WorldWideScience

Sample records for factor influences biofilm

  1. Environmental and centrifugal factors influencing the visco-elastic properties of oral biofilms in vitro.

    Science.gov (United States)

    Peterson, Brandon W; Busscher, Henk J; Sharma, Prashant K; van der Mei, Henny C

    2012-01-01

    Centrifugal compaction causes changes in the surface properties of bacterial cells. It has been shown previously that the surface properties of planktonic cells change with increasing centrifugal compaction. This study aimed to analyze the influences of centrifugal compaction and environmental conditions on the visco-elastic properties of oral biofilms. Biofilms were grown out of a layer of initially adhering streptococci, actinomyces or a combination of these. Different uni-axial deformations were induced on the biofilms and the load relaxations were measured over time. Linear-Regression-Analysis demonstrated that both the centrifugation coefficient for streptococci and induced deformation influenced the percentage relaxation. Centrifugal compaction significantly influenced relaxation only upon compression of the outermost 20% of the biofilm (p centrifugal compaction of initially adhering, centrifuged bacteria extend to the visco-elastic properties of biofilms, indicating that the initial bacterial layer influences the structure of the entire biofilm.

  2. [Influencing factors for operational performance of a biofilm reactor with microbubble aeration using SPG membrane].

    Science.gov (United States)

    Zhang, Lei; Zhang, Ming; Liu, Chun; Zhang, Jing; Liu, Jun-Liang

    2014-08-01

    The microbubble-aerated biofilm reactor provides a feasibility to apply microbubble aeration in aerobic wastewater treatment processes. In this study, Shirasu porous glass (SPG) membranes were used for microbubble aeration in a fixed bed biofilm reactor treating synthetic municipal wastewater. The influencing factors for operational performance of the bioreactor were investigated, including operating parameters, SPG membrane fouling and its structural changes. The results indicated that there was no significant influences of air flux, organic loading rate and packed bed on COD removal and an average COD removal efficiency of 80% -90% could be achieved under different operating conditions. On the other hand, the dissolved oxygen (DO) concentrations decreased significantly along with reducing air flux or increasing organic loading rate. As a result, the ammonia removal deteriorated gradually and the average ammonia removal efficiency decreased from 80% -90% to 20% -30% At the same time, the total nitrogen (TN) removal achieved in the simultaneous nitrification and denitrification process was also reduced from 30% -40% to about 20% , due to nitrification inhibition. Higher available porosity could be obtained when ring packing was used in the fixed bed, resulting in improvement of contaminant removal performance. An oxygen utilization efficiency of close to 100% could be achieved at low air fluxes or high organic loading rates during microbubble aeration. Both biofilm growth and organic foulant accumulation on SPC, membrane surface contributed to membrane fouling after long-term operation. The average pore size and porosity of SPG membrane increased significantly due to the chemical corrosion caused by alkali NaClO solution used for online cleaning. Then the air permeation of SPG membrane was affected by membrane fouling and destroyed pore structure.

  3. Interspecies signalling via the Stenotrophomonas maltophilia diffusible signal factor influences biofilm formation and polymyxin tolerance in Pseudomonas aeruginosa

    DEFF Research Database (Denmark)

    Ryan, R.P.; Fouhy, Y.; Garcia, B.F.

    2008-01-01

    including the rhizosphere of plants and the cystic fibrosis lung. In mixed species biofilms, S. maltophilia substantially influenced the architecture of P. aeruginosa structures, which developed as extended filaments. This effect depended upon the synthesis of the diffusible signal factor (DSF) by S....... maltophilia and could be mimicked by the addition of synthetic DSF. This response of P. aeruginosa to DSF required PA1396, a sensor kinase with an input domain of related amino acid sequence to the sensory input domain of RpfC, which is responsible for DSF perception in xanthomonads. Mutation of PA1396...

  4. Biofilm formation by Streptococcus agalactiae: influence of environmental conditions and implicated virulence factors.

    Science.gov (United States)

    Rosini, Roberto; Margarit, Immaculada

    2015-01-01

    Streptococcus agalactiae (Group B Streptococcus, GBS) is an important human pathogen that colonizes the urogenital and/or the lower gastro-intestinal tract of up to 40% of healthy women of reproductive age and is a leading cause of sepsis and meningitis in the neonates. GBS can also infect the elderly and immuno-compromised adults, and is responsible for mastitis in bovines. Like other Gram-positive bacteria, GBS can form biofilm-like three-dimensional structures that could enhance its ability to colonize and persist in the host. Biofilm formation by GBS has been investigated in vitro and appears tightly controlled by environmental conditions. Several adhesins have been shown to play a role in the formation of GBS biofilm-like structures, among which are the protein components of pili protruding outside the bacterial surface. Remarkably, antibodies directed against pilus proteins can prevent the formation of biofilms. The implications of biofilm formation in the context of GBS asymptomatic colonization and dissemination to cause invasive disease remain to be investigated in detail.

  5. Biofilm formation by Streptococcus agalactiae: influence of environmental conditions and implicated virulence factors

    Directory of Open Access Journals (Sweden)

    Imma eMargarit

    2015-02-01

    Full Text Available Streptococcus agalactiae (Group B Streptococcus, GBS is an important human pathogen that colonizes the urogenital and/or the lower gastro-intestinal tract of up to 40% of healthy women of reproductive age and is a leading cause of sepsis and meningitis in the neonates. GBS can also infect the elderly and immuno-compromised adults, and is responsible for mastitis in bovines. Like other Gram-positive bacteria, GBS can form biofilm-like three-dimensional structures that could enhance its ability to colonize and persist in the host. Biofilm formation by GBS has been investigated in vitro and appears tightly controlled by environmental conditions. Several adhesins have been shown to play a role in the formation of GBS biofilm-like structures, among which are the protein components of pili protruding outside the bacterial surface. Remarkably, antibodies directed against pilus proteins can prevent the formation of biofilms. The implications of biofilm formation in the context of GBS asymptomatic colonization and dissemination to cause invasive disease remain to be investigated in detail.

  6. Environmental factors that shape biofilm formation.

    Science.gov (United States)

    Toyofuku, Masanori; Inaba, Tomohiro; Kiyokawa, Tatsunori; Obana, Nozomu; Yawata, Yutaka; Nomura, Nobuhiko

    2015-01-01

    Cells respond to the environment and alter gene expression. Recent studies have revealed the social aspects of bacterial life, such as biofilm formation. Biofilm formation is largely affected by the environment, and the mechanisms by which the gene expression of individual cells affects biofilm development have attracted interest. Environmental factors determine the cell's decision to form or leave a biofilm. In addition, the biofilm structure largely depends on the environment, implying that biofilms are shaped to adapt to local conditions. Second messengers such as cAMP and c-di-GMP are key factors that link environmental factors with gene regulation. Cell-to-cell communication is also an important factor in shaping the biofilm. In this short review, we will introduce the basics of biofilm formation and further discuss environmental factors that shape biofilm formation. Finally, the state-of-the-art tools that allow us investigate biofilms under various conditions are discussed.

  7. Influence of culture heterogeneity in cell surface charge on adhesion and biofilm formation by Enterococcus faecalis

    NARCIS (Netherlands)

    van Merode, Annet E.J.; van der Mei, HC; Busscher, HJ; Krom, BP

    2006-01-01

    Biofilm formation is an increasing problem in medicine, due to the intrinsic resistance of microorganisms in the biofilm mode of growth against the host immune system and antimicrobial therapy. Adhesion is an important step in biofilm formation, influenced, among other factors, by the surface hydrop

  8. Essential factors of an integrated moving bed biofilm reactor-membrane bioreactor: Adhesion characteristics and microbial community of the biofilm.

    Science.gov (United States)

    Tang, Bing; Yu, Chunfei; Bin, Liying; Zhao, Yiliang; Feng, Xianfeng; Huang, Shaosong; Fu, Fenglian; Ding, Jiewei; Chen, Cuiqun; Li, Ping; Chen, Qianyu

    2016-07-01

    This work aims at revealing the adhesion characteristics and microbial community of the biofilm in an integrated moving bed biofilm reactor-membrane bioreactor, and further evaluating their variations over time. With multiple methods, the adhesion characteristics and microbial community of the biofilm on the carriers were comprehensively illuminated, which showed their dynamic variation along with the operational time. Results indicated that: (1) the roughness of biofilm on the carriers increased very quickly to a maximum value at the start-up stage, then, decreased to become a flat curve, which indicated a layer of smooth biofilm formed on the surface; (2) the tightly-bound protein and polysaccharide was the most important factor influencing the stability of biofilm; (3) the development of biofilm could be divided into three stages, and Gammaproteobacteria were the most dominant microbial species in class level at the last stage, which occupied the largest ratio (51.48%) among all microbes.

  9. Alternating Current Influences Anaerobic Electroactive Biofilm Activity.

    Science.gov (United States)

    Wang, Xin; Zhou, Lean; Lu, Lu; Lobo, Fernanda Leite; Li, Nan; Wang, Heming; Park, Jaedo; Ren, Zhiyong Jason

    2016-09-06

    Alternating current (AC) is known to inactivate microbial growth in suspension, but how AC influences anaerobic biofilm activities has not been systematically investigated. Using a Geobacter dominated anaerobic biofilm growing on the electrodes of microbial electrochemical reactors, we found that high frequency AC ranging from 1 MHz to 1 kHz (amplitude of 5 V, 30 min) showed only temporary inhibition to the biofilm activity. However, lower frequency (100 Hz, 1.2 or 5 V) treatment led to 47 ± 19% permanent decrease in limiting current on the same biofilm, which is attributed to the action of electrohydrodynamic force that caused biofilm damage and loss of intercellular electron transfer network. Confocal microscopy images show such inactivation mainly occurred at the interface between the biofilm and the electrode. Reducing the frequency further to 1 Hz led to water electrolysis, which generated gas bubbles that flushed all attached cells out of the electrode. These findings provide new references on understanding and regulating biofilm growth, which has broader implications in biofouling control, anaerobic waste treatment, energy and product recovery, and general understanding of microbial ecology and physiology.

  10. Mycobacterium biofilms: factors involved in development, dispersal, and therapeutic strategies against biofilm-relevant pathogens.

    Science.gov (United States)

    Xiang, Xiaohong; Deng, Wanyan; Liu, Minqiang; Xie, Jianping

    2014-01-01

    Many bacteria can develop biofilm (BF), a multicellular structure largely combining bacteria and their extracellular polymeric substances (EPS). The formation of biofilm results in an alternative existence in which microbes ensure their survival in adverse environments. Biofilm-relevant infections are more persistent, resistant to most antibiotics, and more recalcitrant to host immunity. Mycobacterium tuberculosis, the causative agent of tuberculosis, can develop biofilm, though whether M. tuberculosis can form biofilm within tuberculosis patients has yet to be determined. Here, we summarize the factors involved in the development and dispersal of mycobacterial biofilms, as well as underlying regulatory factors and inhibitors against biofilm to deepen our understanding of their development and to elucidate potential novel modes of action for future antibiotics. Key factors in biofilm formation identified as drug targets represent a novel and promising avenue for developing better antibiotics.

  11. Influence of Streptococcus mutans on enterococcus faecalis biofilm formation

    NARCIS (Netherlands)

    Deng, D.M.; Hoogenkamp, M.A.; Exterkate, R.A.M.; Jiang, L.M.; van der Sluis, L.W.M.; ten Cate, J.M.; Crielaard, W.

    2009-01-01

    Introduction: An important virulence factor of Enterococcus faecalis is its ability to form biofilms. Most studies on biofilm formation have been carried out by using E. faecalis monocultures. Given the polymicrobial nature of root canal infections, it is important to understand biofilm formation of

  12. Influence of Streptococcus mutans on Enterococcus faecalis Biofilm Formation

    NARCIS (Netherlands)

    Deng, Dong Mei; Hoogenkamp, Michel A.; Exterkate, Rob A. M.; Jiang, Lei Meng; van der Sluis, Lucas W. M.; ten Cate, Jacob M.; Crielaard, Wim

    2009-01-01

    Introduction: An important virulence factor of Enterococcus faecalis is its ability to form biofilms. Most studies on biofilm formation have been carried out by using E. faecalis monocultures. Given the polymicrobial nature of root canal infections, it is important to understand biofilm formation of

  13. Influence of Streptococcus mutans on Enterococcus faecalis Biofilm Formation

    NARCIS (Netherlands)

    Deng, Dong Mei; Hoogenkamp, Michel A.; Exterkate, Rob A. M.; Jiang, Lei Meng; van der Sluis, Lucas W. M.; ten Cate, Jacob M.; Crielaard, Wim

    Introduction: An important virulence factor of Enterococcus faecalis is its ability to form biofilms. Most studies on biofilm formation have been carried out by using E. faecalis monocultures. Given the polymicrobial nature of root canal infections, it is important to understand biofilm formation of

  14. Divergent composition of algal-bacterial biofilms developing under various external factors

    NARCIS (Netherlands)

    Barranguet, C.; Veuger, B.; van Beusekom, S.A.M.; Marvan, P.; Sinke, J.J.; Admiraal, W.

    2005-01-01

    The influence of external factors other than nutrients on biofilm development and composition was studied with a combination of optical (Confocal Laser Scanning Microscopy, PAM fluorometry) and chemical methods (EPS extraction, HPLC, TOC determination). The development of algal-bacterial biofilms wa

  15. Influence of culture conditions for clinically isolated non-albicans Candida biofilm formation.

    Science.gov (United States)

    Tan, Yulong; Leonhard, Matthias; Ma, Su; Schneider-Stickler, Berit

    2016-11-01

    Non-albicans Candida species have been isolated in increasing numbers in patients. Moreover, they are adept at forming biofilms. This study analyzed biofilm formation of clinically isolated non-albicans Candida, including Candida tropicalis, Candida krusei and Candida parapsilosis under the influence of different growth media (RPMI 1640, YPD and BHI) and several culture variables (inoculum concentration, incubation period and feeding conditions). The results showed that culture conditions strongly influenced non-albicans Candida species biofilm formation. YPD and BHI resulted in larger amount of biofilm formation with higher metabolic activity of biofilms. Furthermore, the growth media seems to have varying effects on adhesion and biofilm development. Growth conditions may also influence biofilm formation, which was enhanced when starting the culture with a larger inoculum, longer incubation period and using a fed-batch system. Therefore, the potential influences of external environmental factors should be considered when studying the non-albicans Candida biofilms in vitro. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Screening of biofilm formation by beneficial vaginal lactobacilli and influence of culture media components.

    Science.gov (United States)

    Terraf, M C Leccese; Juárez Tomás, M S; Nader-Macías, M E F; Silva, C

    2012-12-01

    To assess the ability of vaginal lactobacilli to form biofilm under different culture conditions and to determine the relationship between their growth and the capability of biofilm formation by selected strains. Fifteen Lactobacillus strains from human vagina were tested for biofilm formation by crystal violet staining. Only Lactobacillus rhamnosus Centro de Referencia para Lactobacilos Culture Collection (CRL) 1332, Lact. reuteri CRL 1324 and Lact. delbrueckii CRL 1510 were able to grow and form biofilm in culture media without Tween 80. However, Lact. gasseri CRL 1263 (a non-biofilm-forming strain) did not grow in these media. Scanning electron microscopy showed that Lact. rhamnosus CRL 1332 and Lact. reuteri CRL 1324 formed a highly structured biofilm, but only Lact. reuteri CRL 1324 showed a high amount of extracellular material in medium without Tween. Biofilm formation was significantly influenced by the strain, culture medium, inoculum concentration, microbial growth and chemical nature of the support used for the assay. The results allow the selection of biofilm-forming vaginal Lactobacillus strains and the conditions and factors that affect this phenomenon. © 2012 The Society for Applied Microbiology.

  17. [Mechanism and risk factors of oral biofilm formation].

    Science.gov (United States)

    Pasich, Ewa; Walczewska, Maria; Pasich, Adam; Marcinkiewicz, Janusz

    2013-08-02

    Recent microbiological investigations completely changed our understanding of the role of biofilm in the formation of the mucosal immune barrier and in pathogenesis of chronic inflammation of bacterial etiology. It is now clear that formation of bacterial biofilm on dental surfaces is characteristic for existence of oral microbial communities. It has also been proved that uncontrolled biofilms on dental tissues, as well as on different biomaterials (e.g. orthodontic appliances), are the main cause of dental diseases such as dental caries and periodontitis. The aim of this paper is to explain mechanisms and consequences of orthodontic biofilm formation. We will discuss current opinions on the influence of different biomaterials employed for orthodontic treatment in biofilm formation and new strategies employed in prevention and elimination of oral biofilm ("dental plaque").

  18. Hydrophobicity of biofilm coatings influences the transport dynamics of polystyrene nanoparticles in biofilm-coated sand.

    Science.gov (United States)

    Mitzel, Michael R; Sand, Stefanie; Whalen, Joann K; Tufenkji, Nathalie

    2016-04-01

    Engineered nanoparticles (ENPs) are used in the manufacture of over 2000 industrial and consumer products to enhance their material properties and functions or to enable new nanoparticle-dependent functions. The widespread use of ENPs will result in their release to the subsurface and aquatic environments, where they will interact with indigenous biota. Laboratory column experiments were designed to understand the influence of two different Pseudomonas aeruginosa biofilms on the mobility of polystyrene latex nanoparticles in granular porous media representative of groundwater aquifers or riverbank filtration settings. The transport behavior of 20 nm carboxylate-modified (CLPs) and sulfate (SLPs) polystyrene latex ENPs suspended in NaCl or CaCl2 (1 and 10 mM ionic strength, pH 7) was studied in columns packed with quartz sand coated with biofilms formed by two P. aeruginosa strains that differed in cell surface hydrophobicity (P. aeruginosa 9027™, relatively hydrophilic and P. aeruginosa PAO1, relatively hydrophobic). Biofilm-coated quartz sand retained more of the electrostatically-stabilized latex ENPs than clean, uncoated sand, regardless of the serotype. As IS increased, clear differences in the shape of the ENP breakthrough curves were observed for each type of biofilm coating. ENP breakthrough in the P. aeruginosa PAO1 biofilm-coated sand was generally constant with time whereby breakthrough in the P. aeruginosa 9027 biofilm-coated sand showed dynamic behavior. This indicates a fundamental difference in the mechanisms of ENP deposition onto hydrophilic or hydrophobic biofilm coatings due to the hydration properties of these biofilms. The results of this study demonstrate the importance of considering the surface properties of aquifer grain coatings when evaluating ENP fate in natural subsurface environments.

  19. Surface charge influences enterococcal prevalence in mixed-species biofilms

    NARCIS (Netherlands)

    van Merode, Annet; Pothoven, D. C.; van der Mei, H. C.; Busscher, H. J.; Krom, B. P.

    2007-01-01

    Aim: To study the influence of 15 microbial isolates on the prevalence of charge-heterogeneous and charge-homogeneous Enterococcus faecalis strains, all isolated from biliary stents, in mixed-species biofilms. Methods and Results: Six Enterococcus faecalis strains were paired with 15 other microbial

  20. The Influence of Prior Modes of Growth, Temperature, Medium, and Substrate Surface on Biofilm Formation by Antibiotic-Resistant Campylobacter jejuni.

    Science.gov (United States)

    Teh, Amy Huei Teen; Lee, Sui Mae; Dykes, Gary A

    2016-12-01

    Campylobacter jejuni is one of the most common causes of bacterial gastrointestinal food-borne infection worldwide. It has been suggested that biofilm formation may play a role in survival of these bacteria in the environment. In this study, the influence of prior modes of growth (planktonic or sessile), temperatures (37 and 42 °C), and nutrient conditions (nutrient broth and Mueller-Hinton broth) on biofilm formation by eight C. jejuni strains with different antibiotic resistance profiles was examined. The ability of these strains to form biofilm on different abiotic surfaces (stainless steel, glass, and polystyrene) as well as factors potentially associated with biofilm formation (bacterial surface hydrophobicity, auto-aggregation, and initial attachment) was also determined. The results showed that cells grown as sessile culture generally have a greater ability to form biofilm (P < 0.05) compared to their planktonic counterparts. Biofilm was also greater (P < 0.05) in lower nutrient media, while growth at different temperatures affects biofilm formation in a strain-dependent manner. The strains were able to attach and form biofilms on different abiotic surfaces, but none of them demonstrated strong, complex, or structured biofilm formation. There were no clear trends between the bacterial surface hydrophobicity, auto-aggregation, attachment, and biofilm formation by the strains. This finding suggests that environmental factors did affect biofilm formation by C. jejuni, and they are more likely to persist in the environment in the form of mixed-species rather than monospecies biofilms.

  1. Mechanism of biofilm formation and analysis of influencing factors%生物膜形成机理及影响因素探究

    Institute of Scientific and Technical Information of China (English)

    戚韩英; 汪文斌; 郑昱; 朱亮; 徐向阳

    2013-01-01

    Biofilm is a kind of special microbial aggregates, and exists widely in various natural environments. The paper introduced the basic principle of biofilm formation, and reviewed the effects of carrier property, key components of extracellular polymeric substances (EPS) on the formation and stability of biofilms. Finally, the cross-disciplinary research prospect on the biofilm was provided.%生物膜是一种依附于载体材料的特殊微生物聚集体,其大量存在于自然环境中,并在水质净化、废水处理等领域广泛应用.本文介绍了生物膜形成基本原理,综述了有关载体界面性质、胞外多聚物(EPS)关键组分对生物膜形成及其稳定性的影响,并对各学科交叉研究生物膜提供技术思路.

  2. Influence of diatom exopolymers and biofilms on metamorphosis in the barnacle Balanus amphitrite

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    , the proportion of monosaccharides varies with species, indicating a potential role for influencing larval metamorphosis. Free EPS of axenic diatoms had no effect, whereas biofilm EPS induced larvae to metamorphose. Amphora spp. produced more biofilm EPS, but had...

  3. [Influence of poly-β-1-6-N-acetylglucosamine on biofilm formation and drug resistance of Acinetobacter baumannii].

    Science.gov (United States)

    Guo, Haina; Xiang, Jun

    2015-02-01

    Acinetobacter baumannii has emerged as one of the leading bacteria for nosocomial infections, especially in burn wards and ICUs. The bacteria can easily form biofilm and readily attach to abiotic and biotic surfaces, resulting in persistent biofilm-mediated infections. Being surrounded by self-produced extracellular polymeric substance (EPS), the microorganisms in biofilm can acquire protective property against detrimental environment and their tolerance toward antibiotics is increased. Poly-β-1-6-N-acetylglucosamine (PNAG), the common constituent of EPS in Acinetobacter baumannii, acts as the key virulence factor and plays a crucial role in biofilm formation process. This review describes the properties and functions of the PNAG and its influence on biofilm formation and drug resistance of Acinetobacter baumannii.

  4. The influence of Brazilian plant extracts on Streptococcus mutans biofilm

    Directory of Open Access Journals (Sweden)

    Michele BARNABÉ

    2014-10-01

    Full Text Available Nineteen plant extracts obtained from plants from the Brazilian Amazon showed activity against planktonic Streptococcus mutans, an important bacterium involved in the first steps of biofilm formation and the subsequent initiation of several oral diseases. Objective: Our goal was to verify whether plant extracts that showed activity against planktonic S. mutans could prevent the organization of or even disrupt a single-species biofilm made by the same bacteria. Material and Methods: Plant extracts were tested on a single-bacteria biofilm prepared using the Zürich method. Each plant extract was tested at a concentration 5 times higher than its minimum inhibitory concentration (MIC. Discs of hydroxyapatite were submersed overnight in brain-heart infusion broth enriched with saccharose 5%, which provided sufficient time for biofilm formation. The discs were then submersed in extract solutions for one minute, three times per day, for two subsequent days. The discs were then washed with saline three times, at ten seconds each, after each treatment. Supports were allowed to remain in the enriched medium for one additional night. At the end of the process, the bacteria were removed from the discs by vortexing and were counted. Results: Only two of 19 plant extracts showed activity in the present assay: EB1779, obtained from Dioscorea altissima, and EB1673, obtained from Annona hypoglauca. Although the antibacterial activity of the plant extracts was first observed against planktonic S. mutans, influence over biofilm formation was not necessarily observed in the biofilm model. The present results motivate us to find new natural products to be used in dentistry.

  5. Hydrophilicity of dentin bonding systems influences in vitro Streptococcus mutans biofilm formation

    Science.gov (United States)

    Brambilla, Eugenio; Ionescu, Andrei; Mazzoni, Annalisa; Cadenaro, Milena; Gagliani, Massimo; Ferraroni, Monica; Tay, Franklin; Pashley, David; Breschi, Lorenzo

    2014-01-01

    Objectives To evaluate in vitro Streptococcus mutans (S. mutans) biofilm formation on the surface of five light-curing experimental dental bonding systems (DBS) with increasing hydrophilicity. The null hypothesis tested was that resin chemical composition and hydrophilicity does not affect S. mutans biofilm formation. Methods Five light-curing versions of experimental resin blends with increasing hydrophilicity were investigated (R1, R2, R3, R4 and R5). R1 and R2 contained ethoxylated BisGMA/TEGDMA or BisGMA/TEGDMA, respectively, and were very hydrophobic, were representative of pit-and-fissure bonding agents. R3 was representative of a typical two-step etch- and-rinse adhesive, while R4 and R5 were very hydrophilic resins analogous to self-etching adhesives. Twenty-eight disks were prepared for each resin blend. After a 24 h-incubation at 37 °C, a multilayer monospecific biofilm of S. mutans was obtained on the surface of each disk. The adherent biomass was determined using the MTT assay and evaluated morphologically with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Results R2 and R3 surfaces showed the highest biofilm formation while R1 and R4 showed a similar intermediate biofilm formation. R5 was more hydrophilic and acidic and was significantly less colonized than all the other resins. A significant quadratic relationship between biofilm formation and hydrophilicity of the resin blends was found. CLSM and SEM evaluation confirmed MTT assay results. Conclusions The null hypothesis was rejected since S. mutans biofilm formation was influenced by hydrophilicity, surface acidity and chemical composition of the experimental resins. Further studies using a bioreactor are needed to confirm the results and clarify the role of the single factors. PMID:24954666

  6. Hydrophilicity of dentin bonding systems influences in vitro Streptococcus mutans biofilm formation.

    Science.gov (United States)

    Brambilla, Eugenio; Ionescu, Andrei; Mazzoni, Annalisa; Cadenaro, Milena; Gagliani, Massimo; Ferraroni, Monica; Tay, Franklin; Pashley, David; Breschi, Lorenzo

    2014-08-01

    To evaluate in vitro Streptococcus mutans (S. mutans) biofilm formation on the surface of five light-curing experimental dental bonding systems (DBS) with increasing hydrophilicity. The null hypothesis tested was that resin chemical composition and hydrophilicity does not affect S. mutans biofilm formation. Five light-curing versions of experimental resin blends with increasing hydrophilicity were investigated (R1, R2, R3, R4 and R5). R1 and R2 contained ethoxylated BisGMA/TEGDMA or BisGMA/TEGDMA, respectively, and were very hydrophobic, were representative of pit-and-fissure bonding agents. R3 was representative of a typical two-step etch-and-rinse adhesive, while R4 and R5 were very hydrophilic resins analogous to self-etching adhesives. Twenty-eight disks were prepared for each resin blend. After a 24h-incubation at 37°C, a multilayer monospecific biofilm of S. mutans was obtained on the surface of each disk. The adherent biomass was determined using the MTT assay and evaluated morphologically with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). R2 and R3 surfaces showed the highest biofilm formation while R1 and R4 showed a similar intermediate biofilm formation. R5 was more hydrophilic and acidic and was significantly less colonized than all the other resins. A significant quadratic relationship between biofilm formation and hydrophilicity of the resin blends was found. CLSM and SEM evaluation confirmed MTT assay results. The null hypothesis was rejected since S. mutans biofilm formation was influenced by hydrophilicity, surface acidity and chemical composition of the experimental resins. Further studies using a bioreactor are needed to confirm the results and clarify the role of the single factors. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  7. Experimental biofilms within drinking water treatment plant origin; evaluation of nutrient concentration and temperature influences upon their development

    Directory of Open Access Journals (Sweden)

    Anca FARKAS

    2009-11-01

    Full Text Available From the planktonic free-floating state, microorganisms pass to the solid state, the biofilm, cells being strongly attached to each other and usually to the interface. This changing in cells’ behavior induces surface colonization and complex interactions development within the biofilm. If the biofilm’s role into the natural aquatic habitats is, undoubtedly, a positive one, consisting in water self-purification, drinking water pipe networks biofouling can be responsible for a wide range of water quality and operational problems. This exploratory experiment was performed in order to investigate, in a time interval of 7 days, the influence of certain environmental factors such as nutrient concentration and temperature upon in vitro biofilm’s development, origin in the biofilm of water treatment plant. The method used for in vitro biofilm growth monitoring is the colorimetric measurement of the biomass. Descriptive analyses, including the mean value, variability, trends, correlations and graphic displays were performed. The correlation analysis shown that the biofilm development in the discussed experiment was influenced as by the origin source as by the temperature, time and nutrients concentration. The biomass increment was significantly different for the biofilms with clarifier and sand filter sites origin, grown at 22 oC, while at 8 oC, the differences were not significant from a statistical point of view. For all the dilutions, moments and temperatures considered, the biofilm’s development with clarifier origin registered was significantly higher than the biofilm with sand filter origin.

  8. Influence of biofilm thickness on micropollutants removal in nitrifying MBBRs

    DEFF Research Database (Denmark)

    Torresi, Elena; Andersen, Henrik Rasmus; Smets, Barth F.;

    The removal of pharmaceuticals was investigated in nitrifying Moving Bed Biofilm Reactors (MBBRs) containing carriers with different biofilm thicknesses. The biofilm with the thinnest thickness was found to have the highest nitrification and biotransformation rate for some key pharmaceuticals...

  9. Proteomic regulation during Legionella pneumophila biofilm development: decrease of virulence factors and enhancement of response to oxidative stress.

    Science.gov (United States)

    Khemiri, Arbia; Lecheheb, Sandra Ahmed; Chi Song, Philippe Chan; Jouenne, Thierry; Cosette, Pascal

    2014-06-01

    Legionella pneumophila (L. pneumophila) is a Gram-negative bacterium, which can be found worldwide in aquatic environments. It tends to persist because it is often protected within biofilms or amoebae. L. pneumophila biofilms have a major impact on water systems, making the understanding of the bacterial physiological adaptation in biofilms a fundamental step towards their eradication. In this study, we report for the first time the influence of the biofilm mode of growth on the proteome of L. pneumophila. We compared the protein patterns of microorganisms grown as suspensions, cultured as colonies on agar plates or recovered with biofilms formed on stainless steel coupons. Statistical analyses of the protein expression data set confirmed the biofilm phenotype specificity which had been previously observed. It also identified dozens of proteins whose abundance was modified in biofilms. Proteins corresponding to virulence factors (macrophage infectivity potentiator protein, secreted proteases) were largely repressed in adherent cells. In contrast, a peptidoglycan-associated lipoprotein (Lpg2043) and a peroxynitrite reductase (Lpg2965) were accumulated by biofilm cells. Remarkably, hypothetical proteins, that appear to be unique to the Legionella genus (Lpg0563, Lpg1111 and Lpg1809), were over-expressed by sessile bacteria.

  10. Resistance of biofilm-covered mortars to microbiologically influenced deterioration simulated by sulfuric acid exposure

    Energy Technology Data Exchange (ETDEWEB)

    Soleimani, Sahar, E-mail: ssoleima@connect.carleton.ca; Isgor, O. Burkan, E-mail: burkan_isgor@carleton.ca; Ormeci, Banu, E-mail: banu_ormeci@carleton.ca

    2013-11-15

    Following the reported success of biofilm applications on metal surfaces to inhibit microbiologically influenced corrosion, effectiveness and sustainability of E. coli DH5α biofilm on mortar surface to prevent microbiologically influenced concrete deterioration (MICD) are investigated. Experiments simulating microbial attack were carried out by exposing incrementally biofilm-covered mortar specimens to sulfuric acid solutions with pH ranging from 3 to 6. Results showed that calcium concentration in control reactors without biofilm was 23–47% higher than the reactors with biofilm-covered mortar. Formation of amorphous silica gel as an indication of early stages of acid attack was observed only on the control mortar specimens without biofilm. During acidification, the biofilm continued to grow and its thickness almost doubled from ∼ 30 μm before acidification to ∼ 60 μm after acidification. These results demonstrated that E. coli DH5α biofilm was able to provide a protective and sustainable barrier on mortar surfaces against medium to strong sulfuric acid attack. -- Highlights: •Effectiveness of E.coli DH5α biofilm to prevent MICD was studied. •Conditions that lead to MICD were simulated by chemical acidification. •Biofilm-covered mortar specimens were exposed to sulfuric acid solutions. •The presence of biofilm helped reduce the chemically-induced mortar deterioration. •Biofilm remained alive and continued to grow during the acidification process.

  11. Anticorrosive Influence of Acetobacter aceti Biofilms on Carbon Steel

    Science.gov (United States)

    France, Danielle Cook

    2016-09-01

    Microbiologically influenced corrosion (MIC) of carbon steel infrastructure is an emerging environmental and cost issue for the ethanol fuel industry, yet its examination lacks rigorous quantification of microbiological parameters that could reveal effective intervention strategies. To quantitatively characterize the effect of cell concentration on MIC of carbon steel, numbers of bacteria exposed to test coupons were systematically controlled to span four orders of magnitude throughout a seven-day test. The bacterium studied, Acetobacter aceti, has been found in ethanol fuel environments and can convert ethanol to the corrosive species acetic acid. A. aceti biofilms formed during the test were qualitatively evaluated with fluorescence microscopy, and steel surfaces were characterized by scanning electron microscopy. During exposure, biofilms developed more quickly, and test reactor pH decreased at a faster rate, when cell exposure was higher. Resulting corrosion rates, however, were inversely proportional to cell exposure, indicating that A. aceti biofilms are able to protect carbon steel surfaces from corrosion. This is a novel demonstration of corrosion inhibition by an acid-producing bacterium that occurs naturally in corrosive environments. Mitigation techniques for MIC that harness the power of microbial communities have the potential to be scalable, inexpensive, and green solutions to industrial problems.

  12. Carbon Source Influences Population Heterogeneity In Pseudomonas Putida Kt2440 Biofilms

    DEFF Research Database (Denmark)

    Juel Christensen, Anne-Mette; Sternberg, Claus; Molin, Søren

    2015-01-01

    Introduction: Pseudomonas putida is well known as a potential cell factory for many different biochemicals. Biofilm-based production can be advantageous for possibly toxic products due to increased chemical tolerance and robustness. Biofilm cells frequently differentiate, which challenges...... the benefits of biofilm-based production, and knowledge about factors driving the heterogeneity is therefore of importance.Methods: Biofilm flow chamber systems connected to confocal laser scanning microscopy were used to study biofilm structures of P. putida KT2440 at different carbon conditions. Subsequent...... plating of mature biofilm allowed for variant selection followed by pheno- and genotypic analysis.Results: Structure and cell differentiation in mature P. putida KT2440 biofilms were highly dependent on the type of carbon source utilised. Low glucose concentrations (0.3 mM – 10 mM) did not alter biofilm...

