with

  11. History and evolution of antibiotic resistance in coagulase-negative staphylococci: Susceptibility profiles of new anti-staphylococcal agents.

    Science.gov (United States)

    John, Joseph F; Harvin, Alexander M

    2007-12-01

    Coagulase-negative staphylococci (CNS) are a heterogenous group of Gram-positive cocci that are widespread commensals among mammalia. Unlike their coagulase-positive counterpart, Staphylococcus aureus, CNS produce few virulence patterns and normally refrain from invading tissue. Yet, not only can CNS cause infections in normal host tissue, but modern medicine has also seen their rise as opportunists that display adherence to medical device materials to produce a protective biofilm. CNS have historically been more resistant to antimicrobials, including the beta-lactam antibiotics, than S. aureus and some hospitals reveal rates of oxacillin resistance in CNS approaching 90%. Cross resistance to non-beta-lactam agents has been a recurrent theme over the past 40 years in the CNS. Thus, there has been a pressing need for newer antimicrobial agents with good antistaphylococcal activity. Those new agents tend to have excellent antistaphylococcal activity include daptomycin, linezolid, oritavancin, telavancin, tigecycline, dalbavancin, new quinolones, and ceftibiprole, several of which have unique mechanisms of action. The MIC₉₀ for these new compounds typically ranges from 0.5-4 mug/mL. Staphylococcal biofilm formation is quite common in CNS infections and markedly increases the MIC for most older antimicrobials. Several of the newer agents offer some promise of penetration of biofilm to inhibit or kill adherent staphylococci. CNS will likely remain a major cause of infections in the modern age, evolve further antimicrobial resistance mechanisms, and require development of newer antimicrobials for curative therapy.

  12. Negative differential resistance effect induced by metal ion implantation in SiO2 film for multilevel RRAM application

    Science.gov (United States)

    Wu, Facai; Si, Shuyao; Shi, Tuo; Zhao, Xiaolong; Liu, Qi; Liao, Lei; Lv, Hangbing; Long, Shibing; Liu, Ming

    2018-02-01

    Pt/SiO2:metal nanoparticles/Pt sandwich structure is fabricated with the method of metal ion (Ag) implantation. The device exhibits multilevel storage with appropriate R off/R on ratio, good endurance and retention properties. Based on transmission electron microscopy and energy dispersive spectrometer analysis, we confirm that Pt nanoparticles are spurted into SiO2 film from Pt bottom electrode by Ag implantation; during electroforming, the local electric field can be enhanced by these Pt nanoparticles, meanwhile the Ag nanoparticles constantly migrate toward the Pt nanoparticles. The implantation induced nanoparticles act as trap sites in the resistive switching layer and play critical roles in the multilevel storage, which is evidenced by the negative differential resistance effect in the current–voltage (I–V) measurements.

  13. Colistin MIC Variability by Method for Contemporary Clinical Isolates of Multidrug-Resistant Gram-Negative Bacilli

    Science.gov (United States)

    Hindler, Janet A.

    2013-01-01

    In vitro evaluation of colistin susceptibility is fraught with complications, due in part to the inherent cationic properties of colistin. In addition, no reference method has been defined against which to compare the results of colistin susceptibility testing. This study systematically evaluated the available methods for colistin MIC testing in two phases. In phase I, colistin MICs were determined in 107 fresh clinical isolates of multidrug-resistant (MDR) Gram-negative bacilli (GNB) by broth microdilution with polysorbate 80 (BMD-T), broth macrodilution (TDS), and the Etest. In phase II, 50 of these isolates, 10 of which were colistin resistant, were tested in parallel using BMD-T, TDS, agar dilution, broth microdilution without polysorbate 80 (BMD), and the TREK Gram-negative extra MIC format (GNXF) Sensititre. The Etest was also performed on these 50 isolates using Mueller-Hinton agar (MHA) from three different manufacturers. Colistin MIC results obtained from the five methods were compared to the MIC results obtained using BMD-T, the method that enables the highest nominal concentration of colistin in the test medium. Essential agreement ranged from 34% (BMD) to 83% (TDS), whereas categorical agreement was >90% for all methods except for BMD, which was 88%. Very major errors (VMEs) (i.e., false susceptibility) for the Etest were found in 47 to 53% of the resistant isolates, depending on the manufacturer of the MHA that was used. In contrast, VMEs were found for 10% (n = 1) of the resistant isolates by BMD and 0% of the isolates by the TDS, agar dilution, and Sensititre methods. Based on these data, we urge clinical laboratories to be aware of the variable results that can occur when using different methods for colistin MIC testing and, in particular, to use caution with the Etest. PMID:23486719

  14. Metal-semiconductor transition and negative magneto-resistance in degenerate ultrathin tin oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Bansal, Shikha; Kashyap, Subhash C.; Pandya, Dinesh K., E-mail: dkpandya@physics.iitd.ac.in

    2015-10-15

    A study of electron- and magneto-transport behavior of ultrathin SnO{sub 2} films of thickness ≤40 nm with high conductivity of 537 Ω{sup −1} cm{sup −1} deposited on glass substrate by using DC reactive sputtering has been carried out at low temperature. Hall effect measurements revealed these SnO{sub 2} films to be degenerate down to 40 K. The films with thickness >5 nm are found to undergo a metal-semiconductor transition below 140 K, and show a negative MR of ∼1.5% at a magnetic field of 0.9 T below 40 K. Both these phenomena have been ascribed to the presence of weak localization of electrons at low temperature. Electron transport behavior has been explained using quantum correction to conductivity. Estimated inelastic scattering lengths were found to be longer than the film thickness which supports two-dimensional nature of electron- and magneto-transport in these ultrathin films. - Highlights: • Ultrathin SnO{sub 2} films show a high conductivity of the order of 10{sup 2} S. • Metal to semiconductor (MS) transition occurs in all the ultrathin SnO{sub 2} films of thickness > 5 nm. • All the samples show degenerate semiconductor behavior. • A negative MR is observed below 40 K in these ultrathin films. • MS transition and negative MR have been explained using weak localization effect.

  15. National epidemiology of carbapenem-resistant and extensively drug-resistant Gram-negative bacteria isolated from blood samples in China in 2013.

    Science.gov (United States)

    Xu, A; Zheng, B; Xu, Y-C; Huang, Z-G; Zhong, N-S; Zhuo, C

    2016-03-01

    Although antimicrobial resistance poses a great challenge to clinicians in China, there are limited antimicrobial resistance data on Gram-negative bacteria nationwide. We investigated the phenotypic characteristics of carbapenem-resistant Escherichia coli (CREC) and Klebsiella pneumoniae (CRKP) as well as extensively drug-resistant strains of Pseudomonas aeruginosa (XDRPA) and Acinetobacter baumannii (XDRAB) isolated from blood cultures in China. Data were collected on 24113 isolates from the China surveillance of antimicrobial resistance program in 2013, which comprised 208 hospitals located in all seven administrative regions of China. Minimum inhibitory concentrations (MICs) for common antimicrobials were determined by commercial automated systems available at local hospitals, and associations with geographic and clinical distributions was further studied. The overall prevalence of CREC, CRKP, XDRAB and XDRPA strains was 1.0, 5.5, 13.7 and 4.2%, respectively. Except for CREC, which did not differ greatly by region, the prevalence of the remaining three strains varied significantly across regions. The highest prevalence of CRKP (10.6%) and XDRAB (13.1%) were found in the pediatric group, and higher prevalence of all four target strains was found in the intensive care unit. For imipenem, 55.8% of CREC and 22.9% of CRKP strains had MICs of ≤4 μg/mL, while 97.4% XDRAB and 84% XDRPA isolates had MICs of ≥16 μg/mL. All CREC, CRKP and 81.2% of XDRAB strains were susceptible to tigecycline, with MIC90 values of 0.5, 2 and 4 μg/mL, respectively. In conclusion, a high prevalence of CRKP and XDRAB has emerged in China, especially in children and in the intensive care unit. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  16. Diversity of staphylococcal cassette chromosome mec structures in coagulase-negative staphylococci and relationship to drug resistance.

    Science.gov (United States)

    Garza-González, Elvira; López, Daniel; Pezina, Cesar; Muruet, Walter; Bocanegra-García, Virgilio; Muñoz, Ivan; Ramírez, Camilo; Llaca-Díaz, Jorge M

    2010-03-01

    The objective of this study was to determine the distribution of staphylococcal cassette chromosome mec (SCCmec) elements in meticillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from a tertiary-care hospital in Mexico and to examine the relationship to drug resistance. Fifty selected MR-CoNS isolates collected from catheters (n=15), blood (n=15), bone (n=9), bronchial lavage (n=2) and urine (n=2) and one isolate each from an abscess, cerebrospinal fluid, eye, pleural effusion, synovial fluid, tracheal aspirate and wound secretion were examined. Susceptibility testing was performed by the broth microdilution method. SCCmec types were determined by multiplex PCR and PFGE was carried out as described previously for Staphylococcus aureus. Among the MR-CoNS strains studied, the most frequently isolated species were Staphylococcus epidermidis (n=26) and Staphylococcus haemolyticus (n=13). Staphylococcus cohnii (n=5), Staphylococcus hominis (n=3), Staphylococcus sciuri (n=1), Staphylococcus pasteuri (n=1) and the recently described species Staphylococcus pettenkoferi (n=1) were also identified. The most frequent MR-CoNS genotype identified was SCCmec type IVa in S. epidermidis isolates, which also showed a high diversity in their PFGE patterns. A clone was found that amplified both SCCmec III and V elements in five isolates examined. The single MR S. pettenkoferi isolate harboured SCCmec type IVd and the single MR S. pasteuri isolate harboured SCCmec type I. The carriage of SCCmec type III was associated with resistance or intermediate resistance to meropenem (P IVa and the high genetic diversity among MR-CoNS strains. As far as is known, this is the first report describing the newly identified S. pettenkoferi possessing SCCmec IVd and S. pasteuri harbouring SCCmec type I. MR-CoNS harbouring SCCmec type III were found to be more resistant to meropenem.

  17. Occurrence and characteristics of methicillin-resistant and -susceptible Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci from Japanese retail ready-to-eat raw fish.

    Science.gov (United States)

    Hammad, Ahmed M; Watanabe, Wataru; Fujii, Tomoko; Shimamoto, Tadashi

    2012-06-01

    Staphylococci are not part of the normal fish microflora. The presence of staphylococci on fish is an indication of (a) post-harvest contamination due to poor personnel hygiene, or (b) disease in fish. The aim of this study was to determine the prevalence, molecular genetic characteristics, antibiotic resistance and virulence factors of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from 200 samples of retail ready-to-eat raw fish (sashimi) collected from the Japanese prefecture of Hiroshima. We characterized 180 staphylococcal strains. A majority of the grocery stores surveyed (92%, 23/25) contained fish contaminated with Staphylococcus species. We recovered 175 S. aureus isolates from 174 (87%, 174/200) samples, with 170 isolates of MSSA. For the MRSA and MR-CoNS, 10 isolates were obtained from 10 samples (5%, 10/200) collected from 10 shops (40%, 10/25) belonging to four supermarket chains. SCCmec typing revealed the presence of a type IV.1 SCCmec cassette in S. warneri isolates, a type II.1 SCCmec cassette in S. haemolyticus isolates and a cassette in methicillin-resistant S. aureus (MRSA) isolates that could not be typed. Molecular typing of two MRSA isolates by spa sequencing and multilocus sequence typing (MLST) identified t1767 and ST8, respectively. Antibiotic resistance genes that confer resistance to aminoglycosides, tetracyclines, β-lactams, macrolides, lincosamides and streptogramin B (MLS(B)) antibiotics were detected. Genes encoding one or more of the following virulence factors: staphylococcal enterotoxins (seb, and sed), toxic shock syndrome toxin 1 (tst), exfoliative toxin (etaA) were detected in 14.2% (25/175) of S. aureus isolates. The accessory gene regulator (agr) typing of S. aureus isolates revealed that agr type 1 was most prevalent (96.5%, 169/175) followed by type 2 (2.2%, 4/175) and type 3 (1.1%, 2/175). None of

  18. Phototherapeutic spectrum expansion through synergistic effect of mesoporous silica trio-nanohybrids against antibiotic-resistant gram-negative bacterium.

    Science.gov (United States)

    Kuthati, Yaswanth; Kankala, Ranjith Kumar; Busa, Prabhakar; Lin, Shi-Xiang; Deng, Jin-Pei; Mou, Chung-Yuan; Lee, Chia-Hung

    2017-04-01

    The extensive impact of antibiotic resistance has led to the exploration of new anti-bacterial modalities. We designed copper impregnated mesoporous silica nanoparticles (Cu-MSN) with immobilizing silver nanoparticles (SNPs) to apply photodynamic inactivation (PDI) of antibiotic-resistant E. coli. SNPs were decorated over the Cu-MSN surfaces by coordination of silver ions on diamine-functionalized Cu-MSN and further reduced to silver nanoparticles with formalin. We demonstrate that silver is capable of sensitizing the gram-negative bacteria E. coli to a gram-positive specific phototherapeutic agent in vitro; thereby expanding curcumin's phototherapeutic spectrum. The mesoporous structure of Cu-MSN remains intact after the exterior decoration with silver nanoparticles and subsequent curcumin loading through an enhanced effect from copper metal-curcumin affinity interaction. The synthesis, as well as successful assembly of the functional nanomaterials, was confirmed by various physical characterization techniques. Curcumin is capable of producing high amounts of reactive oxygen species (ROS) under light irradiation, which can further improve the silver ion release kinetics for antibacterial activity. In addition, the positive charged modified surfaces of Cu-MSN facilitate antimicrobial response through electrostatic attractions towards negatively charged bacterial cell membranes. The antibacterial action of the synthesized nanocomposites can be activated through a synergistic mechanism of energy transfer of the absorbed light from SNP to curcumin. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. [Antimicrobial resistance pattern for gram-negative uropathogens isolated from hospitalised patients and outpatients in Cartagena, 2005-2008].

    Science.gov (United States)

    Castro-Orozco, Raimundo; Barreto-Maya, Ana C; Guzmán-Álvarez, Heidy; Ortega-Quiroz, Rolando J; Benítez-Peña, Lourdes

    2010-12-01

    Determining the microbial aetiology spectrum and antibiotic resistance pattern of uropathogens causing urinary tract infections in hospitalised patients and outpatients. A descriptive study was carried out between February 2005 and November 2008 at the San Buenaventura University's Clinical Laboratory in Cartagena. Antibiotic sensitivity was determined by the Kirby Bauer method. Out of the total specimens (1,384) analysed over the four-year study period, 455 of the urine samples (32.9 %) were culture positive, most (81.4 %) having come from females. The bacterium isolated most frequently was Escherichia coli (60.1 %) followed by Klebsiella pneumoniae (6.9 %), Pseudomonas aeruginosa (6.6 %), Proteus mirabilis (5.4 %) and Acinetobacter baumannii (1.4 %). The Gram-negative isolates displayed a high level of resistance to ampicillin (range 84.3100 %), amoxicillin/clavulanic acid (range 66.580 %) and ciprofloxacin (range 4057.9 %). Gram-negative bacteria were responsible for urinary tract infections in the patients involved in this study. The most commonly isolated bacteria were E. coli. Empirical administration of a third-generation cephalosporin for initial treatment of urinary tract infections in this population appears prudent from the perspective of antimicrobial susceptibility.

  20. Proof of principle for successful characterization of methicillin-resistant coagulase-negative staphylococci isolated from skin by use of raman spectroscopy and pulsed-field gel electrophoresis

    NARCIS (Netherlands)

    H.F.M. Willemse-Erix; J-W. Jachtenberg (Jan-Willem); H. Barutçi; G.J. Puppels (Gerwin); A.F. van Belkum (Alex); A. Voss (Andreas); K. Maquelin (Kees)

    2010-01-01

    textabstractCoagulase-negative staphylococci (CNS) are among the most frequently isolated bacterial species in clinical microbiology, and most CNS-related infections are hospital acquired. Distinguishing between these frequently multiple-antibiotic-resistant isolates is important for both treatment

  1. In Vitro Activity of Cefepime against Multidrug-Resistant Gram-Negative Bacilli, Viridans Group Streptococci and Streptococcus pneumoniae from a Cross-Canada Surveillance Study

    Directory of Open Access Journals (Sweden)

    Donald E Low

    1999-01-01

    Full Text Available OBJECTIVE: To determine the in vitro activity of cefepime against multidrug-resistant Gram-negative bacilli and Gram-positive cocci obtained from an ongoing cross-Canada surveillance study.

  2. Wide dissemination of SCCfusC in fusidic acid resistant coagulase-negative staphylococci and implication for its spreading to methicillin-resistant S. aureus in Taiwan.

    Science.gov (United States)

    Lin, Yu-Tzu; Hung, Wei-Chun; Tsai, Jui-Chang; Leong, Kin Hong; Chen, Hsiao-Jan; Hsueh, Po-Ren; Teng, Lee-Jene

    2018-01-30

    We examined the fusidic acid resistance determinants fusB, fusC, fusD, and fusF in coagulase-negative staphylococci (CoNS) clinical isolates. Among 208 resistant isolates, the fusB gene was the most common determinant in each species except in S. hominis subsp. hominis or in species carrying fusD or fusF. In S. hominis subsp. hominis, the fusC gene was the major determinant responsible for fusidic acid resistance. To understand the genetic context of fusC in S. hominis subsp. hominis, 31 fusC-positive S. hominis subsp. hominis isolates were examined. Among those isolates, 14 carried SCCfusC, 3 carried an SCC 476 -like element, and 8 carried a new SCC structure, SCC 3390 . As shown by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) analyses, the S. hominis subsp. hominis clinical isolates showed limited clonality. Taken together, SCCfusC has been found in S. hominis subsp. hominis, S. epidermidis, S. haemolyticus, S. capitis subsp. ureolyticus and S. aureus, suggesting its wide distribution and spreading among different species of staphylococci. Copyright © 2018 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

  3. Coagulase-negative staphylococci causing blood stream infection at an Indian tertiary care hospital: Prevalence, antimicrobial resistance and molecular characterisation

    Directory of Open Access Journals (Sweden)

    S Singh

    2016-01-01

    Full Text Available Introduction: Recent years have seen a rise of coagulase-negative staphylococci (CoNS from common contaminants to agents of nosocomial blood stream infections (BSI's. Molecular typing and establishing a correlation with antibiotic resistance is essential particularly in countries like India where genotyping studies for drug-resistant CoNS are sparse. Methods: A prospective study was done over 18 months, wherein 42,693 blood samples were received, and 59 patients with BSI due to CoNS were evaluated. The isolates recovered were identified by a biochemical test panel and matrix-assisted laser desorption ionization – time of flight mass spectrometry followed by antimicrobial susceptibility testing by Kirby–Baur disc diffusion method and E-test strips. Staphylococcal chromosomal cassette mec (SCCmec element was characterised by multiplex polymerase chain reaction for all methicillin-resistant (MR isolates. Results: The majority of CoNS isolated were constituted by Staphylococcus haemolyticus (47.5% followed by Staphylococcus epidermidis (33.9%, Staphylococcus hominis (11.86%, Staphylococcus cohnii (5.08% and Staphylococcus warneri (1.69%. Among all isolates 57.6% were MR with statistically significant higher resistance versus methicillin sensitive-CoNS. This difference was significant for erythromycin (76% vs. 44%, P = 0.011, rifampicin (50% vs. 12%,P= 0.002 and amikacin (26.5% vs. 4%, P = 0.023, ciprofloxacin (64.7% vs. 20%, P = 0.001 and cotrimoxazole (55.9% vs. 20%, P = 0.006. SCCmec type I was predominant (61.8%, P = 0.028 and exhibited multidrug resistance (76.2%. Coexistence of SCCmec type I and III was seen in 8.82% MR isolates. Conclusion: CoNS exhibit high antimicrobial resistance thereby limiting treatment options. The presence of new variants of SCCmec type in hospital-acquired CoNS may predict the antibiotic resistance pattern. This is the first evaluation of the molecular epidemiology of CoNS causing BSI from India and can serve as a

  4. Outcome of Transplantation Using Organs From Donors Infected or Colonized With Carbapenem-Resistant Gram-Negative Bacteria.

    Science.gov (United States)

    Mularoni, A; Bertani, A; Vizzini, G; Gona, F; Campanella, M; Spada, M; Gruttadauria, S; Vitulo, P; Conaldi, P; Luca, A; Gridelli, B; Grossi, P

    2015-10-01

    Donor-derived infections due to multidrug-resistant bacteria are a growing problem in solid organ transplantation, and optimal management options are not clear. In a 2-year period, 30/214 (14%) recipients received an organ from 18/170 (10.5%) deceased donors with infection or colonization caused by a carbapenem-resistant gram-negative bacteria that was unknown at the time of transplantation. Among them, 14/30 recipients (47%) received a transplant from a donor with bacteremia or with infection/colonization of the transplanted organ and were considered at high risk of donor-derived infection transmission. The remaining 16/30 (53%) recipients received an organ from a nonbacteremic donor with colonization of a nontransplanted organ and were considered at low risk of infection transmission. Proven transmission occurred in 4 of the 14 high-risk recipients because donor infection was either not recognized, underestimated, or not communicated. These recipients received late, short or inappropriate posttransplant antibiotic therapy. Transmission did not occur in high-risk recipients who received appropriate and prompt antibiotic therapy for at least 7 days. The safe use of organs from donors with multidrug-resistant bacteria requires intra- and inter-institutional communication to allow appropriate management and prompt treatment of recipients in order to avoid transmission of infection. © Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.

  5. An unusual class of anthracyclines potentiate Gram-positive antibiotics in intrinsically resistant Gram-negative bacteria.

    Science.gov (United States)

    Cox, Georgina; Koteva, Kalinka; Wright, Gerard D

    2014-07-01

    An orthogonal approach taken towards novel antibacterial drug discovery involves the identification of small molecules that potentiate or enhance the activity of existing antibacterial agents. This study aimed to identify natural-product rifampicin adjuvants in the intrinsically resistant organism Escherichia coli. E. coli BW25113 was screened against 1120 actinomycete fermentation extracts in the presence of subinhibitory (2 mg/L) concentrations of rifampicin. The active molecule exhibiting the greatest rifampicin potentiation was isolated using activity-guided methods and identified using mass and NMR spectroscopy. Susceptibility testing and biochemical assays were used to determine the mechanism of antibiotic potentiation. The anthracycline Antibiotic 301A(1) was isolated from the fermentation broth of a strain of Streptomyces (WAC450); the molecule was shown to be highly synergistic with rifampicin (fractional inhibitory concentration index = 0.156) and moderately synergistic with linezolid (FIC index = 0.25) in both E. coli and Acinetobacter baumannii. Activity was associated with inhibition of efflux and the synergistic phenotype was lost when tested against E. coli harbouring mutations within the rpoB gene. Structure-activity relationship studies revealed that other anthracyclines do not synergize with rifampicin and removal of the sugar moiety of Antibiotic 301A(1) abolishes activity. Screening only a subsection of our natural product library identified a small-molecule antibiotic adjuvant capable of sensitizing Gram-negative bacteria to antibiotics to which they are ordinarily intrinsically resistant. This result demonstrates the great potential of this approach in expanding antibiotic effectiveness in the face of the growing challenge of resistance in Gram-negatives. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  6. Evaluating the resistance pattern of gram-negative bacteria during three years at the nephrology ward of a referral hospital in southwest of Iran.

    Science.gov (United States)

    Karimzadeh, Iman; Sadeghimanesh, Niloofar; Mirzaee, Mona; Sagheb, Mohammad Mahdi

    2017-07-01

    Gram-negative bacteria are associated with an increase in rates of antibacterial resistance. In most low- and middle-income countries such as Iran, there is no continuous surveillance system for antibiotic resistance. The purpose of this survey was to determine the pattern of antimicrobial sensitivity of gram-negative bacteria within 3 consecutive years at a nephrology ward of Nemazee hospital in Shiraz. During a 3-year period from 2013 to 2015 at the adult nephrology ward, bacteriological data of all biological samples of hospitalized patients in favor of gram-negative microorganisms were analyzed retrospectively. Antimicrobial susceptibility was performed by the Kirby-Bauer disc diffusion method. The most common gram negative bacterium isolated from biological samples was Escherichia coli (43.9%). The highest (86.3%-94.1%) antibacterial resistance rate was associated with Acinetobacter spp. The most frequent resistance was seen with cephalosporins. In contrast to ceftriaxone, ciprofloxacin, and trimethoprim/sulfamethoxazole, nitrofurantoin and aminoglycosides remained their acceptable activity against E. coli. At least three-fourths (75%) of Acinetobacter spp. isolates was resistant to either aminoglycosides or imipenem. All (100%) isolated Acinetobacter spp. and Pseudomonas aeruginosa species were susceptible to colistin. The rate of Acinetobacter spp. and P. aeruginosa resistant to three or more drugs was 81.7% and 74.6%, respectively. The resistant rate of gram negative pathogens to different tested antibacterial agents was considerably high and has increased during the recent three years in our center.

  7. Analysis of class 2 integrons as a marker for multidrug resistance among Gram negative bacilli

    Directory of Open Access Journals (Sweden)

    Cecilia Rodríguez

    2016-10-01

    Full Text Available Class 1 and 2 integrons are considered the paradigm of multidrug resistant (MDR integrons. Although class 1 integrons have been found statistically associated to Enterobacteriaceae MDR isolates, this type of study has not been conducted for class 2 integrons. and 3 species that were found that harbored more than 20% of class 2 integrons in clinical isolates, were selected to determine the role of intI2 as MDR marker. A total of 234 MDR/191 susceptible non-epidemiologically related isolates were analyzed. Seventy-four intI2 genes were found by PCR and sequencing. An intI2 relationship with MDR phenotypes in Acinetobacter baumannii and Enterobacter cloacae was found. No statistical association was identified with MDR E. coli and Helicobacter pylori isolates. In other words, the likelihood of finding intI2 is the same in susceptible and in MDR E. coli and H. pylori strains, suggesting a particular affinity between the mobile element Tn7 and some species. The use of intI2 as MDR marker was species-dependent, with fluctuating epidemiology at geographical and temporal gradients. The use of intI2 as MDR marker is advisable in A. baumannii, a species that can reach high frequencies of this genetic element.

  8. How to Manage Infections Caused by Antibiotic Resistant Gram-negative Bacteria - EBMT Educational Meeting from the Severe Aplastic Anaemia and Infectious Diseases Working Parties, Naples, Italy, 2014.

    Science.gov (United States)

    Mikulska, Małgorzata

    2015-02-23

    Multidrug resistant (MDR) Gram-negative bacteria are increasingly frequent in hematopoietic stem cell transplant (HSCT) recipients, yet their prevalence is highly variable among transplant centres. Thus, the knowledge of local epidemiology is mandatory for deciding the most appropriate management protocols. Empirical therapy of febrile neutropenia should be individualized. Either escalation or de-escalation strategy could be chosen, based on local epidemiology, individual risk factors for infection due to resistant strains, such as previous infection or colonization with a resistant pathogen, and clinical presentation. De-escalation approach is recommended in case of severe clinical presentation in patients who are at high risk of drug-resistant infection. Targeted therapy of MDR Gram-negatives, in particular carbapenem-resistant strains, calls for a combination treatment, usually including colistin. No large randomized trials exist in this setting. Local epidemiology dictates which resistant bacteria should be routinely screened for, and infection control precautions are mandatory to limit the spread of resistant strains. Antimicrobial stewardship, with the aim of the best possible management of bacterial infections, should be put in place in every transplant centre. In conclusion, infections caused by resistant Gram-negative bacteria in HSCT population warrant currently particular attention in order to limit their negative impact on transplant outcomes.

  9. Antibiotic resistance and mecA characterization of coagulase-negative staphylococci isolated from three hotels in London, UK

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    Zhen eXu

    2015-09-01

    Full Text Available Antibiotic resistance in bacteria isolated from non–healthcare environments, is a potential problem to public health. In our survey a total of 71 coagulase negative staphylococci belonging to 11 different species were isolated from 3 large hotels in London, UK. The most prevalent species was Staphylococcus haemolyticus, with S. hominis, S. warneri, S.cohnii and S. epidermidis commonly detected. Antimicrobial susceptibilities and carriage of the mecA gene were determined for all of these isolates. Most (85.9% staphylococci were resistant to multiple antibiotics with all displaying increased susceptibility towards penicillin, fusidic acid, erythromycin and cefepime. 21 (29.5% of the isolates were mecA positive, however MIC values to oxacillin, normally associated with the carriage of mecA, varied widely in this group (from 0.06 mg/L to 256 mg/L. 15 of the 21 mecA positive isolates carried SCCmec of these 7 were type V, 1 type I, 1 type II and 1 type IV. Additionally, five of these 15 isolates carried a previously unreported type, 1A, which involves an association between class A mec complex and ccr type 1. The remaining 6 of the 21 isolates were non-typeable and carried a combination of class A mec complex and ccrC. In addition to this, we also report on new MLST types which were assigned for 5 Staphylococcus epidermidis isolates. 4 out of these 5 isolates had MICs between 0.06 to 256 mg/L to oxacillin and would be regarded as clinically susceptible but one isolate had a high oxacillin MIC of 256 mg/L. We demonstrated widespread multiple drug resistance among different staphylococcal species isolated from non-healthcare environments highlighting the potential for these species to act as a reservoir for methicillin and other forms of drug resistance.

  10. Chemical resistance of the gram-negative bacteria to different sanitizers in a water purification system

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    Penna Thereza CV

    2006-08-01

    Full Text Available Abstract Background Purified water for pharmaceutical purposes must be free of microbial contamination and pyrogens. Even with the additional sanitary and disinfecting treatments applied to the system (sequential operational stages, Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas alcaligenes, Pseudomonas picketti, Flavobacterium aureum, Acinetobacter lowffi and Pseudomonas diminuta were isolated and identified from a thirteen-stage purification system. To evaluate the efficacy of the chemical agents used in the disinfecting process along with those used to adjust chemical characteristics of the system, over the identified bacteria, the kinetic parameter of killing time (D-value necessary to inactivate 90% of the initial bioburden (decimal reduction time was experimentally determined. Methods Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas alcaligenes, Pseudomonas picketti, Flavobacterium aureum, Acinetobacter lowffi and Pseudomonas diminuta were called in house (wild bacteria. Pseudomonas diminuta ATCC 11568, Pseudomonas alcaligenes INCQS , Pseudomonas aeruginosa ATCC 15442, Pseudomonas fluorescens ATCC 3178, Pseudomonas picketti ATCC 5031, Bacillus subtilis ATCC 937 and Escherichia coli ATCC 25922 were used as 'standard' bacteria to evaluate resistance at 25°C against either 0.5% citric acid, 0.5% hydrochloric acid, 70% ethanol, 0.5% sodium bisulfite, 0.4% sodium hydroxide, 0.5% sodium hypochlorite, or a mixture of 2.2% hydrogen peroxide (H2O2 and 0.45% peracetic acid. Results The efficacy of the sanitizers varied with concentration and contact time to reduce decimal logarithmic (log10 population (n cycles. To kill 90% of the initial population (or one log10 cycle, the necessary time (D-value was for P. aeruginosa into: (i 0.5% citric acid, D = 3.8 min; (ii 0.5% hydrochloric acid, D = 6.9 min; (iii 70% ethanol, D = 9.7 min; (iv 0.5% sodium bisulfite, D = 5.3 min; (v 0.4% sodium hydroxide, D = 14.2 min; (vi 0.5% sodium

  11. Spin-filtering, negative differential resistance, and giant magnetoresistance in (2 × 1) reconstructed zigzag MoS2 nanoribbons

    Science.gov (United States)

    Lv, Y. Z.; Zhao, P.; Liu, D. S.

    2018-01-01

    Based on density functional theory combined with nonequilibrium Green's function method, we have investigated the spin-polarized transport properties of the (2 × 1) reconstructed zigzag MoS2 nanoribbon (ZMoS2NR)-based devices. The results show that these devices can exhibit multiple high-performance spin-dependent transport properties by modulating the applied magnetic field, including spin-filtering, negative differential resistance and giant magnetoresistance effects. These effects are explained by the spin band structures around the Fermi level, as well as their symmetries. Moreover, all effects are robust regardless of the nanoribbon width. These findings suggest the (2 × 1) reconstructed ZMoS2NRs have great potential in the field of spintronics.

  12. Coherent Interlayer Tunneling and Negative Differential Resistance with High Current Density in Double Bilayer Graphene-WSe2 Heterostructures.

    Science.gov (United States)

    Burg, G William; Prasad, Nitin; Fallahazad, Babak; Valsaraj, Amithraj; Kim, Kyounghwan; Taniguchi, Takashi; Watanabe, Kenji; Wang, Qingxiao; Kim, Moon J; Register, Leonard F; Tutuc, Emanuel

    2017-06-14

    We demonstrate gate-tunable resonant tunneling and negative differential resistance between two rotationally aligned bilayer graphene sheets separated by bilayer WSe2. We observe large interlayer current densities of 2 and 2.5 μA/μm2 and peak-to-valley ratios approaching 4 and 6 at room temperature and 1.5 K, respectively, values that are comparable to epitaxially grown resonant tunneling heterostructures. An excellent agreement between theoretical calculations using a Lorentzian spectral function for the two-dimensional (2D) quasiparticle states, and the experimental data indicates that the interlayer current stems primarily from energy and in-plane momentum conserving 2D-2D tunneling, with minimal contributions from inelastic or non-momentum-conserving tunneling. We demonstrate narrow tunneling resonances with intrinsic half-widths of 4 and 6 meV at 1.5 and 300 K, respectively.

  13. Multiple Negative Differential Resistance Device by Using the Ambipolar Behavior of Tunneling Field Effect Transistor with Fast Switching Characteristics.

    Science.gov (United States)

    Jeong, Jae Won; Jang, E-San; Shin, Sunhae; Kim, Kyung Rok

    2016-05-01

    We propose a novel double-peak negative differential resistance (NDR) characteristic at the conventional single-peak MOS-NDR circuit by employing ambipolar behavior of TFET. The fluctuated voltage transfer curve (VTC) from ambipolar inverter is analyzed with simple model and successfully demonstrated with TFET, as a practical example, on the device simulation. We also verified that the fluctuated VTC generates additional peak and valleys on NDR characteristics by using circuit simulations. Moreover, by adjusting the threshold voltage of conventional MOSFET, ultra-high 1st and 2nd peak-to-valley current ratio (PVCR) over 10(7) is obtained with fully suppressed valley currents. The proposed double-peak NDR circuit expected to apply on faster switching and low power multi-functional applications.

  14. Development of the negative-tone molecular resists for EB/EUVL having high EUV absorption capacity and molecular design method

    Science.gov (United States)

    Sato, Takashi; Takigawa, Tomoaki; Togashi, Yuta; Toida, Takumi; Echigo, Masatoshi; Harada, Tetsuo; Watanabe, Takeo; Kudo, Hiroto

    2017-10-01

    In this paper, we designed the synthesis of negative-type molecular resist materials for EB and EUVL exposure tools, and their properties were examined. The resist materials for EUVL have been required showing higher sensitivity for high throughput in the lithographic process, and expecting lower shot noise to improve a roughness. In EUVL process, the resist materials must be ionized by absorbing EUV to emit more secondary electrons. The EUV absorption of the synthesized resist materials was measured using their thin films on the silicon wafer, and it was observed that the ratio of EUV absorption of the synthesized resist was higher than in the comparison of that of PHS as a reference., i.e., 2.4 times higher absorption was shown. Furthermore, we examined the relationship between the ratios of EUV absorptions and functional groups of the resist materials. As the result, the sensitivity of resist materials under EUV exposure tool was consistent with their structures.

  15. Tunable stochastic pulsing in the Escherichia coli multiple antibiotic resistance network from interlinked positive and negative feedback loops.

    Directory of Open Access Journals (Sweden)

    Javier Garcia-Bernardo

    Full Text Available Cells live in uncertain, dynamic environments and have many mechanisms for sensing and responding to changes in their surroundings. However, sudden fluctuations in the environment can be catastrophic to a population if it relies solely on sensory responses, which have a delay associated with them. Cells can reconcile these effects by using a tunable stochastic response, where in the absence of a stressor they create phenotypic diversity within an isogenic population, but use a deterministic response when stressors are sensed. Here, we develop a stochastic model of the multiple antibiotic resistance network of Escherichia coli and show that it can produce tunable stochastic pulses in the activator MarA. In particular, we show that a combination of interlinked positive and negative feedback loops plays an important role in setting the dynamics of the stochastic pulses. Negative feedback produces a pulsatile response that is tunable, while positive feedback serves to amplify the effect. Our simulations show that the uninduced native network is in a parameter regime that is of low cost to the cell (taxing resistance mechanisms are expressed infrequently and also elevated noise strength (phenotypic variability is high. The stochastic pulsing can be tuned by MarA induction such that variability is decreased once stresses are sensed, avoiding the detrimental effects of noise when an optimal MarA concentration is needed. We further show that variability in the expression of MarA can act as a bet hedging mechanism, allowing for survival in time-varying stress environments, however this effect is tunable to allow for a fully induced, deterministic response in the presence of a stressor.

  16. Omentin, an adipokine with insulin-sensitizing properties, is negatively associated with insulin resistance in normal gestation.

    Science.gov (United States)

    Brandt, Benny; Mazaki-Tovi, Shali; Hemi, Rina; Yinon, Yoav; Schiff, Eyal; Mashiach, Roy; Kanety, Hannah; Sivan, Eyal

    2015-05-01

    Omentin, a newly identified adipokine, enhances insulin mediated glucose uptake in human adipocytes, thus, inducing systemic insulin-sensitizing effect. The aims of this study were to determine whether circulating maternal omentin levels are associated with insulin resistance indices and to assess which compartment, maternal, fetal, or placental, is the source of omentin in maternal circulation. Fasting serum glucose, insulin, and omentin were determined in 25 healthy pregnant women at the third trimester, before and 3 days after elective cesarean section. Cord blood omentin was measured in the 25 term neonates. Homeostasis model assessment (HOMA) was used to evaluate insulin sensitivity before and after delivery. Antepartum maternal omentin levels were negatively correlated with insulin levels (r=-0.41, P=0.04) and positively correlated with insulin sensitivity (HOMA%S; r=0.4, P=0.04). Postpartum omentin levels were negatively correlated with maternal body mass index (r=-0.44, P=0.02). Median maternal omentin levels was comparable before and after delivery (57.2, inter-quartile range: 38.2-76.2 ng/mL vs. 53.4, 39.8-69.4 ng/mL, respectively, P=0.25) and highly correlated (r=0.83, P<0.001). Antepartum maternal and neonatal omentin levels did not differ significantly (fetal: 62.2, 44.3-74.2 ng/mL, P=0.77) and did not correlate (P=0.6). Circulating maternal omentin levels are correlated with insulin resistance indices, suggesting that this adipokine may play a role in metabolic adaptations of normal gestation. The strong correlation between anteparum and postpartum maternal omentin levels, as well as the lack of association between maternal and neonatal omentin levels, suggest that placental or fetal compartments are unlikely as the main source of circulating maternal omentin.

  17. Tunable stochastic pulsing in the Escherichia coli multiple antibiotic resistance network from interlinked positive and negative feedback loops.

    Science.gov (United States)

    Garcia-Bernardo, Javier; Dunlop, Mary J

    2013-01-01

    Cells live in uncertain, dynamic environments and have many mechanisms for sensing and responding to changes in their surroundings. However, sudden fluctuations in the environment can be catastrophic to a population if it relies solely on sensory responses, which have a delay associated with them. Cells can reconcile these effects by using a tunable stochastic response, where in the absence of a stressor they create phenotypic diversity within an isogenic population, but use a deterministic response when stressors are sensed. Here, we develop a stochastic model of the multiple antibiotic resistance network of Escherichia coli and show that it can produce tunable stochastic pulses in the activator MarA. In particular, we show that a combination of interlinked positive and negative feedback loops plays an important role in setting the dynamics of the stochastic pulses. Negative feedback produces a pulsatile response that is tunable, while positive feedback serves to amplify the effect. Our simulations show that the uninduced native network is in a parameter regime that is of low cost to the cell (taxing resistance mechanisms are expressed infrequently) and also elevated noise strength (phenotypic variability is high). The stochastic pulsing can be tuned by MarA induction such that variability is decreased once stresses are sensed, avoiding the detrimental effects of noise when an optimal MarA concentration is needed. We further show that variability in the expression of MarA can act as a bet hedging mechanism, allowing for survival in time-varying stress environments, however this effect is tunable to allow for a fully induced, deterministic response in the presence of a stressor.

  18. Antibacterial agents and heavy metal resistance in Gram-negative bacteria isolated from seawater, shrimp and sediment in Iskenderun Bay, Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Matyar, Fatih [Cukurova University, Faculty of Education, Department of Science and Technology Education, 01330 Balcali, Adana (Turkey)], E-mail: fmatyar@cu.edu.tr; Kaya, Aysenur; Dincer, Sadik [Cukurova University, Faculty of Science and Letters, Department of Biology, 01330 Balcali, Adana (Turkey)

    2008-12-15

    The aim of the present study was to determine the level of antibiotic resistance patterns and distribution of heavy metal resistance of bacterial isolates from seawater, sediment and shrimps, and to determine if there is a relationship between antibiotic and heavy metal resistance. We undertook studies in 2007 in the industrially polluted Iskenderun Bay, on the south coast of Turkey. The resistance of 236 Gram-negative bacterial isolates (49 from seawater, 90 from sediment and 97 from shrimp) to 16 different antibiotics, and to 5 heavy metals, was investigated by agar diffusion and agar dilution methods, respectively. A total of 31 species of bacteria were isolated: the most common strains isolated from all samples were Escherichia coli (11.4%), Aeromonas hydrophila (9.7%) and Stenotrophomonas maltophilia (9.3%). There was a high incidence of resistance to ampicillin (93.2%), streptomycin (90.2%) and cefazolin (81.3%), and a low incidence of resistance to imipenem (16.5%), meropenem (13.9%) and cefepime (8.0%). Some 56.8% of all bacteria isolated from seawater, sediment and shrimp were resistant to 7 or more antibiotics. Most isolates showed tolerance to different concentrations of heavy metals, and minimal inhibition concentrations ranged from 12.5 {mu}g/ml to > 3200 {mu}g/ml. The bacteria from seawater, sediment and shrimp showed high resistance to cadmium of 69.4%, 88.9%, and 81.1% respectively, and low resistance to manganese of 2%, 6.7% and 11.3% respectively. The seawater and sediment isolates which were metal resistant also showed a high resistance to three antibiotics: streptomycin, ampicillin and trimethoprim-sulphamethoxazole. In contrast, the shrimp isolates which were metal resistant were resistant to four antibiotics: cefazolin, nitrofurantoin, cefuroxime and ampicillin. Our results show that Iskenderun Bay has a significant proportion of antibiotic and heavy metal resistant Gram-negative bacteria, and these bacteria constitute a potential risk for

  19. Multidrug-resistant gram-negative bacteria colonization of healthy US military personnel in the US and Afghanistan.

    Science.gov (United States)

    Vento, Todd J; Cole, David W; Mende, Katrin; Calvano, Tatjana P; Rini, Elizabeth A; Tully, Charla C; Zera, Wendy C; Guymon, Charles H; Yu, Xin; Cheatle, Kristelle A; Akers, Kevin S; Beckius, Miriam L; Landrum, Michael L; Murray, Clinton K

    2013-02-05

    The US military has seen steady increases in multidrug-resistant (MDR) gram-negative bacteria (GNB) infections in casualties from Iraq and Afghanistan. This study evaluates the prevalence of MDR GNB colonization in US military personnel. GNB colonization surveillance of healthy, asymptomatic military personnel (101 in the US and 100 in Afghanistan) was performed by swabbing 7 anatomical sites. US-based personnel had received no antibiotics within 30 days of specimen collection, and Afghanistan-based personnel were receiving doxycycline for malaria chemoprophylaxis at time of specimen collection. Isolates underwent genotypic and phenotypic characterization. The only colonizing MDR GNB recovered in both populations was Escherichia coli (p=0.01), which was seen in 2% of US-based personnel (all perirectal) and 11% of Afghanistan-based personnel (10 perirectal, 1 foot+groin). Individuals with higher off-base exposures in Afghanistan did not show a difference in overall GNB colonization or MDR E. coli colonization, compared with those with limited off-base exposures. Healthy US- and Afghanistan-based military personnel have community onset-MDR E. coli colonization, with Afghanistan-based personnel showing a 5.5-fold higher prevalence. The association of doxycycline prophylaxis or other exposures with antimicrobial resistance and increased rates of MDR E. coli colonization needs further evaluation.

  20. Improvement in nano-hardness and corrosion resistance of low carbon steel by plasma nitriding with negative DC bias voltage

    Science.gov (United States)

    Alim, Mohamed Mounes; Saoula, Nadia; Tadjine, Rabah; Hadj-Larbi, Fayçal; Keffous, Aissa; Kechouane, Mohamed

    2016-10-01

    In this work, we study the effect of plasma nitriding on nano-hardness and corrosion resistance of low carbon steel samples. The plasma was generated through a radio-frequency inductively coupled plasma source. The substrate temperature increased (by the self-induced heating mechanism) with the treatment time for increasing negative bias voltages. X-rays diffraction analysis revealed the formation of nitride phases (ɛ-Fe2-3N and γ'-Fe4N) in the compound layer of the treated samples. A phase transition occurred from 3.5 kV to 4.0 kV and was accompanied by an increase in the volume fraction of the γ'-Fe4N phase and a decrease in that of the ɛ-Fe2-3N phase. Auger electron spectroscopy revealed a deep diffusion of the implanted nitrogen beyond 320 nm. The nano-hardness increased by ~400% for the nitrogen-implanted samples compared to the untreated state, the nitride phases are believed to participate to the hardening. Potentiodynamic polarization measurements revealed that the plasma nitriding has improved the corrosion resistance behavior of the material. When compared to the untreated state, the sample processed at 4.0 kV exhibits a shift of +500 mV and a reduction to 3% in its corrosion current. These results were obtained for relatively low bias voltages and short treatment time (2 h).

  1. Decreased Susceptibilities to Teicoplanin and Vancomycin among Coagulase-Negative Methicillin-Resistant Clinical Isolates of Staphylococci

    Science.gov (United States)

    Sieradzki, Krzysztof; Villari, Paolo; Tomasz, Alexander

    1998-01-01

    Of 41 methicillin-resistant coagulase-negative staphylococcal clinical isolates collected during a 5-month period between late 1995 and early 1996, 28 showed tube dilution teicoplanin MICs of 4 to 8 μg/ml which increased to 16 to 32 μg/ml upon prolonged incubation. Cultures of such bacteria were heterogeneous; they contained subpopulations with frequencies of 10−5 to 10−4 that could grow on up to 50 μg of teicoplanin per ml. The same cultures were also heterogeneous with respect to susceptibility to vancomycin; while the MICs for the majority of cells were 2 to 4 μg/ml, subpopulations that could grow on 6 to 12 μg of vancomycin per ml were also present at frequencies of 10−5 to 10−7. Selective enrichment of such cultures for the resistant subpopulation occurred with relative ease under laboratory conditions. Heterogeneous phenotypes for teicoplanin (but not for vancomycin) susceptibility were also identified in several Staphylococcus epidermidis isolates collected during the preantibiotic era. The addition of half the MIC of teicoplanin inhibited autolysis and caused formation of cellular aggregates which disintegrated to individual bacteria in the stationary phase when the titer of teicoplanin in the medium fell to undetectable levels, indicating removal of the antibiotic from the culture medium by the bacteria. PMID:9449268

  2. [The development and testing of reagents kit for detection and qualitative evaluation of DNA of methicillin sensitive and methicillin resistant Staphylococcus aureus and also methicillin resistant coagulase negative Staphylococcus spp. applying technique of polymerase chain reaction in "real time" mode].

    Science.gov (United States)

    Skachkova, T S; Shipulina, O Iu; Domonova, É A; Subbotovskaia, A I; Kozyreva, V S; Il'ina, V N; Shipulin, G A

    2013-06-01

    The reagents kit is developed to identify and quantitatively detect DNA of methicillin sensitive and methicillin resistant Staphylococcus aureus, methicillin resistant coagulase negative Staphylococcus spp. in biological material using technique of polymerase chain reaction with hybridizational fluorescent detection and having higher analytical and diagnostic characteristics. The application of the given reagents kit makes it possible to optimize the epidemiologic monitoring of propagation of methicillin resistant strains of Staphylococcus spp. Significantly decreasing duration and laboriousness of study.

  3. Prevalence, risk factors and molecular epidemiology of highly resistant gram negative rods in hospitalized patients in the Dutch region Kennemerland

    Directory of Open Access Journals (Sweden)

    Dennis Souverein

    2016-03-01

    Full Text Available Abstract Background This paper describes (1 the Highly Resistant Gram Negative Rod (HR-GNR prevalence rate, (2 their genotypes, acquired resistance genes and (3 associated risk factors of HR-GNR colonization among the hospitalized population in the Dutch region Kennemerland. Methods Between 1 October 2013 and 31 March 2014, cross-sectional prevalence measurements were performed in three regional hospitals as part of each hospitals infection control program. Rectal swabs were analyzed at the Regional Public Health Laboratory Kennemerland by direct culturing. Genotypes and acquired resistance genes of positive isolates were determined using Whole Genome Sequencing with the MiSeq instrument (Illumina. Association between several independent variables and HR-GNR positivity was examined using logistic regression models. Results Out of 427 patients, 24 HR-GNR positive isolates were recovered from 22 patients, resulting in a regional HR-GNR colonization prevalence (95 % CI of 5.2 % (3.6–7.9. Of these 22 positive patients, 15 were Extended Spectrum Beta-Lactamase (ESBL positive (3.5 % (2.1–5.7, 7 patients were positive for a Fluoroquinolones and Aminoglycosides (Q&A resistant Enterobacteriaceae (1.6 % (0.8–3.3 and from one patient (0.2 % (0–1.3 a Stenotrophomonas maltophilia resistant towards co-trimoxazole was isolated. No carbapenemase producing Enterobacteriaceae (CPE, multi-resistant Acinetobacter species or multi-resistant Pseudomonas aeruginosa were isolated. The ESBL genes found were bla CTX-M-1 (n = 4, 25.0 %, bla CTX-M-15 (n = 3, 18.8 %, bla CTX-M-27 (n = 2, 12.5 %, bla CTX-M-14b (n = 2, 12.5 %, bla CTX-M-9 (n = 2, 12.5 %, bla CTX-M-14 (n = 1, 6.3 %, bla CTX-M-3 (n = 1, 6.3 %, bla SHV-11 (n = 1, 6.3 % and bla SHV-12 (n = 1, 6.3 %. Being known HR-GNR positive in the past was the only significant associated risk factor for HR-GNR positivity, odds ratio (95 % CI: 7.32 (1.82–29.35, p

  4. Identification of ABC transporter genes conferring combined pleuromutilin-lincosamide-streptogramin A resistance in bovine methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci.

    Science.gov (United States)

    Wendlandt, Sarah; Kadlec, Kristina; Feßler, Andrea T; Schwarz, Stefan

    2015-06-12

    The aim of this study was to investigate the genetic basis of combined pleuromutilin-lincosamide-streptogramin A resistance in 26 unrelated methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (CoNS) from dairy cows suffering from mastitis. The 26 pleuromutilin-resistant staphylococcal isolates were screened for the presence of the genes vga(A), vga(B), vga(C), vga(E), vga(E) variant, sal(A), vmlR, cfr, lsa(A), lsa(B), lsa(C), and lsa(E) by PCR. None of the 26 isolates carried the genes vga(B), vga(C), vga(E), vga(E) variant, vmlR, cfr, lsa(A), lsa(B), or lsa(C). Two Staphylococcus haemolyticus and single Staphylococcus xylosus, Staphylococcus lentus, and Staphylococcus hominis were vga(A)-positive. Twelve S. aureus, two Staphylococcus warneri, as well as single S. lentus and S. xylosus carried the lsa(E) gene. Moreover, single S. aureus, S. haemolyticus, S. xylosus, and Staphylococcus epidermidis were positive for both genes, vga(A) and lsa(E). The sal(A) gene was found in a single Staphylococcus sciuri. All ABC transporter genes were located in the chromosomal DNA, except for a plasmid-borne vga(A) gene in the S. epidermidis isolate. The genetic environment of the lsa(E)-positive isolates was analyzed using previously described PCR assays. Except for the S. warneri and S. xylosus, all lsa(E)-positive isolates harbored a part of the previously described enterococcal multiresistance gene cluster. This is the first report of the novel lsa(E) gene in the aforementioned bovine CoNS species. This is also the first identification of the sal(A) gene in a S. sciuri from a case of bovine mastitis. Moreover, the sal(A) gene was shown to also confer pleuromutilin resistance. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Influence of antimicrobial consumption on gram-negative bacteria in inpatients receiving antimicrobial resistance therapy from 2008-2013 at a tertiary hospital in Shanghai, China.

    Science.gov (United States)

    Guo, Wei; He, Qian; Wang, Zhiyong; Wei, Min; Yang, Zhangwei; Du, Yin; Wu, Cheng; He, Jia

    2015-04-01

    Irrational use of antimicrobial agents is a major cause of increased antimicrobial resistance. Effective antibiotic stewardship strategies nationwide or in local health care settings are necessary to reduce antibiotic use and bacteria resistance. We evaluated the effectiveness of China's antimicrobial stewardship policy on antimicrobial use and applied time-series analysis methodology to determine the temporal relationship between antibiotic use and gram-negative bacteria resistance at Changhai Hospital from 2008-2013. Isolates investigated included Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Consumption of 7 restricted-use antibiotics was dramatically reduced. Resistance to ceftazidime in P aeruginosa and A baumannii and resistance to ciprofloxacin in P aeruginosa significantly decreased. By using cross-correlation analysis, associations between ciprofloxacin resistance in P aeruginosa and fluoroquinolones consumption (r = 0.48; lag = 0; P = .02), ceftazidime resistance in P aeruginosa and third-generation cephalosporins consumption (r = 0.54; lag = -1; P = .01) were identified. No substantial association between other pairs was found. Enhanced nationwide antimicrobial stewardship campaigns launched in 2011 have made great achievements in regard to antibiotic use but have had limited effects on the reversal of gram-negative bacteria resistance in health care settings. Sound infection prevention and control programs to reduce the transmission of resistant pathogens for hospitals in China are urgently needed. Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  6. Coagulase-negative staphylococci (CoNS) isolated from ready-to-eat food of animal origin--phenotypic and genotypic antibiotic resistance.

    Science.gov (United States)

    Chajęcka-Wierzchowska, Wioleta; Zadernowska, Anna; Nalepa, Beata; Sierpińska, Magda; Łaniewska-Trokenheim, Łucja

    2015-04-01

    The aim of this work was to study the pheno- and genotypical antimicrobial resistance profile of coagulase negative staphylococci (CoNS) isolated from 146 ready-to-eat food of animal origin (cheeses, cured meats, sausages, smoked fishes). 58 strains were isolated, they were classified as Staphylococcus xylosus (n = 29), Staphylococcus epidermidis (n = 16); Staphylococcus lentus (n = 7); Staphylococcus saprophyticus (n = 4); Staphylococcus hyicus (n = 1) and Staphylococcus simulans (n = 1) by phenotypic and genotypic methods. Isolates were tested for resistance to erythromycin, clindamycin, gentamicin, cefoxitin, norfloxacin, ciprofloxacin, tetracycline, tigecycline, rifampicin, nitrofurantoin, linezolid, trimetoprim, sulphamethoxazole/trimethoprim, chloramphenicol, quinupristin/dalfopristin by the disk diffusion method. PCR was used for the detection of antibiotic resistance genes encoding: methicillin resistance--mecA; macrolide resistance--erm(A), erm(B), erm(C), mrs(A/B); efflux proteins tet(K) and tet(L) and ribosomal protection proteins tet(M). For all the tet(M)-positive isolates the presence of conjugative transposons of the Tn916-Tn1545 family was determined. Most of the isolates were resistant to cefoxitin (41.3%) followed by clindamycin (36.2%), tigecycline (24.1%), rifampicin (17.2%) and erythromycin (13.8%). 32.2% staphylococcal isolates were multidrug resistant (MDR). All methicillin resistant staphylococci harboured mecA gene. Isolates, phenotypic resistant to tetracycline, harboured at least one tetracycline resistance determinant on which tet(M) was most frequent. All of the isolates positive for tet(M) genes were positive for the Tn916-Tn1545 -like integrase family gene. In the erythromycin-resistant isolates, the macrolide resistance genes erm(C) or msr(A/B) were present. Although coagulase-negative staphylococci are not classical food poisoning bacteria, its presence in food could be of public health significance due to the possible spread of

  7. Modeling the effects of positive and negative mood on the ability to resist eating in obese and non-obese individuals.