  13. Oxygen tension during biofilm growth influences the efficacy antimicrobial agents

    Directory of Open Access Journals (Sweden)

    Raquel Pippi ANTONIAZZI

    Full Text Available Abstract Objective To compare the antimicrobial efficacy of a 0.12% chlorhexidine (CHX and herbal green tea (Camellia sinensis solution on established biofilms formed at different oxygen tensions in an in situ model. Method Twenty-five dental students were eligible for the study. In situ devices with standardized enamel specimens (ES facing the palatal and buccal sides were inserted in the mouths of volunteers for a 7 day period. No agent was applied during the first four days. From the fifth day onward, both agents were applied to the test ES group and no agent was applied to the control ES group. After 7 days the ES fragments were removed from the devices, sonicated, plated on agar, and incubated for 24 h at 37 °C to determine and quantify the colony forming units (CFUs. Result CHX had significantly higher efficacy compared to green tea on the buccal (1330 vs. 2170 CFU/µL and palatal (2250 vs. 2520 CFU/µL ES. In addition, intragroup comparisons showed significantly higher efficacy in buccal ES over palatal ES (1330 vs. 2250 CFU/µL for CHX and 2170 vs, 2520 CFU/µL for CV for both solutions. Analysis of the ES controls showed significantly higher biofilm formation in palatal ES compared to buccal ES. Conclusion CHX has higher efficacy than green tea on 4-day biofilms. The efficacy of both agents was reduced for biofilms grown in a low oxygen tension environment. Therefore, the oxygen tension environment seems to influence the efficacy of the tested agents.

  14. Influence of biofilm carriers on membrane fouling propensity in moving biofilm membrane bioreactor.

    Science.gov (United States)

    Jamal Khan, S; Zohaib-Ur-Rehman; Visvanathan, C; Jegatheesan, V

    2012-06-01

    In moving biofilm membrane bioreactor (MB-MBR) sponge carriers for biofilm growth were coupled with conventional submerged membrane bioreactor (C-MBR). This study compared the fouling propensity of C-MBR with MB-MBR and investigated factors affecting fouling variations in both the systems. Membrane fouling tendencies were monitored in terms of trans-membrane pressure (TMP) and the fouling characterization included membrane fouling resistances in situ and specific cake resistance (SCR) in batch filtration cell. Comparison of TMP profiles depicted prolong filtration periods in MB-MBR. Cake layer resistance (R(c)), pore blocking resistance (R(p)) as well as SCR were higher in C-MBR. The study reveals that hybrid biomass in MB-MBR creates relatively more porous cake structure in the absence of filamentous bacteria which were found in abundance in C-MBR. Filamentous bacteria were also responsible for the release of high concentration of carbohydrates in the form of soluble extra polymeric substance (EPS) contributing to higher R(p) in C-MBR.

  15. A fluid dynamics multidimensional model of biofilm growth: stability, influence of environment and sensitivity

    CERN Document Server

    Clarelli, Fabrizio; Natalini, Roberto; Ribot, Magali

    2014-01-01

    In this article, we study in details the fluid dynamics system proposed in Clarelli et al (2013) to model the formation of cyanobacteria biofilms. After analyzing the linear stability of the unique non trivial equilibrium of the system, we introduce in the model the influence of light and temperature, which are two important factors for the development of cyanobacteria biofilm. Since the values of the coefficients we use for our simulations are estimated through information found in the literature, some sensitivity and robustness analyses on these parameters are performed. All these elements enable us to control and to validate the model we have already derived and to present some numerical simulations in the 2D and the 3D cases.

  16. A fluid dynamics multidimensional model of biofilm growth: stability, influence of environment and sensitivity.

    Science.gov (United States)

    Clarelli, F; Di Russo, C; Natalini, R; Ribot, M

    2016-12-01

    In this article, we study in detail the fluid dynamics system proposed in Clarelli et al. (2013, J. Math. Biol., 66, 1387-1408) to model the formation of cyanobacteria biofilms. After analysing the linear stability of the unique non-trivial equilibrium of the system, we introduce in the model the influence of light and temperature, which are two important factors for the development of a cyanobacteria biofilm. Since the values of the coefficients we use for our simulations are estimated through information found in the literature, some sensitivity and robustness analyses on these parameters are performed. All these elements enable us to control and to validate the model we have already derived and to present some numerical simulations in the 2D and the 3D cases.

  17. Biofilm structure and its influence on clogging in drip irrigation emitters distributing reclaimed wastewater

    Institute of Scientific and Technical Information of China (English)

    YAN Dazhuang; BAI Zhihui; Mike Rowan; GU Likun; Ren Shumei; YANG Peiling

    2009-01-01

    Using reclaimed wastewater for crop irrigation is a practical alternative to discharge wastewater treatment plant effluents into surface waters.However,biofouling has been identified as a major contributor to emitter clogging in drip irrigation systems distributing reclaimed wastewater.Little is known about the biofilm structure and its influence on clogging in the drip emitter flow path.This study was first to investigate the microbial characteristics of mature biofilms present in the emitters and the effect of flow path structures on the biofilm microbial communities.The analysis of biofilm matrix structure using a scanning electron microscopy (SEM) revealed that particles in the matrix of the biofilm coupled extracellular polysaccharides (EPS) and formed sediment in the emitter flow path.Analysis of biofilm mass including protein,polysaccharide and phospholipid fatty acids (PLFAs) showed that emitter flow path style influenced biofilm community structure and diversity.The correlations of biofilm biomass and discharge reduction after 360 h irrigation were computed and suggest that PFLAs provide the best correlation coefficient.Comparatively,the emitter with the unsymmetrical dentate structure and shorter flow path (Emitter C) had the best anti-clogging capability.By optimizing the dentate structure,the internal flow pattern within the flow path could be enhanced as an important method to control the biofilm within emitter flow path.This study established electron microscope techniques and biochemical microbial analysis methods that may provide a framework for future emitter biofilm studies.

  18. Influence of Melaleuca alternifolia oil nanoparticles on aspects of Pseudomonas aeruginosa biofilm.

    Science.gov (United States)

    Comin, Vanessa M; Lopes, Leonardo Q S; Quatrin, Priscilla M; de Souza, Márcia E; Bonez, Pauline C; Pintos, Francieli G; Raffin, Renata P; Vaucher, Rodrigo de A; Martinez, Diego S T; Santos, Roberto C V

    2016-04-01

    The Pseudomonas aeruginosa is a gram-negative bacillus and frequent cause of infection. This microorganism is resistant intrinsically to various drugs. The P. aeruginosa is associated with the biofilm formation, which causes worsen the prognosis and difficulty the treatment. The influence of Melaleuca alternifolia oil or "tree of tee" oil (TTO) and TTO nanoparticles on adhesion of P. aeruginosa in buccal epithelial cells was investigated. Also was determined the antimicrobial and antibiofilm activity against this microorganism. The TTO nanoparticles were produced by deposition of preformed polymer and the physic-chemical properties of nanoparticles were measured by electrophoresis and dynamic light scattering. The characterization of nanoparticle showed acceptable values for diameter and zeta potential. The evaluation of antimicrobial and antibiofilm activity against P. aeruginosa PAO1 was performed by microdilution indicating the minimal inhibitory concentration, and the potential antibiofilm. It was verified the action on virulence factors such the motility, besides the influence on adhesion in buccal epithelial cells. Both oil and nanoparticles showed a decrease in adhesion of microorganisms to buccal cells, decrease of biofilm and interfering on P. aeruginosa PAO1 motility. The nanostructuration of TTO, shows be a viable alternative against formed biofilm microorganisms.

  19. Rapid depletion of dissolved oxygen in 96-well microtiter plate Staphylococcus epidermidis biofilm assays promotes biofilm development and is influenced by inoculum cell concentration.

    Science.gov (United States)

    Cotter, John J; O'Gara, James P; Casey, Eoin

    2009-08-01

    Biofilm-related research using 96-well microtiter plates involves static incubation of plates indiscriminate of environmental conditions, making oxygen availability an important variable which has not been considered to date. By directly measuring dissolved oxygen concentration over time we report here that dissolved oxygen is rapidly consumed in Staphylococcus epidermidis biofilm cultures grown in 96-well plates irrespective of the oxygen concentration in the gaseous environment in which the plates are incubated. These data indicate that depletion of dissolved oxygen during growth of bacterial biofilm cultures in 96-well plates may significantly influence biofilm production. Furthermore higher inoculum cell concentrations are associated with more rapid consumption of dissolved oxygen and higher levels of S. epidermidis biofilm production. Our data reveal that oxygen depletion during bacterial growth in 96-well plates may significantly influence biofilm production and should be considered in the interpretation of experimental data using this biofilm model.

  20. Influence of medium composition on the characteristics of a denitrifying biofilm formed by Alcaligenes denitrificans in a fluidised bed reactor

    OpenAIRE

    Alves, C. F.; Melo, L. F.; Vieira, M. J.

    2002-01-01

    The influence of the ratio carbon/nitrogen and phosphorus concentration on the performance of a biofilm fluidised bed reactor used for denitrification and on the properties of the biofilm was studied. Although the removal efficiencies of C and N reached steady-state values, the thickness of the biofilm steadily increased. The dry density of the biofilm did not seem to be dependent on the loading conditions, although a denser biofilm was obtained when there was no nutrient limitation ...

  1. Microbial Biofilms in Endodontic Infections: An Update Review

    Directory of Open Access Journals (Sweden)

    Zahed Mohammadi

    2013-04-01

    Full Text Available Biofilms and microbial aggregates are the common mechanisms for the survival of bacteria in nature. In other words, the ability to form biofilms has been regarded as a virulence factor. Microbial biofilms play an essential role in several infectious diseases such as pulp and periradicular pathosis. The aim of this article was to review the adaptation mechanisms of biofilms, their roles in pulpal and periapical pathosis, factors influencing biofilm formation, mechanisms of their antimicrobial resistance, models developed to create biofilms, observation techniques of endodontic biofilms, and the effects of root canal irrigants and medicaments as well as lasers on endodontic biofilms. The search was performed from 1982 to December 2010, and was limited to papers in English language. The keywords searched on Medline were "biofilms and endodontics," "biofilms and root canal irrigation," "biofilms and intra-canal medicament," and "biofilms and lasers." The reference section of each article was manually searched to find other suitable sources of information.

  2. [The influence of cell surface hydrophobicity Candida sp. on biofilm formation on different biomaterials].

    Science.gov (United States)

    Ciok-Pater, Emilia; Gospodarek, Eugenia; Prazyńska, Małgorzata; Bogiel, Tomasz

    2009-01-01

    The ability of yeasts to form biofilm is believed to play an important role in patomechanism of fungal infection. Candida sp. is considered to form biofilm on surfaces of biomaterials used in production of catheters, drains and prosthesis. Therefore this may lead to serious problems in patients with biomaterials used for diagnostic or therapeutic purposes. The aim of the study was to evaluate the influence of cell surface hydrophobicity (CSH) of Candida sp. on biofilm formation on different biomaterials. CSH was evaluated by two methods: Salt Aggregation Test (SAT) and Microbe Adhesion to Hydrocarbon Test (MATH). Biofilm formation on different biomaterials was measured by Richard's method after 72 hour incubation at 37 degrees C. Candida biofilm formation occurred more frequently in case of strains exhibiting hydrophobic than hydrophilic properties of cell surface. The statistically significant correlation between CSH and ability of biofilm formation on different biomaterials was observed (p < 0.05).

  3. Influence of microleakage, surface roughness and biofilm control on secondary caries formation around composite resin restorations: an in situ evaluation

    Directory of Open Access Journals (Sweden)

    Fábio Garcia Lima

    2009-02-01

    Full Text Available This study was carried out to evaluate in situ the influence of microleakage, surface roughness and biofilm control on caries formation around composite resin restorations. During 28 days, 12 volunteers wore palatal devices containing bovine enamel slabs restored with composite resin. Restorations were made without leakage, when the adhesive system was applied, or with leakage, when adhesive system was omitted. Half of the restorations in each group were finished and the remaining were finished and polished. In one side of the palatal device, biofilm was left to accumulate over the restored slabs, and in the other side dental slabs were brushed, to allow biofilm removal. There was an extraoral application of 20% sucrose solution (8x/day over the enamel slabs. The formation of caries lesions (white spots was evaluated by visual inspection under stereomicroscopy. Additionally, the dental slabs were sectioned and observed under polarized light microscopy. Data were submitted to Kruskal-Wallis test and Spearman's correlation test at 5% significance level. Polishing and bonding were not significant factors regarding white spot formation (p>0.05. Biofilm control (brushing was associated with reduction of caries formation close to the restorations (p<0.01. Polarized light microscopy confirmed the visual inspection findings. These results suggest that while microleakage and surface roughness did not influence caries lesion formation, biofilm control may prevent the enamel demineralization.

  4. Influence of microleakage, surface roughness and biofilm control on secondary caries formation around composite resin restorations: an in situ evaluation.

    Science.gov (United States)

    Lima, Fábio Garcia; Romano, Ana Regina; Correa, Marcos Britto; Demarco, Flávio Fernando

    2009-01-01

    This study was carried out to evaluate in situ the influence of microleakage, surface roughness and biofilm control on caries formation around composite resin restorations. During 28 days, 12 volunteers wore palatal devices containing bovine enamel slabs restored with composite resin. Restorations were made without leakage, when the adhesive system was applied, or with leakage, when adhesive system was omitted. Half of the restorations in each group were finished and the remaining were finished and polished. In one side of the palatal device, biofilm was left to accumulate over the restored slabs, and in the other side dental slabs were brushed, to allow biofilm removal. There was an extraoral application of 20% sucrose solution (8x/day) over the enamel slabs. The formation of caries lesions (white spots) was evaluated by visual inspection under stereomicroscopy. Additionally, the dental slabs were sectioned and observed under polarized light microscopy. Data were submitted to Kruskal-Wallis test and Spearman's correlation test at 5% significance level. Polishing and bonding were not significant factors regarding white spot formation (p>0.05). Biofilm control (brushing) was associated with reduction of caries formation close to the restorations (p<0.01). Polarized light microscopy confirmed the visual inspection findings. These results suggest that while microleakage and surface roughness did not influence caries lesion formation, biofilm control may prevent the enamel demineralization.

  5. Microenvironment and microbiology of skin wounds: the role of bacterial biofilms and related factors.

    Science.gov (United States)

    Scalise, A; Bianchi, A; Tartaglione, C; Bolletta, E; Pierangeli, M; Torresetti, M; Marazzi, M; Di Benedetto, G

    2015-01-01

    Wound healing is a systemic response to injury that impacts the entire body and not just the site of tissue damage; it represents one of the most complex biological processes. Our knowledge of wound healing continues to evolve and it is now clear that the wound microenvironment plays a crucial role. The interactions between cells and the surface microenvironment, referred to as the "biofilm," contributes to skin homeostasis and healing. Understanding the functional complexity of the wound microenvironment informs how various factors such as age, ischemia, or bacterial infections can impair or arrest the normal healing processes, and it also allows for the possibility of acting therapeutically on healing defects with microenvironment manipulation. Microbes represent a particularly important factor for influencing the wound microenvironment and therefore wound healing. Moreover, the role of infections, particularly those that are sustained by biofilm-forming bacteria, is mutually related to other microenvironment aspects, such as humidity, pH, metalloproteinases, and reactive oxygen species, on which the modern research of new therapeutic strategies is focused. Today, chronic wounds are a rapidly growing health care burden and it is progressively understood that many non-healing wounds might benefit from therapies that target microorganisms and their biofilm communities. There is no doubt that host factors like perfusion impairments, venous insufficiency, pressure issues, malnutrition, and comorbidities strongly impact the healing processes and therefore must be targeted in the therapeutic management, but this approach might be not enough. In this article, we detail how bacterial biofilms and related factors impair wound healing, the reasons they must be considered a treatment target that is as important as the host's local and systemic pathologic conditions, and the latest therapeutic strategies derived from the comprehension of the wound microenvironment. Copyright

  6. Quorum Sensing Influences Burkholderia thailandensis Biofilm Development and Matrix Production.

    Science.gov (United States)

    Tseng, Boo Shan; Majerczyk, Charlotte D; Passos da Silva, Daniel; Chandler, Josephine R; Greenberg, E Peter; Parsek, Matthew R

    2016-10-01

    Members of the genus Burkholderia are known to be adept at biofilm formation, which presumably assists in the survival of these organisms in the environment and the host. Biofilm formation has been linked to quorum sensing (QS) in several bacterial species. In this study, we characterized Burkholderia thailandensis biofilm development under flow conditions and sought to determine whether QS contributes to this process. B. thailandensis biofilm formation exhibited an unusual pattern: the cells formed small aggregates and then proceeded to produce mature biofilms characterized by "dome" structures filled with biofilm matrix material. We showed that this process was dependent on QS. B. thailandensis has three acyl-homoserine lactone (AHL) QS systems (QS-1, QS-2, and QS-3). An AHL-negative strain produced biofilms consisting of cell aggregates but lacking the matrix-filled dome structures. This phenotype was rescued via exogenous addition of the three AHL signals. Of the three B. thailandensis QS systems, we show that QS-1 is required for proper biofilm development, since a btaR1 mutant, which is defective in QS-1 regulation, forms biofilms without these dome structures. Furthermore, our data show that the wild-type biofilm biomass, as well as the material inside the domes, stains with a fucose-binding lectin. The btaR1 mutant biofilms, however, are negative for fucose staining. This suggests that the QS-1 system regulates the production of a fucose-containing exopolysaccharide in wild-type biofilms. Finally, we present data showing that QS ability during biofilm development produces a biofilm that is resistant to dispersion under stress conditions. The saprophyte Burkholderia thailandensis is a close relative of the pathogenic bacterium Burkholderia pseudomallei, the causative agent of melioidosis, which is contracted from its environmental reservoir. Since most bacteria in the environment reside in biofilms, B. thailandensis is an ideal model organism for

  7. Study of biofilm influenced corrosion on cast iron pipes in reclaimed water

    Science.gov (United States)

    Zhang, Haiya; Tian, Yimei; Wan, Jianmei; Zhao, Peng

    2015-12-01

    Biofilm influenced corrosion on cast iron pipes in reclaimed water was systemically studied using the weight loss method and electrochemical impedance spectroscopy (EIS). The results demonstrated that compared to sterile water, the existence of the biofilm in reclaimed water promoted the corrosion process significantly. The characteristics of biofilm on cast iron coupons were examined by the surface profiler, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The bacterial counts in the biofilm were determined using the standard plate count method and the most probable number (MPN). The results demonstrated that the corrosion process was influenced by the settled bacteria, EPS, and corrosion products in the biofilm comprehensively. But, the corrosion mechanisms were different with respect to time and could be divided into three stages in our study. Furthermore, several corresponding corrosion mechanisms were proposed for different immersion times.

  8. Influence of methylene blue-mediated photodynamic therapy on the resistance to detachment of streptococcus mutans biofilms from titanium substrata

    Science.gov (United States)

    Sharab, Lina Y.

    In dental settings, as well as in other natural systems, plaque-forming microorganisms develop biofilms in which the microbes become protected via their own phenotypic changes and their polymeric exudates from disinfection by washes and antibiotics. Photodynamic Therapy (PDT) is variably effective against these microorganisms, depending on such factors as whether the bacteria are Gram positive or Gram negative, plaque age and thickness, and internal biofilm oxygen concentration. This investigation applied a novel combination of PDT and water-jet impingement techniques to Streptococcus mutans (ATCC strain 27351)-formed biofilms on commercially pure titanium (cpTi) starting with three different phases (ages) of the bacteria, to examine whether the detachment shear stress --as a signature for the work required for removal of the biofilms- would be affected by prior PDT treatment independently from microbial viability. Biofilms were grown with sucrose addition to Brain Heart Infusion media, producing visible thick films and nearly invisible thin films (within the same piece) having the same numbers of culturable microorganisms, the thicker films having greater susceptibility to detachment by water--jet impingement. Colony-forming-unit (CFU) counts routinely correlated well with results from a spectrophotometric Alamar Blue (AB) assay. Use of Methylene Blue (MB) as a photosensitizer (PS) for PDT of biofilms did not interfere with the AB assay, but did mask AB reduction spectral changes when employed with planktonic organisms. It was discovered in this work that PD-treated microbial biofilms, independently from starting or PS-influenced microorganism viability, were significantly (p<0.05) and differentially more easily delaminated and ultimately removed from their substrata biomaterials by the hydrodynamic forces of water-jet impingement. Control biofilms of varying thickness, not receiving PDT treatment, required between 144 and 228 dynes/cm2 of shear stress to

  9. Effect of Cinnamon Oil on Quorum Sensing-Controlled Virulence Factors and Biofilm Formation in Pseudomonas aeruginosa.

    Science.gov (United States)

    Kalia, Manmohit; Yadav, Vivek Kumar; Singh, Pradeep Kumar; Sharma, Deepmala; Pandey, Himanshu; Narvi, Shahid Suhail; Agarwal, Vishnu

    2015-01-01

    Quorum sensing (QS) is a system of stimuli and responses in bacterial cells governed by their population density, through which they regulate genes that control virulence factors and biofilm formation. Despite considerable research on QS and the discovery of new antibiotics, QS-controlled biofilm formation by microorganisms in clinical settings has remained a problem because of nascent drug resistance, which requires screening of diverse compounds for anti-QS activities. Cinnamon is a dietary phytochemical that is traditionally used to remedy digestive problems and assorted contagions, which suggests that cinnamon might contain chemicals that can hinder the QS process. To test this hypothesis, the anti-QS activity of cinnamon oil against P. aeruginosa was tested, measured by the inhibition of biofilm formation and other QS-associated phenomena, including virulence factors such as pyocyanin, rhamnolipid, protease, alginate production, and swarming activity. To this end, multiple microscopy analyses, including light, scanning electron and confocal microscopy, revealed the ability of cinnamon oil to inhibit P. aeruginosa PAO1 biofilms and their accompanying extracellular polymeric substances. This work is the first to demonstrate that cinnamon oil can influence various QS-based phenomena in P. aeruginosa PAO1, including biofilm formation.

  10. Influence of chemical speciation and biofilm composition on mercury accumulation by freshwater biofilms.

    Science.gov (United States)

    Dranguet, P; Le Faucheur, S; Cosio, C; Slaveykova, V I

    2017-01-25

    Mercury (Hg) is a pollutant of high concern for aquatic systems due to the biomagnification of its methylated form along the food chain. However, in contrast to other metals, gaining knowledge of its bioavailable forms for aquatic microorganisms remains challenging, making Hg risk assessment difficult. Ubiquitous and sessile freshwater biofilms are well known to accumulate and to transform Hg present in their ambient environment. The present study thus aims to evaluate whether non-extractable (proxy of intracellular) Hg accumulated by biofilms could be a good indicator of Hg bioavailability for microorganisms in freshwater. To that end, the link between Hg concentration and speciation, as well as biofilm composition (percentage of abiotic, biotic, chlorophyll and phycocyanin-fractions and abundance of dsrA, gcs, merA and hgcA bacterial genes) and biofilm Hg accumulation was examined. The studied biofilms were grown on artificial substrata in four reservoirs along the Olt River (Romania), which was contaminated by Hg coming from chlor-alkali plant effluents. The 0.45 μm-filterable Hg concentrations in ambient waters were measured and inorganic IHg speciation was modelled. Biofilms were analyzed for their non-extractable IHg and methylmercury (MeHg) contents as well as for their composition. The non-extractable IHg content was related, but not significantly, to the concentration of total IHg (r(2) = 0.88, p = 0.061) whereas a significant correlation was found with the predicted IHg concentration that is not bound to dissolved organic matter (r(2) = 0.95, p = 0.027), despite its extremely low concentrations (10(-25) M), showing a limitation of the thermodynamic Hg modelling to predict Hg bioavailability. The studied biofilms were different in biomass and composition and a principal component analysis showed that the non-extractable IHg content correlated with the abundance of the merA and hgcA genes, while MeHg accumulation was only linked with the abundance of the r

  11. Ambroxol influences voriconazole resistance of Candida parapsilosis biofilm.

    Science.gov (United States)

    Pulcrano, Giovanna; Panellis, Dimitrios; De Domenico, Giovanni; Rossano, Fabio; Catania, Maria Rosaria

    2012-06-01

    The ability to form biofilm on different surfaces is typical of most Candida species. Microscopic structure and genetic aspects of fungal biofilms have been the object of many studies because of very high resistance to antimycotic agents because of the scarce permeability of the external matrix and to the alterations in cell metabolism. In our study, 31 isolates of Candida parapsilosis, isolated from bloodstream infections, were tested for their ability to produce biofilm and were found to be good producers. The susceptibility to voriconazole, assayed by colorimetrical XTT assay, revealed a very elevated minimum inhibitory concentrations for sessile cells in comparison with planktonic ones. The addition of ambroxol, a mucolytic agent, increased the susceptibility of biofilm forming cells to voriconazole. Expression of the efflux pump genes CDR and MDR was analyzed in biofilms alone or treated with ambroxol, evidencing a role of ambroxol in the expression of genes involved in azole resistance mechanisms of C. parapsilosis biofilms. In conclusion, our data seem to encourage the use of different substances in combination with classical antimycotics, with the aim of finding a solution to the increasing problem of the resistance of biofilms formed on medical devices by nonalbicans Candida species.

  12. Impact of food-related environmental factors on the adherence and biofilm formation of natural Staphylococcus aureus isolates.

    Science.gov (United States)

    Vázquez-Sánchez, Daniel; Habimana, Olivier; Holck, Askild

    2013-02-01

    Staphylococcus aureus is a pathogenic bacterium capable of developing biofilms on food-processing surfaces, a pathway leading to cross contamination of foods. The purpose of this study was to investigate the influence of environmental stress factors found during seafood production on the adhesion and biofilm-forming properties of S. aureus. Adhesion and biofilm assays were performed on 26 S. aureus isolated from seafood and two S. aureus reference strains (ATCC 6538 and ATCC 43300). Cell surface properties were evaluated by affinity measurements to solvents in a partitioning test, while adhesion and biofilm assays were performed in polystyrene microplates under different stress conditions of temperature, osmolarity, and nutrient content. The expression of genes implicated in the regulation of biofilm formation (icaA, rbf and σ( B )) was analyzed by reverse transcription and quantitative real time PCR. In general, S. aureus isolates showed moderate hydrophobic properties and a marked Lewis-base character. Initial adhesion to polystyrene was positively correlated with the ionic strength of the growth medium. Most of the strains had a higher biofilm production at 37 °C than at 25 °C, promoted by the addition of glucose, whereas NaCl and MgCl(2) had a lower impact markedly affected by incubation temperatures. Principal Component Analysis revealed a considerable variability in adhesion and biofilm-forming properties between S. aureus isolates. Transcriptional analysis also indicated variations in gene expression between three characteristic isolates under different environmental conditions. These results suggested that the prevalence of S. aureus strains on food-processing surfaces is above all conditioned by the ability to adapt to the environmental stress conditions present during food production. These findings are relevant for food safety and may be of importance when choosing the safest environmental conditions and material during processing, packaging, and

  13. Analysis and modelling of predation on biofilm activated sludge process: Influence on microbial distribution, sludge production and nutrient dosage.

    Science.gov (United States)

    Revilla, Marta; Galán, Berta; Viguri, Javier R

    2016-11-01

    The influence of predation on the biofilm activated sludge (BAS) process is studied using a unified model that incorporates hydrolysis and predation phenomena into the two stages of the BAS system: moving bed biofilm reactor pre-treatment (bacterial-predator stage) and activated sludge (predator stage). The unified model adequately describes the experimental results obtained in a cellulose and viscose full-scale wastewater plant and has been used to evaluate the role and contribution of predator microorganisms towards removal of COD, nutrient requirements, sludge production and microbial distribution. The results indicate that predation is the main factor responsible for the reduction of both nutrient requirements and sludge production. Furthermore, increasing the sludge retention time (SRT) does not influence the total biomass content in the AS reactor of a BAS process in two different industrial wastewater treatments.

  14. Streptococcus Sanguis Biofilm Architecture and Its Influence on Titanium Corrosion in Enriched Artificial Saliva

    Directory of Open Access Journals (Sweden)

    Lei Li

    2017-03-01

    Full Text Available Bacteria biofilm formation on metals is well-known, while biofilm architecture varies under different conditions. To date, few studies have determined the possible contribution to corrosion of titanium made by biofilm architecture. We investigated the interaction between the oral Streptococcus sanguis biofilm architecture and its influence on titanium corrosion in enriched artificial saliva using electrochemical methods and microscopic study. Patchy biofilms were observed on titanium surface after being immersed in solution containing S. sanguis. The thickness and size of the patchy biofilms increased with an increase of immersion time. The extensive pits were clearly observed by scanning electron microscopy, showing that adsorption of S. sanguis on titanium promoted the localized corrosion. The electrochemical results indicated that the corrosion rates were clearly accelerated in the presence of S. sanguis. The low icorr and high Rt in the first 48 h indicated that a typical passive behavior still remained. Our study showed that the pitting corrosion of titanium was mainly attributed to the formation of a self-catalytic corrosion cell by the co-effect of patchy biofilm and organic acid secreted by S. sanguis.

  15. The influence of subminimal inhibitory concentrations of benzalkonium chloride on biofilm formation by Listeria monocytogenes.

    Science.gov (United States)

    Ortiz, Sagrario; López, Victoria; Martínez-Suárez, Joaquín V

    2014-10-17

    Disinfectants, such as benzalkonium chloride (BAC), are commonly used to control Listeria monocytogenes and other pathogens in food processing plants. Prior studies have demonstrated that the resistance to BAC of L. monocytogenes was associated with the prolonged survival of three strains of molecular serotype 1/2a in an Iberian pork processing plant. Because survival in such environments is related to biofilm formation, we hypothesised that the influence of BAC on the biofilm formation potential of L. monocytogenes might differ between BAC-resistant strains (BAC-R, MIC≥10mg/L) and BAC-sensitive strains (BAC-S, MIC≤2.5mg/L). To evaluate this possibility, three BAC-R strains and eight BAC-S strains, which represented all of the molecular serotype 1/2a strains detected in the sampled plant, were compared. Biofilm production was measured using the crystal violet staining method in 96-well microtitre plates. The BAC-R strains produced significantly (p<0.05) less biofilm than the BAC-S in the absence of BAC, independent of the rate of planktonic growth. In contrast, when the biofilm values were measured in the presence of BAC, one BAC-R strain (S10-1) was able to form biofilm at 5mg/L of BAC, which prevented biofilm formation among the rest of the strains. A genetic determinant of BAC resistance recently described in L. monocytogenes (Tn6188) was detected in S10-1. When a BAC-S strain and its spontaneous mutant BAC-R derivative were compared, resistance to BAC led to biofilm formation at 5mg/L of BAC and to a significant (p<0.05) stimulation of biofilm formation at 1.25mg/L of BAC, which significantly (p<0.05) reduced the biofilm level in the parent BAC-S strain. Our results suggest that the effect of subminimal inhibitory concentrations of BAC on biofilm production by L. monocytogenes might differ between strains with different MICs and even between resistant strains with similar MICs but different genetic determinants of BAC resistance. For BAC-R strains similar

  16. Autoinducer-2 influences interactions amongst pioneer colonizing streptococci in oral biofilms.

    Science.gov (United States)

    Cuadra-Saenz, Giancarlo; Rao, Dhana L; Underwood, Adam J; Belapure, Sneha A; Campagna, Shawn R; Sun, Zhichao; Tammariello, Steven; Rickard, Alexander H

    2012-07-01

    Streptococcus gordonii and Streptococcus oralis are among the first bacterial species to colonize clean tooth surfaces. Both produce autoinducer-2 (AI-2): a family of inter-convertible cell-cell signal molecules synthesized by the LuxS enzyme. The overall aim of this work was to determine whether AI-2 alters interspecies interactions between S. gordonii DL1 and S. oralis 34 within dual-species biofilms in flowing human saliva. Based upon AI-2 bioluminescence assays, S. gordonii DL1 produced more AI-2 activity than S. oralis 34 in batch culture, and both were able to remove AI-2 activity from solution. In single-species, saliva-fed flowcell systems, S. oralis 34 formed scant biofilms that were similar to the luxS mutant. Conversely, S. gordonii DL1 formed confluent biofilms while the luxS mutant formed architecturally distinct biofilms that possessed twofold greater biovolume than the wild-type. Supplementing saliva with 0.1-10 nM chemically synthesized AI-2 (csAI-2) restored the S. gordonii DL1 luxS biofilm phenotype to that which was similar to the wild-type; above or below this concentration range, biofilms were architecturally similar to that formed by the luxS mutant. In dual-species biofilms, S. gordonii DL1 was always more abundant than S. oralis 34. Compared with dual-species, wild-type biofilms, the biovolume occupied by S. oralis 34 was reduced by greater than sevenfold when neither species produced AI-2. The addition of 1 nM csAI-2 to the dual-species luxS-luxS mutant biofilms re-established the biofilm phenotype to resemble that of the wild-type pair. Thus, this work demonstrates that AI-2 can alter the biofilm structure and composition of pioneering oral streptococcal biofilms. This may influence the subsequent succession of other species into oral biofilms and the ecology of dental plaque.

  17. Influence of phosphorus availability on the community structure and physiology of cultured biofilms.

    Science.gov (United States)

    Li, Shuangshuang; Wang, Chun; Qin, Hongjie; Li, Yinxia; Zheng, Jiaoli; Peng, Chengrong; Li, Dunhai

    2016-04-01

    Biofilms have important effects on nutrient cycling in aquatic ecosystems. However, publications about the community structure and functions under laboratory conditions are rare. This study focused on the developmental and physiological properties of cultured biofilms under various phosphorus concentrations performed in a closely controlled continuous flow incubator. The results showed that the biomass (Chl a) and photosynthesis of algae were inhibited under P-limitation conditions, while the phosphatase activity and P assimilation rate were promoted. The algal community structure of biofilms was more likely related to the colonization stage than with the phosphorus availability. Cyanobacteria were more competitive than other algae in biofilms, particularly when cultured under low P levels. A dominance shift occurred from non-filamentous algae in the early stage to filamentous algae in the mid and late stages under P concentrations of 0.01, 0.1 and 0.6 mg/L. However, the total N content, dry weight biomass and bacterial community structure of biofilms were unaffected by phosphorus availability. This may be attributed to the low respiration rate, high accumulation of extracellular polymeric substances and high alkaline phosphatase activity in biofilms when phosphorus availability was low. The bacterial community structure differed over time, while there was little difference between the four treatments, which indicated that it was mainly affected by the colonization stage of the biofilms rather than the phosphorus availability. Altogether, these results suggested that the development of biofilms was influenced by the phosphorus availability and/or the colonization stage and hence determined the role that biofilms play in the overlying water.

  18. The influence of oral Veillonella species on biofilms formed by Streptococcus species.

    Science.gov (United States)

    Mashima, Izumi; Nakazawa, Futoshi

    2014-08-01

    Oral Veillonella, Veillonella atypica, Veillonella denticariosi, Veillonella dispar, Veillonella parvula, Veillonella rogosae, and Veillonella tobetsuensis are known as early colonizers in oral biofilm formation. To investigate the role of oral Veillonella, biofilms formed by the co-culture of Streptococcus gordonii, Streptococcus mutans, Streptococcus salivarius, or Streptococcus sanguinis, with oral Veillonella were examined at the species level. The amount of biofilm formed by S. mutans, S. gordonii, and S. salivarius in the presence of the six Veillonella species was greater than that formed in the control experiments, with the exception of S. mutans with V. dispar. In contrast, in the case of biofilm formation by S. sanguinis, the presence of Veillonella species reduced the amount of the biofilm, with the exception of V. parvula and V. dispar. The time-dependent changes in the amount of biofilm and the number of planktonic cells were grouped into four patterns over the 24 combinations. Only that of S. gordonii with V. tobetsuensis showed a unique pattern. These results indicate that the mode of action of this combination differed from that of the other combinations with respect to biofilm formation. It is possible that there may be several factors involved in the interaction between Streptococcus and Veillonella species.