    Science.gov (United States)

    Udo, Tomoko; Grilo, Carlos M; Brownell, Kelly D; Weinberger, Andrea H; Dileone, Ralph J; McKee, Sherry A

    2013-01-01

    This pilot study adapted a well-established drug self-administration paradigm to examine the effects of mood induction on the ability to resist high-calorie foods and subsequent food consumption differently in 15 obese individuals (40.0% women, BMI: 35.1±3.70) and 15 non-obese individuals (46.7% women, BMI: 23.0±1.96). Participants completed two laboratory sessions (positive vs. negative mood conditions) consisting of 3-hour food deprivation, followed by mood induction, and a 3-hour ad-lib eating period, where they were asked to choose between favorite high-calorie snacks and monetary reinforcement. Obese individuals were less able to resist eating and increased high-calorie food consumption during the positive mood condition than the negative condition. Non-obese individuals were less able to resist eating during the negative mood condition than the positive condition, but their total consumption was not affected by the mood conditions. In obese individuals, food craving was associated with less ability to resist eating and greater calorie consumption during the negative mood condition. This is the first study to experimentally demonstrate that mood state may increase vulnerability to food consumption by reducing the ability to resist eating. The ability to resist eating may be a novel dimension of eating behaviors that has a significant contribution to understanding mood-eating relationships. Copyright © 2012. Published by Elsevier Ltd.

  8. Modeling the Effects of Positive and Negative Mood on the Ability to Resist Eating in Obese and Non-obese Individuals

    Science.gov (United States)

    Udo, Tomoko; Grilo, Carlos M.; Brownell, Kelly D.; Weinberger, Andrea H.; DiLeone, Ralph J.; McKee, Sherry A.

    2013-01-01

    This pilot study adapted a well-established drug self-administration paradigm to examine the effects of mood induction on the ability to resist high-calorie foods and subsequent food consumption differently in 15 obese individuals (40.0% women, BMI: 35.1±3.70) and 15 non-obese individuals (46.7% women, BMI: 23.0±1.96). Participants completed two laboratory sessions (positive vs. negative mood conditions) consisting of 3-hour food deprivation, followed by mood induction, and a 3-hour ad-lib eating period, where they were asked to choose between favorite high-calorie snacks and monetary reinforcement. Obese individuals were less able to resist eating and increased high-calorie food consumption during the positive mood condition than the negative condition. Non-obese individuals were less able to resist eating during the negative mood condition than the positive condition, but their total consumption was not affected by the mood conditions. In obese individuals, food craving was associated with less ability to resist eating and greater calorie consumption during the negative mood condition. This is the first study to experimentally demonstrate that mood state may increase vulnerability to food consumption by reducing the ability to resist eating. The ability to resist eating may be a novel dimension of eating behaviors that has a significant contribution to understanding mood-eating relationships. PMID:23265400

  9. Antibiotic susceptibility of coagulase-negative staphylococci (CoNS): emergence of teicoplanin-non-susceptible CoNS strains with inducible resistance to vancomycin.

    Science.gov (United States)

    Ma, Xiao Xue; Wang, En Hua; Liu, Yong; Luo, En Jie

    2011-11-01

    Coagulase-negative staphylococci (CoNS) have become increasingly recognized as important agents of nosocomial infection. One of the characteristics of CoNS is their resistance to multiple antimicrobial agents commonly used for the treatment of staphylococcal infections. CoNS strains (n = 745) isolated from a university teaching hospital in China between 2004 and 2009 were tested for antibiotic resistance. The antibiotics were placed into three categories based on resistance levels of the CoNS strains to these antibiotics: high resistance (resistance rate >70 %), including penicillin G, oxacillin and erythromycin; medium resistance (resistance rate between 30 and 70 %), including tetracycline, clindamycin, ciprofloxacin, trimethoprim/sulfamethoxazole and chloramphenicol; and low resistance (resistance rate teicoplanin increased from 4.5 to 6.7 % between 2008 and 2009. A one-step vancomycin agar selection experiment and subsequent population analysis revealed potentially vancomycin-resistant subpopulations that have been selected from the teicoplanin-non-susceptible strains. Vigilant surveillance of nosocomial isolates of CoNS is needed to determine their resistance to glycopeptides.

  10. Metal-carbonyl organometallic polymers, PFpP, as resists for high-resolution positive and negative electron beam lithography.

    Science.gov (United States)

    Zhang, J; Cao, K; Wang, X S; Cui, B

    2015-12-25

    Metal-containing resists for electron beam lithography (EBL) are attracting attention owing to their high dry etching resistance and possibility for directly patterning metal-containing nanostructures. The newly developed organometallic metal carbonyl polymers, PFpP, can function as EBL resists with strong etching resistance. One significant feature of the PFpP resist is its high resolution. Line arrays with line-widths as narrow as 17 nm have been created. The resist can also be used in positive tone.

  11. Prevalence and antibiotic resistance of coagulase-negative Staphylococci isolated from poultry farms in three regions of Ghana

    DEFF Research Database (Denmark)

    Boamah, Vivian Etsiapa; Agyare, Christian; Odoi, Hayford

    2017-01-01

    infections and high resistance to several antibiotics. This study sought to determine the prevalence, identity, and phenotypic resistance of coagulase-negative Staphylococcus spp. isolated from some selected poultry farms and farm workers in the Ashanti, Brong Ahafo, and Greater Accra regions of Ghana...... (EUCAST) guidelines. Two hundred and fifty-six coagulase-negative Staphylococcus spp., comprising S. sciuri (42.97%), S. lentus (35.94%), S. gallinarum (6.64%), S. xylosus (4.30%), S. haemolyticus (3.91%), S. saprophyticus (1.95%), and S. cohnii (0.39%) were confirmed by MALDI-TOF. CoNS were isolated from......The use of antibiotics in animal production has been associated with the development and spread of antibiotic-resistant organisms including commensals. Coagulase-negative Staphylococcus (CoNS) species, which were until recently considered non-pathogenic, have been associated with opportunistic...

  12. In vitro antibacterial activities of p-toluenesulfonyl-hydrazinothiazoles and hydrazinoselenazoles against multi-drug resistant Gram-negative phenotypes.

    Science.gov (United States)

    Mbaveng, Armelle T; Ignat, Adriana Grozav; Ngameni, Bathélémy; Zaharia, Valentin; Ngadjui, Bonaventure T; Kuete, Victor

    2016-01-19

    Bacterial multidrug resistance (MDR) constitutes a major hurdle in the treatment of infectious diseases worldwide. The present study was designed to evaluate the antibacterial activities of synthetic p-toluenesulfonyl-hydrazinothiazoles against multidrug resistant Gram-negative bacteria. The broth microdilution method was used to determine the minimal inhibitory concentrations (MIC). The results demonstrated that the best activities were obtained with hydrazinoselenazoles. p-Chloro-benzyliden-selenosemicarbazide, 4-methyl-2-[(4-chloro-benzyliden)-hydrazinyl]-1,3-selenazole, p-chloro-benzoyl-selenosemicarbazide and 4-chloromethyl-2-[(4-chlorobenziliden)-N-acetyl-hydrazinyl]-1,3-selenazole were more active than the choramphenicol on Klebsiella pneumoniae KP63. Tested alone, the lowest MIC value of 16 mg/L was obtained with p-methoxy-benzyliden-selenosemicarbazide against Enterobacter aerogenes ATCC13048, K. pneumoniae ATCC112296 and KP55. Tested in the presence of an efflux pump inhibitor, phenylalanine arginine β-naphthylamide (PAβN), the activity of p-chloro-benzyliden-selenosemicarbazide, 4-methyl-2-[(4-chloro-benzyliden)-hydrazinyl]-1,3-selenazole, p-chloro-benzoyl-selenosemicarbazide and p-methoxy-benzyliden-selenosemicarbazide significantly increased with MIC values below 10 mg/L obtained respectively on 43.8 %, 31.3 %, 62.5 % and 100 % of the 16 tested bacterial strains. The lowest MIC value of 0.5 mg/L in the presence of PAβN was recorded with p-chloro-benzoyl-selenosemicarbazide against Escherichia coli ATCC8739 and KP55 as well as p-methoxy-benzyliden-selenosemicarbazide against E. aerogenes KP55. p-Chloro-benzyliden-selenosemicarbazide and p-chloro-benzoyl-selenosemicarbazide contained the same pharmacophore as p-methoxy-benzyliden-selenosemicarbazide. This study indicates that p-chloro-benzyliden-selenosemicarbazide, p-chloro-benzoyl-selenosemicarbazide and p-methoxy-benzyliden-selenosemicarbazide could be explored more to develop novel

  13. Antibiotic susceptibility of methicillin-resistant and methicillin-susceptible coagulase-negative staphylococci isolated from bovine mastitis.

    Science.gov (United States)

    Bochniarz, M; Wawron, W

    2011-01-01

    The aim of the present study was to evaluate the antibiotic susceptibility of methicillin-susceptible (MS) and methicillin-resistant (MR) coagulase-negative Staphylococcus (CNS) strains isolated from milk of cows with mastitis. The study was conducted on 100 CNS strains (20 MRCNS and 80 MSCNS) isolated from milk samples of 86 cows from the Lublin (Poland) region farms. Antibiotic susceptibility of microorganisms was evaluated using the disc-diffusion method on the Mueller-Hinton agar according to the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS). The highest efficacy against MSCNS was demonstrated for cephalosporin antibiotics, i.e. cefacetril (91.3%), ceftiofur (67.5%), cefoperazone (66.3%) and cephalexin (60.0% of susceptible MSCNS strains). Moreover, a high percentage of vancomycin-susceptible strains was demonstrated (83.8%). The activity of combination of amoxicillin with clavulanic acid and gentamicin was found weaker (63.8% and 61.3% of susceptible strains, respectively). About 50.0% of MSCNS were susceptible to erythromycin, enrofloxacine and amoxicillin. A large proportion of CNS was resistant to neomycin, penicillin, tetracycline, streptomycin, lincomycin and ampicillin (28.8%, 30.0%, 31.3%, 31.3%, 33.8% and 33.8% of susceptible strains, respectively). The highest percentage of MRCNS was susceptible to vancomycin (75.0%), erythromycin (65.0%) and streptomycin (50.0%). Their susceptibility to enrofloxacine (35.0%) as well as gentamicin and tetracycline (30.0%) was markedly lower. The lowest activity was found for lincomycin and neomycin (20.0% of susceptible MRCNS strains, each).

  14. Negative CD4 + TIM-3 signaling confers resistance against cold preservation damage in mouse liver transplantation.

    Science.gov (United States)

    Liu, Yuanxing; Ji, Haofeng; Zhang, Yu; Shen, Xiu-da; Gao, Feng; Nguyen, Terry T; Shang, Xuanming; Lee, Nayun; Busuttil, Ronald W; Kupiec-Weglinski, Jerzy W

    2015-04-01

    Ischemia-reperfusion injury (IRI), an innate immunity-driven local inflammation, remains the major problem in clinical organ transplantation. T cell immunoglobulin and mucin domain (TIM-3)-Galectin-9 (Gal-9) signaling regulates CD4+ Th1 immune responses. Here, we explored TIM-3-Gal-9 function in a clinically relevant murine model of hepatic cold storage and orthotopic liver transplantation (OLT). C57BL/6 livers, preserved for 20 h at 4°C in UW solution, were transplanted to syngeneic mouse recipients. Up-regulation of TIM-3 on OLT-infiltrating activated CD4+ T cells was observed in the early IRI phase (1 h). By 6 h of reperfusion, OLTs in recipients treated with a blocking anti-TIM-3 Ab were characterized by: (1) enhanced hepatocellular damage (sALT levels, liver Suzuki's histological score); (2) polarized cell infiltrate towards Th1/Th17-type phenotype; (3) depressed T cell exhaustion markers (PD-1, LAG3); and (4) elevated neutrophil and macrophage infiltration/activation. In parallel studies, adoptive transfer of CD4+ T cells from naïve WT, but not from TIM-3 Tg donors, readily recreated OLT damage in otherwise IR-resistant RAG(-/-) test recipients. Furthermore, pre-treatment of mice with rGal-9 promoted hepatoprotection against preservation-association liver damage, accompanied by enhanced TIM-3 expression in OLTs. Thus, CD4+ T cell-dependent "negative" TIM-3 costimulation is essential for hepatic homeostasis and resistance against IR stress in OLTs. © Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.

  15. Single mode solid state distributed feedback dye laser fabricated by grey scale electron beam lithography on dye doped SU-8 resist

    DEFF Research Database (Denmark)

    Balslev, Søren; Rasmussen, Torben; Shi, Peixiong

    2005-01-01

    are optically pumped at 532 nm, and exhibit low lasing threshold from 530 nJ/mm2 and single mode output at selectable wavelengths from 580 to 630 nm, determined by the grating pitch. The lasers are well suited for integration into polymer based lab-on-chip circuits for interference based sensing....

  16. Bactérias gram negativas resistentes a antimicrobianos em alimentos Gram-negative bacteria resistant to antibiotics in foods

    Directory of Open Access Journals (Sweden)

    José Cavalcante de Albuquerque Ribeiro Dias

    1985-12-01

    Full Text Available A partir de 154 espécimens de alimentos, representados por hortaliças (alface, leite e merenda escolar, obteve-se o isolamento e identificação de 400 amostras de bacilos Gram negativos. Esta amostragem se distribuiu em 339 enterobactérias (Escherichia, Shigella, Citrobacter, Klebsiella, Enterobacter, Serratia e Proteus e 61 de gêneros afins (Acinetobacter, Flavobacterium, Aeromonas e Pseudomonas. Submetendo-se as culturas aos antimicrobianos: sulfadiazina (Su, estreptomicina (Sm, tetraciclina (Tc, cloranfenicol (Cm, canamicina (Km, ampicilina (Ap, ácido nalidíxico (Nal e gentamicina (Gm, observou-se apenas seis estirpes sensíveis a todas as drogas e sensibilidade absoluta à Gm. A predominância dos modelos Su (27,6% e Su-Ap (39,6% incidiu nas enterobactérias, enquanto que, 18,0% para Ap e 9,8% para Su-Ap foram detectados nos gêneros afins. Para caracterização da resistência foram realizados testes de conjugação e a totalidade das culturas não revelou transferência para o gene que confere resistência ao ácido nalidíxico. Relevantes são as taxas de amostras R+ observadas nos bacilos entéricos, oscilando em torno de 90% (leite e merenda escolar e alface, em torno de 70%From 154 food samples, including vegetables (lettuce, milk and meals served at school it was possible to isolate and identify 400 Gram negative bacilli distributed among 339 enteric bacteria (Escherichia, Shigella, Citrobacter, Klebsiella, Enterobacter, Serratia and Proteus and other 61 non enteric bacilli (Acinetobacter, Flavobacterium, Aeromonas and Pseudomonas. Submitting this cultures to the drugs sulfadiazine (Su, streptomycin (Sm, tetracycline (Tc, chloramphenicol (Cm, kanamycin (Km, ampicillin (Ap, nalidixic acid (Nal and gentamycin (Gm it was observed only six stocks susceptible to all drugs and total sensibility to Gm. Among enteric bacteria the profiles Su (27,6% and Su-Ap (39,6% predominated, while for the non enteric bacilli percentages of 18.0 for

  17. HER2-associated radiation resistance of breast cancer stem cells isolated from HER2-negative breast cancer cells

    Science.gov (United States)

    Duru, Nadire; Fan, Ming; Candas, Demet; Menaa, Cheikh; Liu, Hsin-Chen; Nantajit, Danupon; Wen, Yunfei; Xiao, Kai; Eldridge, Angela; Chromy, Brett A.; Li, Shiyong; Spitz, Douglas R.; Lam, Kit S.; Wicha, Max S.; Li, Jian Jian

    2012-01-01

    Purpose To understand the role of HER2-associated signaling network in breast cancer stem cells (BCSCs); using radiation-resistant breast cancer cells and clinical recurrent breast cancers to evaluate HER2-targeted therapy as a tumor eliminating strategy for recurrent HER2−/low breast cancers. Experimental Design HER2-expressing BCSCs (HER2+/CD44+/CD24−/low) were isolated from radiation-treated breast cancer MCF7 cells and in vivo irradiated MCF7 xenograft tumors. Tumor aggressiveness and radiation resistance were analyzed by gap filling, Matrigel invasion, tumor-sphere formation, and clonogenic survival assays. The HER2/CD44 feature was analyzed in 40 primary and recurrent breast cancer specimens. Protein expression profiling in HER2+/CD44+/CD24−/low versus HER2−/CD44+/CD24−/low BCSCs was conducted with 2-D DIGE and HPLC-MS/MS analysis and HER2-mediated signaling network was generated by MetaCore™ program. Results Compared to HER2-negative BCSCs, HER2+/CD44+/CD24−/low cells showed elevated aldehyde dehydrogenase (ALDH) activity and aggressiveness tested by matrigel invasion, tumor sphere formation and in vivo tumorigenesis. The enhanced aggressive phenotype and radioresistance of the HER2+/CD44+/CD24−/low cells were markedly reduced by inhibition of HER2 via siRNA or Herceptin treatments. Clinical breast cancer specimens revealed that cells co-expressing HER2 and CD44 were more frequently detected in recurrent (84.6%) than primary tumors (57.1%). In addition, 2-D DIGE and HPLC-MS/MS of HER2+/CD44+/CD24−/low versus HER2−/CD44+/CD24−/low BCSCs reported a unique HER2-associated protein profile including effectors involved in tumor metastasis, apoptosis, mitochondrial function and DNA repair. A specific feature of HER2-STAT3 network was identified. Conclusion This study provides the evidence that HER2-mediated pro-survival signaling network is responsible for the aggressive phenotype of breast cancer stem cells that could be targeted to control

  18. Coleman-Weinberg symmetry breaking in SU(8) induced by a third rank antisymmetric tensor scalar field II: the fermion spectrum

    Science.gov (United States)

    Adler, Stephen L.

    2017-07-01

    We continue our study of Coleman-Weinberg symmetry breaking induced by a third rank antisymmetric tensor scalar, in the context of the SU(8) model (Adler 2014 Int. J. Mod. Phys. A 29 1450130) we proposed earlier. We focus in this paper on qualitative features that will determine whether the model can make contact with the observed particle spectrum. We discuss the mechanism for giving the spin \\frac{3}{2} field a mass by the BEH mechanism, and analyze the remaining massless spin \\frac{1}{2} fermions, the global chiral symmetries, and the running couplings after symmetry breaking. We note that the smallest gluon mass matrix eigenvalue has an eigenvector suggestive of U(1) B-L , and conjecture that the theory runs to an infrared fixed point at which there is a massless gluon with 3 to  -1 ratios in generator components. Assuming this, we discuss a mechanism for making contact with the standard model, based on a conjectured asymmetric breaking of Sp(4) to SU(2) subgroups, one of which is the electroweak SU(2), and the other of which is a ‘technicolor’ group that binds the original SU(8) model fermions, which play the role of ‘preons’, into composites. Quarks can emerge as 5 preon composites and leptons as 3 preon composites, with consequent stability of the proton against decay to a single lepton plus a meson. A composite Higgs boson can emerge as a two preon composite. Since anomaly matching for the relevant conserved global symmetry current is not obeyed by three fermion families, emergence of three composite families requires formation of a Goldstone boson with quantum numbers matching this current, which can be a light dark matter candidate.

  19. Array based detection of antibiotic resistance genes in Gram negative bacteria isolated from retail poultry meat in the UK and Ireland.

    Science.gov (United States)

    McNeece, Grainne; Naughton, Violetta; Woodward, Martin J; Dooley, James S G; Naughton, Patrick J

    2014-06-02

    The use of antibiotics in birds and animals intended for human consumption within the European Union (EU) and elsewhere has been subject to regulation prohibiting the use of antimicrobials as growth promoters and the use of last resort antibiotics in an attempt to reduce the spread of multi-resistant Gram negative bacteria. Given the inexorable spread of antibiotic resistance there is an increasing need for improved monitoring of our food. Using selective media, Gram negative bacteria were isolated from retail chicken of UK-Intensively reared (n=27), Irish-Intensively reared (n=19) and UK-Free range (n=30) origin and subjected to an oligonucleotide based array system for the detection of 47 clinically relevant antibiotic resistance genes (ARGs) and two integrase genes. High incidences of β-lactamase genes were noted in all sample types, acc (67%), cmy (80%), fox (55%) and tem (40%) while chloramphenicol resistant determinants were detected in bacteria from the UK poultry portions and were absent in bacteria from the Irish samples. Denaturing Gradient Gel Electrophoresis (DGGE) was used to qualitatively analyse the Gram negative population in the samples and showed the expected diversity based on band stabbing and DNA sequencing. The array system proved to be a quick method for the detection of antibiotic resistance gene (ARG) burden within a mixed Gram negative bacterial population. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. An accurate locally active memristor model for S-type negative differential resistance in NbO{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Gibson, Gary A.; Musunuru, Srinitya; Zhang, Jiaming; Lee, James; Hsieh, Cheng-Chih; Jackson, Warren; Jeon, Yoocharn; Henze, Dick; Li, Zhiyong; Stanley Williams, R. [Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, California 94304 (United States); Vandenberghe, Ken [PTD-PPS, Hewlett-Packard Company, 1070 NE Circle Boulevard, Corvallis, Oregon 97330 (United States)

    2016-01-11

    A number of important commercial applications would benefit from the introduction of easily manufactured devices that exhibit current-controlled, or “S-type,” negative differential resistance (NDR). A leading example is emerging non-volatile memory based on crossbar array architectures. Due to the inherently linear current vs. voltage characteristics of candidate non-volatile memristor memory elements, individual memory cells in these crossbar arrays can be addressed only if a highly non-linear circuit element, termed a “selector,” is incorporated in the cell. Selectors based on a layer of niobium oxide sandwiched between two electrodes have been investigated by a number of groups because the NDR they exhibit provides a promisingly large non-linearity. We have developed a highly accurate compact dynamical model for their electrical conduction that shows that the NDR in these devices results from a thermal feedback mechanism. A series of electrothermal measurements and numerical simulations corroborate this model. These results reveal that the leakage currents can be minimized by thermally isolating the selector or by incorporating materials with larger activation energies for electron motion.

  1. Carbon-silica nanocomposite with negative differential resistance for high voltage negatronic devices: Effect of silica concentration

    Science.gov (United States)

    Gouadria, S.; Najeh, I.; El Mir, L.

    2017-11-01

    In this work, carbon-silica nanocomposites have been elaborated by sol-gel technique. SiO2 nanoparticles were added to resorcinol-formaldehyde (RF) carbon precursor solution with different silica weight percentages. The XRD investigations carried out on these samples outline that the material has amorphous phase. The transmission electron microscopy (TEM) images show the presence of nanostructures in RF-30% SiO2 and RF-50% SiO2 samples. The electrical conductivity was investigated in the temperature range 80-300 K and in the frequency range 100 Hz-1 MHz. The dc and ac conductivity can be explained by hopping conduction model. Current-Voltage characteristics exhibit nonlinear and symmetric behavior for all measurement temperatures between 80 K and 300 K. In addition, a negative differential resistance (NDR) phase has been detected even at room temperature in RF-50% SiO2 non dispersive sample. These investigations will contribute to the fabrication of thermal and high voltage negatronic devices working at room temperature where NDR plays an important role.

  2. Escalating risk and the moderating effect of resistance to peer influence on the P200 and feedback-related negativity.

    Science.gov (United States)

    Kiat, John; Straley, Elizabeth; Cheadle, Jacob E

    2016-03-01

    Young people frequently socialize together in contexts that encourage risky decision making, pointing to a need for research into how susceptibility to peer influence is related to individual differences in the neural processing of decisions during sequentially escalating risk. We applied a novel analytic approach to analyze EEG activity from college-going students while they completed the Balloon Analogue Risk Task (BART), a well-established risk-taking propensity assessment. By modeling outcome-processing-related changes in the P200 and feedback-related negativity (FRN) sequentially within each BART trial as a function of pump order as an index of increasing risk, our results suggest that analyzing the BART in a progressive fashion may provide valuable new insights into the temporal neurophysiological dynamics of risk taking. Our results showed that a P200, localized to the left caudate nucleus, and an FRN, localized to the left dACC, were positively correlated with the level of risk taking and reward. Furthermore, consistent with our hypotheses, the rate of change in the FRN was higher among college students with greater self-reported resistance to peer influence. © The Author (2015). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  3. Colistin combination therapy improves microbiologic cure in critically ill patients with multi-drug resistant gram-negative pneumonia.

    Science.gov (United States)

    Parchem, N L; Bauer, K A; Cook, C H; Mangino, J E; Jones, C D; Porter, K; Murphy, C V

    2016-09-01

    Currently, in vitro synergy with colistin has not translated into improved clinical outcomes. This study aimed to compare colistin combination therapy to colistin monotherapy in critically ill patients with multi-drug resistant gram-negative (MDR-GN) pneumonia. This was a retrospective analysis of critically ill adult patients receiving intravenous colistin for MDR-GN pneumonia comparing colistin combination therapy to colistin monotherapy with a primary endpoint of clinical cure. Combination therapy was defined by administration of another antibiotic to which the MDR-GN pathogen was reported as susceptible or intermediate. Ninety patients were included for evaluation (41 combination therapy and 49 monotherapy). Baseline characteristics were similar between groups. No difference in clinical cure was observed between combination therapy and monotherapy in univariate analysis, nor when adjusted for APACHE II score and time to appropriate antibiotic therapy (57.1 vs. 63.4 %, adjusted OR 1.15, p = 0.78). Microbiological cure was significantly higher for combination therapy (87 vs. 35.5 %, p Colistin combination therapy was associated with a significant improvement in microbiological cure, without improvement in clinical cure. Based on the in vitro synergy and improvement in microbiological clearance, colistin combination therapy should be prescribed for MDR-GN pneumonia. Further research is warranted to determine if in vitro synergy with colistin translates into improved clinical outcomes.

  4. Density functional theory investigation of negative differential resistance and efficient spin filtering in niobium-doped armchair graphene nanoribbons.

    Science.gov (United States)

    Kumar, Jitendra; Nemade, Harshal B; Giri, P K

    2017-11-08

    Using density functional theory calculations in combination with a non-equilibrium Green's function method, we explore the transport properties of a niobium-doped (∼3.57%) armchair graphene nanoribbon of dimer length 7 in a two-terminal device configuration. The band structure of the supercell with niobium atoms showed spin splitting near the Fermi level. The spin-dependent transport properties and spin-resolved band structure of electrodes with applied bias values were calculated to understand the spin filter and the negative differential resistance (NDR) effect. The spin filter efficiency of the device was found to be more than 95% in the applied voltage range of 0.15 V to 0.5 V for the antiparallel configuration, and the device is suitable as an efficient spin filter at room temperature. The parallel configuration has a higher range, 0 V to 0.5 V, with an efficiency more than 70%. The peak-to-valley ratios in the parallel configuration for spin-up and spin-down currents were 4.5 and 17.8, respectively, while in the antiparallel configuration, the values were 4.57 and 37.5, respectively. The combined NDR characteristic showed figure of merit with a peak current density of ∼6 mA μm(-1) and a PVR of ∼4.6, useful for logical application. Our findings open a new way to produce multifunctional spintronic devices based on niobium-doped armchair graphene nanoribbons.

  5. Spin-dependent Seebeck Effect, Thermal Colossal Magnetoresistance and Negative Differential Thermoelectric Resistance in Zigzag Silicene Nanoribbon Heterojunciton.