  19. Influence of substratum position and acquired pellicle on Candida albicans biofilm

    Directory of Open Access Journals (Sweden)

    Indira Moraes Gomes Cavalcanti

    2013-11-01

    Full Text Available The purpose of this study was to evaluate the influence of the substratum position and the saliva acquired pellicle (AP on Candida albicans biofilm development. Poly(methylmethacrylate (PMMA disks were fabricated and randomly allocated to experimental groups: HNP (disks placed in a horizontal position and uncoated by pellicle, VNP (disks placed in a vertical position and uncoated by pellicle, HCP (disks placed in a horizontal position and coated by pellicle, and VCP (disks placed in a vertical position and coated by pellicle. Disks were placed in a 24-well plate and a suspension of 107 cells/mL of Candida albicans was added to each well for biofilm development. The plates were aerobically incubated at 35°C. The biofilms were evaluated at 1.5 (adhesion time point, 24, 48, 72, and 96 hours. The number of viable cells was quantified in terms of the colony-forming units per milliliter (CFU/mL. Metabolic activity was measured by the XTT assay. The biofilm structure was analyzed by scanning electron microscopy. The data were analyzed by three-way ANOVA followed by Tukey's test, with significance set at 5%. The vertical groups showed less biofilm formation and lower metabolic activity than the horizontal groups (ppp > 0.05. It can be concluded that the substratum position influenced biofilm development.

  20. Influence of biofilms on transport properties in porous media

    Science.gov (United States)

    Davit, Y.

    2015-12-01

    Microbial activity and biofilm growth in porous media can drastically modify transport properties such as permeability, longitudinal and transverse dispersion or effective reaction rates. Understanding these effects has proven to be a considerable challenge. Advances in this field have been hindered by the difficulty of modeling and visualizing these multi-phase non-linear effects across a broad range of spatial and temporal scales. To address these issues, we are developing a strategy that combines imaging techniques based on x-ray micro-tomography with homogenization of pore-scale transport equations. Here, we review recent progress in x-ray imaging of biofilms in porous media, with a particular focus on the contrast agents that are used to differentiate between the fluid and biofilm phases. We further show how the 3D distribution of the different phases can be used to extract specific information about the biofilm and how effective properties can be calculated via the resolution of closure problems. These closure problems are obtained using the method of volume averaging and must be adapted to the problem of interest. In hydrological systems, we show that a generic formulation for reactive solute transport is based on a domain decomposition approach at the micro-scale yielding macro-scale models reminiscent of multi-rate mass transfer approaches.

  1. Influence of incubation temperature on biofilm formation and corrosion of carbon steel by Serratia marcescens

    Science.gov (United States)

    Harimawan, Ardiyan; Devianto, Hary; Kurniawan, Ignatius Chandra; Utomo, Josephine Christine

    2017-01-01

    Microbial induced corrosion (MIC) or biocorrosion is one type of corrosion, directly or indirectly influenced by microbial activities, by forming biofilm and adhering on the metal surface. When forming biofilm, the microorganisms can produce extracellular products which influence the cathodic and anodic reactions on metal surfaces. This will result in electrochemical changes in the interface between the biofilm and the metal surface, leading to corrosion and deterioration of the metal. MIC might be caused by various types of microorganism which leads to different corrosion mechanism and reaction kinetics. Furthermore, this process will also be influenced by various environmental conditions, such as pH and temperature. This research is aimed to determine the effect of incubation temperature on corrosion of carbon steel caused by Serratia marcescens in a mixture solution of synthetic seawater with Luria Bertani medium with a ratio of 4:1. The incubation was performed for 19 days with incubation temperature of 30, 37, and 50°C. The analyses of biofilm were conducted by total plate count (TPC), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Biofilm was found to be evenly growth on the surface and increasing with increasing incubation temperature. It consists of functional group of alcohol, alkane, amine, nitro, sulfate, carboxylic acid, and polysulfide. The analyses of the corrosion were conducted by gravimetric and X-ray diffraction (XRD). Higher incubation temperature was found to increase the corrosion rate. However, the corrosion products were not detected by XRD analysis.

  2. Biofilm formation of the L. monocytogenes strain 15G01 is influenced by changes in environmental conditions.

    Science.gov (United States)

    Nowak, Jessika; Cruz, Cristina D; Palmer, Jon; Fletcher, Graham C; Flint, Steve

    2015-12-01

    Listeria monocytogenes 15G01, a strain belonging to the persistent pulsotype 5132, was isolated from a seafood processing plant in New Zealand. Simple monoculture assays using crystal violet staining showed good biofilm formation for this strain and it was therefore chosen to be further investigated in regard to its biofilm forming ability. To evaluate its behaviour in different conditions commonly encountered in food processing environments, biofilm assays and growth studies were performed using common laboratory media under a range of temperatures (20 °C, 30 °C and 37 °C). Furthermore, the effects of incubation time and different environmental conditions including static, dynamic and anaerobic incubation on biofilm formation were investigated. Changes in the environmental conditions resulted in different biofilm phenotypes of L. monocytogenes 15G01. We demonstrated that increasing temperature and incubation time led to a higher biofilm mass and that dynamic incubation has little effect on biofilm formation at 37 °C but encourages biofilm formation at 30 °C. Biofilm production at 20 °C was minimal regardless of the medium used. We furthermore observed that anaerobic environment led to reduced biofilm mass at 30 °C for all tested media but not at 37 °C. Biofilm formation could not be narrowed down to one factor but was rather dependent on multiple factors with temperature and medium having the biggest effects.

  3. The Influence of Marine Biofilms on Corrosion: A Concise Review

    Science.gov (United States)

    2008-01-01

    extensive literature on both mechanisms. High-grade stainless steels (e.g., Ni-Cr-Mo alloys), titanium alloys, and noble metals {e.g., platinum, gold) are...deposition of manganese and localized corrosion of 300 series stainless steels has been related directly to the biomineral - ized deposits on the surface [20...Thermodynamic arguments for enno- blement suggest that either a pH decrease at the metal /biofilm interface or a local increase of the partial pressure

  4. Virulence factors and biofilm production by isolates of Bacteroides fragilis recovered from dog intestinal tracts

    Directory of Open Access Journals (Sweden)

    Ana Catarina M. Reis

    2014-06-01

    Full Text Available Bacteroides fragilis colonizes dog guts both as a commensal and as an opportunistic pathogen. This study aims to evaluate virulence factors of 13 B. fragilis strains isolated from dog intestinal tracts and their ability for biofilm formation. Capsules were detected in all the evaluated strains. A total of 61.5% of all strains were biofilm producers. These attributes most likely play an important role in B. fragilis persistent colonization in the gut.

  5. Effects of different osmolarities on bacterial biofilm formation

    OpenAIRE

    2014-01-01

    Biofilm formation depends on several factors. The influence of different osmolarities on bacterial biofilm formation was studied. Two strains (Enterobacter sp. and Stenotrophomonas sp.) exhibited the most remarkable alterations. Biofilm formation is an important trait and its use has been associated to the protection of organisms against environmental stresses.

  6. Interactions of bacteria with diatoms: Influence on natural marine biofilms.

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, L.; DeCosta, P.M.; Anil, A.C.; Sawant, S.S.

    in this study cannot be ruled out. In the case of Vibrio species, a clear trend was noticed for V. cholerae in the ‘initial’ 2-day old biofilm community. V. cholerae was the only Vibrio species that showed a similar trend as diatoms, i.e., maximum abundance... was associated with sharp decrease in silicate and nitrate concentrations in most of the cases (Suppl. Fig. 3), reflecting utilization by the growing fouling diatom community. Effect of streptomycin and chloramphenicol on fouling diatom communities Pre...

  7. Silver colloidal nanoparticle stability: influence on Candida biofilms formed on denture acrylic.

    Science.gov (United States)

    Monteiro, Douglas Roberto; Takamiya, Aline Satie; Feresin, Leonardo Perina; Gorup, Luiz Fernando; de Camargo, Emerson Rodrigues; Delbem, Alberto Carlos Botazzo; Henriques, Mariana; Barbosa, Debora Barros

    2014-08-01

    Our aim in this study was to evaluate how the chemical stability of silver nanoparticles (SNs) influences their efficacy against Candida albicans and C. glabrata biofilms. Several parameters of SN stability were tested, namely, temperature (50ºC, 70ºC, and 100ºC), pH (5.0 and 9.0), and time of contact (5 h and 24 h) with biofilms. The control was defined as SNs without temperature treatment, pH 7, and 24 h of contact. These colloidal suspensions at 54 mg/L were used to treat mature Candida biofilms (48 h) formed on acrylic. Their efficacy was determined by total biomass and colony-forming unit quantification. Data were analyzed using analysis of variance and the Bonferroni post hoc test (α = 0.05). The temperature and pH variations of SNs did not affect their efficacy against the viable cells of Candida biofilms (P > 0.05). Moreover, the treatment periods were not decisive in terms of the susceptibility of Candida biofilms to SNs. These findings provide an important advantage of SNs that may be useful in the treatment of Candida-associated denture stomatitis.

  8. Influence of Biofilm Formation by Gardnerella vaginalis and Other Anaerobes on Bacterial Vaginosis.

    Science.gov (United States)

    Machado, António; Cerca, Nuno

    2015-12-15

    Bacterial vaginosis (BV) is the worldwide leading vaginal disorder among women of reproductive age. BV is characterized by the replacement of beneficial lactobacilli and the augmentation of anaerobic bacteria. Gardnerella vaginalis is a predominant bacterial species, but BV is also associated with other numerous anaerobes, such as Atopobium vaginae, Mobiluncus mulieris, Prevotella bivia, Fusobacterium nucleatum, and Peptoniphilus species. Currently, the role of G. vaginalis in the etiology of BV remains a matter of controversy. However, it is known that, in patients with BV, a biofilm is usually formed on the vaginal epithelium and that G. vaginalis is typically the predominant species. So, the current paradigm is that the establishment of a biofilm plays a key role in the pathogenesis of BV. This review provides background on the influence of biofilm formation by G. vaginalis and other anaerobes, from the time of their initial adhesion until biofilm formation, in the polymicrobial etiology of BV and discusses the commensal and synergic interactions established between them to understand the phenotypic shift of G. vaginalis biofilm formation to BV establishment.

  9. How do changes in dissolved oxygen concentration influence microbially-controlled phosphorus cycling in stream biofilms?

    Science.gov (United States)

    Saia, S. M.; Locke, N. A.; Regan, J. M.; Carrick, H. J.; Buda, A. R.; Walter, M. T.

    2014-12-01

    Advances in molecular microbiology techniques (e.g. epi-fluorescent microscopy and PCR) are making it easier to study the influence of specific microorganisms on nutrient transport. Polyphosphate accumulating organisms (PAOs) are commonly used in wastewater treatment plants to remove excess phosphorus (P) from effluent water. PAOs have also been identified in natural settings but their ecological function is not well known. In this study, we tested the hypothesis that PAOs in natural environments would release and accumulate P during anaerobic and aerobic conditions, respectively. We placed stream biofilms in sealed, covered tubs and subjected them to alternating air (aerobic conditions) and N2 gas (anaerobic condition) bubbling for 12 hours each. Four treatments investigated the influence of changing dissolved oxygen on micribially-controlled P cycling: (1) biofilms bubbled continuously with air, (2) biofilms bubbled alternatively with air and N2, (3) biocide treated biofilms bubbled continuously with air, and (4) biocide treated biofilms bubbled alternatively with air and N2. Treatments 3 and 4 serve as abiotic controls to treatments 1 and 2. We analyzed samples every 12 hours for soluble reactive P (SRP), temperature, dissolved oxygen, and pH. We also used fluorescent microscopy (i.e. DAPI staining) and PCR to verify the presence of PAOs in the stream biofilms. SRP results over the course of the experiment support our hypothesis that anaerobic and aerobic stream conditions may impact PAO mediated P release and uptake, respectively in natural environments. The results of these experiments draw attention to the importance of microbiological controls on P mobility in freshwater ecosystems.

  10. Influence of inoculum and anode surface properties on the selection of Geobacter-dominated biofilms.

    Science.gov (United States)

    Commault, Audrey S; Barrière, Frédéric; Lapinsonnière, Laure; Lear, Gavin; Bouvier, Solène; Weld, Richard J

    2015-11-01

    This study evaluated the impact of inoculum source and anode surface modification (carboxylate -COO(-) and sulfonamide -SO2NH2 groups) on the microbial composition of anode-respiring biofilms. These two factors have not previously been considered in detail. Three different inoculum sources were investigated, a dry aerobic soil, brackish estuarine mud and freshwater sediment. The biofilms were selected using a poised anode (-0.36 V vs Ag/AgCl) and acetate as the electron donor in a three-electrode configuration microbial fuel cell (MFC). Population profiling and cloning showed that all biofilms selected were dominated by Geobacter sp., although their electrochemical properties varied depending on the source inoculum and electrode surface modification. These findings suggest that Geobacter sp. are widespread in soils, even those that do not provide a continuously anaerobic environment, and are better at growing in the MFC conditions than other bacteria.

  11. Virulence factors and ability of staphylococci from bovine milk and the cowshed environment to biofilm formation.

    Science.gov (United States)

    Kot, B; Binek, T; Piechota, M; Wolska, K M; Zdunek, E; Platkowska, K

    2013-01-01

    The aim of this study was to examine virulence factors and the ability of S. aureus and CNS species isolated from milk of cows with mastitis to form biofilm, and to compare them with virulence factors of staphylococci from milk of cows without mastitis and cowshed environment. Most of S. aureus strains from cows with mastitis showed haemolytic activity (93.9%), among them 72.7% and 21.2% produced alpha- and beta-haemolysin, respectively. S. aureus from cows with mastitis symptoms produced proteases (above 48%) and esterase (42.4%). The highly significant relationship between the number of S. xylosus strains producing haemolysins (62%) and the origin of these strains from milk of cows with mastitis was observed. The ability to produce proteases was significantly associated with S. sciuri from milk of cows with mastitis. The ability of biofilm formation by staphylococcal strains from milk of cows with mastitis was greater than in strains from milk of cows without mastitis and the difference was significant (p < or = 0.05). The highest percentage of strains from milk of cows with mastitis were weak biofilm formers (48.6%), while 40% and 11.4% of strains were moderate and strong biofilm producers, respectively. S. xylosus showed the highest ability to form biofilm, while the lowest ability to form biofilm was observed in S. aureus and S. epidermidis. In conclusion, production of exotoxins and enzymes, and ability of biofilm formation shown by many CNS isolated from milk of cows with mastitis symptoms indicates that these features are important in pathogenesis of this disease.

  12. "Sticky Business": the Influence of Surface Biofilm on Particle Deposition and Infiltration in Streams

    Science.gov (United States)

    Salant, N. L.; Hassan, M. A.

    2007-12-01

    Fine particulate matter is an important component of many streambed processes. For example, the deposition and infiltration of fine inorganic sediment has been repeatedly shown to degrade benthic habitat for fish and other organisms (Hynes, 1970). In contrast, fine organic particles are a significant source of carbon to benthic organisms (Webster et al., 1987). The mechanisms and rates of particle entrainment and deposition are highly complex and ill-predicted by simple physical relations. For example, a number of field studies have shown that measured rates of particle deposition often differ from still-water particle settling velocities calculated from particle size and density (e.g. Cushing et al., 1993). Several studies have proposed that adhesion of particles to surface biofilm may explain why deposition rates are faster than predicted, but few have investigated this phenomenon (Battin et al., 2003). In addition, although biofilms have been shown to significantly alter near-bed and interstitial flow velocities (Dodds and Biggs, 2002), the effect of these changes on particle depositionhas not been explored. Biofilm is pervasive in rivers and streams throughout the world, thus it may play an important, and heretofore underestimated, role in the deposition of fine particles to the streambed. This study tests the hypothesis that biofilm amount and structure may alter fine particle deposition, entrainment, and infiltration by either direct adhesion or by changes to near-bed hydraulics. A series of experiments are being conducted in a small recirculating flume to test how the amount and structure of surface biofilm influences the water column distribution, surface deposition, and infiltration of fine particles under two different flow levels ('high' and 'low'). Two types of surface biofilm are being tested: open-weave, filamentous assemblages and low-profile, mucilaginous forms; both are compared to a reference substrate without biofilm. Natural rocks hosting

  13. The influence of marine biofilms on corrosion: A concise review

    Energy Technology Data Exchange (ETDEWEB)

    Little, Brenda J. [Naval Research Laboratory, Stennis Space Center, MS 39529, Code 7303, 228-688-5494 (United States)], E-mail: blittle@nrlssc.navy.mil; Lee, Jason S. [Naval Research Laboratory, Stennis Space Center, MS 39529, Code 7332, 228-688-4494 (United States)], E-mail: jlee@nrlssc.navy.mil; Ray, Richard I. [Naval Research Laboratory, Stennis Space Center, MS 39529, Code 7332, 228-688-4690 (United States)], E-mail: ray@nrlssc.navy.mil

    2008-12-01

    The following is a concise review of the literature that addresses the impact of marine biofilms on two phenomena-ennoblement of corrosion potential and sulfide derivitization due to sulfate-reducing bacteria. A universally defined mechanism of potential ennoblement has not been established. Extent of ennoblement varies among locations and the extent of ennoblement for a particular material cannot be used to predict an increased likelihood of localized corrosion. There is some controversy as to the susceptibility of low- and medium-grade stainless steels. Carbon steel and copper alloys are susceptible to sulfide derivitization but thermodynamic models cannot predict the susceptibility of these materials. Laboratory experiments designed to provide data on susceptibility to sulfide derivitization have produced conflicting results because of the following: (1) laboratory media can contain anions that inhibit localized corrosion, (2) laboratory media can contain yeast extract that interferes with electrochemical measurements, and (3) deaeration procedures can produce environments that are not conducive for the growth of sulfate-reducing bacteria. In general, alloys that undergo ennoblement are not vulnerable to sulfide derivitization and conversely, alloys that are subject to sulfide derivitization do not become ennobled.

  14. Determination of virulence factors and biofilm formation among isolates of vulvovaginal candidiasis

    Directory of Open Access Journals (Sweden)

    Tapan Majumdar

    2016-01-01

    Full Text Available Context: Under morphogenesis-inducing conditions, Candida spp. begins to undergo yeast-to-hypha switch. This shift from commensal to pathogenic state is dependent on several virulence factors. Aim: To find out whether the isolated Candida spp. were pathogens causing vulvovaginal candidiasis or mere bystanders. Settings and Design: Cross-sectional observational study conducted on 275 symptomatic hospital patients in Tripura between August 2012 and April 2015. Subjects and Methods: Discharge was collected from patients and identified by Grams staining and wet mount test. Culturing was done in Sabouraud dextrose agar followed by speciation. To test for virulence factors, assays for adherence, plasma coagulase, phospholipase, lipase, protease, hemolysin, and biofilm formation were carried out. Statistical Analysis Used: Significance between two groups was compared using one-way analysis of variance along with Tukey test, and Chi-square 2 × 2 contingency table at 95% confidence interval. Results: Fifty-six Candida spp. could be isolated in the study which was used for further virulence tests. One hundred percent of isolates expressed adherence. Among other virulence factors, maximum virulence 25 (45% was shown through protease production. Hemolysin production and biofilm formation were the second most 22 (39% expressed virulence factors. In a comparison of virulence factors between biofilm-forming isolates and planktonic cells, significant difference was seen for plasma coagulase and hemolysin production. Conclusions: All the isolates expressed one or more virulence factors. Adherence was expressed in all isolates but highest number was observed for Candida albicans. Furthermore, C. albicans strain number was highest for protease, hemolysin and coagulase expression and biofilm formation. Candida krusei isolates were the least in number for expressing any of the virulence factors. Significantly higher number of biofilm forming isolates produced

  15. Molecular characterization of Candida in the oral cavity and factors involved in biofilm formation and virulence

    NARCIS (Netherlands)

    Kraneveld, E.A.

    2014-01-01

    The research described in this thesis addresses current issues related to oral Candida infections. Interactions of Candida with the oral microbiome were characterized and factors involved in biofilm formation and virulence were studied. All in all, the work described in this thesis contributes

  16. Contact-dependent regulation of a Tannerella forsythia virulence factor, BspA, in biofilms.

    Science.gov (United States)

    Inagaki, Satoru; Kuramitsu, Howard K; Sharma, Ashu

    2005-08-15

    Tannerella forsythia is one of the periodontal organisms implicated in the development of periodontal diseases. The surface associated and secreted protein, BspA (encoded by the bspA gene), of this bacterium is an important virulence factor. The present study was carried out to examine the regulation of the bspA gene during biofilm growth and contact stimuli encountered in interbacterial interactions. The expression levels of the bspA transcript were determined by real-time RT-PCR approach. The levels of bspA transcript were found to be significantly reduced as a result of contact stimulus and in biofilm cells relative to planktonic cells. The results of our study suggest that the likely downregulation of the BspA protein in biofilms and following contact may have implications in pathogenesis as a plausible mechanism of evasion of host immune responses.

  17. Influence of l-amino acids on aggregation and biofilm formation in Azotobacter chroococcum and Trichoderma viride.

    Science.gov (United States)

    Velmourougane, K; Prasanna, R

    2017-07-21

    The effects of l-amino acids on growth and biofilm formation in Azotobacter chroococcum (Az) and Trichoderma viride (Tv) as single (Az, Tv) and staggered inoculated cultures (Az-Tv, Tv-Az) were investigated. A preliminary study using a set of 20 l-amino acids, identified 6 amino acids (l-Glu, l-Gln, l-His, l-Ser, l-Thr and l-Trp) which significantly enhanced growth and biofilm formation. Supplementation of these amino acids at different concentrations revealed that 40 mmol l(-1) was most effective. l-Glu and l-Gln favoured planktonic growth in both single and in staggered inoculated cultures, while l-Trp and l-Thr, enhanced aggregation and biofilm formation. Addition of l-Glu or l-Gln increased carbohydrate content and planktonic population. Principal component analysis revealed the significant role of proteins in growth and biofilm formation, particularly with supplementation of l-Trp, l-Thr and l-Ser. Azotobacter was found to function better as biofilm under staggered inoculated culture with Trichoderma. The results illustrate that amino acids play crucial roles in microbial biofilm formation, by influencing growth, aggregation and carbohydrates synthesized. The differential and specific roles of amino acids on biofilm formation are of significance for agriculturally important micro-organisms that grow as biofilms, colonize and benefit the plants more effectively. © 2017 The Society for Applied Microbiology.

  18. Influence of calcium in extracellular DNA mediated bacterial aggregation and biofilm formation.

    Directory of Open Access Journals (Sweden)

    Theerthankar Das

    Full Text Available Calcium (Ca(2+ has an important structural role in guaranteeing the integrity of the outer lipopolysaccharide layer and cell walls of bacterial cells. Extracellular DNA (eDNA being part of the slimy matrix produced by bacteria promotes biofilm formation through enhanced structural integrity of the matrix. Here, the concurrent role of Ca(2+ and eDNA in mediating bacterial aggregation and biofilm formation was studied for the first time using a variety of bacterial strains and the thermodynamics of DNA to Ca(2+ binding. It was found that the eDNA concentrations under both planktonic and biofilm growth conditions were different among bacterial strains. Whilst Ca(2+ had no influence on eDNA release, presence of eDNA by itself favours bacterial aggregation via attractive acid-base interactions in addition, its binding with Ca(2+ at biologically relevant concentrations was shown further increase in bacterial aggregation via cationic bridging. Negative Gibbs free energy (ΔG values in iTC data confirmed that the interaction between DNA and Ca(2+ is thermodynamically favourable and that the binding process is spontaneous and exothermic owing to its highly negative enthalpy. Removal of eDNA through DNase I treatment revealed that Ca(2+ alone did not enhance cell aggregation and biofilm formation. This discovery signifies the importance of eDNA and concludes that existence of eDNA on bacterial cell surfaces is a key facilitator in binding of Ca(2+ to eDNA thereby mediating bacterial aggregation and biofilm formation.

  19. Virulence factors in Proteus bacteria from biofilm communities of catheter-associated urinary tract infections.

    Science.gov (United States)

    Hola, Veronika; Peroutkova, Tereza; Ruzicka, Filip

    2012-07-01

    More than 40% of nosocomial infections are those of the urinary tract, most of these occurring in catheterized patients. Bacterial colonization of the urinary tract and catheters results not only in infection, but also various complications, such as blockage of catheters with crystalline deposits of bacterial origin, generation of gravels and pyelonephritis. The diversity of the biofilm microbial community increases with duration of catheter emplacement. One of the most important pathogens in this regard is Proteus mirabilis. The aims of this study were to identify and assess particular virulence factors present in catheter-associated urinary tract infection (CAUTI) isolates, their correlation and linkages: three types of motility (swarming, swimming and twitching), the ability to swarm over urinary catheters, biofilm production in two types of media, urease production and adherence of bacterial cells to various types of urinary tract catheters. We examined 102 CAUTI isolates and 50 isolates taken from stool samples of healthy people. Among the microorganisms isolated from urinary catheters, significant differences were found in biofilm-forming ability and the swarming motility. In comparison with the control group, the microorganisms isolated from urinary catheters showed a wider spectrum of virulence factors. The virulence factors (twitching motility, swimming motility, swarming over various types of catheters and biofilm formation) were also more intensively expressed.

  20. Reduction of Influence Factors

    NARCIS (Netherlands)

    Regtien, Paulus P.L.; Sydenham, Peter H.; Thorn, Richard

    Any measurement system has imperfections and any act of measurement is liable to errors. Measurement errors either originate from system deficiencies (for instance system noise, quantization, and drift), or are due to environmental influences such as thermal, electromagnetic, and mechanical

  1. Cold Plasma Inactivation of Bacterial Biofilms and Reduction of Quorum Sensing Regulated Virulence Factors.

    Directory of Open Access Journals (Sweden)

    Dana Ziuzina

    Full Text Available The main objectives of this work were to investigate the effect of atmospheric cold plasma (ACP against a range of microbial biofilms commonly implicated in foodborne and healthcare associated human infections and against P. aeruginosa quorum sensing (QS-regulated virulence factors, such as pyocyanin, elastase (Las B and biofilm formation capacity post-ACP treatment. The effect of processing factors, namely treatment time and mode of plasma exposure on antimicrobial activity of ACP were also examined. Antibiofilm activity was assessed for E. coli, L. monocytogenes and S. aureus in terms of reduction of culturability and retention of metabolic activity using colony count and XTT assays, respectively. All samples were treated 'inpack' using sealed polypropylene containers with a high voltage dielectric barrier discharge ACP generated at 80 kV for 0, 60, 120 and 300 s and a post treatment storage time of 24 h. According to colony counts, ACP treatment for 60 s reduced populations of E. coli to undetectable levels, whereas 300 s was necessary to significantly reduce populations of L. monocytogenes and S. aureus biofilms. The results obtained from XTT assay indicated possible induction of viable but non culturable state of bacteria. With respect to P. aeruginosa QS-related virulence factors, the production of pyocyanin was significantly inhibited after short treatment times, but reduction of elastase was notable only after 300 s and no reduction in actual biofilm formation was achieved post-ACP treatment. Importantly, reduction of virulence factors was associated with reduction of the cytotoxic effects of the bacterial supernatant on CHO-K1 cells, regardless of mode and duration of treatment. The results of this study point to ACP technology as an effective strategy for inactivation of established biofilms and may play an important role in attenuation of virulence of pathogenic bacteria. Further investigation is warranted to propose direct evidence

  2. Salmonella biofilms

    NARCIS (Netherlands)

    Castelijn, G.A.A.

    2013-01-01

    Biofilm formation by Salmonellaspp. is a problem in the food industry, since biofilms may act as a persistent source of product contamination. Therefore the aim of this study was to obtain more insight in the processes involved and the factors contributing to Salmonellabiofilm formation. A collectio

  3. Influence of O polysaccharides on biofilm development and outer membrane vesicle biogenesis in Pseudomonas aeruginosa PAO1.

    Science.gov (United States)

    Murphy, Kathleen; Park, Amber J; Hao, Youai; Brewer, Dyanne; Lam, Joseph S; Khursigara, Cezar M

    2014-04-01

    Pseudomonas aeruginosa is a common opportunistic human pathogen known for its ability to adapt to changes in its environment during the course of infection. These adaptations include changes in the expression of cell surface lipopolysaccharide (LPS), biofilm development, and the production of a protective extracellular exopolysaccharide matrix. Outer membrane vesicles (OMVs) have been identified as an important component of the extracellular matrix of P. aeruginosa biofilms and are thought to contribute to the development and fitness of these bacterial communities. The goal of this study was to examine the relationships between changes in the cell surface expression of LPS O polysaccharides, biofilm development, and OMV biogenesis in P. aeruginosa. We compared wild-type P. aeruginosa PAO1 with three chromosomal knockouts. These knockouts have deletions in the rmd, wbpM, and wbpL genes that produce changes in the expression of common polysaccharide antigen (CPA), O-specific antigen (OSA), or both. Our results demonstrate that changes in O polysaccharide expression do not significantly influence OMV production but do affect the size and protein content of OMVs derived from both CPA(-) and OSA(-) cells; these mutant cells also exhibited different physical properties from wild-type cells. We further examined biofilm growth of the mutants and determined that CPA(-) cells could not develop into robust biofilms and exhibit changes in cell morphology and biofilm matrix production. Together these results demonstrate the importance of O polysaccharide expression on P. aeruginosa OMV composition and highlight the significance of CPA expression in biofilm development.

  4. Biofilm formation is a risk factor for mortality in patients with Candida albicans bloodstream infection—Scotland, 2012–2013

    Science.gov (United States)

    Rajendran, R.; Sherry, L.; Nile, C.J.; Sherriff, A.; Johnson, E.M.; Hanson, M.F.; Williams, C.; Munro, C.A.; Jones, B.J.; Ramage, G.

    2016-01-01

    Bloodstream infections caused by Candida species remain a significant cause of morbidity and mortality in hospitalized patients. Biofilm formation by Candida species is an important virulence factor for disease pathogenesis. A prospective analysis of patients with Candida bloodstream infection (n = 217) in Scotland (2012–2013) was performed to assess the risk factors associated with patient mortality, in particular the impact of biofilm formation. Candida bloodstream isolates (n = 280) and clinical records for 157 patients were collected through 11 different health boards across Scotland. Biofilm formation by clinical isolates was assessed in vitro with standard biomass assays. The role of biofilm phenotype on treatment efficacy was also evaluated in vitro by treating preformed biofilms with fixed concentrations of different classes of antifungal. Available mortality data for 134 patients showed that the 30-day candidaemia case mortality rate was 41%, with predisposing factors including patient age and catheter removal. Multivariate Cox regression survival analysis for 42 patients showed a significantly higher mortality rate for Candida albicans infection than for Candida glabrata infection. Biofilm-forming ability was significantly associated with C. albicans mortality (34 patients). Finally, in vitro antifungal sensitivity testing showed that low biofilm formers and high biofilm formers were differentially affected by azoles and echinocandins, but not by polyenes. This study provides further evidence that the biofilm phenotype represents a significant clinical entity, and that isolates with this phenotype differentially respond to antifungal therapy in vitro. Collectively, these findings show that greater clinical understanding is required with respect to Candida biofilm infections, and the implications of isolate heterogeneity. PMID:26432192

  5. Influence of biofilm formation on corrosion and scaling in geothermal plants

    Science.gov (United States)

    Kleyböcker, Anne; Lerm, Stephanie; Monika, Kasina; Tobias, Lienen; Florian, Eichinger; Andrea, Seibt; Markus, Wolfgramm; Hilke, Würdemann

    2017-04-01

    Process failures may occur due to corrosion and scaling processes in open loop geothermal systems. Especially after heat extraction, sulfate reducing bacteria (SRB) contribute to corrosion processes due to a more favorable temperature for their growth. In biofilms containing FeS scales, corrosion processes are enhanced. Furthermore, scales can lead to reduced pipe profiles, to a diminished heat transfer and a decrease in the wellbore injectivity. Inhibitors are frequently applied to minimize scaling in technical systems. A prerequisite for the application of inhibitors in geothermal plants located in the Molasse basin is their degradability under reservoir conditions, e. g. in a reduced environment. In order to determine the effects of scale-inhibitors on the subsurface and microbial processes, laboratory experiments were performed focusing on the microbial inhibitor degradation. First results indicate that the inhibitor degradation under anaerobic conditions is possible. Besides the inhibitor application also other techniques are investigated to economically reduce corrosion and scaling in geothermal plants. In a mobile bypass system, the influence of biofilm formation on corrosion and scaling was investigated. The bypass system was tested at a geothermal heat store in the North German Basin. The plant is operated with highly saline fluid (salinity 130 g/L) and known to be affected by SRB. The SRB contributed to corrosion damages especially at the pump in the well on the cold side. Heat shocks were successfully used in the bypass system to reduce biofilm formation as well as corrosion and scaling processes.

  6. Phonological Awareness: Factors of Influence

    Science.gov (United States)

    Frohlich, Linda Paulina; Petermann, Franz; Metz, Dorothee

    2013-01-01

    Early child development is influenced by various genetic and environmental factors. This study aims to identify factors that affect the phonological awareness of preschool and first grade children. Based on a sample of 330 German-speaking children (mean age = 6.2 years) the following domains were evaluated: Parent factors, birth and pregnancy,…

  7. Corrosion influencée par les micro-organismes : influence du biofilm sur la corrosion des aciers, techniques et résultats recents

    Science.gov (United States)

    Feugeas, F.; Magnin, J. P.; Cornet, A.; Rameau, J. J.

    1997-03-01

    Microbiologically Influenced Corrosion (M.I.C.) studied since the beginning of this century, is responsible for the degradation of many metallic equipments. This study is a review of results dealing with M.I.C. on several types of steels as: carbon steels, stainless steels, welded steels and covered steels. M.I.C. occurs only in presence of a biofilm. The first part of this study describes chemical and physical factors involved in its development, technical methods for studying biofilms, and its contribution in the corrosion process. The second part is devoted to the study of M.I.C. cases linked with metal nature and different aqueous environments and the last part reviews the mainly mecanisms of biocorrosion. La Corrosion Influencée par les Micro-organismes (C.I.M.) ou biocorrosion, phénomène étudié depuis le début du siècle, est responsable de la dégradation d'un grand nombre d'ouvrages métalliques. Cette étude a pour but de faire le point des connaissances sur la corrosion influencée microbiologiquement de divers types d'aciers au carbone, d'aciers inoxydables, d'assemblages soudés et d'aciers revêtus. La C.I.M. n'apparaît qu'en présence d'un biofilm. La première partie de cette étude décrit les facteurs physico-chimiques impliqués dans la formation du biofilm, ces moyens d'études ainsi que son action dans le processus de biocorrosion. La seconde partie est consacrée à la description des cas de biocorrosion classés en fonction de la nature des métaux et des milieux avec lesquels ils sont en contact. La dernière partie de ce document passe en revue les principaux mécanismes de biocorrosion décrits.

  8. Data on enterobacteria activity on biofilm formation at surface mango fruit (Mangifera indica L. cv Ataulfo

    Directory of Open Access Journals (Sweden)

    Juan A. Ragazzo-Sánchez

    2016-12-01

    Full Text Available Abiotic factors influenced the capacity of the strains to form biofilms. Classification of the adhesion type is related with the optical density measured on the biofilm formation of tested strains. The relationship between the biofilm formation in real values with theoretical values of the strains was used to determine the mechanism involved during mixed cultures.

  9. Influence of physico-chemical material characteristics on staphylococcal biofilm formation--a qualitative and quantitative in vitro analysis of five different calcium phosphate bone grafts.