    Science.gov (United States)

    Fu, Hua-Hua; Wu, Dan-Dan; Zhang, Zu-Quan; Gu, Lei

    2015-05-22

    Spin-dependent Seebeck effect (SDSE) is one of hot topics in spin caloritronics, which examine the relationships between spin and heat transport in materials. Meanwhile, it is still a huge challenge to obtain thermally induced spin current nearly without thermal electron current. Here, we construct a hydrogen-terminated zigzag silicene nanoribbon heterojunction, and find that by applying a temperature difference between the source and the drain, spin-up and spin-down currents are generated and flow in opposite directions with nearly equal magnitudes, indicating that the thermal spin current dominates the carrier transport while the thermal electron current is much suppressed. By modulating the temperature, a pure thermal spin current can be achieved. Moreover, a thermoelectric rectifier and a negative differential thermoelectric resistance can be obtained in the thermal electron current. Through the analysis of the spin-dependent transport characteristics, a phase diagram containing various spin caloritronic phenomena is provided. In addition, a thermal magnetoresistance, which can reach infinity, is also obtained. Our results put forward an effective route to obtain a spin caloritronic material which can be applied in future low-power-consumption technology.

  6. CHROMagar COL-APSE: a selective bacterial culture medium for the isolation and differentiation of colistin-resistant Gram-negative pathogens

    DEFF Research Database (Denmark)

    Abdul Momin, Muhd Haziq F; Bean, David C; Hendriksen, Rene S.

    2017-01-01

    . Using CHROMagar COL-APSE, Gram-negative pathogens (n=71) with intrinsic (n=8) or acquired COL (n=63) resistance were recovered with 100 % specificity down to the lower limit of detection of 101 colony-forming units (c.f.u.). The growth on SuperPolymyxin was similar, but notably weaker for COL...... for the growth of COL-resistant bacterial pathogens. Due to the low limit of detection (101 c.f.u.), it may be useful as a primary isolation medium in the surveillance and recovery of COL-resistant bacteria from complex human, veterinary and environmental samples, especially those with plasmid-mediated MCR-1...

  7. The link between a negative high resolution resist contrast/developer performance and the Flory-Huggins parameter estimated from the Hansen solubility sphere

    Energy Technology Data Exchange (ETDEWEB)

    StCaire, Lorri; Olynick, Deirdre L.; Chao, Weilun L.; Lewis, Mark D.; Lu, Haoren; Dhuey, Scott D.; Liddle, J. Alexander

    2008-07-01

    We have implemented a technique to identify candidate polymer solvents for spinning, developing, and rinsing for a high resolution, negative electron beam resist hexa-methyl acetoxy calix(6)arene to elicit the optimum pattern development performance. Using the three dimensional Hansen solubility parameters for over 40 solvents, we have constructed a Hansen solubility sphere. From this sphere, we have estimated the Flory Huggins interaction parameter for solvents with hexa-methyl acetoxy calix(6)arene and found a correlation between resist development contrast and the Flory-Huggins parameter. This provides new insights into the development behavior of resist materials which are necessary for obtaining the ultimate lithographic resolution.

  8. Heavy metal resistant Arthrobacter sp.--a tool for studying conjugational plasmid transfer between gram-negative and gram-positive bacteria.

    Science.gov (United States)

    Margesin, R; Schinner, F

    1997-01-01

    The role of two heavy metal-resistant strains of the Gram-positive genus Arthrobacter sp. as a tool in studying conjugational plasmid transfer between Gram-positive and Gram-negative bacteria is described. The high nickel resistance and the cobalt resistance of Arthrobacter sp. strain RM1/6 could be transferred to Arthrobacter sp. strain WS14. IncQ plasmids (pKT240, pKT240::czc, pML10) could be mobilized from E. coli into Arthrobacter spp. strains; antibiotic (Km, Ap, Tc) and heavy metal (Co) resistance genes were expressed in the recipient stains. IncQ plasmid pKT240 could be mobilized between Arthrobacter spp. strains. IncP plasmid RP4::Tn4371 was transferred from A. eutrophus to Arthrobacter sp., RP4-mediated antibiotic resistance to Km was expressed in the recipient strain.

  9. Prevalence and antibacterial resistance patterns of extended-spectrum beta-lactamase producing Gram-negative bacteria isolated from ocular infections.

    Science.gov (United States)

    Rameshkumar, G; Ramakrishnan, R; Shivkumar, C; Meenakshi, R; Anitha, V; Venugopal Reddy, Y C; Maneksha, V

    2016-04-01

    Extended-spectrum beta-lactamases (ESBLs) mediated resistance is more prevalent worldwide, especially among Gram-negative bacterial isolates, conferring resistance to the expanded spectrum cephalosporins. As limited data were available on the prevalence of ESBLs in this area, the current study was undertaken to determine the prevalence, antibacterial resistance patterns, and molecular detection and characterization of ESBL encoding resistance genes among ocular Gram-negative bacterial isolates from ocular infections. A prospective study was done on 252 ocular Gram-negative bacterial isolates recovered from ocular infections during a study period from February 2011 to January 2014. All isolates were subjected to detection of ESBLs by cephalosporin/clavulanate combination disc test and their antibacterial resistance pattern was studied. Molecular detection and characterization of ESBL encoding blaTEM -, blaSHV , blaOXA -, and blaCTX-M (phylogenetic groups 1, 2, 9, and 8/25) resistance genes by multiplex polymerase chain reaction and DNA sequence analysis. Of all Gram-negative bacteria, Pseudomonas aeruginosa (44%) was the most common strain, followed by Enterobacter agglomerans and Klebsiella pneumoniae each (10%). Among the 252, 42 (17%) were ESBL producers. The major source of ESBL producers were corneal scraping specimens, highest ESBL production was observed in P. aeruginosa 16 (38%) and Escherichia coli 7 (16.6%). Among ESBL-producing genes, the prevalence of blaTEM -gene was the highest (83%) followed by blaOXA -gene (35%), blaSHV -gene (18.5%), and blaCTX-M-1 -gene (18.5%) alone or together. The higher rate of prevalence of ESBLs-encoding genes among ocular Gram-negative bacteria is of great concern, as it causes limitation to therapeutic options. This regional knowledge will help in guiding appropriate antibiotic use which is highly warranted.

  10. Metallo- β-lactamases among Multidrug Resistant (MDR Gram Negative Bacteria Isolated from Clinical Specimens during 2009 in Sanandaj, Kurdistan Province

    Directory of Open Access Journals (Sweden)

    Himen Salimizand

    2012-08-01

    Full Text Available Background: Today, there are numerous reports about emerging multi drug resistant gram negative bacteria all around the world, especially in ICUs. Rarely, Metallo-β-lactamase (MBL enzymes are responsible for these cases. Study of MBLs for diagnosing and preventing distribution of the origin of infection are critical issues. In addition, we would like to compare the efficacy of Iranian and foreign- made antibiotic disks. Materials and Methods: During 2009 all entered clinical specimens to the laboratory tested for detecting gram negative bacteria. Isolated bacteria were tested by Kirby-Bauer method to antibiotic susceptibility test by Iranian and foreign (MAST disks. For gram negative carbapenem resistant isolates, PCR technique used to detect VIM, GIM, and SIM variants of MBLs.Results: During one year, 17890 clinical specimens referred Besat laboratory. The most specimen was Urine (8172 followed by blood culture (5190 that in which 1110 gram negative and positives isolated. Out of which, 778 (70% of isolates were gram negatives. MDR gram negatives were 157 (20.2%. Imipenem and meropenem were the most efficient antibiotics (all susceptible and ceftriaxone was the least (19 % susceptible. E. coli was the most prevalent isolate. 79 Gram negative isolates (10.1% were resistant to Iranian-made discs but all susceptible for foreign ones. All 79 isolates were tested by PCR for MBL genes, that, all were negative. Besides, Iranian imipenem and cefepime disks have had distinguishable difference in susceptibility of isolates.Conclusion: Fortunately, none of gram negative isolates were MBL producer, which revealed no colonization of MBL producing bacteria. Iranian-made disks appear efficient except for imipenem and cefepime.

  11. Exploring the epidemiology of carbapenem-resistant Gram-negative bacteria in west London and the utility of routinely collected hospital microbiology data.

    Science.gov (United States)

    Freeman, R; Moore, L S P; Charlett, A; Donaldson, H; Holmes, A H

    2015-04-01

    The objective of this study was to identify carbapenem-resistant organisms using routinely collected local microbiology data and describe the epidemiology of carbapenem resistance in two London teaching hospitals. Data on inpatients infected or colonized with Gram-negative organisms between March 2009 and February 2012 were extracted. A computer algorithm was developed incorporating internationally recognized criteria to distinguish carbapenem-resistant organisms. Multivariable analysis was conducted to identify factors associated with infection or colonization with carbapenem-resistant organisms. Binomial regression was performed to detect changes in resistance trends over time. Yearly incidence of carbapenem resistance was observed to be increasing, with significant increasing trends in Acinetobacter baumannii (47.1% in 2009-10 to 77.2% in 2011-12; P<0.001) and Enterobacter spp. (2.2% in 2009-10 to 11.5% in 2011-12; P<0.001). Single-variable and multivariable analysis demonstrated differences in the proportion of carbapenem-resistant isolates across all variables investigated, including age, sex and clinical specialty; in the latter organism-specific niches were identified. Patients in the youngest age group (16-24 years old) had the highest odds of being infected or colonized with carbapenem-resistant isolates of Escherichia coli, Klebsiella spp. or Pseudomonas aeruginosa. Furthermore, proportions of carbapenem-resistant organisms differed between the hospitals. Carbapenem resistance is an emerging problem within the UK inpatient healthcare setting. This is not an issue confined to the Enterobacteriaceae and fine-resolution surveillance is needed to identify at-risk groups. Regular analysis of routinely collected data can provide insight into the evolving carbapenem-resistance threat, with the ability to inform efforts to prevent the spread of resistance. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial

  12. [Sensitivity to mezlocillin Gram-negative aerobic bacilli according to their pattern of resistance to the usual beta-lactam antibiotics (author's transl)].

    Science.gov (United States)

    Witchitz, J L; Faurisson, F; Christol, D

    1982-02-04

    Gram-negative aerobic bacilli (Enterobacteria, Pseudomonas, Acinetobacter) isolated in clinical circumstances at the microbiology of the Claude Bernard Hospital, Paris, are classified according to their resistance to the usual beta-lactam antibiotics routinely tested: ampicillin, carbenicillin, cefalotin. The MICs of mezlocillin were measured on 204 strains and compared to the results obtained with older drugs in each group.

  13. Rapid detection of Gram-negative bacteria and their drug resistance genes from positive blood cultures using an automated microarray assay.

    Science.gov (United States)

    Han, Eunhee; Park, Dong-Jin; Kim, Yukyoung; Yu, Jin Kyung; Park, Kang Gyun; Park, Yeon-Joon

    2015-03-01

    We evaluated the performance of the Verigene Gram-negative blood culture (BC-GN) assay (CE-IVD version) for identification of Gram-negative (GN) bacteria and detection of resistance genes. A total of 163 GN organisms (72 characterized strains and 91 clinical isolates from 86 patients) were tested; among the clinical isolates, 86 (94.5%) isolates were included in the BC-GN panel. For identification, the agreement was 98.6% (146/148, 95% confidence interval [CI], 92.1-100) and 70% (7/10, 95% CI, 53.5-100) for monomicrobial and polymicrobial cultures, respectively. Of the 48 resistance genes harbored by 43 characterized strains, all were correctly detected. Of the 19 clinical isolates harboring resistance genes, 1 CTX-M-producing Escherichia coli isolated in polymicrobial culture was not detected. Overall, BC-GN assay provides acceptable accuracy for rapid identification of Gram-negative bacteria and detection of resistance genes, compared with routine laboratory methods despite that it has limitations in the number of genus/species and resistance gene included in the panel and it shows lower sensitivity in polymicrobial cultures. Copyright © 2015. Published by Elsevier Inc.

  14. Estrogen receptor-positive, progesterone receptor-negative breast cancer: association with growth factor receptor expression and tamoxifen resistance.

    Science.gov (United States)

    Arpino, Grazia; Weiss, Heidi; Lee, Adrian V; Schiff, Rachel; De Placido, Sabino; Osborne, C Kent; Elledge, Richard M

    2005-09-07

    Clinical data indicate that estrogen receptor-positive/progesterone receptor-negative (ER+/PR-) breast cancers are less sensitive to tamoxifen than are ER+/PR+ tumors. It has also been reported that tamoxifen may be less effective in tumors that overexpress either HER-2 or HER-1 (epidermal growth factor receptor) and that signaling through these receptors reduces PR expression in experimental models. We hypothesized that ER+/PR- breast tumors are more likely than ER+/PR+ breast tumors to have an aggressive phenotype, to express HER-1 and overexpress HER-2, and are less likely to benefit from tamoxifen adjuvant therapy. Clinical and biological features of 31 415 patients with ER+/PR+ tumors were compared with those of 13,404 patients with ER+/PR- tumors. Association between disease-free survival (DFS) and HER-1 and HER-2 status was analyzed in a subset of 11,399 patients receiving adjuvant tamoxifen therapy. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression or Kaplan-Meier analyses, and all statistical tests were two-sided. ER+/PR- tumors were more frequent in older patients, were larger in size, had a higher S-phase fraction, and were more likely to be aneuploid than ER+/PR+ tumors. Furthermore, three times as many ER+/PR- tumors as ER+/PR+ tumors expressed HER-1 (25% versus 8%; P HER-1-expressing tumors than with HER-1-negative tumors (HR = 1.9, 95% CI = 1.0 to 3.5; P = .05); a stronger association between worse DFS and HER-2 overexpression was observed (HR = 2.3, 95% CI = 1.2 to 4.3; P = .006). However, results varied by PR status. Among tamoxifen-treated women with ER+/PR+ tumors, HER-1 or HER-2 status was not associated with worse DFS. Among women with ER+/PR- tumors, however, both HER-1 expression (HR = 2.4, 95% CI = 1.0 to 5.4; P = .036) and HER-2 overexpression (HR = 2.6, 95% CI = 1.1 to 6.0; P = .022) were associated with a higher likelihood of recurrence. ER+/PR- tumors express higher levels of HER-1 and HER-2 and

  15. Horizontal transfer of antibiotic resistance genes among gram negative bacteria in sewage and lake water and influence of some physico-chemical parameters of water on conjugation process.

    Science.gov (United States)

    Shakibaie, M R; Jalilzadeh, K A; Yamakanamardi, S M

    2009-01-01

    Transfer of antibiotic resistance genes among gram negative bacteria in sewage and lake water and easy access of these bacteria to the community are major environmental and public health concern. The aim of this study was to determine transfer of the antimicrobial resistance genes from resistant to susceptible gram negative bacteria in the sewage and lake water by conjugation process and to determine the influence of some physico-chemical parameters of sewage and lake water on the transfer of these resistance genes. For this reason, we isolated 20 liter of each sewage and lake water from coconut area within university campus and Lingambudi lake respectively in Mysore city, India, during monsoon season and studied different physical parameters of the water samples like pH, temperature, conductivity turbidity and color as well as chemical parameters like BOD, COD, field DO and total chloride ion. The gram negative bacteria were isolated and identified from the above water samples using microbiological and biochemical methods and their sensitivity to different antibiotics was determined by disc diffusion break point assay. Conjugation between two multiple antibiotic resistant isolates Pseudomonas aeuginosa and E. coli as donor and E. coli Rif(r) (sensitive to antibiotics) as recipient were carried out in 5ml sterile sewage and lake water. All isolates were resistant to Am, moderately resistant to Te and E, while majority were sensitive to Cip, Gm and CAZ antibiotics. Horizontal transfer of antibiotic resistance genes by conjugation process revealed transfer of Gm, Te and E resistant genes from Ps. aeruginosa to E. coli Rif(r) recipient with mean frequency of +/- 2.3 x 10(-4) in sewage and +/- 2.6 x 10(-6) in lake water respectively Frequency of conjugation in sewage was two fold more as compared to lake water (ptransfer study revealed simultaneous transfer of above resistant markers together to the recipient cells. As the above results indicate, due to selective

  16. Multicenter evaluation of the Verigene Gram-negative blood culture nucleic acid test for rapid detection of bacteria and resistance determinants in positive blood cultures.

    Science.gov (United States)

    Uno, Naoki; Suzuki, Hiromichi; Yamakawa, Hiromi; Yamada, Maiko; Yaguchi, Yuji; Notake, Shigeyuki; Tamai, Kiyoko; Yanagisawa, Hideji; Misawa, Shigeki; Yanagihara, Katsunori

    2015-12-01

    The Verigene Gram-Negative Blood Culture Nucleic Acid Test (BC-GN) is a microarray-based assay that enables rapid detection of 9 common Gram-negative bacteria and 6 resistance determinants directly from positive blood cultures. We compared the performance of BC-GN with currently used automated systems, testing 141 clinical blood cultures and 205 spiked blood cultures. For identification of BC-GN target organisms in clinical and spiked blood cultures, the BC-GN assay showed 98.5% (130/132) and 98.9% (182/184) concordance, respectively. Of 140 resistance genes positively detected in clinical and spiked blood cultures with the BC-GN test, 139 (99.3%) were confirmed by PCR, and the detection results were consistent with the resistance phenotypes observed. The BC-GN assay, thus, can potentially improve care for sepsis patients by enabling timely detection and targeted antimicrobial therapy. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Intestinal carriage of multidrug-resistant gram-negative bacteria in preterm-infants during hospitalization in neonatal intensive care unit (NICU).

    Science.gov (United States)

    Yap, Polly Soo Xi; Ahmad Kamar, Azanna; Chong, Chun Wie; Yap, Ivan Kok Seng; Thong, Kwai Lin; Choo, Yao Mun; Md Yusof, Mohd Yasim; Teh, Cindy Shuan Ju

    2016-09-01

    The prevalence and antibiotic susceptibility of intestinal carriage of Gram-negative bacteria among preterm infants admitted to the neonatal intensive care unit (NICU) in a tertiary teaching hospital in Malaysia were determined. A total of 34 stool specimens were obtained from preterm infants upon admission and once weekly up to two weeks during hospitalization. The presumptive colonies of Escherichia coli and Klebsiella pneumoniae were selected for identification, antibiotic susceptibility testing, and subtyping by using pulsed-field gel electrophoresis (PFGE). Out of 76 Gram-negative isolates, highest resistance was detected for amoxicillin/clavulanate (30.8%, n = 16), ceftriaxone (42.3%, n = 22), ceftazidime (28.8%, n = 15), cefoxitin (28.8%, n = 15), aztreonam (36.5%, n = 19), and polymyxin B (23.1%, n = 12). Three colistin resistant K. pneumoniae have also been detected based on E-test analysis. Thirty-nine isolates of K. pneumoniae and 20 isolates of E. coli were resistant to more than three antimicrobial classes and were categorized as multidrug resistant (MDR). PFGE analysis revealed a higher diversity in pulsotypes for K. pneumoniae (18 pulsotypes) in comparison to E. coli (four pulsotypes). In addition, a total of fifteen pulsotypes was observed from 39 MDR K. pneumoniae. The risk factors for antibiotic resistance were assessed using random forest analysis. Gender was found to be the most important predictor for colistin resistant while length, OFC, and delivery mode were showing greater predictive power in the polymyxin B resistance. This study revealed worrying prevalence rates of intestinal carriage of multidrug-resistant K. pneumoniae and E. coli of hospitalized preterm infants in Malaysia, particularly high resistance to polymyxins.

  18. In Vitro antibacterial and antibiotic-potentiation activities of four edible plants against multidrug-resistant gram-negative species

    Science.gov (United States)

    2013-01-01

    Background The present study was designed to investigate the antibacterial activities of the methanol extracts of four Cameroonian edible plants, locally used to treat microbial infections, and their synergistic effects with antibiotics against a panel of twenty nine Gram-negative bacteria including Multi-drug resistant (MDR) phenotypes expressing active efflux pumps. Methods The broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of the extracts [alone and in the presence of the efflux pumps inhibitor (EPI) Phenylalanine-Arginine β-Naphtylamide (PAβN)], and those of antibiotics in association with the two of the most active ones, Piper nigrum and Telfairia occidentalis. The preliminary phytochemical screening of the extracts was conducted according to the standard phytochemical methods. Results Phytochemical analysis showed the presence of alkaloids and flavonoids in all studied extracts. Other chemical classes of secondary metabolites were selectively present in the extracts. The results of the MIC determination indicated that the crude extracts from P. nigrum and V. amygdalina were able to inhibit the growth of all the twenty nine studied bacteria within a concentration range of 32 to 1024 μg/mL. At a similar concentration range (32 to 1024 μg/mL) the extract from T. occidentalis inhibited the growth of 93.1% of the tested microorganisms. At MIC/2 and MIC/5, synergistic effects were noted between the extracts from P. nigrum and T. occidentalis and seven of the tested antibiotics on more than 70% of the tested bacteria. Conclusion The overall results of the present study provide information for the possible use of the studied edible plants extracts in the control of bacterial infections including MDR phenotypes. PMID:23885762

  19. Predictors of mortality in bloodstream infections caused by multidrug-resistant gram-negative bacteria: 4 years of collection.

    Science.gov (United States)

    Wang, Weiwei; Jiang, Ting; Zhang, Weihong; Li, Chunyu; Chen, Jun; Xiang, Dandan; Cao, Kejiang; Qi, Lian-Wen; Li, Ping; Zhu, Wei; Chen, Wensen; Chen, Yan

    2017-01-01

    The study was undertaken to describe the profile of patients and the characteristics of all multidrug-resistant gram-negative bacteria (MDR-GNB) and to assess mortality. We examined 138 patients with bloodstream infections (BSIs) caused by MDR-GNB. Clinical characteristics, antibiotic therapy, and in-hospital mortality were analyzed. Survivor and nonsurvivor subgroups were compared to identify predictors of mortality. The in-hospital mortality rate was 25.4%. Univariate analysis revealed that comorbidities and inadequate initial antimicrobial treatment could increase risk of death. In Cox regression analysis, mortality was independently associated with the age (P = .034), hospitalization in an intensive care unit (ICU) (P = .04), invasive procedures (P < .001), and Acute Physiology and Chronic Health Evaluation II scores (P < .001), whereas combination therapy or monotherapy was not associated with mortality (P = .829). Postantibiogram therapy was associated with hospitalization in an ICU (P = .006), Charlson comorbidity index score (P = .003), and inadequate initial antimicrobial treatment (P < .001). MDR-GNB strains and antimicrobial regimens were not the major risk factors of mortality. Inadequate initial antimicrobial treatment, invasive procedures, high Acute Physiology And Chronic Health Evaluation II scores, hospitalization in an ICU, and comorbidities were the important factors responsible for mortality. Although there was no difference between combination therapy and monotherapy in mortality, combined treatment may be more effective than monotherapy for patients in an ICU, with a Charlson comorbidity index score < 4, or inadequate initial antimicrobial treatment. Copyright © 2017 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  20. Infection with multidrug-resistant gram-negative bacteria in a pediatric oncology intensive care unit: risk factors and outcomes.

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    Costa, Patrícia de Oliveira; Atta, Elias Hallack; Silva, André Ricardo Araújo da

    2015-01-01

    This study aimed at evaluating the predictors and outcomes associated with multidrug-resistant gram-negative bacterial (MDR-GNB) infections in an oncology pediatric intensive care unit (PICU). Data were collected relating to all episodes of GNB infection that occurred in a PICU between January of 2009 and December of 2012. GNB infections were divided into two groups for comparison: (1) infections attributed to MDR-GNB and (2) infections attributed to non-MDR-GNB. Variables of interest included age, gender, presence of solid tumor or hematologic disease, cancer status, central venous catheter use, previous Pseudomonas aeruginosa infection, healthcare-associated infection, neutropenia in the preceding 7 days, duration of neutropenia, length of hospital stay before ICU admission, length of ICU stay, and the use of any of the following in the previous 30 days: antimicrobial agents, corticosteroids, chemotherapy, or radiation therapy. Other variables included initial appropriate antimicrobial treatment, definitive inadequate antimicrobial treatment, duration of appropriate antibiotic use, time to initiate adequate antibiotic therapy, and the 7- and 30-day mortality. Multivariate logistic regression analyses showed significant relationships between MDR-GNB and hematologic diseases (odds ratio [OR] 5.262; 95% confidence interval [95% CI] 1.282-21.594; p=0.021) and healthcare-associated infection (OR 18.360; 95% CI 1.778-189.560; p=0.015). There were significant differences between MDR-GNB and non-MDR-GNB patients for the following variables: inadequate initial empirical antibiotic therapy, time to initiate adequate antibiotic treatment, and inappropriate antibiotic therapy. Hematologic malignancy and healthcare-associated infection were significantly associated with MDR-GNB infection in this sample of pediatric oncology patients. Copyright © 2015 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

  1. Changes in gram negative microorganisms’ resistance pattern during 4 years period in a referral teaching hospital; a surveillance study

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    Khalili Hossein

    2012-09-01

    Full Text Available Abstract Background and purpose Surveillance studies evaluating antimicrobial susceptibilities are of great value in preventing the spread of resistant pathogens by elucidating the trend of resistance in commonly used antibiotics and as a consequence providing information for prescribing the most appropriate agent. This study is a longitudinal antimicrobial resistance surveillance study designed to evaluate the trend in antimicrobial resistance to gram negative microorganisms from 2007 to 2010. Method During a four-year period (2007–2010 isolates derived from all patients admitted to infectious diseases ward of Imam Khomeini Hospital, the major referral center for infectious disease in Iran with the highest admission rates, were evaluated. Based on disk diffusion method and zone of inhibition size, the microorganism was regarded as to be sensitive, resistant or has intermediate susceptibility to the antimicrobial agents. Results The widest spread Gram-negative microorganism in all of isolates taken together in our study was E.coli (30% followed by Stenotrophomonas maltophilia in 28.6% and Enterobacter spp. in 11.9%, respectively. The susceptibility to amikacin, imipenem, piperacillin/tazobactam, and nitrofurantoin was equal or above 50% for all microorganisms over four years. However, the susceptibility to ampicillin, ampicillin/sulbactam, cefotaxim, and ceftriaxone was less than 50% in derived isolates during the study period. Conclusion In conclusion, the finding of the present study revealed that resistance rate to common antimicrobial agents in Iran is growing and isolates were susceptible mostly to broad-spectrum antibiotics including imipenem and piperacillin/tazobactam.

  2. Antibiotic Exposure in a Low-Income Country: Screening Urine Samples for Presence of Antibiotics and Antibiotic Resistance in Coagulase Negative Staphylococcal Contaminants

    DEFF Research Database (Denmark)

    Lerbeck, Anne Mette; Tersbøl, Britt Pinkowski; Styrishave, Bjarne

    2014-01-01

    596 respectively) from patients in two hospitals in Ghana. CoNS were identified using Gram staining, coagulase test, and MALDI-TOF/MS, and the antimicrobial susceptibility to 12 commonly used antimicrobials was determined by disk diffusion. Moreover an analytical method was developed...... for the determination of the nine most commonly used antimicrobial agents in Ghana by using solid-phase extraction in combination with HPLC-MS/MS using electron spray ionization. The highest frequency of resistance to CoNS was observed for penicillin V (98%), trimethoprim (67%), and tetracycline (63%). S. haemolyticus......Development of antimicrobial resistance has been assigned to excess and misuse of antimicrobial agents. Staphylococci are part of the normal flora but are also potential pathogens that have become essentially resistant to many known antibiotics. Resistances in coagulase negative staphylococci (Co...

  3. Antibiotic Exposure in a Low-Income Country: Screening Urine Samples for Presence of Antibiotics and Antibiotic Resistance in Coagulase Negative Staphylococcal Contaminants

    DEFF Research Database (Denmark)

    Lerbech, Anne Mette; Opintan, Japheth A; Bekoe, Samuel Oppong

    2014-01-01

     = 96 respectively) from patients in two hospitals in Ghana. CoNS were identified using Gram staining, coagulase test, and MALDI-TOF/MS, and the antimicrobial susceptibility to 12 commonly used antimicrobials was determined by disk diffusion. Moreover an analytical method was developed...... for the determination of the nine most commonly used antimicrobial agents in Ghana by using solid-phase extraction in combination with HPLC-MS/MS using electron spray ionization. The highest frequency of resistance to CoNS was observed for penicillin V (98%), trimethoprim (67%), and tetracycline (63%). S. haemolyticus......Development of antimicrobial resistance has been assigned to excess and misuse of antimicrobial agents. Staphylococci are part of the normal flora but are also potential pathogens that have become essentially resistant to many known antibiotics. Resistances in coagulase negative staphylococci (Co...