    Science.gov (United States)

    Clauss, M; Furustrand Tafin, U; Betrisey, B; van Garderen, N; Trampuz, A; Ilchmann, T; Bohner, M

    2014-07-18

    Various compositions of synthetic calcium phosphates (CaP) have been proposed and their use has considerably increased over the past decades. Besides differences in physico-chemical properties, resorption and osseointegration, artificial CaP bone graft might differ in their resistance against biofilm formation. We investigated standardised cylinders of 5 different CaP bone grafts (cyclOS, chronOS (both β-TCP (tricalcium phosphate)), dicalcium phosphate (DCP), calcium-deficient hydroxyapatite (CDHA) and α-TCP). Various physico-chemical characterisations e.g., geometrical density, porosity, and specific surface area were investigated. Biofilm formation was carried out in tryptic soy broth (TSB) and human serum (SE) using Staphylococcus aureus (ATCC 29213) and S. epidermidis RP62A (ATCC 35984). The amount of biofilm was analysed by an established protocol using sonication and microcalorimetry. Physico-chemical characterisation showed marked differences concerning macro- and micropore size, specific surface area and porosity accessible to bacteria between the 5 scaffolds. Biofilm formation was found on all scaffolds and was comparable for α-TCP, chronOS, CDHA and DCP at corresponding time points when the scaffolds were incubated with the same germ and/or growth media, but much lower for cyclOS. This is peculiar because cyclOS had an intermediate porosity, mean pore size, specific surface area, and porosity accessible to bacteria. Our results suggest that biofilm formation is not influenced by a single physico-chemical parameter alone but is a multi-step process influenced by several factors in parallel. Transfer from in vitro data to clinical situations is difficult; thus, advocating the use of cyclOS scaffolds over the four other CaP bone grafts in clinical situations with a high risk of infection cannot be clearly supported based on our data.

  10. Influence of physico-chemical material characteristics on staphylococcal biofilm formation – A qualitative and quantitative in vitro analysis of five different calcium phosphate bone grafts

    Directory of Open Access Journals (Sweden)

    M Clauss

    2014-07-01

    Full Text Available Various compositions of synthetic calcium phosphates (CaP have been proposed and their use has considerably increased over the past decades. Besides differences in physico-chemical properties, resorption and osseointegration, artificial CaP bone graft might differ in their resistance against biofilm formation. We investigated standardised cylinders of 5 different CaP bone grafts (cyclOS, chronOS (both β-TCP (tricalcium phosphate, dicalcium phosphate (DCP, calcium-deficient hydroxyapatite (CDHA and α-TCP. Various physico-chemical characterisations e.g., geometrical density, porosity, and specific surface area were investigated. Biofilm formation was carried out in tryptic soy broth (TSB and human serum (SE using Staphylococcus aureus (ATCC 29213 and S. epidermidis RP62A (ATCC 35984. The amount of biofilm was analysed by an established protocol using sonication and microcalorimetry. Physico-chemical characterisation showed marked differences concerning macro- and micropore size, specific surface area and porosity accessible to bacteria between the 5 scaffolds. Biofilm formation was found on all scaffolds and was comparable for α-TCP, chronOS, CDHA and DCP at corresponding time points when the scaffolds were incubated with the same germ and/or growth media, but much lower for cyclOS. This is peculiar because cyclOS had an intermediate porosity, mean pore size, specific surface area, and porosity accessible to bacteria. Our results suggest that biofilm formation is not influenced by a single physico-chemical parameter alone but is a multi-step process influenced by several factors in parallel. Transfer from in vitro data to clinical situations is difficult; thus, advocating the use of cyclOS scaffolds over the four other CaP bone grafts in clinical situations with a high risk of infection cannot be clearly supported based on our data.

  11. Evaluation of E. coli biofilm as a protective barrier against microbiologically influenced deterioration of concrete (MICD) under mesophilic temperatures.

    Science.gov (United States)

    Soleimani, S; Ormeci, B; Isgor, O B

    2013-01-01

    In this study, Escherichia coli DH5α biofilm was evaluated for its potential to control and minimize microbiologically influenced concrete deterioration (MICD) under mesophilic temperatures (37 °C). Escherichia coli DH5α biofilm was first grown on Portland cement mortar disks for 8 days. Mortar disks were then exposed to two different types of sulfur oxidizing bacteria (SOB) (Thiobacillus neapolitanus and Thiobacillus thiooxidans), which use sulfur compounds as substrate and oxidize them to sulfate and sulfuric acid. The effectiveness of the biofilm against MICD was evaluated by measuring pH, sulfate, calcium concentrations in the reactors and surface analysis of the mortar samples using X-ray diffraction and visual inspection. Overall, the results indicate that the E. coli DH5α biofilm showed good protection against MICD induced by SOB at 37 °C.

  12. Biofilms in wounds

    DEFF Research Database (Denmark)

    Cooper, R A; Bjarnsholt, Thomas; Alhede, M

    2014-01-01

    Following confirmation of the presence of biofilms in chronic wounds, the term biofilm became a buzzword within the wound healing community. For more than a century pathogens have been successfully isolated and identified from wound specimens using techniques that were devised in the nineteenth...... extracellular polymeric substances (EPS). Cells within such aggregations (or biofilms) display varying physiological and metabolic properties that are distinct from those of planktonic cells, and which contribute to their persistence. There are many factors that influence healing in wounds and the discovery...... century by Louis Pasteur and Robert Koch. Although this approach still provides valuable information with which to help diagnose acute infections and to select appropriate antibiotic therapies, it is evident that those organisms isolated from clinical specimens with the conditions normally used...

  13. Influence of matrix and filler fraction on biofilm formation on the surface of experimental resin-based composites.

    Science.gov (United States)

    Ionescu, Andrei; Brambilla, Eugenio; Wastl, Daniel S; Giessibl, Franz J; Cazzaniga, Gloria; Schneider-Feyrer, Sibylle; Hahnel, Sebastian

    2015-01-01

    The aim of this study was to investigate the impact of resin matrix chemistry and filler fraction on biofilm formation on the surface of experimental resin-based composites (RBCs). Specimens were prepared from eight experimental RBC formulations differing in resin matrix blend (BisGMA/TEGDMA in a 7:3 wt% ratio or UDMA/aliphatic dimethacrylate in a 1:1 wt% ratio) and filler fraction (no fillers; 65 wt% dental glass with an average diameter of 7 or 0.7 µm or 65 wt% SiO2 with an average diameter of 20 nm). Surface roughness, surface free energy, and chemical surface composition were determined; surface topography was visualized using atomic force microscopy. Biofilm formation was simulated under continuous flow conditions for a 48 h period using a monospecies Streptococcus mutans and a multispecies biofilm model. In the monospecies biofilm model, the impact of the filler fraction overruled the influence of the resin matrix, indicating lowest biofilm formation on RBCs with nano-scaled filler particles and those manufactured from the neat resin blends. The multispecies model suggested a more pronounced effect of the resin matrix blend, as significantly higher biofilm formation was identified on RBCs with a UDMA/dimethacrylate matrix blend than on those including a BisGMA/TEGDMA matrix blend but analogous filler fractions. Although significant differences in surface properties between the various materials were identified, correlations between the surface properties and biofilm formation were poor, which highlights the relevance of surface topography and chemistry. These results may help to tailor novel RBC formulations which feature reduced biofilm formation on their surface.

  14. Influence of plaque biofilm removal on reestablishment of the biocompatibility of contaminated titanium surfaces.

    Science.gov (United States)

    Schwarz, Frank; Papanicolau, Pascal; Rothamel, Daniel; Beck, Brigitte; Herten, Monika; Becker, Jürgen

    2006-06-01

    The aim of the present study was to evaluate the influence of plaque biofilm removal on the mitochondrial activity of human SaOs-2 osteoblasts grown on titanium surfaces. Volunteers wore acrylic splints with structured titanium discs for 72 h to build up plaque biofilms (n = 30). Specimens were randomly instrumented using either (1) an ultrasonic system at two power settings (EMS1, EMS2) + chlorhexidine (CHX), or (2) plastic curettes + CHX. Untreated (NC, n = 10) and sterile (C, n = 10) titanium discs served as controls. Specimens were incubated with SaOs-2 cells for 6 days. Treatment time (T), residual plaque biofilm (RPB)/clean implant surface areas (%), mitochondrial cell activity (MA) (counts/second), and cell morphology (SEM) were assessed. Statistical analysis revealed the following mean scores (+/-SD): RPB areas: P (58.5 +/- 4.9) > EMS1 (38.4 +/- 4.1) > EMS2 (28.3 +/- 2.0); T: PC (292 +/- 30) = EMS1 (244 +/- 24) > EMS2 (199 +/- 25); MA: C (1.544.661 +/- 203.442) > PC (597.559 +/- 566.984) = EMS2 (389.875 +/- 409.300) = EMS1 (356.653 +/- 293.863; n.s.) > NC (138.676 +/- 86.666). In NC and PC groups, cells were predominantly rounded in shape. However, in the EMS groups, some cells had started to spread, showing complete cytoplasmatic extensions of the cell body on the titanium surface. A monolayer of flattened cells was generally observed in the C group. Within the limits of the present study, it was concluded that MA seemed to be impaired by the presence of RPB areas. However, its removal alone might not be the crucial step in the reestablishment of the biocompatibility of titanium surfaces.

  15. Quantitative characterization of the influence of the nanoscale morphology of nanostructured surfaces on bacterial adhesion and biofilm formation.

    Directory of Open Access Journals (Sweden)

    Ajay Vikram Singh

    Full Text Available Bacterial infection of implants and prosthetic devices is one of the most common causes of implant failure. The nanostructured surface of biocompatible materials strongly influences the adhesion and proliferation of mammalian cells on solid substrates. The observation of this phenomenon has led to an increased effort to develop new strategies to prevent bacterial adhesion and biofilm formation, primarily through nanoengineering the topology of the materials used in implantable devices. While several studies have demonstrated the influence of nanoscale surface morphology on prokaryotic cell attachment, none have provided a quantitative understanding of this phenomenon. Using supersonic cluster beam deposition, we produced nanostructured titania thin films with controlled and reproducible nanoscale morphology respectively. We characterized the surface morphology; composition and wettability by means of atomic force microscopy, X-ray photoemission spectroscopy and contact angle measurements. We studied how protein adsorption is influenced by the physico-chemical surface parameters. Lastly, we characterized Escherichia coli and Staphylococcus aureus adhesion on nanostructured titania surfaces. Our results show that the increase in surface pore aspect ratio and volume, related to the increase of surface roughness, improves protein adsorption, which in turn downplays bacterial adhesion and biofilm formation. As roughness increases up to about 20 nm, bacterial adhesion and biofilm formation are enhanced; the further increase of roughness causes a significant decrease of bacterial adhesion and inhibits biofilm formation. We interpret the observed trend in bacterial adhesion as the combined effect of passivation and flattening effects induced by morphology-dependent protein adsorption. Our findings demonstrate that bacterial adhesion and biofilm formation on nanostructured titanium oxide surfaces are significantly influenced by nanoscale morphological

  16. Influence of the Culture Medium in Dose-Response Effect of the Chlorhexidine on Streptococcus mutans Biofilms

    Directory of Open Access Journals (Sweden)

    Vanessa Salvadego de Queiroz

    2016-01-01

    Full Text Available The aim of this study was to evaluate the influence of culture medium on dose-response effect of chlorhexidine (CHX on Streptococcus mutans UA159 biofilm and validate the use of the cation-adjusted-Müller-Hinton broth (MH for the evaluation of antibacterial activity. Ultrafiltered Tryptone-Yeast Extract Broth (UTYEB was compared against MH and MH with blood supplementation (MHS. For each medium, six groups (n=4 were assessed: two negative control groups (baseline 48 and 120 h and four experimental groups (0.0001, 0.001, 0.012, and 0.12% CHX. S. mutans biofilm grew on glass slides of each media containing 1% sucrose. After 48 h of growth, biofilms of baseline 48 h were collected and the other groups were treated for 1 min, twice a day, for 3 days, with their respective treatments. The media were changed daily and pH was measured. After 120 h, biofilms were collected and dry weight and viable microorganisms were determined. Results showed CHX dose-response effect being observed in all media for all the variables. However, MH and MHS showed higher sensitivity than UTYEB (p<0.05. We can conclude that the culture medium does influence dose-response effect of CHX on Streptococcus mutans biofilm and that MH can be used for antibacterial activity.

  17. Influence of the Culture Medium in Dose-Response Effect of the Chlorhexidine on Streptococcus mutans Biofilms

    Science.gov (United States)

    de Queiroz, Vanessa Salvadego; Ccahuana-Vásquez, Renzo Alberto; Tedesco, Alcides Fabiano; Lyra, Luzia; Cury, Jaime Aparecido; Schreiber, Angélica Zaninelli

    2016-01-01

    The aim of this study was to evaluate the influence of culture medium on dose-response effect of chlorhexidine (CHX) on Streptococcus mutans UA159 biofilm and validate the use of the cation-adjusted-Müller-Hinton broth (MH) for the evaluation of antibacterial activity. Ultrafiltered Tryptone-Yeast Extract Broth (UTYEB) was compared against MH and MH with blood supplementation (MHS). For each medium, six groups (n = 4) were assessed: two negative control groups (baseline 48 and 120 h) and four experimental groups (0.0001, 0.001, 0.012, and 0.12% CHX). S. mutans biofilm grew on glass slides of each media containing 1% sucrose. After 48 h of growth, biofilms of baseline 48 h were collected and the other groups were treated for 1 min, twice a day, for 3 days, with their respective treatments. The media were changed daily and pH was measured. After 120 h, biofilms were collected and dry weight and viable microorganisms were determined. Results showed CHX dose-response effect being observed in all media for all the variables. However, MH and MHS showed higher sensitivity than UTYEB (p < 0.05). We can conclude that the culture medium does influence dose-response effect of CHX on Streptococcus mutans biofilm and that MH can be used for antibacterial activity. PMID:27293967

  18. Influence of the Culture Medium in Dose-Response Effect of the Chlorhexidine on Streptococcus mutans Biofilms.

    Science.gov (United States)

    de Queiroz, Vanessa Salvadego; Ccahuana-Vásquez, Renzo Alberto; Tedesco, Alcides Fabiano; Lyra, Luzia; Cury, Jaime Aparecido; Schreiber, Angélica Zaninelli

    2016-01-01

    The aim of this study was to evaluate the influence of culture medium on dose-response effect of chlorhexidine (CHX) on Streptococcus mutans UA159 biofilm and validate the use of the cation-adjusted-Müller-Hinton broth (MH) for the evaluation of antibacterial activity. Ultrafiltered Tryptone-Yeast Extract Broth (UTYEB) was compared against MH and MH with blood supplementation (MHS). For each medium, six groups (n = 4) were assessed: two negative control groups (baseline 48 and 120 h) and four experimental groups (0.0001, 0.001, 0.012, and 0.12% CHX). S. mutans biofilm grew on glass slides of each media containing 1% sucrose. After 48 h of growth, biofilms of baseline 48 h were collected and the other groups were treated for 1 min, twice a day, for 3 days, with their respective treatments. The media were changed daily and pH was measured. After 120 h, biofilms were collected and dry weight and viable microorganisms were determined. Results showed CHX dose-response effect being observed in all media for all the variables. However, MH and MHS showed higher sensitivity than UTYEB (p culture medium does influence dose-response effect of CHX on Streptococcus mutans biofilm and that MH can be used for antibacterial activity.

  19. Some bacterial parameters influencing the neutrophil oxidative burst response to Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Jensen, E T; Kharazmi, A; Høiby, N;

    1992-01-01

    or biofilms is an important protective mechanism of the microorganisms. We examined the human PMN oxidative burst response to P. aeruginosa in biofilm and in planktonic form. The PMN chemiluminescence response to P. aeruginosa in biofilms was reduced to 30.5-47.5% (p less than 0.04) and the superoxide...... conclude that biofilm bacteria, although able to stimulate the PMN, result in a reduced, suboptimal response leading to lack of efficient eradication of the bacteria in the chronic infection....

  20. Factors Influencing Healthcare Service Quality

    OpenAIRE

    Ali Mohammad Mosadeghrad

    2014-01-01

    Background The main purpose of this study was to identify factors that influence healthcare quality in the Iranian context. Methods Exploratory in-depth individual and focus group interviews were conducted with 222 healthcare stakeholders including healthcare providers, managers, policy-makers, and payers to identify factors affecting the quality of healthcare services provided in Iranian healthcare organisations. Results Quality in healthcare is a production o...

  1. Metal-on-metal bearings in total hip arthroplasties : Influence of cobalt chromium ions on bacterial growth and biofilm formation

    NARCIS (Netherlands)

    Hosman, Anton H.; van der Mei, Henny C.; Bulstra, Sjoerd K.; Busscher, Henk J.; Neut, Danielle

    2009-01-01

    Metal-on-metal (MOM) bearings involving cobalt-chromium (Co-Cr) alloys in total hip arthroplasties are becoming more and more popular due to their low wear. Consequences of corrosion products of Co-Cr alloys are for the most part unclear, and the influence of cobalt and chromium ions on biofilm form

  2. Polymicrobial biofilms by diabetic foot clinical isolates.

    Science.gov (United States)

    Mottola, Carla; Mendes, João J; Cristino, José Melo; Cavaco-Silva, Patrícia; Tavares, Luís; Oliveira, Manuela

    2016-01-01

    Diabetes mellitus is a major chronic disease that continues to increase significantly. One of the most important and costly complications of diabetes is foot ulceration that may be colonized by pathogenic and antimicrobial resistant bacteria, which may express several virulence factors that could impair treatment success. These bacterial communities can be organized in polymicrobial biofilms, which may be responsible for diabetic foot ulcer (DFU) chronicity. We evaluated the influence of polymicrobial communities in the ability of DFU isolates to produce biofilm, using a microtiter plate assay and a multiplex fluorescent in situ hybridization, at three time points (24, 48, 72 h), after evaluating biofilm formation by 95 DFU isolates belonging to several bacterial genera (Staphylococcus, Corynebacterium, Enterococcus, Pseudomonas and Acinetobacter). All isolates were biofilm-positive at 24 h, and the amount of biofilm produced increased with incubation time. Pseudomonas presented the higher biofilm production, followed by Corynebacterium, Acinetobacter, Staphylococcus and Enterococcus. Significant differences were found in biofilm formation between the three time points. Polymicrobial communities produced higher biofilm values than individual species. Pseudomonas + Enterococcus, Acinetobacter + Staphylococcus and Corynebacterium + Staphylococcus produced higher biofilm than the ones formed by E. faecalis + Staphylococcus and E. faecalis + Corynebacterium. Synergy between bacteria present in dual or multispecies biofilms has been described, and this work represents the first report on time course of biofilm formation by polymicrobial communities from DFUs including several species. The biological behavior of different bacterial species in polymicrobial biofilms has important clinical implications for the successful treatment of these infections.

  3. THE AGGREGATION OF BACTERIA KLEBSIELLA OXYTOCA AND KLEBSIELLA PNEUMONIAE UNDER THE INFLUENCE OF CHEMICAL FACTOR

    Directory of Open Access Journals (Sweden)

    G. R. Sadrtdinova

    2015-01-01

    Full Text Available The article acknowledges the formation of bacterial biofilms in strains of bacteria species Klebsiella oxytoca and Klebsiella pneumoniae when grown in liquid media under the influence of negative factors (chemical factor — containing agents. Biofilms, as a community of microorganisms cause many chronic infections (meningitis, inflammatory diseases of the oral cavity, urogenital infections and create problems in the industry (fouling of processing equipment, ship hulls, oil platforms, biocorrosion metal products. Ordinary disinfectants, such as chlorine and sodium chlorite, can not remove the biofilm, so finding an effective means of dealing with them is enough actual problem. Various antibacterial agents are ineffective in combating biofilms, since bacteria produce large amounts of polysaccharides — substances that help the colony stay without disintegration. Polysaccharide serves as a barrier layer for substances in water, including for biocides. This is the main reason for the survival of microorganisms even in the heavily chlorinated water. In the study the latest data took into account on the subject, especially concerning adverse effects of oxygen on the growth of bacterial cells and directs action as a factor in the formation of biofilms. In our study we analyzed the latest generation disinfectant as an influencing factor. Working concentrations were shown in three embodiments. The number of strains studied was 6 (3 strains of each species. All strains were obtained from the Department of Museum MVE and VSE Ulyanovsk State Agricultural Academy n.a. P.A. Stolypin. In our research the biofilm community formation phenomenon has been confirmed, marked differences in biofilm formation, depending on the intensity (in this case, concentration of the promoter and bacteria species. In vivo biofilm is easily destroyed by mechanical action (shaking test tubes with the medium. Biofilm recovery after this manipulation was not observed. The results

  4. Influence of Culture Media on Biofilm Formation by Candida Species and Response of Sessile Cells to Antifungals and Oxidative Stress

    Science.gov (United States)

    Serrano-Fujarte, Isela; Reyna-López, Georgina Elena; Martínez-Gámez, Ma. Alejandrina; Vega-González, Arturo; Cuéllar-Cruz, Mayra

    2015-01-01

    The aims of the study were to evaluate the influence of culture media on biofilm formation by C. albicans, C. glabrata, C. krusei, and C. parapsilosis and to investigate the responses of sessile cells to antifungals and reactive oxygen species (ROS) as compared to planktonic cells. For biofilm formation, the Candida species were grown at different periods of time in YP or YNB media supplemented or not with 0.2 or 2% glucose. Sessile and planktonic cells were exposed to increasing concentrations of antifungals, H2O2, menadione or silver nanoparticles (AgNPs). Biofilms were observed by scanning electron microscopy (SEM) and quantified by the XTT assay. C. albicans formed biofilms preferentially in YPD containing 2% glucose (YPD/2%), C. glabrata in glucose-free YNB or supplemented with 0.2% glucose (YNB/0.2%), while C. krusei and C. parapsilosis preferred YP, YPD/0.2%, and YPD/2%. Interestingly, only C. albicans produced an exopolymeric matrix. This is the first report dealing with the in vitro effect of the culture medium and glucose on the formation of biofilms in four Candida species as well as the resistance of sessile cells to antifungals, AgNPs, and ROS. Our results suggest that candidiasis in vivo is a multifactorial and complex process where the nutritional conditions, the human immune system, and the adaptability of the pathogen should be considered altogether to provide an effective treatment of the patient. PMID:25705688

  5. Influence of culture media on biofilm formation by Candida species and response of sessile cells to antifungals and oxidative stress.

    Science.gov (United States)

    Serrano-Fujarte, Isela; López-Romero, Everardo; Reyna-López, Georgina Elena; Martínez-Gámez, Ma Alejandrina; Vega-González, Arturo; Cuéllar-Cruz, Mayra

    2015-01-01

    The aims of the study were to evaluate the influence of culture media on biofilm formation by C. albicans, C. glabrata, C. krusei, and C. parapsilosis and to investigate the responses of sessile cells to antifungals and reactive oxygen species (ROS) as compared to planktonic cells. For biofilm formation, the Candida species were grown at different periods of time in YP or YNB media supplemented or not with 0.2 or 2% glucose. Sessile and planktonic cells were exposed to increasing concentrations of antifungals, H2O2, menadione or silver nanoparticles (AgNPs). Biofilms were observed by scanning electron microscopy (SEM) and quantified by the XTT assay. C. albicans formed biofilms preferentially in YPD containing 2% glucose (YPD/2%), C. glabrata in glucose-free YNB or supplemented with 0.2% glucose (YNB/0.2%), while C. krusei and C. parapsilosis preferred YP, YPD/0.2%, and YPD/2%. Interestingly, only C. albicans produced an exopolymeric matrix. This is the first report dealing with the in vitro effect of the culture medium and glucose on the formation of biofilms in four Candida species as well as the resistance of sessile cells to antifungals, AgNPs, and ROS. Our results suggest that candidiasis in vivo is a multifactorial and complex process where the nutritional conditions, the human immune system, and the adaptability of the pathogen should be considered altogether to provide an effective treatment of the patient.

  6. Different carbon isotope fractionation in developing natural phototrophic biofilms

    NARCIS (Netherlands)

    Staal, M.J.; Thar, R.; Kühl, M.; van Loosdrecht, M.C.M.; Wolf, G.; de Brouwer, J.F.C.; Rijstenbil, J.W.

    2007-01-01

    Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which is expected to lead to a limitation of

  7. The Influences of LuxX in "Escherichia Coli" Biofilm Formation and Improving Teacher Quality through the Bio-Bus Program

    Science.gov (United States)

    Robbins, Chandan Morris

    2012-01-01

    The objectives of this work are: (1) to agarose-stabilize fragile biofilms for quantitative structure analysis; (2) to understand the influences of LuxS on biofilm formation; (3) to improve teacher quality by preparing Georgia's middle school science teachers to integrate inquiry-based, hands-on research modules in the classroom. Quantitative…

  8. The Influences of LuxX in "Escherichia Coli" Biofilm Formation and Improving Teacher Quality through the Bio-Bus Program

    Science.gov (United States)

    Robbins, Chandan Morris

    2012-01-01

    The objectives of this work are: (1) to agarose-stabilize fragile biofilms for quantitative structure analysis; (2) to understand the influences of LuxS on biofilm formation; (3) to improve teacher quality by preparing Georgia's middle school science teachers to integrate inquiry-based, hands-on research modules in the classroom. Quantitative…

  9. Influence of biofilms on colloid transport: investigations with laponite as a model colloid

    Energy Technology Data Exchange (ETDEWEB)

    Leon-Morales, C.F.; Flemming, H.C.; Leis, A. [Duisburg Univ. (Germany). Inst. for Interface Biotechnology

    2003-07-01

    The synthetic clay mineral laponite RD was used as a model compound to investigate colloid transport in the presence of bacterial biofilms. A complex but pronounced delay in the transport of laponite was observed in colonised porous media, clearly demonstrating the influence of attached bacterial biomass on colloid transport. The transport of laponite under conditions which promoted laponite aggregation was associated with release of attached bacteria; this effect was shown to be independent of ionic strength, indicating that the colloids caused detachment of bacteria. Two major mechanisms are proposed to account for the different colloid transport patterns obtained in the presence or absence of biomass: (1) hydrodynamic effects due to aggregation of laponite and subsequent blockage of a proportion of the flow channels, and (2) sorption of laponite by bacterial biomass. (orig.)

  10. Factors influencing pacing in triathlon.

    Science.gov (United States)

    Wu, Sam Sx; Peiffer, Jeremiah J; Brisswalter, Jeanick; Nosaka, Kazunori; Abbiss, Chris R

    2014-01-01

    Triathlon is a multisport event consisting of sequential swim, cycle, and run disciplines performed over a variety of distances. This complex and unique sport requires athletes to appropriately distribute their speed or energy expenditure (ie, pacing) within each discipline as well as over the entire event. As with most physical activity, the regulation of pacing in triathlon may be influenced by a multitude of intrinsic and extrinsic factors. The majority of current research focuses mainly on the Olympic distance, whilst much less literature is available on other triathlon distances such as the sprint, half-Ironman, and Ironman distances. Furthermore, little is understood regarding the specific physiological, environmental, and interdisciplinary effects on pacing. Therefore, this article discusses the pacing strategies observed in triathlon across different distances, and elucidates the possible factors influencing pacing within the three specific disciplines of a triathlon.

  11. 多聚β-1-6-N-乙酰氨基葡萄糖胺对鲍氏不动杆菌生物膜形成及耐药的影响%Influence of poly-β-1-6-N-acetylglucosamine on biofilm formation and drug resistance of Acinetobacter baumannii

    Institute of Scientific and Technical Information of China (English)

    郭海娜; 向军

    2015-01-01

    Acinetobacter baumannii has emerged as one of the leading bacteria for nosocomial infections,especially in burn wards and ICUs.The bacteria can easily form biofilm and readily attach to abiotic and biotic surfaces,resulting in persistent biofilm-mediated infections.Being surrounded by selfproduced extracellular polymeric substance (EPS),the microorganisms in biofilm can acquire protective property against detrimental environment and their tolerance toward antibiotics is increased.Poly-β-1-6-N-acetylglucosamine (PNAG),the common constituent of EPS in Acinetobacter baumannii,acts as the key virulence factor and plays a crucial role in biofilm formation process.This review describes the properties and functions of the PNAG and its influence on biofilm formation and drug resistance of Acinetobacter baumannii.

  12. Detection of alpha-toxin and other virulence factors in biofilms of staphylococcus aureus on polystyrene and a human epidermalmodel

    NARCIS (Netherlands)

    P.M. Den Reijer (P. Martijn); J.A. Haisma (Janneke); N. Lemmens-den Toom; J. Willemse (José); R.A. Koning; J.A.A. Demmers (Jeroen); D.H. Dekkers (Dick); E.J. Rijkers; A. El Ghalbzouri (Abdoelwaheb); P.H. Nibbering (Peter); W.J.B. van Wamel (Willem)

    2016-01-01

    textabstractBackground & Aim: The ability of Staphylococcus aureus to successfully colonize (a)biotic surfaces may be explained by biofilm formation and the actions of virulence factors. The aim of the present study was to establish the presence of 52 proteins, including virulence factors such as al

  13. The effect of burdock leaf fraction on adhesion, biofilm formation, quorum sensing and virulence factors of Pseudomonas aeruginosa.

    Science.gov (United States)

    Lou, Z; Wang, H; Tang, Y; Chen, X

    2017-03-01

    This study aimed to evaluate the effect of a fraction of burdock (Arctium lappa L.) leaf on the initial adhesion, biofilm formation, quorum sensing and virulence factors of Pseudomonas aeruginosa. Antibiofilm activity of the burdock leaf fraction was studied by the method of crystal violet staining. When the concentration of the burdock leaf fraction was 2·0 mg ml(-1) , the inhibition rates on biofilm formation of P. aeruginosa were 100%. The burdock leaf fraction was found to inhibit the formation of biofilm by reducing bacterial surface hydrophobicity, decreasing bacterial aggregation ability and inhibiting swarming motility. Interestingly, the burdock leaf fraction inhibited the secretion of quorum-sensing (QS) signalling molecule 3-oxo-C12-HSL and interfered quorum sensing. Moreover, the QS-regulated pyocyanin and elastase were also inhibited. Chemical composition analysis by UPLC-MS showed 11 active compounds in the burdock leaf fraction. The burdock leaf fraction significantly inhibited the formation of biofilm and quorum sensing, as well as significantly decreased the content of virulence factors. This study introduces a natural and effective bacterial biofilm inhibitor, which could also significantly decrease the content of virulence factors and the drug resistance of P. aeruginosa. © 2016 The Society for Applied Microbiology.

  14. Macrophage migration inhibitory factor enhances Pseudomonas aeruginosa biofilm formation potentially contributing to cystic fibrosis pathogenesis.

    Science.gov (United States)

    Tynan, Aisling; Mawhinney, Leona; Armstrong, Michelle E; O'Reilly, Ciaran; Kennedy, Sarah; Caraher, Emma; Jülicher, Karen; O'Dwyer, David; Maher, Lewena; Schaffer, Kirsten; Fabre, Aurélie; McKone, Edward F; Leng, Lin; Bucala, Richard; Bernhagen, Jürgen; Cooke, Gordon; Donnelly, Seamas C

    2017-08-02

    Macrophage migration inhibitory factor (MIF) is a key proinflammatory mediator that we have previously shown to be associated with an aggressive clinical phenotype in cystic fibrosis. It possesses unique tautomerase enzymatic activity. However, to date, no human-derived substrate has been identified that has the capacity to interact with this cytokine's unique tautomerase activity. This led us to hypothesize that MIF may have the capacity to interact with external substrates. We describe for the first time how Pseudomonas aeruginosa can utilize human recombinant MIF (rMIF) to significantly (P < 0.01) enhance its endogenous biofilm formation. Our in vivo studies demonstrate that utilizing a small-molecular-weight inhibitor targeting MIF's tautomerase activity (SCD-19) significantly reduces the inflammatory response in a murine pulmonary chronic P. aeruginosa model. In addition, we show that in in vitro experiments, pretreatment of P. aeruginosa with rMIF is associated with reduced bacterial killing by tobramycin. Our novel findings support the concept of an anti-MIF strategy that targets this enzymatic activity as a potential future antibacterial therapeutic approach.-Tynan, A., Mawhinney, L., Armstrong, M. E., O'Reilly, C., Kennedy, S., Caraher, E., Jülicher, K., O'Dwyer, D., Maher, L., Schaffer, K., Fabre, A., McKone, E. F., Leng, L., Bucala, R., Bernhagen, J., Cooke, G., Donnelly, S. C. Macrophage migration inhibitory factor enhances Pseudomonas aeruginosa biofilm formation potentially contributing to cystic fibrosis pathogenesis. © FASEB.

  15. Biofilm Formation by Bacillus cereus Is Influenced by PlcR, a Pleiotropic Regulator

    Science.gov (United States)

    Hsueh, Yi-Huang; Somers, Eileen B.; Lereclus, Didier; Wong, Amy C. Lee

    2006-01-01

    The ΔplcR mutant of Bacillus cereus strain ATCC 14579 developed significantly more biofilm than the wild type and produced increased amounts of biosurfactant. Biosurfactant production is required for biofilm formation and may be directly or indirectly repressed by PlcR, a pleiotropic regulator. Coating polystyrene plates with surfactin, a biosurfactant from Bacillus subtilis, rescued the deficiency in biofilm formation by the wild type. PMID:16820512

  16. Intraspecies Variability Affects Heterotypic Biofilms of Porphyromonas gingivalis and Prevotella intermedia: Evidences of Strain-Dependence Biofilm Modulation by Physical Contact and by Released Soluble Factors.