  4. Evaluation of Effective Elastic, Piezoelectric, and Dielectric Properties of SU8/ZnO Nanocomposite for Vertically Integrated Nanogenerators Using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Neelam Mishra

    2017-01-01

    Full Text Available A nanogenerator is a nanodevice which converts ambient mechanical energy into electrical energy. A piezoelectric nanocomposite, composed of vertical arrays of piezoelectric zinc oxide (ZnO nanowires, encapsulated in a compliant polymeric matrix, is one of most common configurations of a nanogenerator. Knowledge of the effective elastic, piezoelectric, and dielectric material properties of the piezoelectric nanocomposite is critical in the design of a nanogenerator. In this work, the effective material properties of a unidirectional, unimodal, continuous piezoelectric composite, consisting of SU8 photoresist as matrix and vertical array of ZnO nanowires as reinforcement, are systematically evaluated using finite element method (FEM. The FEM simulations were carried out on cubic representative volume elements (RVEs. Four different types of arrangements of ZnO nanowires and three sizes of RVEs have been considered. The volume fraction of ZnO nanowires is varied from 0 to a maximum of 0.7. Homogeneous displacement and electric potential are prescribed as boundary conditions. The material properties are evaluated as functions of reinforcement volume fraction. The values obtained through FEM simulations are compared with the results obtained via the Eshelby-Mori-Tanaka micromechanics. The results demonstrate the significant effects of ZnO arrangement, ZnO volume fraction, and size of RVE on the material properties.

  5. Mi-1.2, an R gene for aphid resistance in tomato, has direct negative effects on a zoophytophagous biocontrol agent, Orius insidiosus.

    Science.gov (United States)

    Pallipparambil, Godshen R; Sayler, Ronald J; Shapiro, Jeffrey P; Thomas, Jean M G; Kring, Timothy J; Goggin, Fiona L

    2015-02-01

    Mi-1.2 is a single dominant gene in tomato that confers race-specific resistance against certain phloem-feeding herbivores including aphids, whiteflies, psyllids, and root-knot nematodes. Few prior studies have considered the potential non-target effects of race-specific resistance genes (R genes), and this paper evaluates the compatibility of Mi-mediated resistance in tomato with a beneficial zoophytophagous predator, Orius insidiosus (Say). In addition to preying on aphids and other pests, this piercing-sucking insect also feeds from the xylem, epidermis, and/or mesophyll, and oviposits within plant tissues. Comparison of O. insidiosus confined to isogenic tomato plants with and without Mi-1.2 revealed that immatures of O. insidiosus had lower survival on resistant plants even when the immatures were provisioned with prey that did not feed on the host plant. Molecular gut content analysis confirmed that adults and immatures of O. insidiosus feed on both resistant (Mi-1.2+) and susceptible (Mi-1.2-) genotypes, and bioassays suggest that resistance does not affect oviposition rates, plant sampling, or prey acceptance by O. insidiosus adults. These results demonstrate a direct negative impact of R-gene-mediated host plant resistance on a non-target beneficial species, and reveal that Mi-mediated resistance can impact organisms that do not feed on phloem sap. Through laser capture microdissection and RT-PCR, Mi-1.2 transcripts were detected in the epidermis and mesophyll as well as the phloem of tomato plants, consistent with our observations that Mi-mediated resistance is active outside the phloem. These results suggest that the mode of action and potential ecological impacts of Mi-mediated resistance are broader than previously assumed. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  6. Antibiotic exposure in a low-income country: screening urine samples for presence of antibiotics and antibiotic resistance in coagulase negative staphylococcal contaminants.

    Directory of Open Access Journals (Sweden)

    Anne Mette Lerbech

    Full Text Available Development of antimicrobial resistance has been assigned to excess and misuse of antimicrobial agents. Staphylococci are part of the normal flora but are also potential pathogens that have become essentially resistant to many known antibiotics. Resistances in coagulase negative staphylococci (CoNS are suggested to evolve due to positive selective pressure following antibiotic treatment. This study investigated the presence of the nine most commonly used antimicrobial agents in human urine from outpatients in two hospitals in Ghana in relation to CoNS resistance. Urine and CoNS were sampled (n = 246 and n = 96 respectively from patients in two hospitals in Ghana. CoNS were identified using Gram staining, coagulase test, and MALDI-TOF/MS, and the antimicrobial susceptibility to 12 commonly used antimicrobials was determined by disk diffusion. Moreover an analytical method was developed for the determination of the nine most commonly used antimicrobial agents in Ghana by using solid-phase extraction in combination with HPLC-MS/MS using electron spray ionization. The highest frequency of resistance to CoNS was observed for penicillin V (98%, trimethoprim (67%, and tetracycline (63%. S. haemolyticus was the most common isolate (75%, followed by S. epidermidis (13% and S. hominis (6%. S. haemolyticus was also the species displaying the highest resistance prevalence (82%. 69% of the isolated CoNS were multiple drug resistant (≧ 4 antibiotics and 45% of the CoNS were methicillin resistant. Antimicrobial agents were detected in 64% of the analysed urine samples (n = 121 where the most frequently detected antimicrobials were ciprofloxacin (30%, trimethoprim (27%, and metronidazole (17%. The major findings of this study was that the prevalence of detected antimicrobials in urine was more frequent than the use reported by the patients and the prevalence of resistant S. haemolyticus was more frequent than other resistant CoNS species when antimicrobial

  7. Novel Multiplex PCR Assay for Detection of Chlorhexidine-Quaternary Ammonium, Mupirocin, and Methicillin Resistance Genes, with Simultaneous Discrimination of Staphylococcus aureus from Coagulase-Negative Staphylococci.

    Science.gov (United States)

    McClure, Jo-Ann; Zaal DeLongchamp, Johanna; Conly, John M; Zhang, Kunyan

    2017-06-01

    Methicillin-resistant Staphylococcus aureus (MRSA) is a clinically significant pathogen that is resistant to a wide variety of antibiotics and responsible for a large number of nosocomial infections worldwide. The Agency for Healthcare Research and Quality and the Centers for Disease Control and Prevention recently recommended the adoption of universal mupirocin-chlorhexidine decolonization of all admitted intensive care unit patients rather than MRSA screening with targeted treatments, which raises a serious concern about the selection of resistance to mupirocin and chlorhexidine in strains of staphylococci. Thus, a simple, rapid, and reliable approach is paramount in monitoring the prevalence of resistance to these agents. We developed a simple multiplex PCR assay capable of screening Staphylococcus isolates for the presence of antiseptic resistance genes for chlorhexidine and quaternary ammonium compounds, as well as mupirocin and methicillin resistance genes, while simultaneously discriminating S. aureus from coagulase-negative staphylococci (CoNS). The assay incorporates 7 PCR targets, including the Staphylococcus 16S rRNA gene (specifically detecting Staphylococcus spp.), nuc (distinguishing S. aureus from CoNS), mecA (distinguishing MRSA from methicillin-susceptible S. aureus ), mupA and mupB (identifying high-level mupirocin resistance), and qac and smr (identifying chlorhexidine and quaternary ammonium resistance). Our assay demonstrated 100% sensitivity, specificity, and accuracy in a total of 23 variant antiseptic- and/or antibiotic-resistant control strains. Further validation of our assay using 378 randomly selected and previously well-characterized local clinical isolates confirmed its feasibility and practicality. This may prove to be a useful tool for multidrug-resistant Staphylococcus monitoring in clinical laboratories, particularly in the wake of increased chlorhexidine and mupirocin treatments. Copyright © 2017 American Society for Microbiology.

  8. Antimicrobial susceptibility pattern and SCCmec types of methicillin-resistant coagulase-negative staphylococci from subclinical bovine mastitis in Hatay, Turkey

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    Aslantaş Özkan

    2014-12-01

    Full Text Available Eighty-nine isolates of coagulase-negative staphylococci (CoNS of eight species from subclinical bovine mastitis were screened for the phenotypic and genotypic methicilline-resistance. In addition, all methicillin-resistant (MR isolates indicating the mecA gene were examined by PCR for the antimicrobial susceptibility patterns, and staphylococcal cassette chromosome mec (SCCmec types were also determined by multiplex PCR. A total of 21 (23.6% CoNS isolates were found to be resistant to oxacillin in broth microdilution assay. All isolates phenotypically resistant to oxacillin did not have the mecA gene, which was only found in 14.6% (13 of the isolates. Most MR-CoNS isolates were highly resistant to erythromycin (92.3%, fusidic acid (84.6%, penicillin (76.9%, and rifampycin (61.5%, and susceptible to mupirocin (100%, tetracycline (100%, vancomycin (100%, clindamycin (92.3%, and sulfamethoxazole-trimethoprim (69.2%. In conclusion, a high rate of antimicrobial resistance among MR-CoNS isolated from food producing animals emphasises the need for periodic surveillance of their resistance.

  9. Activity of imipenem, third-generation cephalosporins, aztreonam and ciprofloxacin against multi-resistant gram-negative bacilli isolated from Chilean hospitals.

    Science.gov (United States)

    Zemelman, R; Bello, H; Dominguez, M; Gonzalez, G; Mella, S; Garcia, A

    1993-09-01

    The activity of imipenem against nosocomial strains of Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter spp. and methicillin-resistant Staphylococcus aureus resistant to some third-generation cephalosporins, aztreonam, or ciprofloxacin was assessed. These strains represent the most prevalent multi-resistant nosocomial microorganisms in Chile since they were isolated from clinical specimens in 11 Chilean hospitals. A high proportion of the strains were resistant to several beta-lactams, yet all strains of K. pneumoniae and Acinetobacter spp. were susceptible to imipenem; resistance was exhibited by only one strain of P. aeruginosa and 16 strains of S. aureus. Synergy between cefotaxime and clavulanic acid was found in almost all strains of K. pneumoniae, suggesting the presence of plasmid-coded beta-lactamases, probably with extended-spectrum activity. Killing A. baumannii by imipenem was rapid, but slower for P. aeruginosa. Killing of K. pneumoniae was also somewhat slower despite the lower MIC of imipenem for this strain. Bactericidal activity was even slower against one strain of methicillin-resistant S. aureus. These results suggest that imipenem would be an adequate alternative to other broad-spectrum agents in the treatment of infections due to nosocomial multi-resistant Gram-negative bacilli.

  10. Faecal Carriage of Gram-Negative Multidrug-Resistant Bacteria among Patients Hospitalized in Two Centres in Ulaanbaatar, Mongolia.

    Science.gov (United States)

    Baljin, Bayaraa; Baldan, Ganbaatar; Chimeddorj, Battogtokh; Tulgaa, Khosbayar; Gunchin, Batbaatar; Sandag, Tsogtsaikhan; Pfeffer, Klaus; MacKenzie, Colin R; Wendel, Andreas F

    2016-01-01

    Gram-negative multidrug-resistant organisms (GN-MDRO) producing β-lactamases (ESBL, plasmid-mediated AmpC β-lactamases and carbapenemases) are increasingly reported throughout Asia. The aim of this surveillance study was to determine the rate of bacterial colonization in patients from two hospitals in the Mongolian capital Ulaanbaatar. Rectal swabs were obtained from patients referred to the National Traumatology and Orthopaedics Research Centre (NTORC) or the Burn Treatment Centre (BTC) between July and September 2014, on admission and again after 14 days. Bacteria growing on selective chromogenic media (CHROMagar ESBL/KPC) were identified by MALDI-ToF MS. We performed susceptibility testing by disk diffusion and PCR (blaIMP-1, blaVIM, blaGES, blaNDM, blaKPC, blaOXA-48, blaGIM-1, blaOXA-23, blaOXA-24/40, blaOXA-51, blaOXA-58, blaOXA-143, blaOXA-235, blaCTX-M, blaSHV blaTEM and plasmid-mediated blaAmpC). Carbapenemase-producing isolates were additionally genotyped by PFGE and MLST. During the study period 985 patients in the NTORC and 65 patients in the BTC were screened on admission. The prevalence of GN-MDRO-carriage was 42.4% and 69.2% respectively (p<0.001). Due to the different medical specialities the two study populations differed significantly in age (p<0.029) and gender (p<0.001) with younger and more female patients in the burn centre (BTC). We did not observe a significant difference in colonization rate in the respective age groups in the total study population. In both centres most carriers were colonized with CTX-M-producing E. coli, followed by CTX-M-producing K. pneumoniae and CTX-M-producing E. cloacae. 158 patients from the NTORC were re-screened after 14 days of whom 99 had acquired a new GN-MDRO (p<0.001). Carbapenemases were detected in both centres in four OXA-58-producing A. baumannii isolates (ST642) and six VIM-2-producing P. aeruginosa isolates (ST235). This study shows a high overall prevalence of GN-MDRO in the study population and

  11. Adjunctive aerosolized colistin for multi-drug resistant gram-negative pneumonia in the critically ill: a retrospective study.

    Science.gov (United States)

    Doshi, Neha M; Cook, Charles H; Mount, Kari L; Stawicki, Stanislaw P; Frazee, Erin N; Personett, Heather A; Schramm, Garrett E; Arnold, Heather M; Murphy, Claire V

    2013-11-25

    The incidence of multi-drug resistant (MDR) gram-negative (GN) organisms including Pseudomonas and Acinetobacter spp has increased in the last decade, prompting re-evaluation of colistin for the management of these infections. Aerosolized colistin as an adjunct to intravenous therapy is a current option for the management of MDR-GN pneumonia, although data supporting this practice is limited. This study evaluates the efficacy of adjunctive aerosolized colistin in combination with intravenous colistin in critically ill patients with MDR-GN pneumonia. A retrospective multi-center cohort analysis comparing critically ill patients with MDR-GN pneumonia who received intravenous colistin (IV) alone or in combination with adjunctive aerosolized colistin (IV/AER) with a primary endpoint of clinical cure at the end of colistin therapy. Secondary endpoints included microbiologic cure, duration of mechanical ventilation, length of stay, and hospital mortality. A post-hoc subgroup analysis was performed for patients with high quality cultures used for diagnosis of MDR-GN pneumonia. Dichotomous data were compared using Fisher's exact test while the student's t-test or Mann-Whitney U test were used for continuous variables. Ninety-five patients met criteria for evaluation with 51 patients receiving IV and 44 receiving IV/AER. Baseline characteristics were similar between the two groups. Twenty patients (39.2%) receiving IV and 24 (54.5%) receiving IV/AER achieved clinical cure (p = 0.135). There was no difference in microbiologic cure rates between the IV and IV/AER colistin groups (40.7vs. 44.4%, p = 0.805). The IV group demonstrated a trend towards higher pneumonia attributable mortality (70.4 vs. 40%, p = 0.055). In the subgroup analysis of patients with high quality respiratory cultures, there was a significantly lower clinical cure rate for those in the IV group as compared to the IV/AER group (31.3 vs. 57.1%, p = 0.033). Addition of aerosolized colistin to

  12. Biofilm formation of methicillin-resistant coagulase negative staphylococci (MR-CoNS isolated from community and hospital environments.

    Directory of Open Access Journals (Sweden)

    Rathanin Seng

    Full Text Available Methicillin-resistant coagulase negative staphylococci (MR-CoNS are the major cause of infectious diseases because of their potential ability to form biofilm and colonize the community or hospital environments. This study was designed to investigate the biofilm producing ability, and the presence of mecA, icaAD, bap and fnbA genes in MR-CoNS isolates. The MR-CoNS used in this study were isolated from various samples of community environment and five wards of hospital environments, using mannitol salt agar (MSA supplemented with 4 μg/ml of oxacillin. The specie level of Staphylococcus haemolyticus, Staphylococcus epidermidis, Staphylococcus hominis and Staphylococcus warneri was identified by specific primers of groESL (S. haemolyticus, rdr (S. epidermidis and nuc (S. hominis and S. warneri. The remainder isolates were identified by tuf gene sequencing. Biofilm production was determined using Congo red agar (CRA and Microtiter plate (MTP assay. The mecA and biofilm associated genes (icaAD, fnbA and bap were detected using PCR method. From the 558 samples from community and hospital environments, 292 MR-CoNS were isolated (41 from community environments, and 251 from hospital environments. S. haemolyticus (41.1% and S. epidermidis (30.1% were the predominant species in this study. Biofilm production was detected in 265 (90.7% isolates by CRA, and 260 (88.6% isolates were detected by MTP assay. The staphylococci isolates derived from hospital environments were more associated with biofilm production than the community-derived isolates. Overall, the icaAD and bap genes were detected in 74 (29.5% and 14 (5.6% of all isolates from hospital environments. When tested by MTP, the icaAD gene from hospital environment isolates was associated with biofilm biomass. No association was found between bap gene and biofilm formation. The MR-CoNS isolates obtained from community environments did not harbor the icaAD and bap genes. Conversely, fnbA gene presented

  13. Biofilm formation of methicillin-resistant coagulase negative staphylococci (MR-CoNS) isolated from community and hospital environments.

    Science.gov (United States)

    Seng, Rathanin; Kitti, Thawatchai; Thummeepak, Rapee; Kongthai, Phattaraporn; Leungtongkam, Udomluk; Wannalerdsakun, Surat; Sitthisak, Sutthirat

    2017-01-01

    Methicillin-resistant coagulase negative staphylococci (MR-CoNS) are the major cause of infectious diseases because of their potential ability to form biofilm and colonize the community or hospital environments. This study was designed to investigate the biofilm producing ability, and the presence of mecA, icaAD, bap and fnbA genes in MR-CoNS isolates. The MR-CoNS used in this study were isolated from various samples of community environment and five wards of hospital environments, using mannitol salt agar (MSA) supplemented with 4 μg/ml of oxacillin. The specie level of Staphylococcus haemolyticus, Staphylococcus epidermidis, Staphylococcus hominis and Staphylococcus warneri was identified by specific primers of groESL (S. haemolyticus), rdr (S. epidermidis) and nuc (S. hominis and S. warneri). The remainder isolates were identified by tuf gene sequencing. Biofilm production was determined using Congo red agar (CRA) and Microtiter plate (MTP) assay. The mecA and biofilm associated genes (icaAD, fnbA and bap) were detected using PCR method. From the 558 samples from community and hospital environments, 292 MR-CoNS were isolated (41 from community environments, and 251 from hospital environments). S. haemolyticus (41.1%) and S. epidermidis (30.1%) were the predominant species in this study. Biofilm production was detected in 265 (90.7%) isolates by CRA, and 260 (88.6%) isolates were detected by MTP assay. The staphylococci isolates derived from hospital environments were more associated with biofilm production than the community-derived isolates. Overall, the icaAD and bap genes were detected in 74 (29.5%) and 14 (5.6%) of all isolates from hospital environments. When tested by MTP, the icaAD gene from hospital environment isolates was associated with biofilm biomass. No association was found between bap gene and biofilm formation. The MR-CoNS isolates obtained from community environments did not harbor the icaAD and bap genes. Conversely, fnbA gene presented in MR

  14. Incidence of multiple antibiotic resistant Gram-negative bacteria isolated from surface and underground water sources in south western region of Nigeria.

    Science.gov (United States)

    Oluyege, J O; Dada, A C; Odeyemi, A T

    2009-01-01

    In most rural and urban settlements, particularly in Nigeria, wells, spring, streams or rivers and lakes serves as major sources of water supply for drinking and other domestic purposes. Unfortunately, many of the available water sources are not potable without some form of treatment which is seldom available in most settings. The use of untreated surface water sources for drinking and for domestic purposes remains a major threat to public health as these could serve as reservoirs the for transfer of antibiotic resistant pathogens. The incidence of resistant bacteria isolated from surface and underground water in six rural settlements in Ekiti State Nigeria was thus investigated. Gram-negative bacteria were isolated from wells, streams and boreholes in six rural settlements in Ekiti State Nigeria between January and April, 2006 and the prevalence of organisms exhibiting multiple antibiotic resistance to tetracycline, amoxicillin, cotrimoxazole, nitofurantoin, gentamicin, nalidixic acid and ofloxacin was observed. Gram-negative bacterial isolates comprised Escherichia coli (22.7%), Enterobacter aerogenes (2.5%), Salmonella spp. (13.3%), Shigella spp. (19.3%), Proteus spp. (18.5%), Klebsiella spp. (19.3%) and Pseudomonas aeruginosa (4.2%). Over 10% of the bacteria were resistant to four or more antibiotic. Antibiotic resistance was highest in members of the genera Enterobacter, Pseudomonas, and Proteus. Given the prevalence of appalling sanitary facilities and inappropriate public antibiotic use, the possibility of antibiotic resistance selection, faecal dissemination and subsequent contamination of local water sources available for rural residents of the developing world is highlighted. The implication for clinical practice of infections caused by antibiotic resistant strains especially among immunodeficient individuals is also discussed.

  15. A novel radiation-induced p53 mutation is not implicated in radiation resistance via a dominant-negative effect.

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    Yunguang Sun

    Full Text Available Understanding the mutations that confer radiation resistance is crucial to developing mechanisms to subvert this resistance. Here we describe the creation of a radiation resistant cell line and characterization of a novel p53 mutation. Treatment with 20 Gy radiation was used to induce mutations in the H460 lung cancer cell line; radiation resistance was confirmed by clonogenic assay. Limited sequencing was performed on the resistant cells created and compared to the parent cell line, leading to the identification of a novel mutation (del at the end of the DNA binding domain of p53. Levels of p53, phospho-p53, p21, total caspase 3 and cleaved caspase 3 in radiation resistant cells and the radiation susceptible (parent line were compared, all of which were found to be similar. These patterns held true after analysis of p53 overexpression in H460 cells; however, H1299 cells transfected with mutant p53 did not express p21, whereas those given WT p53 produced a significant amount, as expected. A luciferase assay demonstrated the inability of mutant p53 to bind its consensus elements. An MTS assay using H460 and H1299 cells transfected with WT or mutant p53 showed that the novel mutation did not improve cell survival. In summary, functional characterization of a radiation-induced p53 mutation in the H460 lung cancer cell line does not implicate it in the development of radiation resistance.

  16. Beyond Susceptible and Resistant, Part II: Treatment of Infections Due to Gram-Negative Organisms Producing Extended-Spectrum β-Lactamases

    OpenAIRE

    Curello, Jennifer; MacDougall, Conan

    2014-01-01

    The production of β-lactamase is the most common mechanism of resistance to β-lactam antibiotics among gram-negative bacteria. Extended-spectrum β-lactamases (ESBLs) are capable of hydrolyzing most penicillins, extended-spectrum cephalosporins, and aztreonam, but their activity is suppressed in the presence of a β-lactamase inhibitor. Serious infections with ESBL-producing isolates are associated with high rates of mortality, making early detection and adequate medical management essential to...

  17. Activity of Levofloxacin Alone and in Combination with a DnaK Inhibitor against Gram-Negative Rods, Including Levofloxacin-Resistant Strains▿

    OpenAIRE

    Credito, Kim; Lin, Gengrong; Koeth, Laura; Sturgess, Michael A.; Appelbaum, Peter C.

    2008-01-01

    Synergy time-kill testing of levofloxacin alone and in combination with CHP-105, a representative DnaK inhibitor, against 50 gram-negative rods demonstrated that 34 of the 50 strains tested showed significant synergy between levofloxacin and CHP-105 after 12 h and 24 h. Fourteen of these 34 organisms were quinolone resistant (levofloxacin MICs of ≥4 μg/ml).

  18. Antibacterial activities of the methanol extracts of Canarium schweinfurthii and four other Cameroonian dietary plants against multi-drug resistant Gram-negative bacteria

    OpenAIRE

    Dzotam, Joachim K.; Touani, Francesco K; Kuete, Victor

    2015-01-01

    Bacterial infections are among the major cause of morbidity and mortality worldwide. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of five Cameroonian edible plants namely Colocasia esculenta, Triumfetta pentandra, Hibiscus esculentus, Canarium schweinfurthii and Annona muricata against a panel of 19 multidrug resistant Gram-negative bacterial strains. The liquid broth microdilution was used to determine the minimal inhibitory concen...

  19. Prevalence of enterotoxin-encoding genes and antimicrobial resistance in coagulase-negative and coagulase-positive Staphylococcus isolates from black pudding

    OpenAIRE

    Moura,Tiane Martin de; Campos,Fabrício Souza; d'Azevedo,Pedro Alves; Van Der Sand,Sueli Teresinha; Franco,Ana Cláudia; Frazzon,Jeverson; Frazzon,Ana Paula Guedes

    2012-01-01

    INTRODUCTION: Staphylococcal species are pathogens that are responsible for outbreaks of foodborne diseases. The aim of this study was to investigate the prevalence of enterotoxin-genes and the antimicrobial resistance profile in staphylococcus coagulase-negative (CoNS) and coagulasepositive (CoPS) isolates from black pudding in southern Brazil. METHODS: Two hundred typical and atypical colonies from Baird-Parker agar were inoculated on mannitol salt agar. Eighty-two mannitol-positive staphyl...

  20. Metallo- β-lactamases among Multidrug Resistant (MDR) Gram Negative Bacteria Isolated from Clinical Specimens during 2009 in Sanandaj, Kurdistan Province

    OpenAIRE

    Himen Salimizand; Mehri Habibi; Fereshteh Shahcheraghi

    2012-01-01

    Background: Today, there are numerous reports about emerging multi drug resistant gram negative bacteria all around the world, especially in ICUs. Rarely, Metallo-β-lactamase (MBL) enzymes are responsible for these cases. Study of MBLs for diagnosing and preventing distribution of the origin of infection are critical issues. In addition, we would like to compare the efficacy of Iranian and foreign- made antibiotic disks. Materials and Methods: During 2009 all entered clinical specimens to the...

  1. Prevalence of the Antibiotic Resistance Genes in Coagulase-Positive-and Negative-Staphylococcus in Chicken Meat Retailed to Consumers

    OpenAIRE

    Kamelia Mahmoud Osman; Jihan Badr; Khalid Al-Maary; Ihab Moussa; Ashgan Hessain; Zeinab Girh; Usama Abo-shama; Ahmed Orabi; Aalaa Saad

    2016-01-01

    The use of antibiotics in farm management (growing crops and raising animals) has become a major area of concern. Its implications is the consequent emergence of antibiotic resistant bacteria (ARB) and accordingly their access into the human food chain with passage of antibiotic resistance genes (ARG) to the normal human intestinal microbiota and hence to other pathogenic bacteria causative human disease. Therefore, we pursued in this study to unravel the frequency and the quinolone resista...

  2. Treatment challenges for community oncologists treating postmenopausal women with endocrine-resistant, hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer

    Directory of Open Access Journals (Sweden)

    Abdel-Razeq H

    2016-10-01

    Full Text Available Hikmat Abdel-RazeqDepartment of Internal Medicine, King Hussein Cancer Center, Amman, JordanI read with great interest the review written elegantly by Gradishar addressing the challenges that community oncologists face in treating postmenopausal women with endocrine-resistant, hormone receptor-positive, human epidermal growth factor receptor-2 (HER2-negative advanced breast cancer in your journal.1As the author correctly stated, resistance to endocrine therapy in women with hormone receptor-positive disease is very frequent and almost inevitable.Understanding the multiple known mechanisms for endocrine resistance has helped physicians and researchers target these pathways.2 Many of the recently introduced drugs, such as the mTOR inhibitor everolimus3 and the cyclin-dependent kinase (CDK 4/6 inhibitor palbociclib,4 are in clinical practice and have been already incorporated in international guidelines.5View original paper by Gradishar.