    Science.gov (United States)

    Barbosa, Graziela Murta; Colombo, Andrea Vieira; Rodrigues, Paulo Henrique; Simionato, Maria Regina Lorenzetti

    2015-01-01

    It is well known that strain and virulence diversity exist within the population structure of Porphyromonas gingivalis. In the present study we investigate intra- and inter-species variability in biofilm formation of Porphyromonas gingivalis and partners Prevotella intermedia and Prevotella nigrescens. All strains tested showed similar hydrophobicity, except for P. gingivalis W83 which has roughly half of the hydrophobicity of P. gingivalis ATCC33277. An intraspecies variability in coaggregation of P. gingivalis with P. intermedia was also found. The association P. gingivalis W83/P. intermedia 17 produced the thickest biofilm and strain 17 was prevalent. In a two-compartment system P. gingivalis W83 stimulates an increase in biomass of strain 17 and the latter did not stimulate the growth of P. gingivalis W83. In addition, P. gingivalis W83 also stimulates the growth of P. intermedia ATCC25611 although strain W83 was prevalent in the association with P. intermedia ATCC25611. P. gingivalis ATCC33277 was prevalent in both associations with P. intermedia and both strains of P. intermedia stimulate the growth of P. gingivalis ATCC33277. FISH images also showed variability in biofilm structure. Thus, the outcome of the association P. gingivalis/P. intermedia seems to be strain-dependent, and both soluble factors and physical contact are relevant. The association P. gingivalis-P. nigrescens ATCC33563 produced larger biomass than each monotypic biofilm, and P. gingivalis was favored in consortia, while no differences were found in the two-compartment system. Therefore, in consortia P. gingivalis-P. nigrescens physical contact seems to favor P. gingivalis growth. The intraspecies variability found in our study suggests strain-dependence in ability of microorganisms to recognize molecules in other bacteria which may further elucidate the dysbiosis event during periodontitis development giving additional explanation for periodontal bacteria, such as P. gingivalis and P

  17. Prediction of optimal biofilm thickness for membrane-attached biofilms growing in an extractive membrane bioreactor.

    Science.gov (United States)

    Pavasant, P; Dos Santos, L M; Pistikopoulos, E N; Livingston, A G

    1996-11-05

    This article presents a mathematical model of membrane-attached biofilm (MAB) behavior in a single-tube extractive membrane bioreactor (STEMB). MABs can be used for treatment of wastewaters containing VOCs, treatment of saline wastewaters, and nitrification processes. Extractive membrane bioreactors (EMBs) are employed to prevent the direct contact between a toxic volatile pollutant and the aerated gas by allowing counterdiffusion of substrates; i.e., pollutant diffuses from the tube side into the biofilm, whereas oxygen diffuses from the shell side into the biofilm. This reduces the air stripping problems usually found in conventional bioreactors. In this study, the biodegradation of a toxic VOC (1,2-dichloroethane, DCE) present in a synthetic wastewater has been investigated. An unstructured model is used to describe cell growth and cell decay in the MAB. The model has been verified by comparing model predicted trends with experimental data collected over 5 to 20-day periods, and has subsequently been used to model steady states in biofilm behavior over longer time scales. The model is capable of predicting the correct trends in system variables such as biofilm thickness, DCE flux across the membrane, carbon dioxide evolution, and suspended biomass. Steady states (constant biofilm thickness and DCE flux) are predicted, and factors that affect these steady states, i.e., cell endogeneous decay rate, and biofilm attrition, are investigated. Biofilm attrition does not have a great influence on biofilm behavior at low values of detachment coefficient close to those typically reported in the literature. Steady-state biofilm thickness is found to be an important variable; a thin biofilm results in a high DCE flux across the membrane, but with the penalty of a high loss of DCE via air stripping. The optimal biofilm thickness at steady state can be determined by trading off the decrease in air stripping (desirable) and the decrease in DCE flux (undesirable) which occur

  18. Factors Influencing Healthcare Service Quality

    Directory of Open Access Journals (Sweden)

    Ali Mohammad Mosadeghrad

    2014-07-01

    Full Text Available Background The main purpose of this study was to identify factors that influence healthcare quality in the Iranian context. Methods Exploratory in-depth individual and focus group interviews were conducted with 222 healthcare stakeholders including healthcare providers, managers, policy-makers, and payers to identify factors affecting the quality of healthcare services provided in Iranian healthcare organisations. Results Quality in healthcare is a production of cooperation between the patient and the healthcare provider in a supportive environment. Personal factors of the provider and the patient, and factors pertaining to the healthcare organisation, healthcare system, and the broader environment affect healthcare service quality. Healthcare quality can be improved by supportive visionary leadership, proper planning, education and training, availability of resources, effective management of resources, employees and processes, and collaboration and cooperation among providers. Conclusion This article contributes to healthcare theory and practice by developing a conceptual framework that provides policy-makers and managers a practical understanding of factors that affect healthcare service quality.

  19. A review of factors influencing the incidence and severity of plaque-induced gingivitis.

    Science.gov (United States)

    Trombelli, L; Farina, R

    2013-06-01

    An individual variation in the gingival inflammatory response to the dental biofilm has been demonstrated. This variability can be observed between individuals with neither quantitative nor qualitative differences in plaque accumulation. The reported significant differences in gingival inflammatory response under quantitatively and/or qualitatively almost identical bacterial challenge suggest that the gingival response to plaque accumulation may be an individual trait, possibly genetic in origin. The most recent classification of periodontal diseases acknowledges that the clinical expression of plaque-induced gingival inflammation can be substantially modified by systemic factors, either inherent to the host or related to environmental influences. The aim of the present literature review is to describe (i) the factors influencing the development of plaque-induced gingivitis as well as (ii) those metabolic, environmental and systemic factors which have a direct impact on the etiopathogenetic pathway of plaque-induced gingivitis, thus altering the nature or course of the gingival inflammatory response to dental biofilm.

  20. The influence of dissolved oxygen level and medium on biofilm formation by Campylobacter jejuni.

    Science.gov (United States)

    Teh, Amy Huei Teen; Lee, Sui Mae; Dykes, Gary A

    2017-02-01

    Campylobacter jejuni survival in aerobic environments has been suggested to be mediated by biofilm formation. Biofilm formation by eight C. jejuni strains under both aerobic and microaerobic conditions in different broths (Mueller-Hinton (MH), Bolton and Brucella) was quantified. The dissolved oxygen (DO) content of the broths under both incubation atmospheres was determined. Biofilm formation for all strains was highest in MH broth under both incubation atmospheres. Four strains had lower biofilm formation in MH under aerobic as compared to microaerobic incubation, while biofilm formation by the other four strains did not differ under the 2 atm. Two strains had higher biofilm formation under aerobic as compared to microaerobic atmospheres in Bolton broth. Biofilm formation by all other strains in Bolton, and all strains in Brucella broth, did not differ under the 2 atm. Under aerobic incubation DO levels in MH > Brucella > Bolton broth. Under microaerobic conditions levels in MH = Brucella > Bolton broth. Levels of DO in MH and Brucella broth were lower under microaerobic conditions but those of Bolton did not differ under the 2 atm. Experimental conditions and especially the DO of broth media confound previous conclusions drawn about aerobic biofilm formation by C. jejuni.

  1. Influence of different combinations of bacteria and yeasts in voice prosthesis biofilms on air flow resistance

    NARCIS (Netherlands)

    Elving, GJ; van der Mei, H; Busscher, H; van Weissenbruch, R; Albers, F

    2003-01-01

    Laryngectomized patients use silicone rubber voice prostheses to rehabilitate their voice. However, biofilm formation limits the lifetime of voice prostheses. The presence of particular combinations of bacterial and yeast strains in voice prosthesis biofilms has been suggested to be crucial for

  2. Influence of putative exopolysaccharide genes on Pseudomonas putida KT2440 biofilm stability

    DEFF Research Database (Denmark)

    Nilsson, Martin; Chiang, Wen-Chi; Fazli, Mustafa;

    2011-01-01

    . putida KT2440 biofilm. The gene clusters alg and bcs, which code for proteins mediating alginate and cellulose biosynthesis, were found to play minor roles in P. putida KT2440 biofilm formation and stability under the conditions tested. A P. putida KT2440 derivative devoid of any identifiable...

  3. Compressive strength of fungal and oral biofilms : biological and environmental influences

    NARCIS (Netherlands)

    Paramonova, Ekaterina

    2009-01-01

    Biofilms play an important role in medically-related fields as they are a major cause of many clinical infections. Knowledge about properties of medically-related biofilms can be beneficial for making predictions about effectiveness of treatments and for development of new medications. In my thesis

  4. Biofilm Thickness Influences Biodiversity in Nitrifying MBBRs-Implications on Micropollutant Removal

    DEFF Research Database (Denmark)

    Torresi, Elena; Fowler, Jane; Polesel, Fabio

    2016-01-01

    biofilm (50 μm) exhibited the highest nitrification rate (gN d(-1) g(-1)), amoA gene abundance and kbio values for some of the most recalcitrant micropollutants (i.e., diclofenac and targeted sulfonamides). Although thin biofilms favored nitrification activity and the removal of some micropollutants...

  5. Statistical analysis of the factors that influenced the mechanical properties improvement of cassava starch films

    Science.gov (United States)

    Monteiro, Mayra; Oliveira, Victor; Santos, Francisco; Barros Neto, Eduardo; Silva, Karyn; Silva, Rayane; Henrique, João; Chibério, Abimaelle

    2017-08-01

    In order to obtain cassava starch films with improved mechanical properties in relation to the synthetic polymer in the packaging production, a complete factorial design 23 was carried out in order to investigate which factor significantly influences the tensile strength of the biofilm. The factors to be investigated were cassava starch, glycerol and modified clay contents. Modified bentonite clay was used as a filling material of the biofilm. Glycerol was the plasticizer used to thermoplastify cassava starch. The factorial analysis suggested a regression model capable of predicting the optimal mechanical property of the cassava starch film from the maximization of the tensile strength. The reliability of the regression model was tested by the correlation established with the experimental data through the following statistical analyse: Pareto graph. The modified clay was the factor of greater statistical significance on the observed response variable, being the factor that contributed most to the improvement of the mechanical property of the starch film. The factorial experiments showed that the interaction of glycerol with both modified clay and cassava starch was significant for the reduction of biofilm ductility. Modified clay and cassava starch contributed to the maximization of biofilm ductility, while glycerol contributed to the minimization.

  6. The influence of biofilm formation on electricity production from tempe wastewater using tubular membraneless microbial fuel cell reactor

    Science.gov (United States)

    Siagian, Nathania Dwi Karina; Arbianti, Rita; Utami, Tania Surya

    2017-05-01

    Microbial fuel cell (MFC) technology can be potentially developed as an alternative energy source since it can convert various substrates from renewable sources into electricity using bacteria as biocatalyst. Tempe wastewater as MFC substrate gives advantages in tempe wastewater treatment and reducing the purchasing cost of bacteria. Currently, the applications of MFCs are still limited due to the relatively low electricity production, so many studies have been conducted to improve the electricity production by MFC. This study focused on investigating the influence of biofilm formation time and the use of macromolecule as additional substrate towards electricity production from MFC system with tubular membranless reactor and tempe wastewater as substrate. This study suggested that biofilm formation on anode could improve the electricity production up to 10-folds while the use of glucose as substrate addition reduce the electricity production up to 60%. The biggest electricity output was obtained from the experiment of biofilm formation for 14 days with EPS content in biofilm 0,13 mg/cm2 where the maximum voltage and power density produced was respectively 34,81 mV and 0,26 mW/m2.

  7. Factors influencing pacing in triathlon

    Directory of Open Access Journals (Sweden)

    Wu SSX

    2014-09-01

    Full Text Available Sam SX Wu,1 Jeremiah J Peiffer,2 Jeanick Brisswalter,3 Kazunori Nosaka,1 Chris R Abbiss1 1Centre for Exercise and Sports Science Research, School of Exercise and Health Sciences, Edith Cowan University, Perth, WA, Australia; 2School of Psychology and Exercise Science, Murdoch University, Perth, WA, Australia; 3Laboratory of Human Motricity, Education Sport and Health, University of Nice Sophia Antipolis, Nice, France Abstract: Triathlon is a multisport event consisting of sequential swim, cycle, and run disciplines performed over a variety of distances. This complex and unique sport requires athletes to appropriately distribute their speed or energy expenditure (ie, pacing within each discipline as well as over the entire event. As with most physical activity, the regulation of pacing in triathlon may be influenced by a multitude of intrinsic and extrinsic factors. The majority of current research focuses mainly on the Olympic distance, whilst much less literature is available on other triathlon distances such as the sprint, half-Ironman, and Ironman distances. Furthermore, little is understood regarding the specific physiological, environmental, and interdisciplinary effects on pacing. Therefore, this article discusses the pacing strategies observed in triathlon across different distances, and elucidates the possible factors influencing pacing within the three specific disciplines of a triathlon. Keywords: cycle, endurance, multisport, pacing strategy, run, swim

  8. Factors influencing women's decisions to purchase specific ...

    African Journals Online (AJOL)

    Keywords: multi-nutrient supplements; survey; children; women's decisions. Factors influencing .... associations between level of education and various factors influencing women's ..... Social marketing improved the use of multivitamin and ...

  9. Factors Influencing Learner Permit Duration

    Directory of Open Access Journals (Sweden)

    Johnathon P. Ehsani

    2016-12-01

    Full Text Available An increasing number of countries are requiring an extended learner permit prior to independent driving. The question of when drivers begin the learner permit period, and how long they hold the permit before advancing to independent licensure has received little research attention. Licensure timing is likely to be related to “push” and “pull” factors which may encourage or inhibit the process. To examine this question, we recruited a sample of 90 novice drivers (49 females and 41 males, average age of 15.6 years soon after they obtained a learner permit and instrumented their vehicles to collect a range of driving data. Participants completed a series of surveys at recruitment related to factors that may influence licensure timing. Two distinct findings emerged from the time-to-event analysis that tested these push and pull factors in relation to licensure timing. The first can be conceptualized as teens’ motivation to drive (push, reflected in a younger age when obtaining a learner permit and extensive pre-permit driving experience. The second finding was teens’ perceptions of their parents’ knowledge of their activities (pull; a proxy for a parents’ attentiveness to their teens’ lives. Teens who reported higher levels of their parents’ knowledge of their activities took longer to advance to independent driving. These findings suggest time-to-licensure may be related to teens’ internal motivation to drive, and the ability of parents to facilitate or impede early licensure.

  10. Influences of trans-trans farnesol, a membrane-targeting sesquiterpenoid, on Streptococcus mutans physiology and survival within mixed-species oral biofilms.

    Science.gov (United States)

    Jeon, Jae-Gyu; Pandit, Santosh; Xiao, Jin; Gregoire, Stacy; Falsetta, Megan L; Klein, Marlise I; Koo, Hyun

    2011-04-01

    Trans-trans farnesol (tt-farnesol) is a bioactive sesquiterpene alcohol commonly found in propolis (a beehive product) and citrus fruits, which disrupts the ability of Streptococcus mutans (S. mutans) to form virulent biofilms. In this study, we investigated whether tt-farnesol affects cell-membrane function, acid production and/or acid tolerance by planktonic cells and biofilms of S. mutans UA159. Furthermore, the influence of the agent on S. mutans gene expression and ability to form biofilms in the presence of other oral bacteria (Streptococcus oralis (S. oralis) 35037 and Actinomyces naeslundii (A. naeslundii) 12104) was also examined. In general, tt-farnesol (1 mmol x L(-1)) significantly increased the membrane proton permeability and reduced glycolytic activity of S. mutans in the planktonic state and in biofilms (P biofilms after introduction of 1% sucrose. S. oralis (a non-cariogenic organism) became the major species after treatments with tt-farnesol, whereas vehicle-treated biofilms contained mostly S. mutans (>90% of total bacterial population). However, the agent did not affect significantly the expression of S. mutans genes involved in acidogenicity, acid tolerance or polysaccharide synthesis in the treated biofilms. Our data indicate that tt-farnesol may affect the competitiveness of S. mutans in a mixed-species environment by primarily disrupting the membrane function and physiology of this bacterium. This naturally occurring terpenoid could be a potentially useful adjunctive agent to the current anti-biofilm/anti-caries chemotherapeutic strategies.

  11. Microscale geochemical gradients in Hanford 300 Area sediment biofilms and influence of uranium.

    Science.gov (United States)

    Nguyen, Hung Duc; Cao, Bin; Mishra, Bhoopesh; Boyanov, Maxim I; Kemner, Kenneth M; Fredrickson, Jim K; Beyenal, Haluk

    2012-01-01

    The presence and importance of microenvironments in the subsurface at contaminated sites were suggested by previous geochemical studies. However, no direct quantitative characterization of the geochemical microenvironments had been reported. We quantitatively characterized microscale geochemical gradients (dissolved oxygen (DO), H(2), pH, and redox potential) in Hanford 300A subsurface sediment biofilms. Our results revealed significant differences in geochemical parameters across the sediment biofilm/water interface in the presence and absence of U(VI) under oxic and anoxic conditions. While the pH was relatively constant within the sediment biofilm, the redox potential and the DO and H(2) concentrations were heterogeneous at the microscale (<500-1000 μm). We found microenvironments with high DO levels (DO hotspots) when the sediment biofilm was exposed to U(VI). On the other hand, we found hotspots (high concentrations) of H(2) under anoxic conditions both in the presence and in the absence of U(VI). The presence of anoxic microenvironments inside the sediment biofilms suggests that U(VI) reduction proceeds under bulk oxic conditions. To test this, we operated our biofilm reactor under air-saturated conditions in the presence of U(VI) and characterized U speciation in the sediment biofilm. U L(III)-edge X-ray absorption spectroscopy (XANES and EXAFS) showed that 80-85% of the U was in the U(IV) valence state.

  12. Arsenate Retention by Epipsammic Biofilms Developed on Streambed Sediments: Influence of Phosphate

    Directory of Open Access Journals (Sweden)

    D. M. Prieto

    2013-01-01

    Full Text Available Natural geological conditions together with the impact of human activities could produce environmental problems due to high As concentrations. The aim of this study was to assess the role of epipsammic biofilm-sediment systems onto As (V sorption and to evaluate the effect of the presence of equimolar P concentrations on As retention. A natural biofilm was grown on sediment samples in the laboratory, using river water as nutrient supplier. Sorption experiments with initial As concentrations 0, 5, 25, 50, 100, 250, and 500 μg L−1 were performed. The average percentage of As sorbed was 78.9±3.5 and 96.9±6.6% for the sediment and biofilm-sediment systems, respectively. Phosphate decreased by 25% the As sorption capactity in the sediment devoid of biofilm, whereas no significant effect was observed in the systems with biofilm. Freundlich, Sips, and Toth models were the best to describe experimental data. The maximum As sorption capacity of the sediment and biofilm-sediment systems was, respectively, 6.6 and 6.8 μg g−1 and 4.5 and 7.8 μg g−1 in the presence of P. In conclusion, epipsammic biofilms play an important role in the environmental quality of river systems, increasing As retention by the system, especially in environments where both As and P occur simultaneously.

  13. Biofilm Cohesive Strength as a Basis for Biofilm Recalcitrance: Are Bacterial Biofilms Overdesigned?

    Science.gov (United States)

    Aggarwal, Srijan; Stewart, Philip S; Hozalski, Raymond M

    2015-01-01

    Bacterial biofilms are highly resistant to common antibacterial treatments, and several physiological explanations have been offered to explain the recalcitrant nature of bacterial biofilms. Herein, a biophysical aspect of biofilm recalcitrance is being reported on. While engineering structures are often overdesigned with a factor of safety (FOS) usually under 10, experimental measurements of biofilm cohesive strength suggest that the FOS is on the order of thousands. In other words, bacterial biofilms appear to be designed to withstand extreme forces rather than typical or average loads. In scenarios requiring the removal or control of unwanted biofilms, this emphasizes the importance of considering strategies for structurally weakening the biofilms in conjunction with bacterial inactivation.

  14. Influence and mechanism of N-(3-oxooxtanoyl)-L-homoserine lactone (C8-oxo-HSL) on biofilm behaviors at early stage

    Institute of Scientific and Technical Information of China (English)

    Siqing Xia; Lijie Zhou; Zhiqiang Zhang; Jixiang Li

    2012-01-01

    N-acyl-homoserines quenching,enzymatic quenching of bacterial quorum sensing,has recently applied to mitigate biofilm in membrane bioreactor.However,the effect of AHLs on the behavior of biofilm formation is still sparse.In this study,Pseudomonas aeruginosa biofilm was formed on ultra-filtration membrane under a series of N-(3-oxooxtanoyl)-L-homoserine lactone (Cs-oxo-HSL)concentrations.Diffusing Cs-oxo-HSL increased the growth rate of cells on biofilm where the concentration of Cs-oxo-HSL was over 10-7 g/L.The C8-oxo-HSL gradient had no observable influence on cell density and extracellular polymeric substances of biofilm with over 10-7 g/L Cs-oxo-HSL.Surprisingly,10-11-10-8 g/L of Cs-oxo-HSL had no effect on cell growth in liquid culture.The cell analysis demonstrated that the quorum sensing system might enhance the growth of neighboring cells in contact with surfaces into biofilm and may influence the structure and organization of biofilm.

  15. Influence and mechanism of N-(3-oxooxtanoyl)-L-homoserine lactone (C8-oxo-HSL) on biofilm behaviors at early stage.

    Science.gov (United States)

    Xia, Siqing; Zhou, Lijie; Zhang, Zhiqiang; Li, Jixiang

    2012-01-01

    N-acyl-homoserines quenching, enzymatic quenching of bacterial quorum sensing, has recently applied to mitigate biofilm in membrane bioreactor. However, the effect of AHLs on the behavior of biofilm formation is still sparse. In this study, Pseudomonas aeruginosa biofilm was formed on ultra-filtration membrane under a series of N-(3-oxooxtanoyl)-L-homoserine lactone (Cs-oxo-HSL) concentrations. Diffusing C8-oxo-HSL increased the growth rate of cells on biofilm where the concentration of C8-oxo-HSL was over 10(-7) g/L. The C8-oxo-HSL gradient had no observable influence on cell density and extracellular polymeric substances of biofilm with over 10(-7) g/L C8-oxo-HSL. Surprisingly, 10(-11)-10(-8) g/L of C8-oxo-HSL had no effect on cell growth in liquid culture. The cell analysis demonstrated that the quorum sensing system might enhance the growth of neighboring cells in contact with surfaces into biofilm and may influence the structure and organization of biofilm.

  16. Pathogenic factors of Pseudomonas aeruginosa – the role of biofilm in pathogenicity and as a target for phage therapy

    Directory of Open Access Journals (Sweden)

    Fairoz Al-Wrafy

    2017-02-01

    Full Text Available Pseudomonas aeruginosa is an opportunistic pathogen that can cause several acute and chronic infections in humans, and it has become an important cause of nosocomial infections and antibiotic resistance. Biofilm represents an important virulence factor for these bacteria, plays a role in P. aeruginosa infections and avoidance of immune defence mechanisms, and has the ability to protect the bacteria from antibiotics. Alginate, Psl and Pel, three exopolysaccharides, are the main components in biofilm matrix, with many biological functions attributed to them, especially with respect to the protection of the bacterial cell from antibiotics and the immune system. Pseudomonas infections, biofilm formation and development of resistance to antibiotics all require better understanding to achieve the best results using alternative treatment with phage therapy. This review describes the P. aeruginosa pathogenicity and virulence factors with a special focus on the biofilm and its role in infection and resistance to antibiotics and summarizes phage therapy as an alternative approach in treatment of P. aeruginosa infections.

  17. XTT assay of ex vivo saliva biofilms to test antimicrobial influences

    OpenAIRE

    Koban, I; Matthes, R.; Hübner, NO; Welk, A; Sietmann, R; Lademann, J.; Kramer, A.; Kocher, T.

    2012-01-01

    Objective: Many dental diseases are attributable to biofilms. The screening of antimicrobial substances, in particular, requires a high sample throughput and a realistic model, the evaluation must be as quick and as simple as possible. For this purpose, a colorimetric assay of the tetrazolium salt XTT (sodium 3'-[1-[(phenylamino)-carbony]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzene-sulfonic acid hydrate) converted by saliva biofilms is recommended. Cleavage of XTT by dehydrogenase enzymes...

  18. Influence of flow velocity on biofilm growth in a tubular heat exchanger-condenser cooled by seawater.

    Science.gov (United States)

    Trueba, Alfredo; García, Sergio; Otero, Félix M; Vega, Luis M; Madariaga, Ernesto

    2015-01-01

    The influence of flow velocity (FV) on the heat transfer process in tubes made from AISI 316L stainless steel in a heat exchanger-condenser cooled by seawater was evaluated based on the characteristics of the resulting biofilm that adhered to the internal surface of the tubes at velocities of 1, 1.2, 1.6, and 3 m s(-1). The results demonstrated that at a higher FV, despite being more compact and consistent, the biofilm was thinner with a lower concentration of solids, and smoother, which favoured the heat transfer process within the equipment. However, higher velocities increase the initial cost of the refrigerating water-pumping equipment and its energy consumption cost to compensate for the greater pressure drops produced in the tube. The velocity of 1.6 m s(-1) represented the equilibrium between the advantages and disadvantages of the variables analysed for the test conditions in this study.

  19. Influence of Temperature, Source, and Serotype on Biofilm Formation of Salmonella enterica Isolates from Pig Slaughterhouses.

    Science.gov (United States)

    Piras, Francesca; Fois, Federica; Consolati, Simonetta Gianna; Mazza, Roberta; Mazzette, Rina

    2015-10-01

    Quantitative assessment of in vitro biofilm formation by 40 Salmonella enterica isolates isolated in pig abattoirs from animal and environmental sources (surfaces in contact and not in contact with meat) and classified in eight seroytpes was carried out by using a microtiter plate assay with spectrophotometric reading (optical density at 620 nm). Biofilm-forming ability was statistically correlated with the temperature of incubation (22 and 35°C), the source of the isolates, and the antimicrobial resistance profile. After incubation at 35°C, 9 isolates (22.5%) were classified as weak biofilm producers. After incubation at 22°C, 25 isolates (62.5%) were classified as weak producers and 3 (7.5%) as moderate producers. The quantity of biofilm formed after incubation at 22°C was significantly higher (P < 0.01) than at 35°C. This result is notable because 22°C is a common temperature in meat processing facilities and in slaughterhouses. At 35°C, isolates detected from surfaces in contact with meat showed significantly higher (P < 0.1) optical density values compared to isolates from other samples, highlighting the risk of cross-contamination for carcasses and offal. No correlation was detected between quantity of biofilm and serotype or between biofilm formation and resistance to antimicrobials.

  20. Influence of Amphibian Antimicrobial Peptides and Short Lipopeptides on Bacterial Biofilms Formed on Contact Lenses

    Directory of Open Access Journals (Sweden)

    Magdalena Maciejewska

    2016-10-01

    Full Text Available The widespread use of contact lenses is associated with several complications, including ocular biofilm-related infections. They are very difficult to manage with standard antimicrobial therapies, because bacterial growth in a biofilm is associated with an increased antibiotic resistance. The principal aim of this study was to evaluate the efficacy of antimicrobial peptides (AMPs in eradication of bacterial biofilms formed on commercially available contact lenses. AMPs were synthesized according to Fmoc/tBu chemistry using the solid-phase method. Minimum inhibitory concentration (MIC and minimum biofilm eradication concentration (MBEC of the compounds were determined. Anti-biofilm activity of the antimicrobial peptides determined at different temperatures (25 °C and 37 °C were compared with the effectiveness of commercially available contact lens solutions. All of the tested compounds exhibited stronger anti-biofilm properties as compared to those of the tested lens solutions. The strongest activity of AMPs was noticed against Gram-positive strains at a temperature of 25 °C. Conclusions: The results of our experiments encourage us toward further studies on AMPs and their potential application in the prophylaxis of contact lens-related eye infections.

  1. Influence of volatile organic compounds emitted by Pseudomonas and Serratia strains on Agrobacterium tumefaciens biofilms.

    Science.gov (United States)

    Plyuta, Vladimir; Lipasova, Valentina; Popova, Alexandra; Koksharova, Olga; Kuznetsov, Alexander; Szegedi, Erno; Chernin, Leonid; Khmel, Inessa

    2016-07-01

    The ability to form biofilms plays an important role in bacteria-host interactions, including plant pathogenicity. In this work, we investigated the action of volatile organic compounds (VOCs) produced by rhizospheric strains of Pseudomonas chlororaphis 449, Pseudomonas fluorescens B-4117, Serratia plymuthica IC1270, as well as Serratia proteamaculans strain 94, isolated from spoiled meat, on biofilms formation by three strains of Agrobacterium tumefaciens which are causative agents of crown-gall disease in a wide range of plants. In dual culture assays, the pool of volatiles emitted by the tested Pseudomonas and Serratia strains suppressed the formation of biofilms of A. tumefaciens strains grown on polycarbonate membrane filters and killed Agrobacterium cells in mature biofilms. The individual VOCs produced by the tested Pseudomonas strains, that is, ketones (2-nonanone, 2-heptanone, 2-undecanone), and dimethyl disulfide (DMDS) produced by Serratia strains, were shown to kill A. tumefaciens cells in mature biofilms and suppress their formation. The data obtained in this study suggest an additional potential of some ketones and DMDS as protectors of plants against A. tumefaciens strains, whose virulence is associated with the formation of biofilms on the infected plants.

  2. Influence of operational conditions on biofilm specific activity of an anaerobic fluidized bed reactor.

    Science.gov (United States)

    García-Morales, J L; Romero, L I; Sales, D

    2003-01-01

    A key parameter in water and wastewater treatment technology is the biomass activity in terms of substrate removal ability. The effects of organic load rate and percentage of bed expansion on biofilm specific methanogenic activity were determined in an anaerobic fluidized bed reactor treating wine-distillery wastes in the thermophilic range (55 degrees C). The proposed activity tests are highly reproducible: an experiment with three identical tests has shown that the standard deviation with respect to the mean values is less than 3%. Specific tests are applied to measure the maximum methanogenic activities of the biomass carrier in lab-scale anaerobic biofilm reactors. These tests have been successfully applied for monitoring the support colonization process and the evolution of biofilm activity in reactors, anaerobic filter and fluidized bed, with different operating conditions. The results show a dependence between the percentage of bed expansion and the specific activity of methanogenic microbiote on biofilm. There is a relationship between the percentage of bed expansion, the sheer stress on the biofilm and the hydrodynamic conditions in the system. Initial biofilm detachment can be compensated with the increase of biomass and of its activity due to the reduction of the substrate diffusional limitations to the microorganism growth inside the support pores.

  3. Biofilms produced by Burkholderia cenocepacia: influence of media and solid supports on composition of matrix exopolysaccharides.

    Science.gov (United States)

    Pellizzoni, Elena; Ravalico, Fabio; Scaini, Denis; Delneri, Ambra; Rizzo, Roberto; Cescutti, Paola

    2016-02-01

    Bacteria usually grow forming biofilms, which are communities of cells embedded in a self-produced dynamic polymeric matrix, characterized by a complex three-dimensional structure. The matrix holds cells together and above a surface, and eventually releases them, resulting in colonization of other surfaces. Although exopolysaccharides (EPOLs) are important components of the matrix, determination of their structure is usually performed on samples produced in non-biofilm conditions, or indirectly through genetic studies. Among the Burkholderia cepacia complex species, Burkholderia cenocepacia is an important pathogen in cystic fibrosis (CF) patients and is generally more aggressive than other species. In the present investigation, B. cenocepacia strain BTS2, a CF isolate, was grown in biofilm mode on glass slides and cellulose membranes, using five growth media, one of which mimics the nutritional content of CF sputum. The structure of the matrix EPOLs was determined by 1H-NMR spectroscopy, while visualization of the biofilms on glass slides was obtained by means of confocal laser microscopy, phase-contrast microscopy and atomic force microscopy. The results confirmed that the type of EPOLs biosynthesized depends both on the medium used and on the type of support, and showed that mucoid conditions do not always lead to significant biofilm production, while bacteria in a non-mucoid state can still form biofilm containing EPOLs.

  4. Influence of supragingival biofilm control and smoking habit on Interleukin-1β concentration

    Directory of Open Access Journals (Sweden)

    Sabrina Carvalho GOMES

    2015-01-01

    Full Text Available This investigation compared gingival crevicular fluid (GCF interleukin-1β (IL-1β concentrations in periodontitis patients subjected to a strict supragingival biofilm control (Supra for 6 months. Never-smokers (23 and smokers (n = 20; 19.6 ± 11.8 cigarettes/day moderate-to-severe chronic periodontitis patients underwent a 6 months period of supragingival control with weekly recall visits. Periodontal probing depth (PPD, bleeding on probing (BOP and GCF samples (from different PPD category sites: 3-5 mm and 6–10 mm were obtained at the baseline, 30, and 180 days. IL-1β was assessed by enzyme-linked immunosorbent assay. Generalized estimating equations were used to fit prediction models of IL-1β changes, considering the dependence between the examinations, and using only data from experimental sites. Overall IL-1β concentrations decreased from 3.2 pg/µL to 1.9 pg/µL. Higher baseline IL-1β concentrations were associated with higher baseline PPD values in both groups. There were no differences in IL-1β concentrations between never-smokers and smokers over time for any PPD category. Higher baseline PPD values and the presence of BOP on day 180 were significantly associated with higher IL-1β concentrations. A strict Supra regimen reduced IL-1β concentrations over time in periodontitis patients. The benefits observed for smokers underline the importance of oral hygiene measures, even considering the presence of this important risk factor.

  5. Effect of biofilm formation on virulence factor secretion via the general secretory pathway in Streptococcus mutans.

    NARCIS (Netherlands)

    Huang, M.; Meng, L.; Fan, M.; Hu, P.; Bian, Z.

    2008-01-01

    OBJECTIVES: To investigate the role of SecA in protein secretion, and to evaluate the effect of biofilm formation on protein secretion in Streptococcus mutans. DESIGN: S. mutans strains UA159 and GS-5 were used in this study. Cells grown in biofilm and planktonic conditions were observed using immun

  6. FACTORS INFLUENCING THE EVOLUTION OF YOUTH TRAVEL

    Directory of Open Access Journals (Sweden)

    Student Claudia MOISĂ

    2010-01-01

    Full Text Available Youth travel is an important part of global tourism, consequently, getting to know the evolution of this form of tourism requires an approach of the aspects regarding the permissive and restrictive factors that influence the youth travel dynamic worldwide. In terms of the factors that influence youth travel, we highlighted these two categories of factors (permissive and restrictive and, within each category, we tried to singularize the influence of every factor over youth travel.

  7. The Danger Signal Extracellular ATP Is an Inducer of Fusobacterium nucleatum Biofilm Dispersal

    Science.gov (United States)

    Ding, Qinfeng; Tan, Kai Soo

    2016-01-01

    Plaque biofilm is the primary etiological agent of periodontal disease. Biofilm formation progresses through multiple developmental stages beginning with bacterial attachment to a surface, followed by development of microcolonies and finally detachment and dispersal from a mature biofilm as free planktonic bacteria. Tissue damage arising from inflammatory response to biofilm is one of the hallmark features of periodontal disease. A consequence of tissue damage is the release of ATP from within the cell into the extracellular space. Extracellular ATP (eATP) is an example of a danger associated molecular pattern (DAMP) employed by mammalian cells to elicit inflammatory and damage healing responses. Although, the roles of eATP as a signaling molecule in multi-cellular organisms have been relatively well studied, exogenous ATP also influences bacteria biofilm formation. Since plaque biofilms are continuously exposed to various stresses including exposure to the host damage factors such as eATP, we hypothesized that eATP, in addition to eliciting inflammation could potentially influence the biofilm lifecycle of periodontal associated bacteria. We found that eATP rather than nutritional factors or oxidative stress induced dispersal of Fusobacterium nucleatum, an organism associated with periodontal disease. eATP induced biofilm dispersal through chelating metal ions present in biofilm. Dispersed F. nucleatum biofilm, regardless of natural or induced dispersal by exogenous ATP, were more adhesive and invasive compared to planktonic or biofilm counterparts, and correspondingly activated significantly more pro-inflammatory cytokine production in infected periodontal fibroblasts. Dispersed F. nucleatum also showed higher expression of fadA, a virulence factor implicated in adhesion and invasion, compared to planktonic or biofilm bacteria. This study revealed for the first time that periodontal bacterium is capable of co-opting eATP, a host danger signaling molecule to detach

  8. Physiological factors influencing capillary growth.

    Science.gov (United States)

    Egginton, S

    2011-07-01

    (1) Angiogenesis (growth of new capillaries from an existing capillary bed) may result from a mismatch in microvascular supply and metabolic demand (metabolic error signal). Krogh examined the distribution and number of capillaries to explore the correlation between O(2) delivery and O(2) consumption. Subsequently, the heterogeneity in angiogenic response within a muscle has been shown to reflect either differences in fibre type composition or mechanical load. However, local control leads to targetted angiogenesis in the vicinity of glycolytic fibre types following muscle stimulation, or oxidative fibres following endurance training, while heterogeneity of capillary spacing is maintained during ontogenetic growth. (2) Despite limited microscopy resolution and lack of specific markers, Krogh's interest in the structure of the capillary wall paved the way for understanding the mechanisms of capillary growth. Angiogenesis may be influenced by the response of perivascular or stromal cells (fibroblasts, macrophages and pericytes) to altered activity, likely acting as a source for chemical signals modulating capillary growth such as vascular endothelial growth factor. In addition, haemodynamic factors such as shear stress and muscle stretch play a significant role in adaptive remodelling of the microcirculation. (3) Most indices of capillarity are highly dependent on fibre size, resulting in possible bias because of scaling. To examine the consequences of capillary distribution, it is therefore helpful to quantify the area of tissue supplied by individual capillaries. This allows the spatial limitations inherent in most models of tissue oxygenation to be overcome generating an alternative approach to Krogh's tissue cylinder, the capillary domain, to improve descriptions of intracellular oxygen diffusion. © 2010 The Author. Acta Physiologica © 2010 Scandinavian Physiological Society.

  9. Detection of Alpha-Toxin and Other Virulence Factors in Biofilms of Staphylococcus aureus on Polystyrene and a Human Epidermal Model

    Science.gov (United States)

    Lemmens-den Toom, N. A.; Willemse, J.; Koning, R. A.; Demmers, J. A. A.; Dekkers, D. H. W.; Rijkers, E.; El Ghalbzouri, A.; Nibbering, P. H.; van Wamel, W.

    2016-01-01

    Background & Aim The ability of Staphylococcus aureus to successfully colonize (a)biotic surfaces may be explained by biofilm formation and the actions of virulence factors. The aim of the present study was to establish the presence of 52 proteins, including virulence factors such as alpha-toxin, during biofilm formation of five different (methicillin resistant) S. aureus strains on Leiden human epidermal models (LEMs) and polystyrene surfaces (PS) using a competitive Luminex-based assay. Results All five S. aureus strains formed biofilms on PS, whereas only three out of five strains formed biofilms on LEMs. Out of the 52 tested proteins, six functionally diverse proteins (ClfB, glucosaminidase, IsdA, IsaA, SACOL0688 and nuclease) were detected in biofilms of all strains on both PS and LEMs. At the same time, four toxins (alpha-toxin, gamma-hemolysin B and leukocidins D and E), two immune modulators (formyl peptide receptor-like inhibitory protein and Staphylococcal superantigen-like protein 1), and two other proteins (lipase and LytM) were detectable in biofilms by all five S. aureus strains on LEMs, but not on PS. In contrast, fibronectin-binding protein B (FnbpB) was detectable in biofilms by all S. aureus biofilms on PS, but not on LEMs. These data were largely confirmed by the results from proteomic and transcriptomic analyses and in case of alpha-toxin additionally by GFP-reporter technology. Conclusion Functionally diverse virulence factors of (methicillin-resistant) S. aureus are present during biofilm formation on LEMs and PS. These results could aid in identifying novel targets for future treatment strategies against biofilm-associated infections. PMID:26741798

  10. Detection of Alpha-Toxin and Other Virulence Factors in Biofilms of Staphylococcus aureus on Polystyrene and a Human Epidermal Model.

    Directory of Open Access Journals (Sweden)

    P M den Reijer

    Full Text Available The ability of Staphylococcus aureus to successfully colonize (abiotic surfaces may be explained by biofilm formation and the actions of virulence factors. The aim of the present study was to establish the presence of 52 proteins, including virulence factors such as alpha-toxin, during biofilm formation of five different (methicillin resistant S. aureus strains on Leiden human epidermal models (LEMs and polystyrene surfaces (PS using a competitive Luminex-based assay.All five S. aureus strains formed biofilms on PS, whereas only three out of five strains formed biofilms on LEMs. Out of the 52 tested proteins, six functionally diverse proteins (ClfB, glucosaminidase, IsdA, IsaA, SACOL0688 and nuclease were detected in biofilms of all strains on both PS and LEMs. At the same time, four toxins (alpha-toxin, gamma-hemolysin B and leukocidins D and E, two immune modulators (formyl peptide receptor-like inhibitory protein and Staphylococcal superantigen-like protein 1, and two other proteins (lipase and LytM were detectable in biofilms by all five S. aureus strains on LEMs, but not on PS. In contrast, fibronectin-binding protein B (FnbpB was detectable in biofilms by all S. aureus biofilms on PS, but not on LEMs. These data were largely confirmed by the results from proteomic and transcriptomic analyses and in case of alpha-toxin additionally by GFP-reporter technology.Functionally diverse virulence factors of (methicillin-resistant S. aureus are present during biofilm formation on LEMs and PS. These results could aid in identifying novel targets for future treatment strategies against biofilm-associated infections.

  11. Factors contributing to the biofilm-deficient phenotype of Staphylococcus aureus sarA mutants.

    Directory of Open Access Journals (Sweden)

    Laura H Tsang

    Full Text Available Mutation of sarA in Staphylococcus aureus results in a reduced capacity to form a biofilm, but the mechanistic basis for this remains unknown. Previous transcriptional profiling experiments identified a number of genes that are differentially expressed both in a biofilm and in a sarA mutant. This included genes involved in acid tolerance and the production of nucleolytic and proteolytic exoenzymes. Based on this we generated mutations in alsSD, nuc and sspA in the S. aureus clinical isolate UAMS-1 and its isogenic sarA mutant and assessed the impact on biofilm formation. Because expression of alsSD was increased in a biofilm but decreased in a sarA mutant, we also generated a plasmid construct that allowed expression of alsSD in a sarA mutant. Mutation of alsSD limited biofilm formation, but not to the degree observed with the corresponding sarA mutant, and restoration of alsSD expression did not restore the ability to form a biofilm. In contrast, concomitant mutation of sarA and nuc significantly enhanced biofilm formation by comparison to the sarA mutant. Although mutation of sspA had no significant impact on the ability of a sarA mutant to form a biofilm, a combination of protease inhibitors (E-64, 1-10-phenanthroline, and dichloroisocoumarin that was shown to inhibit the production of multiple extracellular proteases without inhibiting growth was also shown to enhance the ability of a sarA mutant to form a biofilm. This effect was evident only when all three inhibitors were used concurrently. This suggests that the reduced capacity of a sarA mutant to form a biofilm involves extracellular proteases of all three classes (serine, cysteine and metalloproteases. Inclusion of protease inhibitors also enhanced biofilm formation in a sarA/nuc mutant, with the combined effect of mutating nuc and adding protease inhibitors resulting in a level of biofilm formation with the sarA mutant that approached that of the UAMS-1 parent strain. These results

  12. Influence of clove oil on certain quorum-sensing-regulated functions and biofilm of Pseudomonas aeruginosa and Aeromonas hydrophila

    Indian Academy of Sciences (India)

    Fohad Mabood Husain; Iqbal Ahmad; Mohammad Asif; Qudsia Tahseen

    2013-12-01

    Quorum sensing (QS) plays an important role in virulence, biofilm formation and survival of many pathogenic bacteria including Pseudomonas aeruginosa. This signalling pathway is considered as novel and promising target for anti-infective agents. In the present investigation, effect of the Sub-MICs of clove oil on QS regulated virulence factors and biofilm formation was evaluated against P. aeruginosa PAO1 and Aeromonas hydrophila WAF-38 strain. Sub-inhibitory concentrations of the clove oil demonstrated statistically significant reduction of las- and rhl-regulated virulence factors such as LasB, total protease, chitinase and pyocyanin production, swimming motility and exopolysaccharide production. The biofilm forming capability of PAO1 and A. hydrophila WAF-38 was also reduced in a concentration-dependent manner at all tested sub-MIC values. Further, the PAO1-preinfected Caenorhabditis elegans displayed an enhanced survival when treated with 1.6% v/v of clove oil. The above findings highlight the promising anti-QS-dependent therapeutic function of clove oil against P. aeruginosa.

  13. Influence of Nutrient Availability and Quorum Sensing on the Formation of Metabolically Inactive Microcolonies Within Structurally Heterogeneous Bacterial Biofilms: An Individual-Based 3D Cellular Automata Model.

    Science.gov (United States)

    Machineni, Lakshmi; Rajapantul, Anil; Nandamuri, Vandana; Pawar, Parag D

    2017-03-01

    The resistance of bacterial biofilms to antibiotic treatment has been attributed to the emergence of structurally heterogeneous microenvironments containing metabolically inactive cell populations. In this study, we use a three-dimensional individual-based cellular automata model to investigate the influence of nutrient availability and quorum sensing on microbial heterogeneity in growing biofilms. Mature biofilms exhibited at least three structurally distinct strata: a high-volume, homogeneous region sandwiched between two compact sections of high heterogeneity. Cell death occurred preferentially in layers in close proximity to the substratum, resulting in increased heterogeneity in this section of the biofilm; the thickness and heterogeneity of this lowermost layer increased with time, ultimately leading to sloughing. The model predicted the formation of metabolically dormant cellular microniches embedded within faster-growing cell clusters. Biofilms utilizing quorum sensing were more heterogeneous compared to their non-quorum sensing counterparts, and resisted sloughing, featuring a cell-devoid layer of EPS atop the substratum upon which the remainder of the biofilm developed. Overall, our study provides a computational framework to analyze metabolic diversity and heterogeneity of biofilm-associated microorganisms and may pave the way toward gaining further insights into the biophysical mechanisms of antibiotic resistance.

  14. Legionella-protozoa-nematode interactions in aquatic biofilms and influence of Mip on Caenorhabditis elegans colonization.

    Science.gov (United States)

    Rasch, Janine; Krüger, Stefanie; Fontvieille, Dominique; Ünal, Can M; Michel, Rolf; Labrosse, Aurélie; Steinert, Michael

    2016-09-01

    Legionella pneumophila, the causative agent of Legionnaireś disease, is naturally found in aquatic habitats. The intracellular life cycle within protozoa pre-adapted the "accidental" human pathogen to also infect human professional phagocytes like alveolar macrophages. Previous studies employing the model organism Caenorhabditis elegans suggest that also nematodes might serve as a natural host for L. pneumophila. Here, we report for the first time from a natural co-habitation of L. pneumophila and environmental nematode species within biofilms of a warm water spring. In addition, we identified the protozoan species Oxytricha bifaria, Stylonychia mytilus, Ciliophrya sp. which have never been described as potential interaction partners of L. pneumophila before. Modeling and dissection of the Legionella-protozoa-nematode interaction revealed that C. elegans ruptures Legionella-infected amoebal cells and by this means incorporate the pathogen. Further infection studies revealed that the macrophage infectivity potentiator (Mip) protein of L. pneumophila, which is known to bind collagen IV during human lung infection, promotes the colonization of the intestinal tract of L4 larvae of C. elegans and negatively influences the life span of the worms. The Mip-negative L. pneumophila mutant exhibited a 32-fold reduced colonization rate of the nematodes after 48h when compared to the wild-type strain. Taken together, these studies suggest that nematodes may serve as natural hosts for L. pneumophila, promote their persistence and dissemination in the environment, and co-evolutionarily pre-adapt the pathogen for interactions with extracellular constituents of human lung tissue. Copyright © 2016 Elsevier GmbH. All rights reserved.

  15. Influence of artificial saliva in biofilm formation of Candida albicans in vitro

    Directory of Open Access Journals (Sweden)

    Michelle Peneluppi Silva

    2012-02-01

    Full Text Available Due to the increase in life expectancy, new treatments have emerged which, although palliative, provide individuals with a better quality of life. Artificial saliva is a solution that contains substances that moisten a dry mouth, thus mimicking the role of saliva in lubricating the oral cavity and controlling the existing normal oral microbiota. This study aimed to assess the influence of commercially available artificial saliva on biofilm formation by Candida albicans. Artificial saliva I consists of carboxymethylcellulose, while artificial saliva II is composed of glucose oxidase, lactoferrin, lysozyme and lactoperoxidase. A control group used sterile distilled water. Microorganisms from the oral cavity were transferred to Sabouraud Dextrose Agar and incubated at 37°C for 24 hours. Colonies of Candida albicans were suspended in a sterile solution of NaCl 0.9%, and standardisation of the suspension to 106 cells/mL was achieved. The acrylic discs, immersed in artificial saliva and sterile distilled water, were placed in a 24-well plate containing 2 mL of Sabouraud Dextrose Broth plus 5% sucrose and 0.1 mL aliquot of the Candida albicans suspension. The plates were incubated at 37°C for 5 days, the discs were washed in 2 mL of 0.9% NaCl and placed into a tube containing 10 mL of 0.9% NaCl. After decimal dilutions, aliquots of 0.1 mL were seeded on Sabouraud Dextrose Agar and incubated at 37°C for 48 hours. Counts were reported as CFU/mL (Log10. A statistically significant reduction of 29.89% (1.45 CFU/mL of Candida albicans was observed in saliva I when compared to saliva II (p = 0.002, considering p≤0.05.

  16. Compaction and relaxation of biofilms

    KAUST Repository

    Valladares Linares, R.

    2015-06-18

    Operation of membrane systems for water treatment can be seriously hampered by biofouling. A better characterization of biofilms in membrane systems and their impact on membrane performance may help to develop effective biofouling control strategies. The objective of this study was to determine the occurrence, extent and timescale of biofilm compaction and relaxation (decompaction), caused by permeate flux variations. The impact of permeate flux changes on biofilm thickness, structure and stiffness was investigated in situ and non-destructively with optical coherence tomography using membrane fouling monitors operated at a constant crossflow velocity of 0.1 m s−1 with permeate production. The permeate flux was varied sequentially from 20 to 60 and back to 20 L m−2 h−1. The study showed that the average biofilm thickness on the membrane decreased after elevating the permeate flux from 20 to 60 L m−2 h−1 while the biofilm thickness increased again after restoring the original flux of 20 L m−2 h−1, indicating the occurrence of biofilm compaction and relaxation. Within a few seconds after the flux change, the biofilm thickness was changed and stabilized, biofilm compaction occurred faster than the relaxation after restoring the original permeate flux. The initial biofilm parameters were not fully reinstated: the biofilm thickness was reduced by 21%, biofilm stiffness had increased and the hydraulic biofilm resistance was elevated by 16%. Biofilm thickness was related to the hydraulic biofilm resistance. Membrane performance losses are related to the biofilm thickness, density and morphology, which are influenced by (variations in) hydraulic conditions. A (temporarily) permeate flux increase caused biofilm compaction, together with membrane performance losses. The impact of biofilms on membrane performance can be influenced (increased and reduced) by operational parameters. The article shows that a (temporary) pressure increase leads to more

  17. Influence of dental biofilm on release of mercury from amalgam exposed to carbamide peroxide.

    Science.gov (United States)

    Steinberg, Doron; Blank, Ori; Rotstein, Ilan

    2003-10-15

    Tooth bleaching is a popular procedure in modern aesthetic dentistry. Bleaching agents may affect amalgam restorations by altering the release of mercury. The aim of this study was to explore the effect of biofilm-coated amalgam restorations on the release of mercury in the presence of carbamide peroxide. Samples of SDI and Valliant amalgams were submerged for either 14 days or 7 months in buffered KCl after which they were coated with saliva, bacteria, and polysaccharides. The samples were exposed to 10% carbamide peroxide (CP) for 24 h. The amount of mercury released was examined for 120 h. Results showed that most of mercury release occurred within the first 24 h, after which the release rate decreased sharply. After 120 h the release of mercury from the tested samples was minimal and similar to the control group. The presence of biofilm coating on the amalgam samples did not induce the release of mercury but tended to reduce mercury release into the surrounding environment. CP induces the release of mercury from amalgam samples. However, the presence of biofilm did not prevent large amounts of mercury release from amalgam coated with biofilms and exposed to CP. This study indicates that dental biofilm may retard the release of mercury from amalgam restorations.

  18. Influence of MDPB-containing primer on Streptococcus mutans biofilm formation in simulated Class I restorations.

    Science.gov (United States)

    Brambilla, Eugenio; Ionescu, Andrei; Fadini, Luigi; Mazzoni, Annalisa; Imazato, Satoshi; Pashley, David; Breschi, Lorenzo; Gagliani, Massimo

    2013-10-01

    To evaluate the activity of a methacryloyloxydodecylpyridinium bromide (MDPB)-containing self-etching primer (Clearfil Protect Bond) against Streptococcus mutans and its ability to reduce biofilm formation on standardized experimental Class I restorations in vitro. Forty experimental Class I round restorations were prepared on enamel-dentin slabs using different adhesive strategies: group 1 = MDPB-containing adhesive system (Clearfil Protect Bond); group 2 = MDPB-free self-etching adhesive system (Clearfil SE Bond); group 3: MDPB-containing self-etching primer in combination with a fluoride-free bonding agent; group 4: MDPB-free self-etching primer in combination with a fluoride-containing bonding agent; group 5: a three-step etch-and-rinse adhesive system (Adper Scotchbond Multi Purpose). A Streptococcus mutans biofilm was grown for 48 h on the restoration surfaces and subsequently evaluated using scanning electron microscopy on three different areas: enamel, composite, and interface surfaces. Statistical analysis was performed by multiple ANOVA after data transformation. Specimens in groups 2, 4 and 5 showed greater biofilm formation than those in groups 1 and 3 (p composite, and interface areas). Specimens prepared with an MDPB-containing primer exhibited significant decreases in biofilm formation on Class I restorations in vitro. Further in vitro and in vivo studies are required to clarify the role of quaternary ammonium compounds in reducing bacterial biofilm formation on restoration surfaces.

  19. Beta-hexosaminidase activity of the oral pathogen Tannerella forsythia influences biofilm formation on glycoprotein substrates.

    Science.gov (United States)

    Roy, Sumita; Phansopa, Chatchawal; Stafford, Prachi; Honma, Kiyonobu; Douglas, C W Ian; Sharma, Ashu; Stafford, Graham P

    2012-06-01

    Tannerella forsythia is an important pathogen in periodontal disease. Previously, we showed that its sialidase activity is key to utilization of sialic acid from a range of human glycoproteins for biofilm growth and initial adhesion. Removal of terminal sialic acid residues often exposes β-linked glucosamine or galactosamine, which may also be important adhesive molecules. In turn, these residues are often removed by a group of enzymes known as β-hexosaminidases. We show here that T. forsythia has the ability to cleave glucosamine and galactosamine from model substrates and that this activity can be inhibited by the hexosaminidase inhibitor PugNAc (O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino N-phenyl carbamate). We now demonstrate for the first time that β-hexosaminidase activity plays a role in biofilm growth on glycoprotein-coated surfaces because biofilm growth and initial cell adhesion are inhibited by PugNAc. In contrast, adhesion to siallo-glycoprotein-coated surfaces is unaltered by PugNAc in the absence of sialidase activity (using a sialidase-deficient mutant) or surprisingly on the clinically relevant substrates saliva or serum. These data indicate that β-hexosaminidase activity has a significant role in biofilm formation in combination with sialidase activity in the biofilm lifestyle of T. forsythia.

  20. Determination of the external mass transfer coefficient and influence of mixing intensity in moving bed biofilm reactors for wastewater treatment.

    Science.gov (United States)

    Nogueira, Bruno L; Pérez, Julio; van Loosdrecht, Mark C M; Secchi, Argimiro R; Dezotti, Márcia; Biscaia, Evaristo C

    2015-09-01

    In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies.

  1. Biofilm Risks

    DEFF Research Database (Denmark)

    Wirtanen, Gun Linnea; Salo, Satu

    2016-01-01

    This chapter on biofilm risks deals with biofilm formation of pathogenic microbes, sampling and detection methods, biofilm removal, and prevention of biofilm formation. Several common pathogens produce sticky and/or slimy structures in which the cells are embedded, that is, biofilms, on various s...

  2. Vibriophages differentially influence biofilm formation by Vibrio anguillarum strains

    DEFF Research Database (Denmark)

    Tan, Demeng; Dahl, Amalie; Middelboe, Mathias

    2015-01-01

    and surface-associated growth conditions. In this study, we explored in vitro phage-host interactions in two different strains of V. anguillarum (BA35 and PF430-3) during growth in microcolonies, biofilms, and free-living cells. Two vibriophages, ΦH20 (Siphoviridae) and KVP40 (Myoviridae), had completely......Vibrio anguillarum is an important pathogen in marine aquaculture, responsible for vibriosis. Bacteriophages can potentially be used to control bacterial pathogens; however, successful application of phages requires a detailed understanding of phage-host interactions under both free-living...... different effects on the biofilm development. Addition of phage ΦH20 to strain BA35 showed efficient control of biofilm formation and density of free-living cells. The interactions between BA35 and ΦH20 were thus characterized by a strong phage control of the phage-sensitive population and subsequent...

  3. Influence of glyphosate in planktonic and biofilm growth of Pseudomonas aeruginosa

    Directory of Open Access Journals (Sweden)

    Ilana Schneider Lima

    2014-09-01

    Full Text Available This study evaluated the impact of different concentrations of glyphosate (Rondup® on planktonic and biofilm growth of P. aeruginosa. Aerobic and anaerobic cultures of P. aeruginosa ATCC®15442 inoculated in MHB + glyphosate (0.845 ppm, 1.690 ppm, 8.45 ppm, 16.90 ppm, 84.50 ppm, 169 ppm, 845 ppm, and 1690 ppm and cultured in normoxia and anoxia, following their OD560nm every hour for 24 h. Biofilms of adapted cells were formed in the presence of glyphosate (0.845 to 1690 ppm in normoxia and anoxia for 36 h. Glyphosate at concentrations higher than 84.5 ppm reduces the cell density of planktonic aerobic cultures (p 0.05, and more pronounced over 169 ppm. Anaerobic biofilms have their growth more readily favored (p < 0.05, regardless of concentration. In a concentration-dependent manner, glyphosate interferes with the growth ability of P. aeruginosa ATCC®15442.

  4. Influence of nutrient inputs, hexadecane, and temporal variations on denitrification and community composition of river biofilms.

    Science.gov (United States)

    Chénier, M R; Beaumier, D; Fortin, N; Roy, R; Driscoll, B T; Lawrence, J R; Greer, C W

    2006-01-01

    Biofilms were cultivated on polycarbonate strips in rotating annular reactors using South Saskatchewan River water during the fall of 1999 and the fall of 2001, supplemented with carbon (glucose), nitrogen (NH4Cl), phosphorus (KH2PO4), or combined nutrients (CNP), with or without hexadecane, a model compound representing aliphatic hydrocarbons used to simulate a pollutant. In fall 1999 and fall 2001, comparable denitrification activities and catabolic potentials were observed in the biofilms, implying that denitrifying populations showed similar activity patterns and catabolic potentials during the fall from year to year in this river ecosystem, when environmental conditions were similar. Both nirS and nirK denitrification genes were detected by PCR amplification, suggesting that both denitrifying bacterial subpopulations can potentially contribute to total denitrification. Between 91.7 and 99.8% of the consumed N was emitted in the form of N2, suggesting that emission of N2O, a major potent greenhouse gas, by South Saskatchewan River biofilms is low. Denitrification was markedly stimulated by the addition of CNP, and nirS and nirK genes were predominant only in the presence of CNP. In contrast, individual nutrients had no impact on denitrification and on the occurrence of nirS and nirK genes detected by PCR amplification. Similarly, only CNP resulted in significant increases in algal and bacterial biomass relative to control biofilms. Biomass measurements indicated a linkage between autotrophic and heterotrophic populations in the fall 1999 biofilms. Correlation analyses demonstrated a significant relationship (P < or = 0.05) between the denitrification rate and the biomass of algae and heterotrophic bacteria but not cyanobacteria. At the concentration assessed (1 ppb), hexadecane partially inhibited denitrification in both years, slightly more in the fall of 2001. This study suggested that the response of the anaerobic heterotrophic biofilm community may be

  5. Red fluorescent biofilm: the thick, the old, and the cariogenic

    Directory of Open Access Journals (Sweden)

    Catherine M.C. Volgenant

    2016-04-01

    Full Text Available Background: Some dental plaque fluoresces red. The factors involved in this fluorescence are yet unknown. Objective: The aim of this study was to assess systematically the effect of age, thickness, and cariogenicity on the extent of red fluorescence produced by in vitro microcosm biofilms. Design: The effects of biofilm age and thickness on red fluorescence were tested in a constant depth film fermentor (CDFF by growing biofilms of variable thicknesses that received a constant supply of defined mucin medium (DMM and eight pulses of sucrose/day. The influence of cariogenicity on red fluorescence was tested by growing biofilm on dentin disks receiving DMM, supplemented with three or eight pulses of sucrose/day. The biofilms were analyzed at different time points after inoculation, up to 24 days. Emission spectra were measured using a fluorescence spectrophotometer (λexc405 nm and the biofilms were photographed with a fluorescence camera. The composition of the biofilms was assessed using 454-pyrosequecing of the 16S rDNA gene. Results: From day 7 onward, the biofilms emitted increasing intensities of red fluorescence as evidenced by the combined red fluorescence peaks. The red fluorescence intensity correlated with biofilm thickness but not in a linear way. Biofilm fluorescence also correlated with the imposed cariogenicity, evidenced by the induced dentin mineral loss. Increasing the biofilm age or increasing the sucrose pulsing frequency led to a shift in the microbial composition. These shifts in composition were accompanied by an increase in red fluorescence. Conclusions: The current study shows that a thicker, older, or more cariogenic biofilm results in a higher intensity of red fluorescence.

  6. Red fluorescent biofilm: the thick, the old, and the cariogenic

    Science.gov (United States)

    Volgenant, Catherine M.C.; Hoogenkamp, Michel A.; Buijs, Mark J.; Zaura, Egija; ten Cate, Jacob (Bob) M.; van der Veen, Monique H.

    2016-01-01

    Background Some dental plaque fluoresces red. The factors involved in this fluorescence are yet unknown. Objective The aim of this study was to assess systematically the effect of age, thickness, and cariogenicity on the extent of red fluorescence produced by in vitro microcosm biofilms. Design The effects of biofilm age and thickness on red fluorescence were tested in a constant depth film fermentor (CDFF) by growing biofilms of variable thicknesses that received a constant supply of defined mucin medium (DMM) and eight pulses of sucrose/day. The influence of cariogenicity on red fluorescence was tested by growing biofilm on dentin disks receiving DMM, supplemented with three or eight pulses of sucrose/day. The biofilms were analyzed at different time points after inoculation, up to 24 days. Emission spectra were measured using a fluorescence spectrophotometer (λexc405 nm) and the biofilms were photographed with a fluorescence camera. The composition of the biofilms was assessed using 454-pyrosequecing of the 16S rDNA gene. Results From day 7 onward, the biofilms emitted increasing intensities of red fluorescence as evidenced by the combined red fluorescence peaks. The red fluorescence intensity correlated with biofilm thickness but not in a linear way. Biofilm fluorescence also correlated with the imposed cariogenicity, evidenced by the induced dentin mineral loss. Increasing the biofilm age or increasing the sucrose pulsing frequency led to a shift in the microbial composition. These shifts in composition were accompanied by an increase in red fluorescence. Conclusions The current study shows that a thicker, older, or more cariogenic biofilm results in a higher intensity of red fluorescence. PMID:27060056

  7. Functional Relationship between Sucrose and a Cariogenic Biofilm Formation.

    Directory of Open Access Journals (Sweden)

    Jian-Na Cai

    Full Text Available Sucrose is an important dietary factor in cariogenic biofilm formation and subsequent initiation of dental caries. This study investigated the functional relationships between sucrose concentration and Streptococcus mutans adherence and biofilm formation. Changes in morphological characteristics of the biofilms with increasing sucrose concentration were also evaluated. S. mutans biofilms were formed on saliva-coated hydroxyapatite discs in culture medium containing 0, 0.05, 0.1, 0.5, 1, 2, 5, 10, 20, or 40% (w/v sucrose. The adherence (in 4-hour biofilms and biofilm composition (in 46-hour biofilms of the biofilms were analyzed using microbiological, biochemical, laser scanning confocal fluorescence microscopic, and scanning electron microscopic methods. To determine the relationships, 2nd order polynomial curve fitting was performed. In this study, the influence of sucrose on bacterial adhesion, biofilm composition (dry weight, bacterial counts, and water-insoluble extracellular polysaccharide (EPS content, and acidogenicity followed a 2nd order polynomial curve with concentration dependence, and the maximum effective concentrations (MECs of sucrose ranged from 0.45 to 2.4%. The bacterial and EPS bio-volume and thickness in the biofilms also gradually increased and then decreased as sucrose concentration increased. Furthermore, the size and shape of the micro-colonies of the biofilms depended on the sucrose concentration. Around the MECs, the micro-colonies were bigger and more homogeneous than those at 0 and 40%, and were surrounded by enough EPSs to support their structure. These results suggest that the relationship between sucrose concentration and cariogenic biofilm formation in the oral cavity could be described by a functional relationship.

  8. Influence of biofilms on iron and manganese deposition in drinking water distribution systems.

    Science.gov (United States)

    Ginige, Maneesha P; Wylie, Jason; Plumb, Jason

    2011-02-01

    Although health risk due to discoloured water is minimal, such water continues to be the source of one of the major complaints received by most water utilities in Australia. Elevated levels of iron (Fe) and/or manganese (Mn) in bulk water are associated with discoloured water incidents. The accumulation of these two elements in distribution systems is believed to be one of the main causes for such elevated levels. An investigation into the contribution of pipe wall biofilms towards Fe and Mn deposition, and discoloured water events is reported in this study. Eight laboratory-scale reactors were operated to test four different conditions in duplicate. Four reactors were exposed to low Fe (0.05 mg l(-1)) and Mn (0.02 mg l(-1)) concentrations and the remaining four were exposed to a higher (0.3 and 0.4 mg l(-1) for Fe and Mn, respectively) concentration. Two of the four reactors which received low and high Fe and Mn concentrations were chlorinated (3.0 mg l(-1) of chlorine). The biological activity (measured in terms of ATP) on the glass rings in these reactors was very low (∼1.5 ng cm(-2) ring). Higher concentrations of Fe and Mn in bulk water and active biofilms resulted in increased deposition of Fe and Mn on the glass rings. Moreover, with an increase in biological activity, an increase in Fe and Mn deposition was observed. The observations in the laboratory-scale experiments were in line with the results of field observations that were carried out using biofilm monitors. The field data additionally demonstrated the effect of seasons, where increased biofilm activities observed on pipe wall biofilms during late summer and early autumn were found to be associated with increased deposition of Fe and Mn. In contrast, during the cooler months, biofilm activities were a magnitude lower and the deposited metal concentrations were also significantly less (ie a drop of 68% for Fe and 86% for Mn). Based on the laboratory-scale investigations, detachment of pipe wall

  9. The influence of biofilms on the migration of uranium in acid mine drainage (AMD) waters

    Energy Technology Data Exchange (ETDEWEB)

    Krawczyk-Baersch, E., E-mail: E.Krawczyk-Baersch@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiochemistry, P.O. Box 51 01 19, D-01314 Dresden (Germany); Luensdorf, H. [Helmholtz Centre for Infection Research, Department of Vaccinology and Applied Microbiology, Inhoffenstr. 7, D-38124 Braunschweig (Germany); Arnold, T.; Brendler, V. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiochemistry, P.O. Box 51 01 19, D-01314 Dresden (Germany); Eisbein, E. [TU Bergakademie Freiberg, Institute of Physical Chemistry, Akademiestrasse 6, D-09596 Freiberg (Germany); Jenk, U.; Zimmermann, U. [Wismut GmbH, Jagdschaenkenstr. 29, D-09117 Chemnitz (Germany)

    2011-07-15

    The uranium mine in Koenigstein (Germany) is currently in the process of being flooded. Huge mass of Ferrovum myxofaciens dominated biofilms are growing in the acid mine drainage (AMD) water as macroscopic streamers and as stalactite-like snottites hanging from the ceiling of the galleries. Microsensor measurements were performed in the AMD water as well as in the biofilms from the drainage channel on-site and in the laboratory. The analytical data of the AMD water was used for the thermodynamic calculation of the predominance fields of the aquatic uranium sulfate (UO{sub 2}SO{sub 4}) and UO{sub 2}{sup ++} speciation as well as of the solid uranium species Uranophane [Ca(UO{sub 2}){sub 2}(SiO{sub 3}OH){sub 2}{center_dot}5H{sub 2}O] and Coffinite [U(SiO{sub 4}){sub 1-x}(OH){sub 4x}], which are defined in the stability field of pH > 4.8 and Eh < 960 mV and pH > 0 and Eh < 300 mV, respectively. The plotting of the measured redox potential and pH of the AMD water and the biofilm into the calculated pH-Eh diagram showed that an aqueous uranium(VI) sulfate complex exists under the ambient conditions. According to thermodynamic calculations a retention of uranium from the AMD water by forming solid uranium(VI) or uranium(IV) species will be inhibited until the pH will increase to > 4.8. Even analysis by Energy-filtered Transmission Electron Microscopy (EF-TEM) and electron energy loss spectroscopy (EELS) within the biofilms did not provide any microscopic or spectroscopic evidence for the presence of uranium immobilization. In laboratory experiments the first phase of the flooding process was simulated by increasing the pH of the AMD water. The results of the experiments indicated that the F. myxofaciens dominated biofilms may have a substantial impact on the migration of uranium. The AMD water remained acid although it was permanently neutralized with the consequence that the retention of uranium from the aqueous solution by the formation of solid uranium species will be

  10. Influence of pH of Candida albicans biofilm in the susceptibility to fluconazole

    OpenAIRE

    2012-01-01

    Resumo: Na cavidade oral, a colonização por Candida albicans em nichos com valores distintos de pH contribui para o desenvolvimento de candidose associada ao uso de prótese. O tratamento dessa infecção tem sido facilitado utilizando-se o fluconazol (FLZ). Entretanto, não está claro se o pH dos biofilmes de C. albicans interfere na susceptibilidade destes ao FLZ. Dessa forma, neste trabalho foi avaliada a influência do pH de biofilmes de C. albicans na susceptibilidade ao FLZ. Testes de suscep...

  11. Demotivating factors influencing rubber production workers

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Iravani

    2012-01-01

    Full Text Available Motivation is one of the most important factors influencing workers' productivity. An increase in workers' motivation could add more value to organizations' structure and influence the profitability, significantly. In this paper, we study different factors on demotivating workers using questionnaire consist of various questions. The questionnaire is distributed among some employees who work for rubber production units located in Esfahan, Iran. The results of this survey indicate that discrimination on annual job compensation, entrusting responsibilities and unpleasant relationship with family partner are some of the most important factors influencing employees' motivation. While financial factors play important role on increasing employees' motivation, non-financial factors are considered more important.

  12. Impact of Hydrodynamics on Oral Biofilm Strength

    NARCIS (Netherlands)

    Paramonova, E.; Kalmykowa, O. J.; van der Mei, H. C.; Busscher, H. J.; Sharma, P. K.

    2009-01-01

    Mechanical removal of oral biofilms is ubiquitously accepted as the best way to prevent caries and periodontal diseases. Removal effectiveness strongly depends on biofilm strength. To investigate the influence of hydrodynamics on oral biofilm strength, we grew single- and multi-species biofilms of S

  13. Biofilm formation of Francisella noatunensis subsp. orientalis

    Science.gov (United States)

    Soto, Esteban; Halliday-Wimmonds, Iona; Francis , Stewart; Kearney, Michael T; Hansen, John D.

    2015-01-01

    Francisella noatunensis subsp. orientalis (Fno) is an emergent fish pathogen in both marine and fresh water environments. The bacterium is suspected to persist in the environment even without the presence of a suitable fish host. In the present study, the influence of different abiotic factors such as salinity and temperature were used to study the biofilm formation of different isolates of Fno including intracellular growth loci C (iglC)and pathogenicity determinant protein A (pdpA) knockout strains. Finally, we compared the susceptibility of planktonic and biofilm to three disinfectants used in the aquaculture and ornamental fish industry, namely Virkon®, bleach and hydrogen peroxide. The data indicates that Fno is capable of producing biofilms within 24 h where both salinity as well as temperature plays a role in the growth and biofilm formation of Fno. Mutations in theiglC or pdpA, both known virulence factors, do not appear to affect the capacity of Fno to produce biofilms, and the minimum inhibitory concentration, and minimum biocidal concentration for the three disinfectants were lower than the minimum biofilm eradication concentration values. This information needs to be taken into account if trying to eradicate the pathogen from aquaculture facilities or aquariums.