  3. FUNCTIONAL MSBB ACYLTRANSFERASE OF PHOTORHABDUS LUMINESCENS, REQUIRED FOR SECONDARY LIPID A ACYLATION IN GRAM-NEGATIVE BACTERIA, CONFERS RESISTANCE TO ANTI-MICROBIAL PEPTIDES

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    Z. Abi Khattar

    2016-06-01

    Full Text Available Abi Khattar Z., S. Gaudriault and A. Givaudan. 2016. A functional msbB acyltransferase of Photorhabdus luminescens, required for secondary lipid a acylation in gram-negative bacteria, confers resistance to anti-microbial peptides. Lebanese Science Journal, 17(1: 47-58. Lipid A is a potent endotoxin, and its fatty acids (lauric, myristic, and sometimes palmitic acid anchors lipopolysaccharide (LPS into the outer leaflet of the outer membrane of most Gram-negative bacteria. The highly anionic charge of the glucosamine lipid A moiety makes the LPS a powerful attractant for cationic antimicrobial peptides (AMPs. AMPs are major component of innate immunity that kill bacteria by permeabilization of lipid bilayers. Secondary lipid A acylation of Klebsiella pneumoniae, involving the acyltransferase LpxM (formally, msbB or WaaN that acylates (KDO2-(lauroyl-lipid IV-A with myristate during lipid A biosynthesis, has been associated with bacterial resistance to AMPs contributing to virulence in animal models. We investigated here the role of the msbB gene of the entomopathogenic bacterium Photorhabdus luminescens in AMP resistance, by functional complementation of the AMP susceptible K. pneumoniae lpxM mutant with the P. luminescens msbB gene. We showed that msbB (lpxM gene of P. luminescens is able to enhance polymyxin B, colistin and cecropin A resistance of K. pneumoniae lpxM mutant, compared to the non-complemented mutant. However, we could not obtain any msbB mutant of Photorhabdus by performing allelic exchange experiments based on positive selection of sucrose highly resistant mutants. We thus suggest that msbB-mediated Photorhabdus lipid A acylation is essential for outer membrane low-permeability and that modification of lipid A composition, fluidity and osmosis-resistance have an important role in the ability of Photorhabdus to grow in sucrose at high concentrations.

  4. Antimicrobial Resistance Pattern and Minimum Inhibitory Concentration of Vancomycin among Staphylococcus aureus and Coagulase-Negative Staphylococci Isolated from Clinical Specimens of Children in Tabriz

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    Shahram Abdoli Oskouie

    2013-04-01

    Full Text Available Background & Objectives: Staphylococci are among common causes of community acquired and nosocomial infections around the world. Over the last decade, the resistance of these bacteria in hospital environments is increasing to various antibiotics such as vancomycin. The aim of present study was to determine the antimicrobial resistance pattern and Minimum Inhibitory Concentration (MIC values among a clinical collection of staphylococci isolated from hospitalized children in Tabriz.   Methods: In this prospective and descriptive study, 88 staphylococcal isolates including 53 S. aureus and 35 coagulase-negative staphylococcus species were recovered from various clinical specimens referred to microbiology laboratory of Children Hospital during study period (April 2011 to March 2012. Susceptibility of the isolates against 15 different antimicrobial agents and MIC values of vancomycin was tested using standard disk diffusion and E-test methods respectively.   Results: According to the results of drug susceptibility testing, vancomycin and rifampin were the most effective but clindamycin and penicillin were the least effective drugs against tested isolates. Accordingly, the prevalence of methicillin resistant Staphylococcus aureus (MRSA strains was determined more than 80%. According to MIC values, 13.2% of S. aureus and 3.3% of coagulase-negative staphylococcus isolates showed intermediate resistance to vancomycin. None of the isolates was fully resistant to vancomycin isolates in this study.   Conclusion: Although fully vancomycin resistant staphylococci was not found among tested isolates in this study, there was VISA strains. Since there are reports on the emergence of VRSA strains from Iran and other countries, it is necessary for the clinician to care in prescription of vancomycin as a selective drug against staphylococcal infections. Moreover, the necessity of MIC measurement in determining of vancomycin susceptibility is more apparent.

  5. Resistance among Gram-negative ESKAPE pathogens isolated from hospitalized patients with intra-abdominal and urinary tract infections in Latin American countries: SMART 2013-2015

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    James A. Karlowsky

    Full Text Available ABSTRACT Gram-negative ESKAPE pathogens (Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species are important etiologic agents of nosocomial infection that are frequently resistant to broad-spectrum antimicrobial agents. Gram-negative ESKAPE pathogens were collected from hospitalized patients in 11 Latin American countries from 2013 to 2015 as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART global surveillance program. In total, 2113 isolates from intra-abdominal infections (IAI and 970 isolates from urinary tract infections (UTI were tested against antimicrobial agents using standardized CLSI broth microdilution methodology. Of the agents tested, amikacin demonstrated the highest rates of susceptibility (% for K. pneumoniae (92.2, 92.3, Enterobacter spp. (97.5, 92.1, and P. aeruginosa (85.3, 75.2 isolates from both IAI and UTI, respectively. Ertapenem (68.5, 62.6 and imipenem (79.2, 75.9 showed substantially higher rates of susceptibility (% than other β-lactams, including piperacillin-tazobactam (35.9, 37.4 against ESBL-positive isolates of K. pneumoniae from IAI and UTI, respectively. Rates of susceptibility to all agents tested against A. baumannii were ≤30.9%. Gram-negative ESKAPE pathogens isolated from Latin America demonstrated compromised in vitro susceptibility to commonly prescribed broad-spectrum, parenteral antimicrobial agents. Continued surveillance is warranted. New antimicrobial agents with potent activity against Gram-negative ESKAPE pathogens are urgently needed.

  6. Resistance among Gram-negative ESKAPE pathogens isolated from hospitalized patients with intra-abdominal and urinary tract infections in Latin American countries: SMART 2013–2015

    Directory of Open Access Journals (Sweden)

    James A. Karlowsky

    2017-05-01

    Full Text Available Gram-negative ESKAPE pathogens (Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species are important etiologic agents of nosocomial infection that are frequently resistant to broad-spectrum antimicrobial agents. Gram-negative ESKAPE pathogens were collected from hospitalized patients in 11 Latin American countries from 2013 to 2015 as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART global surveillance program. In total, 2113 isolates from intra-abdominal infections (IAI and 970 isolates from urinary tract infections (UTI were tested against antimicrobial agents using standardized CLSI broth microdilution methodology. Of the agents tested, amikacin demonstrated the highest rates of susceptibility (% for K. pneumoniae (92.2, 92.3, Enterobacter spp. (97.5, 92.1, and P. aeruginosa (85.3, 75.2 isolates from both IAI and UTI, respectively. Ertapenem (68.5, 62.6 and imipenem (79.2, 75.9 showed substantially higher rates of susceptibility (% than other β-lactams, including piperacillin-tazobactam (35.9, 37.4 against ESBL-positive isolates of K. pneumoniae from IAI and UTI, respectively. Rates of susceptibility to all agents tested against A. baumannii were ≤30.9%. Gram-negative ESKAPE pathogens isolated from Latin America demonstrated compromised in vitro susceptibility to commonly prescribed broad-spectrum, parenteral antimicrobial agents. Continued surveillance is warranted. New antimicrobial agents with potent activity against Gram-negative ESKAPE pathogens are urgently needed.

  7. Nonfermentative gram-negative microorganisms isolated from intensive care units and their resistance profiles in a training and research hospital

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    Fulya Bayındır Bilman

    2014-09-01

    Full Text Available Objective: The aim of this study was to determine the pathogenic agents, which have been isolated in ICUs and determine their antimicrobial susceptibility in the first two years of our hospital. Methods: A total 368 strains (194 Pseudomonas aeruginosa, and 174 Acinetobacter baumannii that were considered as an infectious agent and isolated from different clinical samples of hospitalized patients in intensive care units between January 2011 and December 2012 were included in the study. Conventional methods and automatized system were used for the identification and antibiotic susceptibility of the isolates with according to guidelines of Clinical and Laboratory Standarts Institute (CLSI. Imipenem and meropenem resistance has been confirmed by the E test method and interpreted according to CLSI. Results: Resistance rates of P.aeruginosa strains were as follows: Meropenem 35%, imipenem 36%, cefepim 21%, ceftazidim and ciprofloxacin 29%, gentamicin 33%, piperacilin/tazobactam 35%, amikacin 37%. Resistance rates of A.baumannii strains were as follows: Meropenem 85%, imipenem 87%, amikacin 22%, trimethoprim/sulfamethoxazole 25%, gentamicin 46%, piperacilin/tazobactam 54%, ampicilin/sulbactam 59%, cefepim 64%, ciprofloxacin 71%, ceftazidim 83%. Conclusion: Increased carbapenem resistance in our ICUs demonstrates importance of antimicrobial susceptibility tests. The antibiotic susceptibility tests should be surveyed continuously to avoid the spread of intensive care unit isolates carrying high level antibiotic resistance for better achievement of treatment regimens. J Clin Exp Invest 2014; 5 (3: 391-396

  8. Reciprocal regulation of annexin A2 and EGFR with Her-2 in Her-2 negative and herceptin-resistant breast cancer.

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    Praveenkumar K Shetty

    Full Text Available Alternative survival pathways are commonly seen to be upregulated upon inhibition of receptor tyrosine kinases (RTK, including Her-2. It is established that treatment with Herceptin leads to selective overexpression and activation of epidermal growth factor receptor (EGFR and Src which further contributes to oncogenesis in Herceptin resistant and triple negative breast cancer (TNBC patients. Here, we show a co-regulated upregulation in the expression of Annexin A2 (AnxA2, a known substrate of Src and one of the regulators of EGFR receptor endocytosis, in Herceptin resistant and Her-2 negative breast cancer. Immunohistochemical expression analysis revealed a reciprocal regulation between Her-2 and AnxA2 in breast cancer clinical samples as well as in cell lines as confirmed by protein and RNA analysis. The siRNA and Herceptin mediated downregulation/inhibition of Her-2 in Her-2 amplified cells induced AnxA2 expression and membrane translocation. In this study we report a possible involvement of AnxA2 in maintaining constitutively activated EGFR downstream signaling intermediates and hence in cell proliferation, migration and viability. This effect was consistent in Herceptin resistant JIMT-1 cells as well as in Her-2 negative breast cancer. The siRNA mediated AnxA2 downregulation leads to increased apoptosis, decreased cell viability and migration. Our studies further indicate the role of AnxA2 in EGFR-Src membrane bound signaling complex and ligand induced activation of downstream signaling pathways. Targeting this AnxA2 dependent positive regulation of EGFR signaling cascade may be of therapeutic value in Her-2 negative breast cancer.

  9. Fecal Microbiota Transfer for Multidrug-Resistant Gram-Negatives: A Clinical Success Combined With Microbiological Failure.

    Science.gov (United States)

    Stalenhoef, Janneke E; Terveer, Elisabeth M; Knetsch, Cornelis W; Van't Hof, Peter J; Vlasveld, Imro N; Keller, Josbert J; Visser, Leo G; Kuijper, Eduard J

    2017-01-01

    Combined fecal microbiota transfer and antibiotic treatment prevented recurrences of urinary tract infections with multidrug-resistant (MDR) Pseudomonas aeruginosa, but it failed to eradicate intestinal colonization with MDR Escherichia coli. Based on microbiota analysis, failure was not associated with distinct diminished microbiota diversity.

  10. Herd-level relationship between antimicrobial use and presence or absence of antimicrobial resistance in gram-negative bovine mastitis pathogens on Canadian dairy farms.

    Science.gov (United States)

    Saini, Vineet; McClure, J T; Scholl, Daniel T; DeVries, Trevor J; Barkema, Herman W

    2013-08-01

    Concurrent data on antimicrobial use (AMU) and resistance are needed to contain antimicrobial resistance (AMR) in bacteria. The present study examined a herd-level association between AMU and AMR in Escherichia coli (n=394) and Klebsiella species (n=139) isolated from bovine intramammary infections and mastitis cases on 89 dairy farms in 4 regions of Canada [Alberta, Ontario, Québec, and Maritime Provinces (Prince Edward Island, Nova Scotia, and New Brunswick)]. Antimicrobial use data were collected using inventory of empty antimicrobial containers and antimicrobial drug use rate was calculated to quantify herd-level AMU. Minimum inhibitory concentrations (MIC) were determined using Sensititre National Antimicrobial Resistance Monitoring System (NARMS) gram-negative MIC plate (Trek Diagnostic Systems Inc., Cleveland, OH). Isolates were classified as susceptible, intermediate, or resistant. Intermediate and resistant category isolates were combined to form an AMR category, and multivariable logistic regression models were built to determine herd-level odds of AMR to tetracycline, ampicillin, cefoxitin, chloramphenicol, trimethoprim-sulfamethoxazole combination, sulfisoxazole, streptomycin and kanamycin in E. coli isolates. In the case of Klebsiella species isolates, logistic regression models were built for tetracycline and sulfisoxazole; however, no associations between AMU and AMR in Klebsiella species were observed. Ampicillin-intermediate or -resistant E. coli isolates were associated with herds that used intramammarily administered cloxacillin, penicillin-novobiocin combination, and cephapirin used for dry cow therapy [odds ratios (OR)=26, 32, and 189, respectively], and intramammary ceftiofur administered for lactating cow therapy and systemically administered penicillin (OR=162 and 2.7, respectively). Use of systemically administered penicillin on a dairy farm was associated with tetracycline and streptomycin-intermediate or -resistant E. coli isolates (OR=5

  11. Identification of Variable Traits among the Methicillin Resistant and Sensitive Coagulase Negative Staphylococci in Milk Samples from Mastitic Cows in India

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    Sudipta Mahato

    2017-07-01

    Full Text Available Methicillin resistant Staphylococcus aureus causing bovine mastitis has been very well investigated worldwide. However, there are only limited reports on the characterization of methicillin resistant and sensitive coagulase negative staphylococci (CoNS across the globe. Hence, in the present study, we aim to determine the phenotypic traits based on antimicrobial susceptibility profile and genotypic characterization by verifying the presence of resistance determinants, virulence and toxin genes present in the CoNS causing clinical mastitis. We obtained 62 CoNS isolates from 167 mastitic milk samples collected from three different states of India. The 62 isolates comprises of 10 different CoNS species S. sciuri, S. haemolyticus, S. chromogenes, S. saprophyticus, S. xylosus, S. simulans, S. agnetis, S. epidermidis, S. gallinarum, and S. cohinii. Susceptibility screening against 11 antibiotics determined 45.16% isolates as multidrug resistant (resistant to more than two class of antibiotic, 46.74% resistant (one or two antibiotic class and 8.06% isolates were pan-sensitive (sensitive to all drugs. High resistance was observed against oxacillin and cefoxitin, whereas all isolates were susceptible toward vancomycin and linezolid. Fifty three isolates were methicillin resistant and 9 isolates were sensitive as determined by oxacillin susceptibility assay. The methicillin resistance gene, mecA was found in 95.16% isolates and staphylococcal cassette chromosome mec (SCCmec typing predominantly revealed Type III (n = 34 and Type V (n = 18. Interestingly, 11.9% of mecA positive isolates were oxacillin susceptible and referred as oxacillin susceptible mecA positive staphylococci (OS-MRS. Additionally, genes encoding for enterotoxin, (sea, seb, seh, see toxic shock syndrome (tsst, exfoliatin (eta, etb, etd and virulence (pvl, Y-hlg were also screened. Of all the genes examined, 67.74% of isolate were positive for the Y-hlg gene, followed by the sea gene in

  12. From Farms to Markets: Gram-Negative Bacteria Resistant to Third-Generation Cephalosporins in Fruits and Vegetables in a Region of North Africa.

    Science.gov (United States)

    Mesbah Zekar, Ferielle; Granier, Sophie A; Marault, Muriel; Yaici, Lydia; Gassilloud, Benoit; Manceau, Charles; Touati, Abdelaziz; Millemann, Yves

    2017-01-01

    The role of food in human exposure to antimicrobial-resistant bacteria is a growing food safety issue. The contribution of fruits and vegetables eaten raw to this exposure is still unclear. The evaluation of contamination levels of fruits, vegetables and the agricultural environment by third-generation cephalosporin (3GC)-resistant Gram-negative bacteria was performed by analyzing 491 samples of fruits and vegetables collected from 5 markets and 7 farms in Bejaia area, north-eastern Mediterranean coast of Algeria. Ninety soil samples and 45 irrigation water samples were also sampled in farms in order to assess them as potential inoculum sources. All samples were investigated at the same time on ceftazidime-containing selective media for 3GC-resistant Gram-negative bacteria detection and on Hektoen media, for Salmonella spp. presence. The bacteria isolated (n = 30) from fruits and vegetables, soil and irrigation water collected in the farms were almost all non-fermenting bacterial species (Stenotrophomonas, Acinetobacter, Pseudomonas, Ochrobactrum) except one strain of Enterobacter cloacae and two strains of Citrobacter murliniae, isolated on one cucumber and two tomato samples in the same farm. Greater diversity in bacterial species and antimicrobial resistance profiles was observed at markets: Enterobacteriaceae (n = 41) were as strongly represented as non-fermenting bacteria (n = 37). Among Enterobacteriaceae, E. cloacae (n = 21), and Klebsiella pneumoniae (n = 13) were the most common isolates. Most of the K. pneumoniae isolates were extended-spectrum beta-lactamase (ESBL) producers (n = 11). No Salmonella spp. was recovered in any sample. This study showed that fruits and vegetables including those which may be eaten up raw constitute a reservoir of 3GC-resistant Gram-negative bacteria and multi-drug resistant-bacteria in general that can be transferred to humans through food. The general public should be informed of this hazard for health in order to encourage

  13. From Farms to Markets: Gram-Negative Bacteria Resistant to Third-Generation Cephalosporins in Fruits and Vegetables in a Region of North Africa

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    Ferielle Mesbah Zekar

    2017-08-01

    Full Text Available The role of food in human exposure to antimicrobial-resistant bacteria is a growing food safety issue. The contribution of fruits and vegetables eaten raw to this exposure is still unclear. The evaluation of contamination levels of fruits, vegetables and the agricultural environment by third-generation cephalosporin (3GC-resistant Gram-negative bacteria was performed by analyzing 491 samples of fruits and vegetables collected from 5 markets and 7 farms in Bejaia area, north-eastern Mediterranean coast of Algeria. Ninety soil samples and 45 irrigation water samples were also sampled in farms in order to assess them as potential inoculum sources. All samples were investigated at the same time on ceftazidime-containing selective media for 3GC-resistant Gram-negative bacteria detection and on Hektoen media, for Salmonella spp. presence. The bacteria isolated (n = 30 from fruits and vegetables, soil and irrigation water collected in the farms were almost all non-fermenting bacterial species (Stenotrophomonas, Acinetobacter, Pseudomonas, Ochrobactrum except one strain of Enterobacter cloacae and two strains of Citrobacter murliniae, isolated on one cucumber and two tomato samples in the same farm. Greater diversity in bacterial species and antimicrobial resistance profiles was observed at markets: Enterobacteriaceae (n = 41 were as strongly represented as non-fermenting bacteria (n = 37. Among Enterobacteriaceae, E. cloacae (n = 21, and Klebsiella pneumoniae (n = 13 were the most common isolates. Most of the K. pneumoniae isolates were extended-spectrum beta-lactamase (ESBL producers (n = 11. No Salmonella spp. was recovered in any sample. This study showed that fruits and vegetables including those which may be eaten up raw constitute a reservoir of 3GC-resistant Gram-negative bacteria and multi-drug resistant-bacteria in general that can be transferred to humans through food. The general public should be informed of this hazard for health in order

  14. On conditions of negativity of friction resistance for nonstationary modes of blood flow and possible mechanism of affecting of environmental factors on energy effectiveness of cardiovascular system function

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    Sergey G. Chefranov

    2013-05-01

    Full Text Available It is shown that initiated by action of molecular viscosity impulse flow, directed usually from the moving fluid to limiting it solid surface, can, under certain conditions, turn to zero and get negative values in the case of non-stationary flow caused by alternating in time longitudinal (along the pipe axis pressure gradient. It is noted that this non-equilibrium mechanism of negative friction resistance in the similar case of pulsating blood flow in the blood vessels, in addition to the stable to turbulent disturbances swirled blood flow structure providing, can also constitute hydro-mechanical basis of the observed but not explained yet paradoxically high energy effectiveness of the normal functioning of the cardiovascular system (CVS. We consider respective mechanism of affecting on the stability of the normal work of CVS by environmental variable factors using shifting of hydro-dynamic mode with negative resistance realization range boundaries and variation of linear hydrodynamic instability leading to the structurally stable swirled blood flow organization.

  15. Evaluation of a Decision-Making Curriculum for Teaching Adolescents with Disabilities to Resist Negative Peer Pressure

    Science.gov (United States)

    Khemka, Ishita; Hickson, Linda; Mallory, Sarah B.

    2016-01-01

    This study was designed to assess the impact of a decision-making curriculum (PEER-DM) on the social peer relationship knowledge and self-protective decision-making skills of adolescents with disabilities in hypothetical situations involving negative peer pressure. A randomized design was used to assign students with disabilities from…

  16. Antibacterial activity of the Antarctic bacterium Janthinobacterium sp. SMN 33.6 against multi-resistant Gram-negative bacteria

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    Geraldine Asencio

    2014-01-01

    Conclusions: The ethanolic extract of Janthinobacterium sp. SMN 33.6 possesses antibacterial activity against a chromosomal AmpC beta-lactamase-producing strain of Serratia marcescens, an extended-spectrum beta-lactamase-producing Escherichia coli and also against carbapenemase-producing strains of Acinetobacter baumannii and Pseudomonas aeruginosa. This becomes a potential and interesting biotechnological tool for the control of bacteria with multi-resistance to commonly used antibiotics.

  17. Prevalence, antimicrobial resistance, and virulence characteristics of mecA-encoding coagulase-negative staphylococci isolated from soft cheese in Brazil.

    Science.gov (United States)

    Fontes, Cláudia Oliveira; Silva, Vânia Lúcia; de Paiva, Mayara Rodrigues Brandão; Garcia, Rafaela Alvim; Resende, Juliana Alves; Ferreira-Machado, Alessandra Barbosa; Diniz, Cláudio Galuppo

    2013-04-01

    Coagulase-negative staphylococci (CoNS), which are generally neglected as foodborne bacteria, are emerging as significant opportunistic pathogens that may be highly resistant to available antimicrobial drugs. In this study, antimicrobial susceptibility patterns, mecA gene occurrence, and virulence-associated characteristics were evaluated in CoNS isolated from soft cheese in Brazil. A total of 227 bacterial isolates were recovered from 35 cheese samples belonging to 5 batches with 7 different trademarks. The CoNS counts ranged from 10(6) to 10(7) CFU/g. High antimicrobial resistance percentages were observed for oxacillin (76.2%), penicillin (78.5%), erythromycin (67.8%), gentamicin (47.2%), clindamycin (35.7%), rifampicin (26.8%), azithromycin (14.7%), tetracycline (14.7%), levofloxacin (14.2%), and sulfamethoxazole-trimethoprim (11.9%). A low antimicrobial resistance percentage was observed for chloramphenicol (2.3%), and all of the tested bacteria were susceptible to vancomycin and linezolid. In total, a multiple antibiotic resistance (MAR) index of >0.2 was observed for 80.6% of the isolated CoNS. However, the MAR index ranged from 50% to 92.6% when only bacterial cheese isolates belonging to the same trademark were considered. Regarding to the prevalence of CoNS carrying mecA gene, 81.5% of the isolated strains were mecA(+) , and 76.2% of these were phenotypically resistant to oxacillin. Three isolates carried the enterotoxin A gene (sea), 29.5% produced biofilm in a laboratory test, and α- or ß-hemolysis were observed for 3% and 5.2%, respectively. This study highlights the extent of the antimicrobial resistance phenomenon in neglected foodborne microorganisms and the potential public health risks that are related to the consumption of CoNS-contaminated soft cheese. © 2013 Institute of Food Technologists®

  18. Surveillance of Gram-negative bacteria: impact of variation in current European laboratory reporting practice on apparent multidrug resistance prevalence in paediatric bloodstream isolates.

    Science.gov (United States)

    Bielicki, J A; Cromwell, D A; Johnson, A; Planche, T; Sharland, M

    2017-05-01

    This study evaluates whether estimated multidrug resistance (MDR) levels are dependent on the design of the surveillance system when using routine microbiological data. We used antimicrobial resistance data from the Antibiotic Resistance and Prescribing in European Children (ARPEC) project. The MDR status of bloodstream isolates of Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa was defined using European Centre for Disease Prevention and Control (ECDC)-endorsed standardised algorithms (non-susceptible to at least one agent in three or more antibiotic classes). Assessment of MDR status was based on specified combinations of antibiotic classes reportable as part of routine surveillance activities. The agreement between MDR status and resistance to specific pathogen-antibiotic class combinations (PACCs) was assessed. Based on all available antibiotic susceptibility testing, the proportion of MDR isolates was 31% for E. coli, 30% for K. pneumoniae and 28% for P. aeruginosa isolates. These proportions fell to 9, 14 and 25%, respectively, when based only on classes collected by current ECDC surveillance methods. Resistance percentages for specific PACCs were lower compared with MDR percentages, except for P. aeruginosa. Accordingly, MDR detection based on these had low sensitivity for E. coli (2-41%) and K. pneumoniae (21-85%). Estimates of MDR percentages for Gram-negative bacteria are strongly influenced by the antibiotic classes reported. When a complete set of results requested by the algorithm is not available, inclusion of classes frequently tested as part of routine clinical care greatly improves the detection of MDR. Resistance to individual PACCs should not be considered reflective of MDR percentages in Enterobacteriaceae.

  19. Azithromycin Synergizes with Cationic Antimicrobial Peptides to Exert Bactericidal and Therapeutic Activity Against Highly Multidrug-Resistant Gram-Negative Bacterial Pathogens

    Directory of Open Access Journals (Sweden)

    Leo Lin

    2015-07-01

    Full Text Available Antibiotic resistance poses an increasingly grave threat to the public health. Of pressing concern, rapid spread of carbapenem-resistance among multidrug-resistant (MDR Gram-negative rods (GNR is associated with few treatment options and high mortality rates. Current antibiotic susceptibility testing guiding patient management is performed in a standardized manner, identifying minimum inhibitory concentrations (MIC in bacteriologic media, but ignoring host immune factors. Lacking activity in standard MIC testing, azithromycin (AZM, the most commonly prescribed antibiotic in the U.S., is never recommended for MDR GNR infection. Here we report a potent bactericidal action of AZM against MDR carbapenem-resistant isolates of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. This pharmaceutical activity is associated with enhanced AZM cell penetration in eukaryotic tissue culture media and striking multi-log-fold synergies with host cathelicidin antimicrobial peptide LL-37 or the last line antibiotic colistin. Finally, AZM monotherapy exerts clear therapeutic effects in murine models of MDR GNR infection. Our results suggest that AZM, currently ignored as a treatment option, could benefit patients with MDR GNR infections, especially in combination with colistin.

  20. Discovery and development of new antibacterial agents targeting Gram-negative bacteria in the era of pandrug resistance: is the future promising?

    Science.gov (United States)

    Page, Malcolm G P; Bush, Karen

    2014-10-01

    Multidrug-resistant Gram-negative bacteria continue to pose a threat, with many infections caused by these pathogens being virtually untreatable. A number of new antibacterial agents are in late stage clinical development to treat these infections. Drugs in known classes such as new quinolones, aminoglycosides, tetracyclines, and β-lactams have been designed to evade many of the known resistance mechanisms, whereas newer drug classes include novel β-lactamase inhibitors in combination with new or approved β-lactams, and a peptidomimetic that have entered full clinical development. The establishment of public-private partnerships and an increase in pharmaceutical interest in antibacterial R&D are encouraging signs for the future. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Spread of TEM, VIM, SHV, and CTX-M β-Lactamases in Imipenem-Resistant Gram-Negative Bacilli Isolated from Egyptian Hospitals

    Directory of Open Access Journals (Sweden)

    El sayed Hamdy Mohammed

    2016-01-01

    Full Text Available Carbapenem-resistant Gram-negative bacilli resulting from β-lactamases have been reported to be an important cause of nosocomial infections and are a critical therapeutic problem worldwide. This study aimed to describe the prevalence of imipenem-resistant Gram-negative bacilli isolates and detection of blaVIM, blaTEM, blaSHV, blaCTX-M-1, and blaCTX-M-9 genes in these clinical isolates in Egyptian hospitals. The isolates were collected from various clinical samples, identified by conventional methods and confirmed by API 20E. Antibiotic susceptibility testing was determined by Kirby-Bauer technique and interpreted according to CLSI. Production of blaVIM, blaTEM, blaSHV, and blaCTX-M genes was done by polymerase chain reaction (PCR. Direct sequencing from PCR products was subsequently carried out to identify and confirm these β-lactamases genes. Out of 65 isolates, (46.1% Escherichia coli, (26.2% Klebsiella pneumoniae, and (10.7% Pseudomonas aeruginosa were identified as the commonest Gram-negative bacilli. 33(50.8% were imipenem-resistant isolates. 22 isolates (66.7% carried blaVIM, 24(72.7% had blaTEM, and 5(15% showed blaSHV, while 12(36%, 6(18.2%, and 0(0.00% harbored blaCTX-M-1, blaCTX-M-9, and blaCTX-M-8/25, respectively. There is a high occurrence of β-lactamase genes in clinical isolates and sequence analysis of amplified genes showed differences between multiple SNPs (single nucleotide polymorphism sites in the same gene among local isolates in relation to published sequences.