  14. Overview of biofilm formation in distribution systems and its impact on the deterioration of water quality

    CSIR Research Space (South Africa)

    Momba, MNB

    2000-01-01

    Full Text Available and significance of biofilms on the microbial quality of drinking water. The review addresses the main factors governing the formation of biofilms such as the types of disinfectants and residual concentrations, resistance of bacteria to disinfectants, the influence...

  15. Different carbon isotope fractionation patterns during the development of phototrophic freshwater and marine biofilms

    NARCIS (Netherlands)

    Staal, M.; Thar, R.; Kühl, M.; Van Loosdrecht, M.C.M.; Wolf, G.; De Brouwer, J.F.C.; Rijstenbil, J.W.

    2007-01-01

    Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which is expected to lead to a limitation of

  16. Combating biofilms

    DEFF Research Database (Denmark)

    Yang, Liang; Liu, Yang; Wu, Hong;

    2012-01-01

    Biofilms are complex microbial communities consisting of microcolonies embedded in a matrix of self-produced polymer substances. Biofilm cells show much greater resistance to environmental challenges including antimicrobial agents than their free-living counterparts. The biofilm mode of life...... is believed to significantly contribute to successful microbial survival in hostile environments. Conventional treatment, disinfection and cleaning strategies do not proficiently deal with biofilm-related problems, such as persistent infections and contamination of food production facilities. In this review......, strategies to control biofilms are discussed, including those of inhibition of microbial attachment, interference of biofilm structure development and differentiation, killing of biofilm cells and induction of biofilm dispersion....

  17. Rapid depletion of dissolved oxygen in 96 well microtitre plate Staphylococcus epidermidis biofilm assays promotes biofilm development and is influenced by inoculum cell concentration

    OpenAIRE

    Cotter, John J.; O'Gara, James P.; Casey, Eoin

    2009-01-01

    Biofilm-related research using 96-well microtiter plates involves static incubation of plates indiscriminate of environmental conditions, making oxygen availability an important variable which has not been considered to date. By directly measuring dissolved oxygen concentration over time we report here that dissolved oxygen is rapidly consumed in Staphylococcus epidermidis biofilm cultures grown in 96-well plates irrespective of the oxygen concentration in the gaseous environment in which the...

  18. Influence of lysogeny of Tectiviruses GIL01 and GIL16 on Bacillus thuringiensis growth, biofilm formation, and swarming motility.

    Science.gov (United States)

    Gillis, Annika; Mahillon, Jacques

    2014-12-01

    Bacillus thuringiensis is an entomopathogenic bacterium that has been used as an efficient biopesticide worldwide. Despite the fact that this bacterium is usually described as an insect pathogen, its life cycle in the environment is still largely unknown. B. thuringiensis belongs to the Bacillus cereus group of bacteria, which has been associated with many mobile genetic elements, such as species-specific temperate or virulent bacteriophages (phages). Temperate (lysogenic) phages are able to establish a long-term relationship with their host, providing, in some cases, novel ecological traits to the bacterial lysogens. Therefore, this work focuses on evaluating the potential influence of temperate tectiviruses GIL01 and GIL16 on the development of different life traits of B. thuringiensis. For this purpose, a B. thuringiensis serovar israelensis plasmid-cured (nonlysogenic) strain was used to establish bacterial lysogens for phages GIL01 and GIL16, and, subsequently, the following life traits were compared among the strains: kinetics of growth, metabolic profiles, antibiotics susceptibility, biofilm formation, swarming motility, and sporulation. The results revealed that GIL01 and GIL16 lysogeny has a significant influence on the bacterial growth, sporulation rate, biofilm formation, and swarming motility of B. thuringiensis. No changes in metabolic profiles or antibiotic susceptibilities were detected. These findings provide evidence that tectiviruses have a putative role in the B. thuringiensis life cycle as adapters of life traits with ecological advantages.

  19. Assessing the influence of biofilm surface roughness on mass transfer by combining optical coherence tomography and two-dimensional modeling.

    Science.gov (United States)

    Li, Chunyan; Wagner, Michael; Lackner, Susanne; Horn, Harald

    2016-05-01

    Imaging and modeling are two major approaches in biofilm research to understand the physical and biochemical processes involved in biofilm development. However, they are often used separately. In this study we combined these two approaches to investigate substrate mass transfer and mass flux. Cross-sectional biofilm images were acquired by means of optical coherence tomography (OCT) for biofilms grown on carriers. A 2D biofilm model was developed incorporating OCT images as well as a simplified biofilm geometry serving as structural templates. The model incorporated fluid flow, substrate transfer and biochemical conversion of substrates and simulated the hydrodynamics surrounding the biofilm structure as well as the substrate distribution. The method allowed detailed analysis of the hydrodynamics and mass transfer characteristics at the micro-scale. Biofilm activity with respect to substrate fluxes was compared among different combinations of flow, substrate availability and biomass density. The combined approach revealed that higher substrate fluxes at heterogeneous biofilm surface under two conditions: pure diffusion and when high flow velocity along the biofilms surface renders the whole liquid-biofilm interface to be highly active. In-between the two conditions the substrate fluxes across the surface of smooth biofilm geometry were higher than that of the heterogeneous biofilms.

  20. Coexistence facilitates interspecific biofilm formation in complex microbial communities

    DEFF Research Database (Denmark)

    Madsen, Jonas Stenløkke; Røder, Henriette Lyng; Russel, Jakob

    2016-01-01

    , the underlying role of fundamental ecological factors, specifically coexistence and phylogenetic history, in biofilm formation remains unclear. This study examines how social interactions affect biofilm formation in multi-species co-cultures from five diverse environments. We found prevalence of increased......Social interactions in which bacteria respond to one another by modifying their phenotype are central determinants of microbial communities. It is known that interspecific interactions influence the biofilm phenotype of bacteria; a phenotype that is central to the fitness of bacteria. However...

  1. Psychological Factors Influencing Consumer Behaviour

    OpenAIRE

    Vainikka, Bianca

    2015-01-01

    This paper’s aim is to provide an in-depth elucidation of the many aspects that influence consumer behaviour. The study of consumer behaviour emphasizes the “why” and “how” questions involved in decision making and buying behaviour. This exciting field visits a dynamic blend of themes of consumer marketing strategies, psychology and behavioural discipline. Consumer behaviour in this day and age is highly applicable to modern society as it is an integral part of our everyday lives. This paper ...

  2. The role of biofilms in persistent infections and factors involved in ica-independent biofilm development and gene regulation in Staphylococcus aureus.

    Science.gov (United States)

    Figueiredo, Agnes Marie Sá; Ferreira, Fabienne Antunes; Beltrame, Cristiana Ossaille; Côrtes, Marina Farrel

    2017-09-01

    Staphylococcus aureus biofilms represent a unique micro-environment that directly contribute to the bacterial fitness within hospital settings. The accumulation of this structure on implanted medical devices has frequently caused the development of persistent and chronic S. aureus-associated infections, which represent an important social and economic burden worldwide. ica-independent biofilms are composed of an assortment of bacterial products and modulated by a multifaceted and overlapping regulatory network; therefore, biofilm composition can vary among S. aureus strains. In the microniches formed by biofilms-produced by a number of bacterial species and composed by different structural components-drug refractory cell subpopulations with distinct physiological characteristics can emerge and result in therapeutic failures in patients with recalcitrant bacterial infections. In this review, we highlight the importance of biofilms in the development of persistence and chronicity in some S. aureus diseases, the main molecules associated with ica-independent biofilm development and the regulatory mechanisms that modulate ica-independent biofilm production, accumulation, and dispersion.

  3. The influence of biofilms on the migration of uranium in acid mine drainage (AMD) waters.

    Science.gov (United States)

    Krawczyk-Bärsch, E; Lünsdorf, H; Arnold, T; Brendler, V; Eisbein, E; Jenk, U; Zimmermann, U

    2011-07-15

    The uranium mine in Königstein (Germany) is currently in the process of being flooded. Huge mass of Ferrovum myxofaciens dominated biofilms are growing in the acid mine drainage (AMD) water as macroscopic streamers and as stalactite-like snottites hanging from the ceiling of the galleries. Microsensor measurements were performed in the AMD water as well as in the biofilms from the drainage channel on-site and in the laboratory. The analytical data of the AMD water was used for the thermodynamic calculation of the predominance fields of the aquatic uranium sulfate (UO(2)SO(4)) and UO(2)(++) speciation as well as of the solid uranium species Uranophane [Ca(UO(2))(2)(SiO(3)OH)(2)∙5H(2)O] and Coffinite [U(SiO(4))(1-x)(OH)(4x)], which are defined in the stability field of pH>4.8 and Eh0 and Eh4.8. Even analysis by Energy-filtered Transmission Electron Microscopy (EF-TEM) and electron energy loss spectroscopy (EELS) within the biofilms did not provide any microscopic or spectroscopic evidence for the presence of uranium immobilization. In laboratory experiments the first phase of the flooding process was simulated by increasing the pH of the AMD water. The results of the experiments indicated that the F. myxofaciens dominated biofilms may have a substantial impact on the migration of uranium. The AMD water remained acid although it was permanently neutralized with the consequence that the retention of uranium from the aqueous solution by the formation of solid uranium species will be inhibited. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Presence of environmental coagulase-positive staphylococci, their clonal relationship, resistance factors and ability to form biofilm.

    Science.gov (United States)

    Velázquez-Guadarrama, Norma; Olivares-Cervantes, Alma L; Salinas, Eva; Martínez, Leticia; Escorcia, Magdalena; Oropeza, Ricardo; Rosas, Irma

    Coagulase-positive staphylococci (CoPS) are opportunistic pathogens carrying various mechanisms of resistance that have a large number of virulence factors, and whose ability to induce illness is associated with the host. This study aimed to investigate the presence of environmental coagulase-positive staphylococci, their susceptibility profile, clonal relationship and ability to form biofilm. The 16S rRNA genes from CoPS isolates were analyzed, and their antibiotic susceptibility was evaluated using the agar dilution method in accordance with Clinical and Laboratory Standards Institute guidelines. The clonal profile was obtained by pulsed-field gel electrophoresis (PFGE) and biofilm formation was measured by a crystal violet retention assay. A total of 72 Staphylococcus spp. strains were isolated from air, metal surfaces, and nostrils from humans, dogs, cats, and birds. Three species were identified: Staphylococcus aureus (17%), Staphylococcus intermedius (63%), and Staphylococcus pseudintermedius (21%). Ninety three percent (93%) of the strains were resistant to at least one of 13 tested antibiotics. S. pseudintermedius strains were the only resistant ones to methicillin while most of these isolates were multidrug-resistant, had significantly higher ability to form biofilm and PFGE grouped into seven different patterns, without showing clonal dispersion among animals and environmental isolates. This study suggests that dogs, cat, and air are environmental sources potentially carrying multidrug-resistant S. pseudintermedius, which survives in different environments through biofilm formation and multidrug resistance, characteristics that can be transmitted horizontally to other bacteria and exacerbate the problem of antibiotic resistance in humans. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

  5. L-fucose influences chemotaxis and biofilm formation in Campylobacter jejuni.

    Science.gov (United States)

    Dwivedi, Ritika; Nothaft, Harald; Garber, Jolene; Xin Kin, Lin; Stahl, Martin; Flint, Annika; van Vliet, Arnoud H M; Stintzi, Alain; Szymanski, Christine M

    2016-08-01

    Campylobacter jejuni and Campylobacter coli are zoonotic pathogens once considered asaccharolytic, but are now known to encode pathways for glucose and fucose uptake/metabolism. For C. jejuni, strains with the fuc locus possess a competitive advantage in animal colonization models. We demonstrate that this locus is present in > 50% of genome-sequenced strains and is prevalent in livestock-associated isolates of both species. To better understand how these campylobacters sense nutrient availability, we examined biofilm formation and chemotaxis to fucose. C. jejuni NCTC11168 forms less biofilms in the presence of fucose, although its fucose permease mutant (fucP) shows no change. In a newly developed chemotaxis assay, both wild-type and the fucP mutant are chemotactic towards fucose. C. jejuni 81-176 naturally lacks the fuc locus and is unable to swim towards fucose. Transfer of the NCTC11168 locus into 81-176 activated fucose uptake and chemotaxis. Fucose chemotaxis also correlated with possession of the pathway for C. jejuni RM1221 (fuc+) and 81116 (fuc-). Systematic mutation of the NCTC11168 locus revealed that Cj0485 is necessary for fucose metabolism and chemotaxis. This study suggests that components for fucose chemotaxis are encoded within the fuc locus, but downstream signals only in fuc + strains, are involved in coordinating fucose availability with biofilm development. © 2016 John Wiley & Sons Ltd.

  6. Influence of elevated temperature, pCO2, and nutrients on larva-biofilm interaction: Elucidation with acorn barnacle, Balanus amphitrite Darwin (Cirripedia: Thoracica)

    Science.gov (United States)

    Baragi, Lalita V.; Anil, Arga Chandrashekar

    2017-02-01

    Selection of optimal habitat by larvae of sessile organism is influenced by cues offered by the biofilm. Ocean warming and acidification are likely to enforce changes in the biofilm community and inturn influence the settlement process. Hence, we evaluated the influence of biofilm (multispecies and unialgal) and diet-mediated changes on the settlement of Balanus amphitrite cyprids (presettlement non-feeding larval stage) under different combinations of temperature (28, 30, 32 and 34 °C), pCO2 (400, 750 and 1500 μatm) and nutrient (unenriched and f/2 enriched). Nutrient enrichment enhanced the diatom and bacterial abundance at ambient temperature (30 °C) and pCO2 (400 μatm), which inturn increased larval settlement. Elevated pCO2 (750 and 1500 μatm) had no direct effect but a variable cascading effect on the settlement via biofilm-mediated changes was observed, depending on the type of biofilm. In contrast, elevated temperature (32 and 34 °C), either individually or in combination with elevated pCO2 had direct negative effect on settlement. However, biofilm-mediated changes compensated this negative effect. The larval settlement was also influenced by changes in the larval diet. Under elevated temperature and pCO2, cyprids raised with a feed (Chaetoceros calcitrans) from ambient temperature and pCO2 were of poor quality (lower RNA:DNA ratio, lower protein synthetic capacity) and yielded lower settlement. However, cyprids raised with a feed from elevated temperature and pCO2 were of better quality (higher RNA:DNA ratio, higher protein synthetic capacity) and yielded higher settlement. Overall, the observations from the present study provide insights into the significance of biotic interactions on the coastal biofouling communities under future climatic scenario and emphasise the need for future experiments on these aspects.

  7. Comparative transcriptional profiling reveals differential expression of pathways directly and indirectly influencing biofilm formation in Escherichia coli O157:H7

    Science.gov (United States)

    Introduction: Escherichia coli O157:H7 (O157) is a frequent cause of foodborne disease outbreaks. O157 encodes virulence factors for colonizing and survival in reservoir animals and the environment. For example, genetic factors promoting biofilm formation are linked to survival of O157 in and outsid...

  8. Thymic Output: Influence Factors and Molecular Mechanism

    Institute of Scientific and Technical Information of China (English)

    Rong Jin; Jun Zhang; Weifeng Chen

    2006-01-01

    Thymus is a primary lymphoid organ, able to generate mature T cells that eventually colonize secondary lymphoid organs, and is therefore essential for peripheral T cell renewal. Recent data showed that normal thymocyte export can be altered by several influence factors including several chemokines,sphingosinel-phosphate (S1P),transcription factors such as Foxjl, Kruppel-like transcription factor 2 (KLF2) and antigen stimulation, etc. In this review, we summarized the recent reports about study strategies, influence factors and possible molecular mechanisms in thymic output.

  9. 31. FACTORS INFLUENCING UTILIZATION OF INTERMITTENT ...

    African Journals Online (AJOL)

    Esem

    treatment of malaria during pregnancy(IPTp), effective IPTp service utilization ... effective case management of malaria. Despite the ... Factors influencing IPTp utilization identified in the study included; educational status of a woman,. Medical ...

  10. Home Environmental Factors Influencing Performance and Progress ...

    African Journals Online (AJOL)

    ... Factors Influencing Performance and Progress of Primary School Pupils in ... found that parents' educational level and income level have a bearing on school ... on school progress and performance, however; home language did play a role.

  11. Factors Influencing Self Employment Media Service Providers ...

    African Journals Online (AJOL)

    Factors Influencing Self Employment Media Service Providers among Tertiary ... role stereotype and common business practices on media self employment in ... Sex, Psycho-social Characteristics, self Employment, Providing Media Services.

  12. Age-Related Factors That Influence Fertility

    Science.gov (United States)

    ... can be found at the NICHD Pregnancy Loss topic page . Committee on Gynecologic Practice of American College of ... 2012, from http://www.nichd.nih.gov/health/topics/pregnancyloss/researchinfo/Pages/default.aspx [top] « Lifestyle Factors That Influence Fertility ...

  13. Factors that negatively influence consumption of traditionally ...

    African Journals Online (AJOL)

    Factors that negatively influence consumption of traditionally fermented milk ... of sub-Saharan Africa and a number of health benefits to human beings are ... Key words: Mursik, Lactic acid bacteria (LAB), probiotic, Preschoolers, Focus group

  14. FACTORS INFLUENCING THE SELECTION OF DENTAL NURSING ...

    African Journals Online (AJOL)

    drclement

    FACTORS INFLUENCING THE SELECTION OF DENTAL NURSING AS A. PROFESSION ... Colleges of Health Technology undergoing external ... questionnaire requested information on age ... individual with good communication skills and ...

  15. Factors that Influence Adolescents to Smoke.

    Science.gov (United States)

    Smith, Karen H.; Stutts, Mary Ann

    1999-01-01

    A survey of the factors that influence adolescents (n=246) to smoke found that family smoking behavior, peer pressure, and prior beliefs were more important in predicting smoking level than were advertising and antismoking information. (Author/JOW)

  16. FACTORS INFLUENCING SUSTAINED MANAGERIAL EFFICIENCY

    Directory of Open Access Journals (Sweden)

    Alexandru Marius RIZESCU

    2017-04-01

    Full Text Available The concept of effectiveness is learnable in economic theory and practice with various forms of manifestation of the results obtained by the managers, such as profitability, the productivity of factors of production, capital efficiency, cost savings, etc. Regarded as the organizing principle and driving activity in the market economy, it has a much richer content and also favorable results of generalizing all derived by managers. Choosing effective in meeting needs with limited resources or powerlessness to maximize resource needs under restrains, are expressions through which efficiency is situated at the heart of economic theory and practice.

  17. Effects of operating conditions on the adhesive strength of Pseudomonas fluorescens biofilms in tubes.

    Science.gov (United States)

    Chen, M J; Zhang, Z; Bott, T R

    2005-06-25

    Understanding the mechanical properties of biofilms, especially the force required to disrupt them and remove them from substrata is very important to development of antibiofouling strategies. In this work, a novel micromanipulation technique with a specially designed T-shaped probe has been developed to serve as an experimental means to measure directly the adhesive strength of biofouling deposits on the surface of a glass test stud. The basic principle of this novel technique is to pull away a whole biofilm accumulated on the surface of a glass test stud with T-shaped probe, and to measure simultaneously the force imposed on the biofilm. The adhesive strength between the biofilms and the surface to which they are attached, is defined as the work per unit area required to remove the biofilms from the surface. The biofouling experiments were performed on an elaborate design of a simulated heat exchanger system. A monoculture of Pseudomonas fluorescens was chosen as the fouling microorganism for the laboratory studies. Results indicate that the adhesive strength of the biofilm was affected by the conditions of operation, such as biofilm age, nutrient concentration, suspended cell concentration, pH, surface roughness of the substratum and fluid velocity. As noted, the effect of fluid velocity on the biofilm adhesive strength seemed to overwhelm other factors. At the same operating conditions, the biofilm adhesive strength increased as the fluid velocity increased within the range of 0.6-1.6m/s. In addition, the flow-related biofilm structures were observed that biofilms generally grew as a more compact pattern at the higher fluid velocity. Apparently, the fluid velocity can affect the biofilm structure, which in turn determines the biofilm adhesive strength. The knowledge of the biofilm adhesive strength with associated influences of the operating conditions may be used to define better cleaning procedures.

  18. ENERGY EFFICIENCY. TRENDS AND INFLUENCE FACTORS

    Directory of Open Access Journals (Sweden)

    Zizi GOSCHIN

    2006-12-01

    Full Text Available Energy efficiency is correlated with many factors of influence: Gross National Income per capita, energy imports (% of energy use, renewable combustible and waste (% of total, energy use per capita, services as % of GDP and others. In this paper we are testing a model of piecewise linear regression with breakpoint in order to measure the influence of these factors on the variation of GDP per unit of energy use in Europe in the year 2003.

  19. Variation properties of ionospheric eclipse factor and ionospheric influence factor

    Institute of Scientific and Technical Information of China (English)

    ZHAO Chunmei; YUAN Yunbin; OU Jikun; CHEN Jinping

    2005-01-01

    The concepts and calculation methods of ionospheric eclipse factor (IEF) and ionospheric influence factor (IFF) are further illustrated. The temporal and spacial variation properties of IEF and IFF are studied, which shows that the properties are influenced by the geographic position and season. The possibility of improving the precision of using GPS data to determine ionospheric delay based on the above variation properties is also analysed.

  20. FACTORS INFLUENCING COMPOSTING POULTRY WASTE

    Directory of Open Access Journals (Sweden)

    Michał Kopeć

    2015-11-01

    Full Text Available Organic recycling of waste, taking into account sanitary safety, should be a fundamental method for recovering the nutrients present in the waste for plants and organic matter. It also refers to by-products of animal origin, which are not intended for consumption by humans. In the present research , composting of hydrated poultry slaughterhouse waste with maize straw was carried out. A combination with fodder yeast and post-cellulose lime was also introduced, which modified chemical and physico-chemical properties of the mixtures. The experiment was carried out by recording the biomass temperature for 110 days in 1.2×1.0×0.8 m reactors with perforated bottoms enabling active aeration. The following parameters were taken into consideration in the composted material: carbon, nitrogen, sulfur, respiratory activity, microorganisms, fractions of compost obtained after washing on sieves. Small amounts of fodder yeast favoured the development of microorganisms and caused a sanitary risk in the final product. At the initial stage, the temperature of raw compost in that object was several degrees lower than in the case of the composted mass without yeast addition. The addition of post-cellulose lime at ratios 6.5:1:6.5 (maize straw: poultry slaughterhouse waste: post-cellulose lime caused a change in the time of microbiological activity, and led to its inhibition in the final process. In comparison to objects with poultry waste, the highest degree of hygienization was found in the compost with post-cellulose lime (with pH close to neutral. By adjusting the ratios of substrates we can influence the microbiological activity, but the amounts of individual substrates should be determined taking into account the quality of the obtained compost.

  1. Inhibitory Effects of Chrysanthemum boreale Essential Oil on Biofilm Formation and Virulence Factor Expression of Streptococcus mutans

    Directory of Open Access Journals (Sweden)

    Beom-Su Kim

    2015-01-01

    Full Text Available The aim of the study was to evaluate the antibacterial activity of essential oil extracted from Chrysanthemum boreale (C. boreale on Streptococcus mutans (S. mutans. To investigate anticariogenic properties, and bacterial growth, acid production, biofilm formation, bacterial adherence of S. mutans were evaluated. Then gene expression of several virulence factors was also evaluated. C. boreale essential oil exhibited significant inhibition of bacterial growth, adherence capacity, and acid production of S. mutans at concentrations 0.1–0.5 mg/mL and 0.25–0.5 mg/mL, respectively. The safranin staining and scanning electron microscopy results showed that the biofilm formation was also inhibited. The result of live/dead staining showed the bactericidal effect. Furthermore, real-time PCR analysis showed that the gene expression of some virulence factors such as gtfB, gtfC, gtfD, gbpB, spaP, brpA, relA, and vicR of S. mutans was significantly decreased in a dose dependent manner. In GC and GC-MS analysis, seventy-two compounds were identified in the oil, representing 85.42% of the total oil. The major components were camphor (20.89%, β-caryophyllene (5.71%, α-thujone (5.46%, piperitone (5.27%, epi-sesquiphellandrene (5.16%, α-pinene (4.97%, 1,8-cineole (4.52%, β-pinene (4.45%, and camphene (4.19%. These results suggest that C. boreale essential oil may inhibit growth, adhesion, acid tolerance, and biofilm formation of S. mutans through the partial inhibition of several of these virulence factors.

  2. Inhibitory Effects of Chrysanthemum boreale Essential Oil on Biofilm Formation and Virulence Factor Expression of Streptococcus mutans.

    Science.gov (United States)

    Kim, Beom-Su; Park, Sun-Ju; Kim, Myung-Kon; Kim, Young-Hoi; Lee, Sang-Bong; Lee, Kwang-Hee; Choi, Na-Young; Lee, Young-Rae; Lee, Young-Eun; You, Yong-Ouk

    2015-01-01

    The aim of the study was to evaluate the antibacterial activity of essential oil extracted from Chrysanthemum boreale (C. boreale) on Streptococcus mutans (S. mutans). To investigate anticariogenic properties, and bacterial growth, acid production, biofilm formation, bacterial adherence of S. mutans were evaluated. Then gene expression of several virulence factors was also evaluated. C. boreale essential oil exhibited significant inhibition of bacterial growth, adherence capacity, and acid production of S. mutans at concentrations 0.1-0.5 mg/mL and 0.25-0.5 mg/mL, respectively. The safranin staining and scanning electron microscopy results showed that the biofilm formation was also inhibited. The result of live/dead staining showed the bactericidal effect. Furthermore, real-time PCR analysis showed that the gene expression of some virulence factors such as gtfB, gtfC, gtfD, gbpB, spaP, brpA, relA, and vicR of S. mutans was significantly decreased in a dose dependent manner. In GC and GC-MS analysis, seventy-two compounds were identified in the oil, representing 85.42% of the total oil. The major components were camphor (20.89%), β-caryophyllene (5.71%), α-thujone (5.46%), piperitone (5.27%), epi-sesquiphellandrene (5.16%), α-pinene (4.97%), 1,8-cineole (4.52%), β-pinene (4.45%), and camphene (4.19%). These results suggest that C. boreale essential oil may inhibit growth, adhesion, acid tolerance, and biofilm formation of S. mutans through the partial inhibition of several of these virulence factors.

  3. Factors Influencing the Quality of Mobile Applications

    Directory of Open Access Journals (Sweden)

    Alin ZAMFIROIU

    2014-01-01

    Full Text Available Mobile applications are becoming increasingly used. Mobile devices are becoming indispensable for the user. In the material are claiming the sales of mobile devices internationally and the use of mobile applications compared to traditional internet use on desktop systems for the United States. Are presented influences the quality of mobile applications and based on these influencing factors built a model of choice for optimal application of mobile applications and traditional desktop application. At the end of the material presented methods to increase quality by tracking the influence factors during the development of mobile applications.

  4. Factors influencing alginate gel biocompatibility.

    Science.gov (United States)

    Tam, Susan K; Dusseault, Julie; Bilodeau, Stéphanie; Langlois, Geneviève; Hallé, Jean-Pierre; Yahia, L'Hocine

    2011-07-01

    Alginate remains the most popular polymer used for cell encapsulation, yet its biocompatibility is inconsistent. Two commercially available alginates were compared, one with 71% guluronate (HiG), and the other with 44% (IntG). Both alginates were purified, and their purities were verified. After 2 days in the peritoneal cavity of C57BL/6J mice, barium (Ba)-gel and calcium (Ca)-gel beads of IntG alginate were clean, while host cells were adhered to beads of HiG alginate. IntG gel beads, however, showed fragmentation in vivo while HiG gel beads stayed firm. The physicochemical properties of the sodium alginates and their gels were thoroughly characterized. The intrinsic viscosity of IntG alginate was 2.5-fold higher than that of HiG alginate, suggesting a greater molecular mass. X-ray photoelectron spectroscopy indicated that both alginates were similar in elemental composition, including low levels of counterions in all gels. The wettabilities of the alginates and gels were also identical, as measured by contact angles of water on dry films. Ba-gel beads of HiG alginate resisted swelling and degradation when immersed in water, much more than the other gel beads. These results suggest that the main factors contributing to the biocompatibility of gels of purified alginate are the mannuronate/guluronate content and/or intrinsic viscosity.

  5. Influence of fluoride on the bacterial composition of a dual-species biofilm composed of Streptococcus mutans and Streptococcus oralis.

    Science.gov (United States)

    Jung, Ji-Eun; Cai, Jian-Na; Cho, Sung-Dae; Song, Kwang-Yeob; Jeon, Jae-Gyu

    2016-10-01

    Despite the widespread use of fluoride for the prevention of dental caries, few studies have demonstrated the effects of fluoride on the bacterial composition of dental biofilms. This study investigated whether fluoride affects the proportion of Streptococcus mutans and S. oralis in mono- and dual-species biofilm models, via microbiological, biochemical, and confocal fluorescence microscope studies. Fluoride did not affect the bacterial count and bio-volume of S. mutans and S. oralis in mono-species biofilms, except for the 24-h-old S. mutans biofilms. However, fluoride reduced the proportion and bio-volume of S. mutans but did not decrease those of S. oralis during both S. oralis and S. mutans dual-species biofilm formation, which may be related to the decrease in extracellular polysaccharide formation by fluoride. These results suggest that fluoride may prevent the shift in the microbial proportion to cariogenic bacteria in dental biofilms, subsequently inhibiting the cariogenic bacteria dominant biofilm formation.

  6. Morphological changes in Proteus mirabilis O18 biofilm under the influence of a urease inhibitor and a homoserine lactone derivative.

    Science.gov (United States)

    Czerwonka, Grzegorz; Arabski, Michał; Wąsik, Sławomir; Jabłońska-Wawrzycka, Agnieszka; Rogala, Patrycja; Kaca, Wiesław

    2014-03-01

    Proteus mirabilis is a pathogenic gram-negative bacterium that frequently causes kidney infections, typically established by ascending colonization of the urinary tract. The present study is focused on ureolytic activity and urease inhibition in biofilms generated by P. mirabilis O18 cells. Confocal microscopy revealed morphological alterations in biofilms treated with urea and a urease inhibitor (acetohydroxamic acid, AHA), as some swarmer cells were found to protrude from the biofilm. The presence of a quorum-sensing molecule (N-butanoyl homoserine lactone, BHL) increased biofilm thickness and its ureolytic activity. Laser interferometric determination of diffusion showed that urea easily diffuses through P. mirabilis biofilm, while AHA is blocked. This may suggest that the use of urease inhibitors in CAUTIs may by less effective than in other urease-associated infections. Spectroscopic studies revealed differences between biofilm and planktonic cells indicating that polysaccharides and nucleic acids are involved in extracellular matrix and biofilm formation.

  7. Influence of humic acid addition on the degradation of pharmaceuticals by biofilms in effluent wastewater

    DEFF Research Database (Denmark)

    Tang, Kai; Escola Casas, Monica; Ooi, Gordon Tze Hoong

    2017-01-01

    in relation to the biodegradation of pharmaceuticals by suspended biofilm carriers adapted to polishing effluent water from a tertiary sewage treatment plant. Twelve out of 22 investigated pharmaceuticals were significantly biodegradable. The biodegradation rate constants of ten of those compounds were...... increasing with increased humic acid concentrations. At the highest humic acid concentration (30. mgC/L), the biodegradation rate constants were four times higher than the biodegradation rate constants without added humic acid. This shows that the presence of complex substrate stimulates degradation via a co......-metabolism-like mechanism and competitive inhibition does not occur. Increases of rate constant per mgC/L are tentatively calculated....

  8. What Factors Influence Wind Perceptions

    Science.gov (United States)

    Stein, Tatiana

    Over the last decade, wind power has emerged as a possible source of energy and has attracted the attention of homeowners and policy makers worldwide. Many technological hurdles have been overcome in the last few years that make this technology feasible and economical. The United States has added more wind power than any other type of electric generation in 2012. Depending on the location, wind resources have shown to have the potential to offer 20% of the nation's electricity; a single, large wind turbine has the capacity to produce enough electricity to power 350 homes. Throughout the development of wind turbines, however, energy companies have seen significant public opposition towards the tall white structures. The purpose of this research was to measure peoples' perceptions on wind turbine development throughout their growth, from proposal to existing phase. Three hypotheses were developed based on the participant's political affiliation, proximity and knowledge of wind turbines. To validate these hypotheses, participants were asked an array of questions regarding their perception on economic, environmental, and social impacts of wind turbines with an online service called Amazon Mechanical Turk. The responses were from residents living in the United States and required them to provide their zip code for subsequent analysis. The analysis from the data obtained suggests that participants are favorable towards wind turbine development and would be supportive of using the technology in their community. Political affiliation and proximity to the nearest wind turbine in any phase of development (proposal, construction, existing) were also analyzed to determine if they had an effect on a person's overall perception on wind turbines and their technology. From the analysis, political affiliation was seen to be an indirect factor to understanding favorability towards wind turbines; the more liberal you are, the more supportive you will be towards renewable energy use

  9. Patient factors that influence warfarin dose response.

    Science.gov (United States)

    White, Pamela J

    2010-06-01

    Warfarin has long been the mainstay of oral anticoagulation therapy for the treatment and prevention of venous and arterial thrombosis. The narrow therapeutic index of warfarin, and the complex number of factors that influence international normalized ratio (INR) response, makes optimization of warfarin therapy challenging. Determination of the appropriate warfarin dose during initiation and maintenance therapy requires an understanding of patient factors that influence dose response: age, body weight, nutritional status, acute and chronic disease states, and changes in concomitant drug therapy and diet. This review will examine specific clinical factors that can affect the pharmacokinetics and pharmacodynamics of warfarin, as well as the role of pharmacogenetics in optimizing warfarin therapy.

  10. Extracellular Electron Transfer Is a Bottleneck in the Microbiologically Influenced Corrosion of C1018 Carbon Steel by the Biofilm of Sulfate-Reducing Bacterium Desulfovibrio vulgaris.

    Directory of Open Access Journals (Sweden)

    Huabing Li

    Full Text Available Carbon steels are widely used in the oil and gas industry from downhole tubing to transport trunk lines. Microbes form biofilms, some of which cause the so-called microbiologically influenced corrosion (MIC of carbon steels. MIC by sulfate reducing bacteria (SRB is often a leading cause in MIC failures. Electrogenic SRB sessile cells harvest extracellular electrons from elemental iron oxidation for energy production in their metabolism. A previous study suggested that electron mediators riboflavin and flavin adenine dinucleotide (FAD both accelerated the MIC of 304 stainless steel by the Desulfovibrio vulgaris biofilm that is a corrosive SRB biofilm. Compared with stainless steels, carbon steels are usually far more prone to SRB attacks because SRB biofilms form much denser biofilms on carbon steel surfaces with a sessile cell density that is two orders of magnitude higher. In this work, C1018 carbon steel coupons were used in tests of MIC by D. vulgaris with and without an electron mediator. Experimental weight loss and pit depth data conclusively confirmed that both riboflavin and FAD were able to accelerate D. vulgaris attack against the carbon steel considerably. It has important implications in MIC failure analysis and MIC mitigation in the oil and gas industry.

  11. Antimicrobial efficacy against Pseudomonas aeruginosa biofilm formation in a three-dimensional lung epithelial model and the influence of fetal bovine serum

    Science.gov (United States)

    Crabbé, Aurélie; Liu, Yulong; Matthijs, Nele; Rigole, Petra; De La Fuente-Nùñez, César; Davis, Richard; Ledesma, Maria A.; Sarker, Shameema; Van Houdt, Rob; Hancock, Robert E. W.; Coenye, Tom; Nickerson, Cheryl A.