  2. ANALYSIS OF MUTATIONS OF TUBERCULOUS MYCOBACTERIA DEFINING DRUG RESISTANCE IN HIV POSITIVE AND HIV NEGATIVE TUBERCULOSIS PATIENTS WITHOUT PRIOR HISTORY OF TREATMENT IN SVERDLOVSK REGION

    Directory of Open Access Journals (Sweden)

    G. V. Panov

    2017-01-01

    Full Text Available Goal of the study: to identify profile of mutations of tuberculous mycobacteria responsible for resistance to anti-tuberculosis drugs in HIV positive and HIV negative tuberculosis patients without prior history of treatment.Materials and methods. 165 strains of tuberculous mycobacteria from HIV positive patients and 166 strains of tuberculous mycobacteria from HIV negative patients were studied in Sverdlovsk Region (TB Dispensary, Yekaterinburg. Mutations in genes were identified using microchips of TB-BIOCHIP® and TB-BIOCHIP®-2 in compliance with the manufacturer's guidelines (OOO Biochip-IMB, Moscow.Results. It was observed that 85/165 (51.52% strains isolated from HIV positive tuberculosis patients and 58/166 (34.94% strains isolated from tuberculosis patients not associated with HIV possessed MDR genotype (p < 0.01. The majority of MDR strains had mutations in the 531th codon of rpoB (Ser→Leu and 315th codon of katG (Ser→Thr (64/85, 75.29% and 38/58, 65.52% respective the groups, resulting in the high level of resistance to rifampicin and isoniazid. Each group also had approximately equal ratio (11/165, 6.67% and 12/166, 7.23% respective the groups of strains with genomic mutations defining the resistance to isoniazid, rifampicin and fluoruquinolones. No confident difference was found in mutation patterns of genome of tuberculous mycobacteria isolated from HIV positive and HIV negative tuberculosis patients. 

  3. Rapid detection of extensively drug-resistant (XDR-TB) strains from multidrug-resistant tuberculosis (MDR-TB) cases isolated from smear-negative pulmonary samples in an Intermediate Reference Laboratory in India.

    Science.gov (United States)

    Vashistha, Himanshu; Hanif, M; Saini, Sanjeev; Khanna, Ashwani; Sharma, Srashty; Sidiq, Zeeshan; Ahmed, Vasim; Dubey, Manoj; Chopra, K K; Shrivastava, Divya

    2016-07-01

    Direct sputum smear microscopy is commonly used for diagnosing tuberculosis (TB). The objectives of the study were first, to determine the recovery of Mycobacterium tuberculosis in smear-negative sputum samples through liquid culture (using MGIT 960) and solid culture (using LJ slant) and second, to screen multidrug-resistant isolates through line probe assay and further third, to identify XDR isolates through MGIT second-line DST from these positive MDR cultures in Delhi region. In this study, the sample size was 717 (sputum smear AFB negative and culture positive for M. tuberculosis complex by both solid and liquid culture methods) MDRTB suspects who were enrolled from January 2014 to December 2014 at the Intermediate Reference Laboratory in New Delhi Tuberculosis Centre, New Delhi. Rapid line probe assay was performed on all culture-positive samples, which were direct smear-negative specimens, and LPA-confirmed MDR samples were tested on MGIT 960 second-line DST for identification of XDR strains. An overall increase in the culture positivity (9.4%) among these smear-negative cases shows a good sign of recovery from M. tuberculosis infection in these samples. 717 (9.4%) positive cultures (MGIT+LJ) were subjected to line probe assay. Out of these 717 cultures, 9 (1.2%) were confirmed as NTM, 50 (7%) were MDR, 4 (0.6%) were mono-rifampicin resistant and 654 (91.2%) cultures were sensitive to both drugs Rif and Inh, respectively. Out of these 54 (50 MDR +4 mono-RIF resistant) cultures as screened by LPA, 1 (1.8%) was XDR, 10 (18.6%) were mono-ofloxacin resistant and 1 (1.8%) was mono-Kanamycin resistant. Sensitivity to both drugs KAN and OFX was seen in 42 (77.8%) cultures. Since the bacterial load in direct smear-negative suspected MDR samples is less, it is important to recover mycobacteria by rapid liquid culture method in such samples. Initial screening for MDRTB is to be done in such cases by performing rapid molecular genotypic drug susceptibility test such as

  4. History and evolution of antibiotic resistance in coagulase-negative staphylococci: Susceptibility profiles of new anti-staphylococcal agents

    OpenAIRE

    John, Joseph F.; Harvin, Alexander M

    2007-01-01

    Coagulase-negative staphylococci (CNS) are a heterogenous group of Gram-positive cocci that are widespread commensals among mammalia. Unlike their coagulase-positive counterpart, Staphylococcus aureus, CNS produce few virulence patterns and normally refrain from invading tissue. Yet, not only can CNS cause infections in normal host tissue, but modern medicine has also seen their rise as opportunists that display adherence to medical device materials to produce a protective biofilm. CNS have h...

  5. Trivalued Memory Circuit Using Metal-Oxide-Semiconductor Field-Effect Transistor Bipolar-Junction-Transistor Negative-Differential-Resistance Circuits Fabricated by Standard SiGe Process

    Science.gov (United States)

    Gan, Kwang-Jow; Tsai, Cher-Shiung; Liang, Dong-Shong; Wen, Chun-Ming; Chen, Yaw-Hwang

    2006-09-01

    A trivalued memory circuit based on two cascoded metal-oxide-semiconductor field-effect transistor bipolar-junction-transistor negative-differential-resistance (MOS-BJT-NDR) devices is investigated. The MOS-BJT-NDR device is made of MOS and BJT devices, but it can show the NDR current-voltage characteristic by suitably arranging the MOS parameters. We demonstrate a trivalued memory circuit using the two-peak MOS-BJT-NDR circuit as the driver and a resistor as the load. The MOS-BJT-NDR devices and memory circuits are fabricated by the standard 0.35 μm SiGe process.

  6. Physico-Chemical-Managed Killing of Penicillin-Resistant Static and Growing Gram-Positive and Gram-Negative Vegetative Bacteria

    Science.gov (United States)

    Richmond, Robert Chaffee (Inventor); Schramm, Jr., Harry F. (Inventor); Defalco, Francis G. (Inventor); Farris, III, Alex F. (Inventor)

    2012-01-01

    Systems and methods for the use of compounds from the Hofmeister series coupled with specific pH and temperature to provide rapid physico-chemical-managed killing of penicillin-resistant static and growing Gram-positive and Gram-negative vegetative bacteria. The systems and methods represent the more general physico-chemical enhancement of susceptibility for a wide range of pathological macromolecular targets to clinical management by establishing the reactivity of those targets to topically applied drugs or anti-toxins.

  7. Electric-line-source illumination of a circular cylinder of lossless double-negative material: an investigation of near field, directivity, and radiation resistance

    DEFF Research Database (Denmark)

    Arslanagic, Samel; Breinbjerg, Olav

    2006-01-01

    This work investigates the properties of an antenna-like configuration with an electric line source radiating in the presence of a double-negative circular cylinder. First, the analytical eigenfunction-series solution is derived. Second, this solution is employed in numerical calculations to study...... the properties of the near field, inside as well as outside the cylinder, and the far-field. Third, the variations of these fields are examined, as well as the radiation resistance and radiation pattern, as functions of the geometrical and electromagnetic parameters of the configuration. It is demonstrated...... that the scattering properties of the double-negative cylinder are vastly different from those of the corresponding double-positive cylinder. In particular, the focusing effect inside the cylinder and the angular variation of the directivity exhibit distinct characteristics...

  8. Identification of a PVL-negative SCCmec-IVa sub-lineage of the methicillin-resistant Staphylococcus aureus CC80 lineage

    DEFF Research Database (Denmark)

    Edslev, Sofie Marie; Westh, Henrik Torkil; Andersen, Paal Skytt

    2018-01-01

    of the CC80 S. aureus lineage was conducted from whole-genome sequences of 217 isolates (23 MSSA and 194 MRSA) from 22 countries. All isolates were further genetically characterized in regard to resistance determinants and PVL carriage, and epidemiological data was obtained for selected isolates. RESULTS......OBJECTIVES: Community-acquired MRSA (CA-MRSA) isolates belonging to clonal complex 80 (CC80) are recognized as the European CA-MRSA. The prevailing European CA-MRSA clone carries a type IVc staphylococcal cassette chromosome mec (SCCmec) and expresses Panton-Valentine leukocidin (PVL). Recently......, a significant increase of PVL-negative CC80 MRSA has been observed in Denmark. The aim of this study was to examine the genetics and the epidemiology of these, and to compare them to the European CA-MRSA clone in order to understand the emergence of PVL-negative CC80 MRSA. METHODS: Phylogenetic analysis...

  9. Metal resistance mechanisms in Gram-negative bacteria and their potential to remove Hg in the presence of other metals.

    Science.gov (United States)

    Giovanella, Patricia; Cabral, Lucélia; Costa, Alexandre Pereira; de Oliveira Camargo, Flávio Anastácio; Gianello, Clesio; Bento, Fátima Menezes

    2017-06-01

    Contamination of the environment by heavy metals has been increasing in recent years due to industrial activities. Thus research involving microorganisms capable of surviving in multi-contaminated environments is extremely important. The objectives of the present study were to evaluate the removal of mercury alone and in the presence of cadmium, nickel and lead by four mercury-resistant microorganisms; estimate the removal of Cd, Ni and Pb; understand the mechanisms involved (reduction, siderophores, biofilms, biosorption and bioaccumulation) in the metal resistance of the isolate Pseudomonas sp. B50D; and determine the capacity of Pseudomonas sp. B50D in removing Hg, Cd, Ni and Pb from an industrial effluent. It was shown that the four isolates evaluated were capable of removing from 62% to 95% of mercury from a culture medium with no addition of other metals. The isolate Pseudomonas sp. B50D showed the best performance in the removal of mercury when evaluated concomitantly with other metals. This isolate was capable of removing 75% of Hg in the presence of Cd and 91% in the presence of Ni and Pb. With respect to the other metals it removed 60%, 15% and 85% of Cd, Ni and Pb, respectively. In tests with effluent, the isolate Pseudomonas sp. B50D removed 85% of Hg but did not remove the other metals. This isolate presented reduction, biosorption, biofilm production and siderophore production as its metal resistance mechanisms. Pseudomonas sp. B50D was thus a candidate with potential for application in the bioremediation of effluents with complex metal contaminations. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. The costs of nosocomial resistant gram negative intensive care unit infections among patients with the systemic inflammatory response syndrome- a propensity matched case control study.

    Science.gov (United States)

    Vasudevan, Anupama; Memon, Babar Irfan; Mukhopadhyay, Amartya; Li, Jialiang; Tambyah, Paul Ananth

    2015-01-01

    Infections due to multi-drug resistant gram negative bacilli (RGNB) in critically ill patients have been reported to be associated with increased morbidity and costs and only a few studies have been done in Asia. We examined the financial impact of nosocomial RGNB infections among critically ill patients in Singapore. A nested case control study was done for patients at medical and surgical ICUs of a tertiary university hospital (August 2007-December 2011) matched by propensity scores. Two groups of propensity-matched controls were selected for each case patient with nosocomial drug resistant gram negative infection: at-risk patients with no gram negative infection or colonization (Control A) and patients with ICU acquired susceptible gram negative infection (SGNB) (Control B). The costs of the hospital stay, laboratory tests and antibiotics prescribed as well as length of stay were compared using the Wilcoxon matched-pairs signed rank test. Of the 1539 patients included in the analysis, 76 and 65 patients had ICU acquired RGNB and SGNB infection respectively. The median(range) total hospital bill per day for patients with RGNB infection was 1.5 times higher than at-risk patients without GNB infection [Singapore dollars 2637.8 (458.7-20610.3) vs. 1757.4 (179.9-6107.4), p0.0001]. The same trend was observed when compared with SGNB infected patients. The median costs per day of antibiotics and laboratory investigations were also found to be significantly higher for patients with RGNB infection. The length of stay post infection was not found to be different between those infected with RGNB and SGNB. The economic burden of RGNB infections to the patients and the hospital is considerable. Efforts need to be taken to prevent their occurrence by cost effective infection control practices.

  11. Trends of Bloodstream Infections in a University Greek Hospital during a Three-Year Period: Incidence of Multidrug-Resistant Bacteria and Seasonality in Gram-negative Predominance.

    Science.gov (United States)

    Kolonitsiou, Fevronia; Papadimitriou-Olivgeris, Matthaios; Spiliopoulou, Anastasia; Stamouli, Vasiliki; Papakostas, Vasileios; Apostolopoulou, Eleni; Panagiotopoulos, Christos; Marangos, Markos; Anastassiou, Evangelos D; Christofidou, Myrto; Spiliopoulou, Iris

    2017-07-06

    The aim of the study was to assess the epidemiology, the incidence of multidrug-resistant bacteria and bloodstream infections' (BSIs) seasonality in a university hospital. This retrospective study was carried out in the University General Hospital of Patras, Greece, during 2011-13 y. Blood cultures from patients with clinical presentation suggestive of bloodstream infection were performed by the BacT/ALERT System. Isolates were identified by Vitek 2 Advanced Expert System. Antibiotic susceptibility testing was performed by the disk diffusion method and E-test. Resistance genes (mecA in staphylococci; vanA/vanB/vanC in enterococci; blaKPC/blaVIM/blaNDM in Klebsiella spp.) were detected by PCR. In total, 4607 (9.7%) blood cultures were positive from 47451 sets sent to Department of Microbiology, representing 1732 BSIs. Gram-negative bacteria (52.3%) were the most commonly isolated, followed by Gram-positive (39.5%), fungi (6.6%) and anaerobes bacteria (1.8%). The highest contamination rate was observed among Gram-positive bacteria (42.3%). Among 330 CNS and 150 Staphylococcus aureus, 281 (85.2%) and 60 (40.0%) were mecA-positive, respectively. From 113 enterococci, eight were vanA, two vanB and two vanC-positives. Of the total 207 carbapenem-resistant Klebsiella pneumoniae (73.4%), 202 carried blaKPC, four blaKPC and blaVIM and one blaVIM. A significant increase in monthly BSIs' incidence was shown (R2: 0.449), which may be attributed to a rise of Gram-positive BSIs (R2: 0.337). Gram-positive BSIs were less frequent in spring (P Gram-negative bacteria (P Gram-negative bacteria increased during the study period. The increasing incidence of BSIs can be attributed to an increase of Gram-positive BSI incidence, even though Gram-negative bacteria remained the predominant ones. Seasonality may play a role in the predominance of Gram-negative's BSI.

  12. The Transcription Factor OsWRKY45 Negatively Modulates the Resistance of Rice to the Brown Planthopper Nilaparvata lugens

    Directory of Open Access Journals (Sweden)

    Jiayi Huangfu

    2016-05-01

    Full Text Available WRKY transcription factors play a central role not only in plant growth and development but also in plant stress responses. However, the role of WRKY transcription factors in herbivore-induced plant defenses and their underlying mechanisms, especially in rice, remains largely unclear. Here, we cloned a rice WRKY gene OsWRKY45, whose expression was induced by mechanical wounding, by infestation of the brown planthopper (BPH, Nilaparvata lugens and by treatment with jasmonic acid (JA or salicylic acid (SA. The antisense expression of OsWRKY45 (as-wrky enhanced BPH-induced levels of H2O2 and ethylene, reduced feeding and oviposition preference as well as the survival rate of BPH, and delayed the development of BPH nymphs. Consistently, lower population densities of BPH on as-wrky lines, compared to those on wild-type (WT plants, were observed in field experiments. On the other hand, as-wrky lines in the field had lower susceptibility to sheath blight (caused by Rhizoctonia solani but higher susceptibility to rice blast (caused by Magnaporthe oryzae than did WT plants. These findings suggest that OsWRKY45 plays important but contrasting roles in regulating the resistance of rice to pathogens and herbivores, and attention should be paid if OsWRKY45 is used to develop disease or herbivore-resistant rice.

  13. Prevalence of macrolide-non-susceptible isolates among β-lactamase-negative ampicillin-resistant Haemophilus influenzae in a tertiary care hospital in Japan.

    Science.gov (United States)

    Wajima, Takeaki; Seyama, Shoji; Nakamura, Yuka; Kashima, Chihiro; Nakaminami, Hidemasa; Ushio, Masanobu; Fujii, Takeshi; Noguchi, Norihisa

    2016-09-01

    β-Lactamase-negative ampicillin-resistant (BLNAR) Haemophilus influenzae account for a large portion of H. influenzae clinical isolates in Japan. The aim of this study was to clarify the antimicrobial susceptibility of BLNAR H. influenzae clinical isolates as well as the annual changes in susceptibility. BLNAR H. influenzae isolates were collected from a tertiary care hospital from 2007 to 2012. Antimicrobial susceptibility testing was performed and resistance mechanisms were analysed. All of the isolates (n=304) had amino acid substitutions in penicillin-binding protein 3 (PBP3) and isolates were classified by these amino acid substitutions: R517H or N526K (class I); S385T and R517H (class II); and S385T and N526K (class III). Classes I, II and III represented 8.2% (n=25), 9.5% (n=29) and 81.6% (n=248) of the isolates, respectively; 2 isolates could not be classified because they had a PBP3 with a substantially mutated FtsI transpeptidase domain. All of the isolates were highly susceptible to fluoroquinolones and carbapenems. The number of clarithromycin (CAM)-non-susceptible [minimum inhibitory concentration (MIC) ≥16μg/mL] H. influenzae isolates increased significantly between 2010 and 2012. Moreover, CAM-non-susceptible H. influenzae isolates were prevalent among class II and class III BLNAR H. influenzae. Multilocus sequence typing (MLST) of the CAM-resistant (MIC ≥32μg/mL) H. influenzae isolates showed that they were not specific sequence types, suggesting that CAM resistance may occur in any isolates. These results raise concern regarding the occurrence of multidrug-resistant BLNAR H. influenzae. Copyright © 2016 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.

  14. Environmental stewardship and corporate social responsibility: Implication for consumers’ resistance to negative information. The case of apple in China

    Directory of Open Access Journals (Sweden)

    Martin Larbi

    2014-11-01

    Full Text Available There are several studies that have investigated the effect of corporate social responsibility (CSR on consumer behavior. However, these studies demonstrate conflicting results on how CSR influences consumer purchasing behavior and retention; for example, in event of negative information about a firm. Therefore, the effectiveness of CSR in advancing the core business of firms remains unresolved. This research uses a qualitative approach to examine how CSR affords firms greater levels of goodwill with consumers. The study focuses on the case of Apple in China. Both primary and secondary data were collected through interviews, review of literature, newspaper reports, blogs, social media, and official websites of institutions and corporate entities. A deductive analytical approach was used to examine how consumers perceive CSR, and how that impacts on their attitude towards a firm when confronted with negative information. The study found low level of awareness of CSR in consumers. Moreover, the findings demonstrate that consumers tend to attach more importance to CSR when they identify with the problems associated with the actions or inactions of a firm. The study shows that firms can only enjoy the full benefits of CSR by creating public awareness of such endeavours

  15. Development and evaluation of hexaplex PCR for rapid detection of methicillin, cadmium/zinc and antiseptic-resistant staphylococci, with simultaneous identification of PVL-positive and -negative Staphylococcus aureus and coagulase negative staphylococci.

    Science.gov (United States)

    Panda, Sasmita; Kar, Sarita; Choudhury, Ranginee; Sharma, Savitri; Singh, Durg V

    2014-03-01

    We developed a multiplex PCR to detect the presence of methicillin- (mecA), cadmium/zinc-(czrC) and antiseptic-resistant (qacA/B) staphylococci and to identify Panton-Valentine leukocidin (PVL)-positive and -negative Staphylococcus aureus and coagulase-negative staphylococci (CoNS) from infected and healthy eyes. The assay was validated on 177 staphylococci comprising of 55 each of S. aureus and CoNS isolated from infected eyes and five S. aureus and 62 CoNS isolated from healthy eyes and nine direct ocular samples. Nine direct ocular samples for in situ testing consisted of corneal scrapings (4), conjunctiva swabs (2) and others (3). Multiplex PCR result was correlated with genotype data obtained with single PCR and dot-blot assay. The control strains that were positive in multiplex PCR for 16S rRNA, nuc, mecA, pvl, czrC and qacA/B genes were also positive in the dot-blot assay. The specificity of amplified genes obtained with reference strains was further confirmed by DNA sequencing. The single step-hexaplex PCR method can be used for rapid detection of mecA, nuc, pvl, czrC and qacA/B genes in staphylococci with simultaneous identification of PVL-positive and -negative S. aureus and CoNS from a variety of ocular samples. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  16. Specific Clinical Profile and Risk Factors for Mortality in General Surgery Patients with Infections by Multi-Drug-Resistant Gram-Negative Bacteria.

    Science.gov (United States)

    Rubio-Perez, Ines; Martin-Perez, Elena; Domingo-García, Diego; Garcia-Olmo, Damian

    2017-07-01

    The incidence of gram-negative multi-drug-resistant (MDR) infections is increasing worldwide. This study sought to determine the incidence, clinical profiles, risk factors, and mortality of these infections in general surgery patients. All general surgery patients with a clinical infection by gram-negative MDR bacteria were studied prospectively for a period of five years (2007-2011). Clinical, surgical, and microbiologic parameters were recorded, with a focus on the identification of risk factors for MDR infection and mortality. Incidence of MDR infections increased (5.6% to 15.2%) during the study period; 106 patients were included, 69.8% presented nosocomial infections. Mean age was 65 ± 15 years, 61% male. Extended-spectrum β-lactamases (ESBL) Escherichia coli was the most frequent MDR bacteria. Surgical site infections and abscesses were the most common culture locations. The patients presented multiple pre-admission risk factors and invasive measures during hospitalization. Mortality was 15%, and related to older age (odds ratio [OR] 1.07), malnutrition (OR 13.5), chronic digestive conditions (OR 4.7), chronic obstructive pulmonary disease (OR 3.9), and surgical re-intervention (OR 9.2). Multi-drug resistant infections in the surgical population are increasing. The most common clinical profile is a 65-year-old male, with previous comorbidities, who has undergone a surgical intervention, intensive care unit (ICU) admission, and invasive procedures and who has acquired the MDR infection in the nosocomial setting.

  17. Novel Pharmacotherapy for the Treatment of Hospital-Acquired and Ventilator-Associated Pneumonia Caused by Resistant Gram-Negative Bacteria.

    Science.gov (United States)

    Kidd, James M; Kuti, Joseph L; Nicolau, David P

    2018-02-07

    Introduction Hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP) are among the most prevalent infections in hospitalized patients, particularly those in the intensive care unit. Importantly, the frequency of multidrug resistant (MDR) Gram-negative (GN) bacteria as the bacteriologic cause of HABP/VABP is increasing. These include MDR Pseudomonas aeruginosa, Acinetobacter baumannii, and carbapenem resistant Enterobactericeae (CRE). Few antibiotics are currently available when such MDR Gram-negatives are encountered and older agents such as polymyxin B, colistin (polymyxin E), and tigecycline have typically performed poorly in HABP/VABP. Areas Covered In this review, the authors summarize novel antibiotics which have reached phase 3 clinical trials including patients with HABP/VABP. For each agent, the spectrum of activity, pertinent pharmacological characteristics, clinical trial data, and potential utility in the treatment of MDR-GN HABP/VABP is discussed. Expert opinion Novel antibiotics currently available, and those soon to be, will expand opportunities to treat HABP/VABP caused by MDR-GN organisms and minimize the use of more toxic, less effective drugs. However, with sparse clinical data available, defining the appropriate role for each of the new agents is challenging. In order to maximize the utility of these antibiotics, combination therapy and the role of therapeutic drug monitoring should be investigated.

  18. Novel phage lysin capable of killing the multidrug-resistant gram-negative bacterium Acinetobacter baumannii in a mouse bacteremia model.

    Science.gov (United States)

    Lood, Rolf; Winer, Benjamin Y; Pelzek, Adam J; Diez-Martinez, Roberto; Thandar, Mya; Euler, Chad W; Schuch, Raymond; Fischetti, Vincent A

    2015-04-01

    Acinetobacter baumannii, a Gram-negative multidrug-resistant (MDR) bacterium, is now recognized as one of the more common nosocomial pathogens. Because most clinical isolates are found to be multidrug resistant, alternative therapies need to be developed to control this pathogen. We constructed a bacteriophage genomic library based on prophages induced from 13 A. baumannii strains and screened it for genes encoding bacteriolytic activity. Using this approach, we identified 21 distinct lysins with different activities and sequence diversity that were capable of killing A. baumannii. The lysin (PlyF307) displaying the greatest activity was further characterized and was shown to efficiently kill (>5-log-unit decrease) all tested A. baumannii clinical isolates. Treatment with PlyF307 was able to significantly reduce planktonic and biofilm A. baumannii both in vitro and in vivo. Finally, PlyF307 rescued mice from lethal A. baumannii bacteremia and as such represents the first highly active therapeutic lysin specific for Gram-negative organisms in an array of native lysins found in Acinetobacter phage. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  19. Subcellular distribution of daunorubicin in P-glycoprotein-positive and -negative drug-resistant cell lines using laser-assisted confocal microscopy.

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    Gervasoni, J E; Fields, S Z; Krishna, S; Baker, M A; Rosado, M; Thuraisamy, K; Hindenburg, A A; Taub, R N

    1991-09-15

    Four well defined multidrug-resistant cell lines and their drug-sensitive counterparts were examined for intracellular distribution of daunorubicin (DNR) by laser-assisted confocal fluorescence microscopy: P-glycoprotein-negative HL-60/AR cells, and P-glycoprotein-positive P388/ADR, KBV-1, and MCF-7/ADR cells. Both drug sensitive cell lines (HL-60/S, P388/S, KB3-1, and MCF-7/S) and drug-resistant cell lines (HL-60/AR, P388/ADR, KBV-1, and MCF-7/ADR) exposed to DNR showed a similar rapid distribution of drug from the plasma membrane to the perinuclear region within the first 2 min. From 2-10 min, the drug sensitive HL-60/S, P388/S, and MCF-7/S cells redistributed drug to the nucleus and to the cytoplasm in a diffuse pattern. In contrast, drug-resistant HL-60/AR, P388/ADR, and MCF-7/ADR redistributed DNR from the perinuclear region into vesicles distinct from nuclear structures, thereby assuming a "punctate" pattern. This latter redistribution could be inhibited by glucose deprivation (indicating energy dependence), or by lowering the temperature of the medium below 18 degrees C. The differences in distribution between sensitive and resistant cells did not appear to be a function of intracellular DNR content, nor the result of drug cytotoxicity. Drug-sensitive KB3-1 and -resistant KBV-1 cells did not fully follow this pattern in that they demonstrated an intracellular DNR distribution intermediate between HL-60/S and HL-60/AR cells with both "punctate" and nuclear/cytoplasmic uptake sometimes in the same cell. These data indicate that the intracellular distribution of DNR is an important determinant of drug resistance regardless of the overexpression of P-glycoprotein. The intracellular movement of drug requires the presence of glucose and a temperature above 18 degrees C, implicating energy-dependent processes and vesicle fusion in the distribution process. This intracellular transport of DNR away from the nucleus in multidrug-resistant cells may protect putative

  20. Treatment of Triple Negative Breast Cancer With TORC1/2 Inhibitors Sustains a Drug-resistant and Notch-dependent Cancer Stem Cell Population

    Science.gov (United States)

    Bhola, Neil E.; Jansen, Valerie M.; Koch, James P.; Li, Hua; Formisano, Luigi; Williams, Janice A.; Grandis, Jennifer R.; Arteaga, Carlos L.

    2015-01-01

    Approximately 30% of triple negative breast cancers (TNBC) harbor molecular alterations in PI3K/mTOR signaling, but therapeutic inhibition of this pathway has not been effective. We hypothesized that intrinsic resistance to TORC1/2 inhibition is driven by cancer stem cell (CSC)-like populations that could be targeted to enhance the antitumor action of these drugs. Therefore, we investigated the molecular mechanisms by which PI3K/mTOR inhibitors affect the stem-like properties of TNBC cells. Treatment of established TNBC cell lines with a PI3K/mTOR inhibitor or a TORC1/2 inhibitor increased the expression of CSC markers and mammosphere formation. A CSC-specific PCR array revealed that inhibition of TORC1/2 increased FGF1 and Notch1 expression. Notch1 activity was also induced in TNBC cells treated with TORC1/2 inhibitors and associated with increased mitochondrial metabolism and FGFR1 signaling. Notably, genetic and pharmacological blockade of Notch1 abrogated the increase in CSC markers, mammosphere formation, and in vivo tumor-initiating capacity induced by TORC1/2 inhibition. These results suggest that targeting the FGFR-mitochondrial metabolism-Notch1 axis prevents resistance to TORC1/2 inhibitors by eradicating drug-resistant CSCs in TNBC, and may thus represent an attractive therapeutic strategy to improve drug responsiveness and efficacy. PMID:26676751

  1. Prevalence and antimicrobial resistance of beta-lactamase-producing Gram-negative isolates from outpatient clinical and environmental samples in the Zenica-Doboj Canton, Bosnia and Herzegovina

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    Amir Ibrahimagić

    2016-07-01

    Full Text Available Introduction: Infections due to extended-spectrum beta-lactamase (ESBL-producing isolates in patients are hard to treat and cause high morbidity and mortality. ESBL-producing bacteria have been increasingly detected in environmental samples in different countries since 2002, and have gained considerable attention worldwide.Methods: Antibiotic susceptibility of all isolates was determined using the disk diffusion method. The production of ESBLs was determined by the double-disk synergy test.Results: Among the outpatient clinical samples, out of 2857 Gram-negative bacteria, 184 (6.5% ESBL-producing bacteria were isolated. In this group, 143 (77.7% were from urine samples, 26 (14.1% from surgical wounds, 6 (3.3% from umbilical swabs, and 9 (4.9% from other patients sites (upper respiratory tract, cannula, eyes, genital swabs. Escherichia coli was isolated in 62 (33.7%, and Klebsiella spp. in 50 (27.8% cases. Among the environmental samples, out of 381 Gram-negative bacteria, 52 (13.6% were ESBL-producing isolates. In this group, 37 (71.2% were sampled from water, 7 (13.5% from food, and 8 (15.4% from environmental surfaces. The most prevalent ESBL-producing bacteria isolated from the environmental samples were E. coli (isolated from 26 samples, Klebsiella spp. (10, non-fermenters (9, and other bacteria isolated from 7 samples. The clinical outpatient ESBL-producing isolates showed resistance to all cephalosporins, ranging from 25% (cefepime to 100% (cefuroxime. The environmental ESBL-producing isolates showed resistance to cefuroxime, aztreonam, cefpodoxime, amoxicillin/clavulanate, and cefoxitin in the range of 65-100%.Conclusions: Prevalence of antibiotic resistance of ESBL-producing strains is high and requires routine detection of ESBL-producing isolates in the laboratories, designing of appropriate antibiotic prescribing policies and control of the risk factors.

  2. Third generation cephalosporin resistant Enterobacteriaceae and multidrug resistant gram-negative bacteria causing bacteremia in febrile neutropenia adult cancer patients in Lebanon, broad spectrum antibiotics use as a major risk factor, and correlation with poor prognosis.

    Science.gov (United States)

    Moghnieh, Rima; Estaitieh, Nour; Mugharbil, Anas; Jisr, Tamima; Abdallah, Dania I; Ziade, Fouad; Sinno, Loubna; Ibrahim, Ahmad

    2015-01-01

    Bacteremia remains a major cause of life-threatening complications in patients receiving anticancer chemotherapy. The spectrum and susceptibility profiles of causative microorganisms differ with time and place. Data from Lebanon are scarce. We aim at evaluating the epidemiology of bacteremia in cancer patients in a university hospital in Lebanon, emphasizing antibiotic resistance and risk factors of multi-drug resistant organism (MDRO)-associated bacteremia. This is a retrospective study of 75 episodes of bacteremia occurring in febrile neutropenic patients admitted to the hematology-oncology unit at Makassed General Hospital, Lebanon, from October 2009-January 2012. It corresponds to epidemiological data on bacteremia episodes in febrile neutropenic cancer patients including antimicrobial resistance and identification of risk factors associated with third generation cephalosporin resistance (3GCR) and MDRO-associated bacteremia. Out of 75 bacteremias, 42.7% were gram-positive (GP), and 57.3% were gram-negative (GN). GP bacteremias were mostly due to methicillin-resistant coagulase negative staphylococci (28% of total bacteremias and 66% of GP bacteremias). Among the GN bacteremias, Escherichia coli (22.7% of total, 39.5% of GN organisms) and Klebsiella pneumoniae(13.3% of total, 23.3% of GN organisms) were the most important causative agents. GN bacteremia due to 3GC sensitive (3GCS) bacteria represented 28% of total bacteremias, while 29% were due to 3GCR bacteria and 9% were due to carbapenem-resistant organisms. There was a significant correlation between bacteremia with MDRO and subsequent intubation, sepsis and mortality. Among potential risk factors, only broad spectrum antibiotic intake >4 days before bacteremia was found to be statistically significant for acquisition of 3GCR bacteria. Using carbapenems or piperacillin/tazobactam>4 days before bacteremia was significantly associated with the emergence of MDRO (p < 0.05). Our findings have major

  3. Increased Costs Associated with Bloodstream Infections Caused by Multidrug-Resistant Gram-Negative Bacteria Are Due Primarily to Patients with Hospital-Acquired Infections.

    Science.gov (United States)

    Thaden, Joshua T; Li, Yanhong; Ruffin, Felicia; Maskarinec, Stacey A; Hill-Rorie, Jonathan M; Wanda, Lisa C; Reed, Shelby D; Fowler, Vance G

    2017-03-01

    The clinical and economic impacts of bloodstream infections (BSI) due to multidrug-resistant (MDR) Gram-negative bacteria are incompletely understood. From 2009 to 2015, all adult inpatients with Gram-negative BSI at our institution were prospectively enrolled. MDR status was defined as resistance to ≥3 antibiotic classes. Clinical outcomes and inpatient costs associated with the MDR phenotype were identified. Among 891 unique patients with Gram-negative BSI, 292 (33%) were infected with MDR bacteria. In an adjusted analysis, only history of Gram-negative infection was associated with MDR BSI versus non-MDR BSI (odds ratio, 1.60; 95% confidence interval [CI], 1.19 to 2.16; P = 0.002). Patients with MDR BSI had increased BSI recurrence (1.7% [5/292] versus 0.2% [1/599]; P = 0.02) and longer hospital stay (median, 10.0 versus 8.0 days; P = 0.0005). Unadjusted rates of in-hospital mortality did not significantly differ between MDR (26.4% [77/292]) and non-MDR (21.7% [130/599]) groups (P = 0.12). Unadjusted mean costs were 1.62 times higher in MDR than in non-MDR BSI ($59,266 versus $36,452; P = 0.003). This finding persisted after adjustment for patient factors and appropriate empirical antibiotic therapy (means ratio, 1.18; 95% CI, 1.03 to 1.36; P = 0.01). Adjusted analysis of patient subpopulations revealed that the increased cost of MDR BSI occurred primarily among patients with hospital-acquired infections (MDR means ratio, 1.41; 95% CI, 1.10 to 1.82; P = 0.008). MDR Gram-negative BSI are associated with recurrent BSI, longer hospital stays, and increased mean inpatient costs. MDR BSI in patients with hospital-acquired infections primarily account for the increased cost. Copyright © 2017 American Society for Microbiology.

  4. Prevalence and characteristics of methicillin-resistant coagulase-negative staphylococci from livestock, chicken carcasses, bulk tank milk, minced meat, and contact persons

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    Zweifel Claudio

    2011-01-01

    Full Text Available Abstract Background Methicillin-resistant coagulase-negative staphylococci (MR-CNS are of increasing importance to animal and public health. In veterinary medicine and along the meat and milk production line, only limited data were so far available on MR-CNS characteristics. The aim of the present study was to evaluate the prevalence of MR-CNS, to identify the detected staphylococci to species level, and to assess the antibiotic resistance profiles of isolated MR-CNS strains. Results After two-step enrichment and growth on chromogenic agar, MR-CNS were detected in 48.2% of samples from livestock and chicken carcasses, 46.4% of samples from bulk tank milk and minced meat, and 49.3% of human samples. Using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS, 414 selected MR-CNS strains belonged to seven different species (S. sciuri, 32.6%; S. fleurettii, 25.1%; S. haemolyticus, 17.4%; S. epidermidis, 14.5%, S. lentus, 9.2%; S. warneri, 0.7%; S. cohnii, 0.5%. S. sciuri and S. fleurettii thereby predominated in livestock, BTM and minced meat samples, whereas S. epidermidis and S. haemolyticus predominated in human samples. In addition to beta-lactam resistance, 33-49% of all 414 strains were resistant to certain non-beta-lactam antibiotics (ciproflaxacin, clindamycin, erythromycin, tetracycline. Conclusions A high prevalence of MR-CNS was found in livestock production. This is of concern in view of potential spread of mecA to S. aureus (MRSA. Multiresistant CNS strains might become an emerging problem for veterinary medicine. For species identification of MR-CNS isolated from different origins, MALDI-TOF MS proved to be a fast and reliable tool and is suitable for screening of large sample amounts.

  5. Prevalence and characteristics of methicillin-resistant coagulase-negative staphylococci from livestock, chicken carcasses, bulk tank milk, minced meat, and contact persons.

    Science.gov (United States)

    Huber, Helen; Ziegler, Dominik; Pflüger, Valentin; Vogel, Guido; Zweifel, Claudio; Stephan, Roger

    2011-01-27

    Methicillin-resistant coagulase-negative staphylococci (MR-CNS) are of increasing importance to animal and public health. In veterinary medicine and along the meat and milk production line, only limited data were so far available on MR-CNS characteristics. The aim of the present study was to evaluate the prevalence of MR-CNS, to identify the detected staphylococci to species level, and to assess the antibiotic resistance profiles of isolated MR-CNS strains. After two-step enrichment and growth on chromogenic agar, MR-CNS were detected in 48.2% of samples from livestock and chicken carcasses, 46.4% of samples from bulk tank milk and minced meat, and 49.3% of human samples. Using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), 414 selected MR-CNS strains belonged to seven different species (S. sciuri, 32.6%; S. fleurettii, 25.1%; S. haemolyticus, 17.4%; S. epidermidis, 14.5%, S. lentus, 9.2%; S. warneri, 0.7%; S. cohnii, 0.5%). S. sciuri and S. fleurettii thereby predominated in livestock, BTM and minced meat samples, whereas S. epidermidis and S. haemolyticus predominated in human samples. In addition to beta-lactam resistance, 33-49% of all 414 strains were resistant to certain non-beta-lactam antibiotics (ciproflaxacin, clindamycin, erythromycin, tetracycline). A high prevalence of MR-CNS was found in livestock production. This is of concern in view of potential spread of mecA to S. aureus (MRSA). Multiresistant CNS strains might become an emerging problem for veterinary medicine. For species identification of MR-CNS isolated from different origins, MALDI-TOF MS proved to be a fast and reliable tool and is suitable for screening of large sample amounts.

  6. Prevalence of enterotoxin-encoding genes and antimicrobial resistance in coagulase-negative and coagulase-positive Staphylococcus isolates from black pudding.

    Science.gov (United States)

    Moura, Tiane Martin de; Campos, Fabrício Souza; d'Azevedo, Pedro Alves; Van Der Sand, Sueli Teresinha; Franco, Ana Cláudia; Frazzon, Jeverson; Frazzon, Ana Paula Guedes

    2012-10-01

    Staphylococcal species are pathogens that are responsible for outbreaks of foodborne diseases. The aim of this study was to investigate the prevalence of enterotoxin-genes and the antimicrobial resistance profile in staphylococcus coagulase-negative (CoNS) and coagulasepositive (CoPS) isolates from black pudding in southern Brazil. Two hundred typical and atypical colonies from Baird-Parker agar were inoculated on mannitol salt agar. Eighty-two mannitol-positive staphylococci were submitted to conventional biochemical tests and antimicrobial susceptibility profiling. The presence of coagulase (coa) and enterotoxin (se) genes was investigated by polymerase chain reaction. The isolates were divided into 2 groups: 75.6% (62/82) were CoNS and 24.4% (20/82) were CoPS. The biochemical tests identified 9 species, of which Staphylococcus saprophyticus (37.8%) and Staphylococcus carnosus (15.9%) were the most prevalent. Antimicrobial susceptibility tests showed resistance phenotypes to antibiotics widely administered in humans, such as gentamicin, tetracycline, chloramphenicol, and erythromycin. The coa gene was detected in 19.5% (16/82) of the strains and 4 polymorphic DNA fragments were observed. Five CoNS isolates carrying the coa gene were submitted for 16S rRNA sequencing and 3 showed similarity with CoNS. Forty strains were positive for at least 1 enterotoxin-encoding gene, the genes most frequently detected were sea (28.6%) and seb (27.5%). The presence of antimicrobial resistant and enterotoxin-encoding genes in staphylococci isolates from black pudding indicated that this fermented food may represent a potential health risk, since staphylococci present in food could cause foodborne diseases or be a possible route for the transfer of antimicrobial resistance to humans.

  7. Prevalence of carbapenem-resistant organisms and other Gram-negative MDRO in German ICUs: first results from the national nosocomial infection surveillance system (KISS).

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    Maechler, F; Peña Diaz, L A; Schröder, C; Geffers, C; Behnke, M; Gastmeier, P

    2015-04-01

    Standardized prevalence and incidence data on carbapenem-resistant organisms (CRO) and, as a relevant subgroup, carbapenem-resistant Enterobacteriaceae (CRE) are scarce. CRO-surveillance within the German nosocomial infection surveillance system (KISS) aims to provide epidemiological surveillance data on CRO colonizations and infections. CRO-surveillance is part of a KISS-module for the surveillance of multidrug-resistant organisms (MDRO). MDRO-KISS methods require surveillance of all patients admitted to the ward and standardized documentation of imported and ICU-acquired cases. Data on all MDRO-carriers including colonization and infection with MDRO are collected. All presented data were routine data collected from January 1st 2013 until December 1st 2013 in accordance with the German Protection against Infection Act (IfSG). 341 ICUs submitted data on MDRO during the first year. In total, 5,171 cases of multidrug-resistant Gram-negative bacteria (MRGN) were identified. 848 were CRO (16%). 325 CRO-cases were acquired within the ICU (38%), and 373 CRO-patients had an infection (44%). CRO-prevalence was 0.29 per 100 patients. Acquisition rate of MRGN was 1.32 per 1,000 patient days. This rate is more than doubled the acquisition rates of other MDRO under surveillance within MDRO-KISS (0.57 MRSA, 0.49 VRE). CRO-acquisition rate was 0.3 per 1,000 patient days. Incidence density of MRGN infections bacteria was 0.58 per 1,000 patient days (CRO 0.15/1,000 patient days). To date, CRO are common in German ICUs and the relatively large proportions of ICU-acquired CRO and infections emphasize their potential to cause outbreaks. High MRGN infection rates and high ESBL prevalence data from clinical studies suggest a lack of MRGN identification in asymptomatic carriers.

  8. Evaluation of BD MAX Staph SR Assay for Differentiating Between Staphylococcus aureus and Coagulase-Negative Staphylococci and Determining Methicillin Resistance Directly From Positive Blood Cultures.

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    Lee, Jaewoong; Park, Yeon Joon; Park, Dong Jin; Park, Kang Gyun; Lee, Hae Kyung

    2017-01-01

    We evaluated the performance of the BD MAX StaphSR Assay (SR assay; BD, USA) for direct detection of Staphylococcus aureus and methicillin resistance not only in S. aureus but also in coagulase-negative Staphylococci (CNS) from positive blood cultures. From 228 blood culture bottles, 103 S. aureus [45 methicillin-resistant S. aureus (MRSA), 55 methicillin-susceptible S. aureus (MSSA), 3 mixed infections (1 MRSA+Enterococcus faecalis, 1 MSSA+MRCNS, 1 MSSA+MSCNS)], and 125 CNS (102 MRCNS, 23 MSCNS) were identified by Vitek 2. For further analysis, we obtained the cycle threshold (Ct) values from the BD MAX system software to determine an appropriate cutoff value. For discrepancy analysis, conventional mecA/mecC PCR and oxacillin minimum inhibitory concentrations (MICs) were determined. Compared to Vitek 2, the SR assay identified all 103 S. aureus isolates correctly but failed to detect methicillin resistance in three MRSA isolates. All 55 MSSA isolates were correctly identified by the SR assay. In the concordant cases, the highest Ct values for nuc, mecA, and mec right-extremity junction (MREJ) were 25.6, 22, and 22.2, respectively. Therefore, we selected Ct values from 0-27 as a range of positivity, and applying this cutoff, the sensitivity/specificity of the SR assay were 100%/100% for detecting S. aureus, and 97.9%/98.1% and 99.0%/95.8% for detecting methicillin resistance in S. aureus and CNS, respectively. We propose a Ct cutoff value for nuc/mec assay without considering MREJ because mixed cultures of MSSA and MRCNS were very rare (0.4%) in the positive blood cultures.

  9. Prevalence of enterotoxin-encoding genes and antimicrobial resistance in coagulase-negative and coagulase-positive Staphylococcus isolates from black pudding

    Directory of Open Access Journals (Sweden)

    Tiane Martin de Moura

    2012-10-01

    Full Text Available INTRODUCTION: Staphylococcal species are pathogens that are responsible for outbreaks of foodborne diseases. The aim of this study was to investigate the prevalence of enterotoxin-genes and the antimicrobial resistance profile in staphylococcus coagulase-negative (CoNS and coagulasepositive (CoPS isolates from black pudding in southern Brazil. METHODS: Two hundred typical and atypical colonies from Baird-Parker agar were inoculated on mannitol salt agar. Eighty-two mannitol-positive staphylococci were submitted to conventional biochemical tests and antimicrobial susceptibility profiling. The presence of coagulase (coa and enterotoxin (se genes was investigated by polymerase chain reaction. RESULTS: The isolates were divided into 2 groups: 75.6% (62/82 were CoNS and 24.4% (20/82 were CoPS. The biochemical tests identified 9 species, of which Staphylococcus saprophyticus (37.8% and Staphylococcus carnosus (15.9% were the most prevalent. Antimicrobial susceptibility tests showed resistance phenotypes to antibiotics widely administered in humans, such as gentamicin, tetracycline, chloramphenicol, and erythromycin. The coa gene was detected in 19.5% (16/82 of the strains and 4 polymorphic DNA fragments were observed. Five CoNS isolates carrying the coa gene were submitted for 16S rRNA sequencing and 3 showed similarity with CoNS. Forty strains were positive for at least 1 enterotoxin-encoding gene, the genes most frequently detected were sea (28.6% and seb (27.5%. CONCLUSIONS: The presence of antimicrobial resistant and enterotoxin-encoding genes in staphylococci isolates from black pudding indicated that this fermented food may represent a potential health risk, since staphylococci present in food could cause foodborne diseases or be a possible route for the transfer of antimicrobial resistance to humans.

  10. Molecular epidemiology of coagulase-negative bloodstream isolates: detection of Staphylococcus epidermidis ST2, ST7 and linezolid-resistant ST23.

    Science.gov (United States)

    Martínez-Meléndez, Adrián; Morfín-Otero, Rayo; Villarreal-Treviño, Licet; Camacho-Ortíz, Adrián; González-González, Gloria; Llaca-Díaz, Jorge; Rodríguez-Noriega, Eduardo; Garza-González, Elvira

    2016-01-01

    The mechanisms contributing to persistence of coagulase-negative staphylococci are diverse; to better understanding of their dynamics, the characterization of nosocomial isolates is needed. Our aim was to characterize phenotypic and molecular characteristics of Staphylococcus epidermidis and Staphylococcus haemolyticus human blood isolates from two tertiary care hospitals in Mexico, the Hospital Universitario in Monterrey and the Hospital Civil in Guadalajara. Antimicrobial susceptibility was determined. Biofilm formation was assessed by crystal violet staining. Detection of the ica operon and Staphylococcal Cassette Chromosome mec typing were performed by PCR. Clonal relatedness was determined by Pulsed-fiel gel electrophoresis and Multi locus sequence typing. Methicillin-resistance was 85.5% and 93.2% for S. epidermidis and S. haemolyticus, respectively. Both species showed resistance >70% to norfloxacin, clindamycin, levofloxacin, trimethoprim/sulfamethoxazole, and erythromycin. Three S. epidermidis and two S. haemolyticus isolates were linezolid-resistant (one isolate of each species was cfr+). Most isolates of both species were strong biofilm producers (92.8% of S. epidermidis and 72.9% of S. haemolyticus). The ica operon was amplified in 36 (43.4%) S. epidermidis isolates. SCCmec type IV was found in 47.2% of the S. epidermidis isolates and SCCmec type V in 14.5% of S. haemolyticus isolates. No clonal relatedness was found in either species. Resistance to clindamycin, levofloxacin, erythromycin, oxacillin, and cefoxitin was associated with biofilm production for both species (pepidermidis isolates belonged to ST23; isolate with SCCmec type IV belonged to ST7, and isolate with SCCmec type III belonged to ST2. This is the first report of ST7 in Mexico. There was a high genetic diversity in both species, though both species shared characteristics that may contibute to virulence. Copyright © 2016 Elsevier Editora Ltda. All rights reserved.

  11. Induction of ErbB-3 expression by alpha6beta4 integrin contributes to tamoxifen resistance in ERbeta1-negative breast carcinomas.

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    Valentina Folgiero

    Full Text Available BACKGROUND: Tamoxifen is still the most widely used drug in hormone therapy for the treatment of breast cancer. Its benefits in adjuvant treatment are well documented in controlled and randomized clinical studies, which have demonstrated an increase in disease-free intervals of patients with positive hormonal receptors. However, the mechanisms involved in endocrine resistance are not clear. Laboratory and clinical data now indicate that bi-directional molecular cross-talk between nuclear or membrane ER and growth factor receptor pathways may be involved in endocrine resistance. We recently found a functional interaction between alpha6beta4 integrin and ErbB-3 receptor to maintain the PI3K/Akt survival pathway of mammary tumour cells. We sought to improve understanding of this process in order to provide the involvement of both receptors insight into mechanism of Tamoxifen resistance. METHODS AND FINDINGS: Using human breast cancer cell lines displaying different levels of alpha6beta4 and ErbB-3 receptors and a series of 232 breast cancer biopsies from patients submitted to adjuvant Tamoxifen monotherapy for five years, we evaluated the functional interaction between both receptors in relationship to Tamoxifen responsiveness. In mammary carcinoma cells, we evidenced that the alpha6beta4 integrin strongly influence Akt phosphorylation through ErbB-3 protein regulation. Moreover, the ErbB-3 inactivation inhibits Akt phosphorylation, induces apoptosis and inhibits in vitro invasion favouring Tamoxifen responsiveness. The analysis of human tumors revealed a significant relationship between alpha6beta4 and ErbB-3 in P-Akt-positive and ERbeta1-negative breast cancers derived from patients with lower disease free survival. CONCLUSIONS: We provided evidence that a strong relationship occurs between alpha6beta4 and ErbB-3 positivity in ERbeta1-negative breast cancers. We also found that the association between ErbB-3 and P-Akt positivity mainly occurs in

  12. Induction of ErbB-3 Expression by α6β4 Integrin Contributes to Tamoxifen Resistance in ERβ1-Negative Breast Carcinomas

    Science.gov (United States)

    Bon, Giulia; Di Carlo, Selene E.; Fabi, Alessandra; Nisticò, Cecilia; Vici, Patrizia; Melucci, Elisa; Buglioni, Simonetta; Perracchio, Letizia; Sperduti, Isabella; Rosanò, Laura; Sacchi, Ada; Mottolese, Marcella; Falcioni, Rita

    2008-01-01

    Background Tamoxifen is still the most widely used drug in hormone therapy for the treatment of breast cancer. Its benefits in adjuvant treatment are well documented in controlled and randomized clinical studies, which have demonstrated an increase in disease-free intervals of patients with positive hormonal receptors. However, the mechanisms involved in endocrine resistance are not clear. Laboratory and clinical data now indicate that bi-directional molecular cross-talk between nuclear or membrane ER and growth factor receptor pathways may be involved in endocrine resistance. We recently found a functional interaction between α6β4 integrin and ErbB-3 receptor to maintain the PI3K/Akt survival pathway of mammary tumour cells. We sought to improve understanding of this process in order to provide the involvement of both receptors insight into mechanism of Tamoxifen resistance. Methods and Findings Using human breast cancer cell lines displaying different levels of α6β4 and ErbB-3 receptors and a series of 232 breast cancer biopsies from patients submitted to adjuvant Tamoxifen monotherapy for five years, we evaluated the functional interaction between both receptors in relationship to Tamoxifen responsiveness. In mammary carcinoma cells, we evidenced that the α6β4 integrin strongly influence Akt phosphorylation through ErbB-3 protein regulation. Moreover, the ErbB-3 inactivation inhibits Akt phosphorylation, induces apoptosis and inhibits in vitro invasion favouring Tamoxifen responsiveness. The analysis of human tumors revealed a significant relationship between α6β4 and ErbB-3 in P-Akt-positive and ERβ1-negative breast cancers derived from patients with lower disease free survival. Conclusions We provided evidence that a strong relationship occurs between α6β4 and ErbB-3 positivity in ERβ1-negative breast cancers. We also found that the association between ErbB-3 and P-Akt positivity mainly occurs in ERβ1-negative breast cancer derived from patients

  13. Induction of ErbB-3 expression by alpha6beta4 integrin contributes to tamoxifen resistance in ERbeta1-negative breast carcinomas.

    Science.gov (United States)

    Folgiero, Valentina; Avetrani, Paolo; Bon, Giulia; Di Carlo, Selene E; Fabi, Alessandra; Nisticò, Cecilia; Vici, Patrizia; Melucci, Elisa; Buglioni, Simonetta; Perracchio, Letizia; Sperduti, Isabella; Rosanò, Laura; Sacchi, Ada; Mottolese, Marcella; Falcioni, Rita

    2008-02-13

    Tamoxifen is still the most widely used drug in hormone therapy for the treatment of breast cancer. Its benefits in adjuvant treatment are well documented in controlled and randomized clinical studies, which have demonstrated an increase in disease-free intervals of patients with positive hormonal receptors. However, the mechanisms involved in endocrine resistance are not clear. Laboratory and clinical data now indicate that bi-directional molecular cross-talk between nuclear or membrane ER and growth factor receptor pathways may be involved in endocrine resistance. We recently found a functional interaction between alpha6beta4 integrin and ErbB-3 receptor to maintain the PI3K/Akt survival pathway of mammary tumour cells. We sought to improve understanding of this process in order to provide the involvement of both receptors insight into mechanism of Tamoxifen resistance. Using human breast cancer cell lines displaying different levels of alpha6beta4 and ErbB-3 receptors and a series of 232 breast cancer biopsies from patients submitted to adjuvant Tamoxifen monotherapy for five years, we evaluated the functional interaction between both receptors in relationship to Tamoxifen responsiveness. In mammary carcinoma cells, we evidenced that the alpha6beta4 integrin strongly influence Akt phosphorylation through ErbB-3 protein regulation. Moreover, the ErbB-3 inactivation inhibits Akt phosphorylation, induces apoptosis and inhibits in vitro invasion favouring Tamoxifen responsiveness. The analysis of human tumors revealed a significant relationship between alpha6beta4 and ErbB-3 in P-Akt-positive and ERbeta1-negative breast cancers derived from patients with lower disease free survival. We provided evidence that a strong relationship occurs between alpha6beta4 and ErbB-3 positivity in ERbeta1-negative breast cancers. We also found that the association between ErbB-3 and P-Akt positivity mainly occurs in ERbeta1-negative breast cancer derived from patients with lower DFS

  14. Carbapenem-resistant Gram-negative bacteria - analysis of the data obtained through a mandatory reporting system in the Rhine-Main region, Germany, 2012-2015.