    2017-01-01

    In vitro models that mimic in vivo host-pathogen interactions are needed to evaluate candidate drugs that inhibit bacterial virulence traits. We established a new approach to study Pseudomonas aeruginosa biofilm susceptibility on biotic surfaces, using a three-dimensional (3-D) lung epithelial cell model. P. aeruginosa formed antibiotic resistant biofilms on 3-D cells without affecting cell viability. The biofilm-inhibitory activity of antibiotics and/or the anti-biofilm peptide DJK-5 were evaluated on 3-D cells compared to a plastic surface, in medium with and without fetal bovine serum (FBS). In both media, aminoglycosides were more efficacious in the 3-D cell model. In serum-free medium, most antibiotics (except polymyxins) showed enhanced efficacy when 3-D cells were present. In medium with FBS, colistin was less efficacious in the 3-D cell model. DJK-5 exerted potent inhibition of P. aeruginosa association with both substrates, only in serum-free medium. DJK-5 showed stronger inhibitory activity against P. aeruginosa associated with plastic compared to 3-D cells. The combined addition of tobramycin and DJK-5 exhibited more potent ability to inhibit P. aeruginosa association with both substrates. In conclusion, lung epithelial cells influence the efficacy of most antimicrobials against P. aeruginosa biofilm formation, which in turn depends on the presence or absence of FBS. PMID:28256611

  12. Influence of denture plaque biofilm on oral mucosal membrane in patients with chronic obstructive pulmonary disease.

    Science.gov (United States)

    Przybyłowska, D; Mierzwińska-Nastalska, E; Rubinsztajn, R; Chazan, R; Rolski, D; Swoboda-Kopeć, E

    2015-01-01

    Patients with chronic obstructive pulmonary disease (COPD) have the lower airways colonized with pathogenic bacteria in a stable period of the disease and during exacerbations. The etiology of bacterial exacerbations of COPD depends on the underlying disease, the frequency of exacerbations and antibiotic therapy. Microorganisms can be aspirated off the denture plaque biofilm into the lower respiratory tract and could reduce the patient's immunity and cause pneumonia. COPD patients, who are using acrylic dentures in oral cavity, are exposed to denture stomatitis and oral candidiasis. The aim of this study was to establish the composition of denture plaque biofilm and its impact on the oral mucosa in COPD patients. The study included patients in a stable phase of COPD using removable denture and the control group included healthy wearer's appliances. Examinations concerned the oral mucosal membrane and the hygienic condition of prosthetic restorations. Microbiological examinations were performed by taking a direct swab from the surface of acrylic dentures. Seventeen bacterial and fungal strains were isolated from denture plaque of COPD patients, which could be a reservoir of pathogens in the upper and lower airways. The results showed a greater frequency of prosthetic stomatitis complicated by mucosal infections among COPD patients compared to healthy subjects.

  13. Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans.

    Science.gov (United States)

    Lara, René H; García-Meza, J Viridiana; Cruz, Roel; Valdez-Pérez, Donato; González, Ignacio

    2012-08-01

    Massive pyrite (FeS₂) electrodes were potentiostatically modified by means of variable oxidation pulse to induce formation of diverse surface sulfur species (S(n)²⁻, S⁰). The evolution of reactivity of the resulting surfaces considers transition from passive (e.g., Fe(1-x )S₂) to active sulfur species (e.g., Fe(1-x )S(2-y ), S⁰). Selected modified pyrite surfaces were incubated with cells of sulfur-oxidizing Acidithiobacillus thiooxidans for 24 h in a specific culture medium (pH 2). Abiotic control experiments were also performed to compare chemical and biological oxidation. After incubation, the attached cells density and their exopolysaccharides were analyzed by confocal laser scanning microscopy (CLMS) and atomic force microscopy (AFM) on bio-oxidized surfaces; additionally, S(n)²⁻/S⁰ speciation was carried out on bio-oxidized and abiotic pyrite surfaces using Raman spectroscopy. Our results indicate an important correlation between the evolution of S(n)²⁻/S⁰ surface species ratio and biofilm formation. Hence, pyrite surfaces with mainly passive-sulfur species were less colonized by A. thiooxidans as compared to surfaces with active sulfur species. These results provide knowledge that may contribute to establishing interfacial conditions that enhance or delay metal sulfide (MS) dissolution, as a function of the biofilm formed by sulfur-oxidizing bacteria.

  14. Influence of femtosecond laser produced nanostructures on biofilm growth on steel

    Science.gov (United States)

    Epperlein, Nadja; Menzel, Friederike; Schwibbert, Karin; Koter, Robert; Bonse, Jörn; Sameith, Janin; Krüger, Jörg; Toepel, Jörg

    2017-10-01

    Biofilm formation poses high risks in multiple industrial and medical settings. However, the robust nature of biofilms makes them also attractive for industrial applications where cell biocatalysts are increasingly in use. Since tailoring material properties that affect bacterial growth or its inhibition is gaining attention, here we focus on the effects of femtosecond laser produced nanostructures on bacterial adhesion. Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e., a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laser-induced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten identical samples were laser-processed. Subsequently, the samples were subjected to microbial adhesion tests. Bacteria of different shape and adhesion behavior (Escherichia coli and Staphylococcus aureus) were exposed to laser structures and to polished reference surfaces. Our results indicate that E. coli preferentially avoids adhesion to the LIPSS-covered areas, whereas S. aureus favors these areas for colonization.

  15. Manipulation of Biofilm Microbial Ecology

    Energy Technology Data Exchange (ETDEWEB)

    White, D.C.; Palmer, R.J., Jr.; Zinn, M.; Smith, C.A.; Burkhalter, R.; Macnaughton, S.J.; Whitaker, K.W.; Kirkegaard, R.D.

    1998-08-15

    The biofilm mode of growth provides such significant advantages to the members of the consortium that most organisms in important habitats are found in biofilms. The study of factors that allow manipulation of biofilm microbes in the biofilm growth state requires that reproducible biofilms be generated. The most effective monitoring of biofilm formation, succession and desaturation is with on-line monitoring of microbial biofilms with flowcell for direct observation. The biofilm growth state incorporates a second important factor, the heterogeneity in distribution in time and space of the component members of the biofilm consortium. This heterogeneity is reflected not only in the cellular distribution but in the metabolic activity within a population of cells. Activity and cellular distribution can be mapped in four dimensions with confocal microscopy, and function can be ascertained by genetically manipulated reporter functions for specific genes or by vital stains. The methodology for understanding the microbial ecology of biofilms is now much more readily available and the capacity to manipulate biofilms is becoming an important feature of biotechnology.

  16. Pleurotus ostreatus biofilm-forming ability and ultrastructure are significantly influenced by growth medium and support type.

    Science.gov (United States)

    Pesciaroli, L; Petruccioli, M; Federici, F; D'Annibale, A

    2013-06-01

    To investigate the effect of support and growth medium (GM) on Pleurotus ostreatus biofilm production, specific metabolic activity (SMA) and ultrastructure. Biofilms were developed on membranes covering a broad range of surface properties and, due to the applicative implications of mixed biofilms, on standard bacterial GM in stationary and shaken culture. Hydrophilic (glass fibre, Duran glass and hydroxyapatite) and mild hydrophobic (polyurethane, stainless steel, polycarbonate, nylon) supports were more adequate for biofilm attachment than the hydrophobic Teflon. Among the GM, sucrose-asparagine (SA) was more conducive to biofilm production than Luria-Bertani and M9. GM was more influential than support type on biofilm ultrastructure, and a high compactness was evident in biofilms developed on SA. Biofilms on Duran glass were more efficient than planktonic cultures in olive-mill wastewater treatment. The main effects of support and GM variables and their binary interactions on both biofilm production and SMA were all highly significant (P ostreatus biofilms. To our knowledge, this is the first attempt to fill this gap, thus representing a basis for future studies. © 2013 The Society for Applied Microbiology.

  17. Artemisia princeps Inhibits Biofilm Formation and Virulence-Factor Expression of Antibiotic-Resistant Bacteria

    Directory of Open Access Journals (Sweden)

    Na-Young Choi

    2015-01-01

    Full Text Available In this study, we used ethanol extract of A. princeps and investigated its antibacterial effects against MRSA. Ethanol extract of A. princeps significantly inhibited MRSA growth and organic acid production during glucose metabolism at concentrations greater than 1 mg/mL (P < 0.05. MRSA biofilm formation was observed using scanning electron microscopy (SEM and safranin staining. A. princeps extract was found to inhibit MRSA biofilm formation at concentrations higher than 2 mg/mL significantly (P < 0.05. Bactericidal effects of the A. princeps were observed using confocal laser microscopy, which showed that A. princeps was bactericidal in a dose-dependent manner. Using real-time PCR, expression of mecA, an antibiotic-resistance gene of MRSA, was observed, along with that of sea, agrA, and sarA. A. princeps significantly inhibited mecA, sea, agrA, and sarA, mRNA expression at the concentrations greater than 1 mg/mL (P < 0.05. The phytochemical analysis of A. princeps showed a relatively high content of organic acids and glycosides. The results of this study suggest that the ethanol extract of A. princeps may inhibit proliferation, acid production, biofilm formation, and virulence gene expressions of MRSA, which may be related to organic acids and glycosides, the major components in the extract.

  18. Extracellular Polysaccharides Matrix - An Often Forgotten Virulence Factor in Oral Biofilm Research

    Institute of Scientific and Technical Information of China (English)

    Hyun Koo; Jin Xiao; Marlise I. Klein

    2009-01-01

    @@ Oral diseases related to dental biofilms continue to afflict the majority of the world's population. Among them, dental caries continues to be the single most prevalent and costly oral infectious disease (Marsh, 2003; Dye et al., 2007). Dental caries results from the interaction of specific bacteria with constituents of the diet within a dental biofilm known as plaque (Bowen, 2002). Sucrose is considered to be the "arch criminal" from the dietary aspect because it serves as a substrate for synthesis of extracellular (EPS) and intracellular (IPS) polysaccharides in dental biofilm and is also fermentable (Bowen, 2002). However, it is important to emphasize that additional sugars and starch can certainly contribute to the pathogenesis (Bowen et al., 1980; Firestone et al., 1982; Thurnheer et al., 2008). Streptococcus mutans (S. mutans), a member of the oral microbial community, is generally regarded as the primary microbial culprit although additional microorganisms may be involved (Hamada and Slade, 1980; Loesche, 1986; Beighton, 2005). This bacterium (i) effectively utilizes dietary sucrose (and possibly starch) to synthesize large amounts of EPS through glucosyltransferases (Gtfs) and a fructosyltransferase (Ftfs), (ii) adheres tenaciously to glucan-coated surfaces, and (iii) is also acidogenic and acid-tolerant, which are critical virulence properties involved in the pathogenesis of dental caries.

  19. Real-time PCR expression profiling of genes encoding potential virulence factors in Candida albicans biofilms: identification of model-dependent and -independent gene expression

    Directory of Open Access Journals (Sweden)

    Řičicová Markéta

    2010-04-01

    Full Text Available Abstract Background Candida albicans infections are often associated with biofilm formation. Previous work demonstrated that the expression of HWP1 (hyphal wall protein and of genes belonging to the ALS (agglutinin-like sequence, SAP (secreted aspartyl protease, PLB (phospholipase B and LIP (lipase gene families is associated with biofilm growth on mucosal surfaces. We investigated using real-time PCR whether genes encoding potential virulence factors are also highly expressed in biofilms associated with abiotic surfaces. For this, C. albicans biofilms were grown on silicone in microtiter plates (MTP or in the Centres for Disease Control (CDC reactor, on polyurethane in an in vivo subcutaneous catheter rat (SCR model, and on mucosal surfaces in the reconstituted human epithelium (RHE model. Results HWP1 and genes belonging to the ALS, SAP, PLB and LIP gene families were constitutively expressed in C. albicans biofilms. ALS1-5 were upregulated in all model systems, while ALS9 was mostly downregulated. ALS6 and HWP1 were overexpressed in all models except in the RHE and MTP, respectively. The expression levels of SAP1 were more pronounced in both in vitro models, while those of SAP2, SAP4 and SAP6 were higher in the in vivo model. Furthermore, SAP5 was highly upregulated in the in vivo and RHE models. For SAP9 and SAP10 similar gene expression levels were observed in all model systems. PLB genes were not considerably upregulated in biofilms, while LIP1-3, LIP5-7 and LIP9-10 were highly overexpressed in both in vitro models. Furthermore, an elevated lipase activity was detected in supernatans of biofilms grown in the MTP and RHE model. Conclusions Our findings show that HWP1 and most of the genes belonging to the ALS, SAP and LIP gene families are upregulated in C. albicans biofilms. Comparison of the fold expression between the various model systems revealed similar expression levels for some genes, while for others model-dependent expression

  20. Microbially influenced corrosion: studies on enterobacteria isolated from seawater environment and influence of toxic metals on bacterial biofilm and bio-corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Bermond-Tilly, D.; Pineau, S.; Dupont-Morral, I. [Corrodys, 50 - Equeurdreville (France); Janvier, M.; Grimont, P.A.D. [Institut Pasteur, Unite BBPE, 75 - Paris (France)

    2004-07-01

    of microbial clusters and the increase production of the EPS by bacteria (Fang et al., 2002). This study was conducted to test the corrosive activity of Citrobacter freundii, Proteus mirabilis and Klebsiella planticola on carbon steel coupons and the influence of a toxic metal Cr(III) found in polluted marine environment) on these bacteria and the EPS production of the biofilm formed on carbon steel by appropriate in vitro experiments. (authors)

  1. Biofilm Testing and Effects of Environmental Factors on the Biofilm Formation of Staphylococcus aureus Isolates%金黄色葡萄球菌分离株的菌膜测定及其影响因素

    Institute of Scientific and Technical Information of China (English)

    李琼琼; 胡瑜; 姚晓敏; 史贤明; 张建华

    2011-01-01

    采用96孔细胞培养板法,对10株不同来源的金黄色葡萄球菌分离株的菌膜形成能力进行调查,并研究外部环境因素对金黄色葡萄球菌菌膜形成的影响.首先以金黄色葡萄球菌标准菌株ATCC6538为模式菌株,确定了亲水性细胞培养板、培养48 h为适宜的菌膜体外培养条件.在此条件下测定了10株分离株的菌膜形成量,并研究了不同培养温度(25~46℃)和不同营养条件(葡萄糖和氯化钠)对菌膜形成的影响.结果显示,体外培养条件下,金黄色葡萄球菌普遍可以形成菌膜,10株菌中仅1株为菌膜阴性,不同菌株菌膜形成能力差异较大;较高的培养温度有利于菌膜的形成,有3株菌在46℃时菌膜形成量达到最大;0.5%葡萄糖和1%氯化钠的添加可显著改变各菌株的菌膜形成,葡萄糖倾向于促进临床分离株菌膜形成量的增加,而氯化钠倾向于促进食品分离株菌膜形成量的增加.这一结果,可以为实际环境中菌膜的预防及控制提供指导和方向,同时也说明金黄色葡萄球菌的菌膜形成存在着不同的调控模式.%10 strains of Staphylococcus aureus were cultured on the microtitre 96-well plate to investigate the biofilm characteristics and the effect of the environmental factors in the biofilm formation. The optimized incubation conditions including the application of the hydrophilic microtitre plates and 48 h of culture time were established using ATCC6538 as the standard strain. The biofilm production of 10 S. Aureus isolates was determined,and the effect of culturing temperature (25~46 ℃) and nutrients (glucose and NaCl) on the biofilm formation was also investigated. The results showed that the biofilm was usually synthesized in the majority of S. Aureus strains and only 1 out of 10 isolates was found negative (without mature biofilm). Significant differences of the capability in the biofilm formation were indicated among different strains. Higher

  2. Study on Hydro-Alcoholic Extract Effect of Pomegranate Peel on Pseudomonas aeruginosa Biofilm Formation

    Directory of Open Access Journals (Sweden)

    R. Habibipour

    2015-10-01

    Full Text Available Introduction & Objective: Microorganisms form biomass as biofilm in response to many factors, in order to adapt to hostile extracellular environments and biocides. Using different herbal compounds are of those strategies to deal with biofilm. It has been proved that plants extracts such as pomegranate, raspberry and chamomile essential oils have anti-biofilm effects. This study aimed to evaluate the effect of different concentrations of black peel pomegranate ex-tract on Pseudomonas aeruginosa biofilm formation. Materials & Methods: In this experimental research the anti-biofilm effect, reducing the amount of biofilm formation and growth kinetics of Pseudomonas aeruginosa in different treatments was measured by microtiter and plate colorimetric crystal violet method. Biofilm formation was also examined using a microscope. Statistical analysis of data obtained from the reading of the ELISA was performed using SPSS software, P value 0.05. Results: Findings of this study showed that bacteria cannot form any biofilm in first 6 hours of incubation, in all treatments. The amount of biofilm formation after 12 hours in 0.01 and 0.05 g/ mL treatments were medium. Among treatments, after 18 and 24 hours of incubation 0.001 g/ mL concentration of pomegranate peel extract had medium and strong inhibitory effect on biofilm formation, respectively. Conclusion: Results of this study showed that biofilm formation and biofilm reduction percent-age is directly related to the duration of exposure of bacteria that could be due to the different phases of growth. Growth kinetics study also revealed that in the majority of treatments the growth was incremental up to about 15 hours and decrement afterwards due to the effective-ness of different treatments. After 18 hours, treatments have greatest influence on biofilm formation. The foregoing has been fully confirmed by the results of microscopic slides. (Sci J Hamadan Univ Med Sci 2015; 22 (3: 195-202

  3. Influencing factors in MMR immunisation decision making.

    Science.gov (United States)

    Hill, Marie C; Cox, Carol L

    Immunisation decision making is not a straightforward process for parents. Many factors influence parental decision making on whether they immunise their child with the measles, mumps and rubella (MMR) vaccine. The feasibility study described in this article provides insight into influencing factors associated with decisions regarding the immunisation of children by parents. The study findings suggest that the practice nurse is a credible source of information for parents seeking informed decision making. At a time when the incidence of measles and mumps is rising in the UK, the provision of appropriate information by the practice nurse has the potential to increase uptake of the MMR vaccine.

  4. Current and future trends for biofilm reactors for fermentation processes.

    Science.gov (United States)

    Ercan, Duygu; Demirci, Ali

    2015-03-01

    Biofilms in the environment can both cause detrimental and beneficial effects. However, their use in bioreactors provides many advantages including lesser tendencies to develop membrane fouling and lower required capital costs, their higher biomass density and operation stability, contribution to resistance of microorganisms, etc. Biofilm formation occurs naturally by the attachment of microbial cells to the support without use of any chemicals agent in biofilm reactors. Biofilm reactors have been studied and commercially used for waste water treatment and bench and pilot-scale production of value-added products in the past decades. It is important to understand the fundamentals of biofilm formation, physical and chemical properties of a biofilm matrix to run the biofilm reactor at optimum conditions. This review includes the principles of biofilm formation; properties of a biofilm matrix and their roles in the biofilm formation; factors that improve the biofilm formation, such as support materials; advantages and disadvantages of biofilm reactors; and industrial applications of biofilm reactors.

  5. Permeabilizing biofilms

    Science.gov (United States)

    Soukos, Nikolaos S.; Lee, Shun; Doukas,; Apostolos G.

    2008-02-19

    Methods for permeabilizing biofilms using stress waves are described. The methods involve applying one or more stress waves to a biofilm, e.g., on a surface of a device or food item, or on a tissue surface in a patient, and then inducing stress waves to create transient increases in the permeability of the biofilm. The increased permeability facilitates delivery of compounds, such as antimicrobial or therapeutic agents into and through the biofilm.

  6. Influence of Organic Material and Biofilms on Disinfectant Efficacy Against Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Hilda Nyati

    2012-04-01

    Full Text Available The effects of organic material and biofilm formation on the efficacy of Suma Tab D4 chlorine tablets and Suma Bac D10 quaternary ammonium compound (QAC against Listeria monocytogenes was determined in suspension and on stainless steel and polystyrene surfaces according to standard disinfectant test methodology. Exposure to 200 and 740 mg L-1 QAC and to 150 mg L-1 active chlorine resulted in a > 5.0 log10 CFU mL-1 and > 5.0 log10 CFU/coupon reduction of six L. monocytogenes strains within one minute, in suspension tests, and on stainless steel surfaces, respectively. Additionally, there was a reduction by as much as 5 log10 CFU/coupon or 5 log10 CFU/well of reference strains EGDe and Scott A biofilms within five minutes on stainless steel and polystyrene surfaces. Organic material, added as bovine serum albumin at 0.3% (w/v completely prevented the inactivation of L. monocytogenes in 150 mg L-1 chlorine, while reductions of only 0.6 +- 0.1 log10 CFU mL-1 were recorded in the presence of UHT milk at 3% (v/v. In contrast, reductions of 5 log10 CFU mL-1 were recorded within one minute on exposure to 740 mg L-1 QAC in the presence of 0.3% (w/v bovine serum albumin and within two minutes in the presence of 20 % (v/v UHT milk. Although Suma D4 chlorine tablets and Suma Bac D10 QAC are effective listericidal agents at recommended concentrations, Suma Tab D4 chlorine efficacy against L. monocytogenes is impaired by the presence of low concentrations of organic material, while Suma Bac D10 QAC maintains its listericidal activity in high organic loads.

  7. DNA-microarrays identification of Streptococcus mutans genes associated with biofilm thickness

    Directory of Open Access Journals (Sweden)

    Feldman Mark

    2008-12-01

    Full Text Available Abstract Background A biofilm is a complex community of microorganisms that develop on surfaces in diverse environments. The thickness of the biofilm plays a crucial role in the physiology of the immobilized bacteria. The most cariogenic bacteria, mutans streptococci, are common inhabitants of a dental biofilm community. In this study, DNA-microarray analysis was used to identify differentially expressed genes associated with the thickness of S. mutans biofilms. Results Comparative transcriptome analyses indicated that expression of 29 genes was differentially altered in 400- vs. 100-microns depth and 39 genes in 200- vs. 100-microns biofilms. Only 10 S. mutans genes showed differential expression in both 400- vs. 100-microns and 200- vs. 100-microns biofilms. All of these genes were upregulated. As sucrose is a predominant factor in oral biofilm development, its influence was evaluated on selected genes expression in the various depths of biofilms. The presence of sucrose did not noticeably change the regulation of these genes in 400- vs. 100-microns and/or 200- vs. 100-microns biofilms tested by real-time RT-PCR. Furthermore, we analyzed the expression profile of selected biofilm thickness associated genes in the luxS- mutant strain. The expression of those genes was not radically changed in the mutant strain compared to wild-type bacteria in planktonic condition. Only slight downregulation was recorded in SMU.2146c, SMU.574, SMU.609, and SMU.987 genes expression in luxS- bacteria in biofilm vs. planktonic environments. Conclusion These findings reveal genes associated with the thickness of biofilms of S. mutans. Expression of these genes is apparently not regulated directly by luxS and is not necessarily influenced by the presence of sucrose in the growth media.

  8. INFLUENCE FACTORS FOR LEASING MARKET CONTRACTS

    Directory of Open Access Journals (Sweden)

    Oana BĂRBULESCU

    2016-11-01

    Full Text Available This paper aims to investigate the relationship between leasing contracts and some factors that influence the value of these contracts. In order to do this, we have decided on some quantitative marketing research by appealing to statistics for accomplishing the objectives that we have set: to find a correlation between the turnover percentage assigned to leasing expenses and several influence factors. This study indicated that the more contracts are signed by a firm, the more likely is to assign a bigger fraction of the income to each new leasing contract. The study confirmed that bigger companies are relying more on leasing as a way of financing than small companies. This study also discovered that companies with more employees are using larger contracts in order to sustain their activity. The findings are expected to contribute to adjusting the offers by the leasing companies, taking into consideration these factors and to using these factors in order to better predict the market evolution.

  9. A factor analysis to detect factors influencing building national brand

    Directory of Open Access Journals (Sweden)

    Naser Azad

    Full Text Available Developing a national brand is one of the most important issues for development of a brand. In this study, we present factor analysis to detect the most important factors in building a national brand. The proposed study uses factor analysis to extract the most influencing factors and the sample size has been chosen from two major auto makers in Iran called Iran Khodro and Saipa. The questionnaire was designed in Likert scale and distributed among 235 experts. Cronbach alpha is calculated as 84%, which is well above the minimum desirable limit of 0.70. The implementation of factor analysis provides six factors including “cultural image of customers”, “exciting characteristics”, “competitive pricing strategies”, “perception image” and “previous perceptions”.

  10. Calcium carbonate precipitation by heterotrophic bacteria isolated from biofilms formed on deteriorated ignimbrite stones: influence of calcium on EPS production and biofilm formation by these isolates.

    Science.gov (United States)

    López-Moreno, Angélica; Sepúlveda-Sánchez, José David; Mercedes Alonso Guzmán, Elia Mercedes; Le Borgne, Sylvie

    2014-01-01

    Heterotrophic CaCO3-precipitating bacteria were isolated from biofilms on deteriorated ignimbrites, siliceous acidic rocks, from Morelia Cathedral (Mexico) and identified as Enterobacter cancerogenus (22e), Bacillus sp. (32a) and Bacillus subtilis (52g). In solid medium, 22e and 32a precipitated calcite and vaterite while 52g produced calcite. Urease activity was detected in these isolates and CaCO3 precipitation increased in the presence of urea in the liquid medium. In the presence of calcium, EPS production decreased in 22e and 32a and increased in 52g. Under laboratory conditions, ignimbrite colonization by these isolates only occurred in the presence of calcium and no CaCO3 was precipitated. Calcium may therefore be important for biofilm formation on stones. The importance of the type of stone, here a siliceous stone, on biological colonization is emphasized. This calcium effect has not been reported on calcareous materials. The importance of the effect of calcium on EPS production and biofilm formation is discussed in relation to other applications of CaCO3 precipitation by bacteria.

  11. Electrochemical sensors for biofilm and biocorrosion

    Energy Technology Data Exchange (ETDEWEB)

    Tribollet, B. [UPR 15 du CNRS, Universite Paris 6, 4 Place Jussieu, 75252 Paris Cedex05 (France)

    2003-07-01

    The presence of biofilm modifies the electrochemical properties of the interface and the mass transport near the interface. Two biofilm effects are damageable: the reduction of heat and/or mass transfer and the biocorrosion or microbiologically influenced corrosion (MIC). Two kinds of electrochemical sensors were developed: the first kind for the biofilm detection and the second one to evaluate the MIC risk. The biofilm detection is obtained by considering either the potential modification of the interface or the mass transport modification. The mass transport modification is analysed by considering the limiting diffusion current measured on a gold electrode where the biofilm development occurs. The MIC risk is evaluated with a sensor composed of two concentric electrodes in the material under investigation (e.g. carbon steel): a small disk electrode in the centre and a large ring. In a first step, a pit is artificially initiated by applying a current through these electrodes. In a second step, the risk factors of MIC are investigated by analysing the free coupling current circulating between these two short-circuited electrodes. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  12. On factors influencing students’ listening abilities

    Institute of Scientific and Technical Information of China (English)

    胡天秀

    2012-01-01

    As we all know,listening,speaking,reading,and writing are four basic skills in language teaching and learning.Listening plays an important role in improving other skills.There are some factors influencing students’ listening abilities.So it’s important for teachers to improve students’ listening abilities.

  13. Factors Influencing High School Students' Career Aspirations

    Science.gov (United States)

    Tang, Mei; Pan, Wei; Newmeyer, Mark D.

    2008-01-01

    This article explores the factors influencing high school students' career aspirations with a study analyzing 141 high school students. The Social Cognitive Career Development Model was utilized to examine the interactive relationships among learning experiences, career self-efficacy, outcome expectations, career interests, and career choices. The…

  14. Factors influencing laser cutting of wood

    Science.gov (United States)

    V.G. Barnekov; C.W. McMillin; H.A. Huber

    1986-01-01

    Factors influencing the ability of lasers to cut wood may be generally classified into these three areas: 1) characteristics of the laser beam; 2) equipment and processing variables; and 3) properties of the workpiece. Effects of beam power, mode, polarization, and stability are discussed as are aspects of optics, location of focal point, feed speed, gas-jet assist...

  15. Factors influencing the process of farm liquidation

    Directory of Open Access Journals (Sweden)

    Michał Dudek

    2010-01-01

    Full Text Available In the paper the logit analysis was used in order to define the factors influencing farm liquidation. The prevalence of this phenomenon and its regional differences were analysed. Significant and negative impact of the number of people in a family farm and the number of machinery and technical equipment, as well as the positive impact of the farmer’ age are reported.

  16. Social Factors Influencing Child Health in Ghana.

    Directory of Open Access Journals (Sweden)

    Emmanuel Quansah

    Full Text Available Social factors have profound effects on health. Children are especially vulnerable to social influences, particularly in their early years. Adverse social exposures in childhood can lead to chronic disorders later in life. Here, we sought to identify and evaluate the impact of social factors on child health in Ghana. As Ghana is unlikely to achieve the Millennium Development Goals' target of reducing child mortality by two-thirds between 1990 and 2015, we deemed it necessary to identify social determinants that might have contributed to the non-realisation of this goal.ScienceDirect, PubMed, MEDLINE via EBSCO and Google Scholar were searched for published articles reporting on the influence of social factors on child health in Ghana. After screening the 98 articles identified, 34 of them that met our inclusion criteria were selected for qualitative review.Major social factors influencing child health in the country include maternal education, rural-urban disparities (place of residence, family income (wealth/poverty and high dependency (multiparousity. These factors are associated with child mortality, nutritional status of children, completion of immunisation programmes, health-seeking behaviour and hygiene practices.Several social factors influence child health outcomes in Ghana. Developing more effective responses to these social determinants would require sustainable efforts from all stakeholders including the Government, healthcare providers and families. We recommend the development of interventions that would support families through direct social support initiatives aimed at alleviating poverty and inequality, and indirect approaches targeted at eliminating the dependence of poor health outcomes on social factors. Importantly, the expansion of quality free education interventions to improve would-be-mother's health knowledge is emphasised.

  17. Metabolism links bacterial biofilms and colon carcinogenesis.

    Science.gov (United States)

    Johnson, Caroline H; Dejea, Christine M; Edler, David; Hoang, Linh T; Santidrian, Antonio F; Felding, Brunhilde H; Ivanisevic, Julijana; Cho, Kevin; Wick, Elizabeth C; Hechenbleikner, Elizabeth M; Uritboonthai, Winnie; Goetz, Laura; Casero, Robert A; Pardoll, Drew M; White, James R; Patti, Gary J; Sears, Cynthia L; Siuzdak, Gary

    2015-06-02

    Bacterial biofilms in the colon alter the host tissue microenvironment. A role for biofilms in colon cancer metabolism has been suggested but to date has not been evaluated. Using metabolomics, we investigated the metabolic influence that microbial biofilms have on colon tissues and the related occurrence of cancer. Patient-matched colon cancers and histologically normal tissues, with or without biofilms, were examined. We show the upregulation of polyamine metabolites in tissues from cancer hosts with significant enhancement of N(1), N(12)-diacetylspermine in both biofilm-positive cancer and normal tissues. Antibiotic treatment, which cleared biofilms, decreased N(1), N(12)-diacetylspermine levels to those seen in biofilm-negative tissues, indicating that host cancer and bacterial biofilm structures contribute to the polyamine metabolite pool. These results show that colonic mucosal biofilms alter the cancer metabolome to produce a regulator of cellular proliferation and colon cancer growth potentially affecting cancer development and progression.

  18. Metabolism links bacterial biofilms and colon carcinogenesis

    Science.gov (United States)

    Johnson, Caroline H.; Dejea, Christine M.; Edler, David; Hoang, Linh T.; Santidrian, Antonio F.; Felding, Brunhilde H.; Cho, Kevin; Wick, Elizabeth C.; Hechenbleikner, Elizabeth M.; Uritboonthai, Winnie; Goetz, Laura; Casero, Robert A.; Pardoll, Drew M.; White, James R.; Patti, Gary J.; Sears, Cynthia L.; Siuzdak, Gary

    2015-01-01

    SUMMARY Bacterial biofilms in the colon alter the host tissue microenvironment. A role for biofilms in colon cancer metabolism has been suggested but to date has not been evaluated. Using metabolomics, we investigated the metabolic influence that microbial biofilms have on colon tissues and the related occurrence of cancer. Patient-matched colon cancers and histologically normal tissues, with or without biofilms, were examined. We show the upregulation of polyamine metabolites in tissues from cancer hosts with significant enhancement of N1, N12-diacetylspermine in both biofilm positive cancer and normal tissues. Antibiotic treatment, which cleared biofilms, decreased N1, N12-diacetylspermine levels to those seen in biofilm negative tissues, indicating that host cancer and bacterial biofilm structures contribute to the polyamine metabolite pool. These results show that colonic mucosal biofilms alter the cancer metabolome, to produce a regulator of cellular proliferation and colon cancer growth potentially affecting cancer development and progression. PMID:25959674

  19. The roles of epithelial cell contact, respiratory bacterial interactions and phosphorylcholine in promoting biofilm formation by Streptococcus pneumoniae and nontypeable Haemophilus influenzae.

    Science.gov (United States)

    Krishnamurthy, Ajay; Kyd, Jennelle

    2014-08-01

    Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) often share a common niche within the nasopharynx, both associated with infections such as bronchitis and otitis media. This study investigated how the association between NTHi and S. pneumoniae and the host affects their propensity to form biofilms. We investigated a selection of bacterial strain and serotype combinations on biofilm formation, and the effect of contact with respiratory epithelial cells. Measurement of biofilm showed that co-infection with NTHi and S. pneumoniae increased biofilm formation following contact with epithelial cells compared to no contact demonstrating the role of epithelial cells in biofilm formation. Additionally, the influence of phosphorylcholine (ChoP) on biofilm production was investigated using the licD mutant strain of NTHi 2019 and found that ChoP had a role in mixed biofilm formation but was not the only requirement. The study highlights the complex interactions between microbes and the host epithelium during biofilm production, suggesting the importance of understanding why certain strains and serotypes differentially influence biofilm formation. A key contributor to increased biofilm formation was the upregulation of biofilm formation by epithelial cell factors.

  20. Problem solving III: factors influencing classroom problem

    Directory of Open Access Journals (Sweden)

    Sayonara Salvador Cabral da Costa

    1997-05-01

    Full Text Available This paper presents a review of the literature in the area of problem solving, particularly in physics, focusing only on factors that influence classroom problem solving. Fifty-seven papers have been analyzed in terms of theoretical basis, investigated factors/methodology and findings/relevant factors, which were organized in a table that served as support for a synthesis made by the authors. It is the third of a four-paper series reviewing different aspects of the problem solving subject.

  1. The influence of flow cell geometry related shear stresses on the distribution, structure and susceptibility of Pseudomonas aeruginosa 01 biofilms.

    Science.gov (United States)

    Salek, M Mehdi; Jones, Steven M; Martinuzzi, Robert J

    2009-11-01

    The effects of non-uniform hydrodynamic conditions resulting from flow cell geometry (square and rectangular cross-section) on Pseudomonas aeruginosa 01 (PAO1) biofilm formation, location, and structure were investigated for nominally similar flow conditions using a combination of confocal scanning laser microscope (CSLM) and computational fluid dynamics (CFD). The thickness and surface coverage of PAO1 biofilms were observed to vary depending on the location in the flow cell and thus also the local wall shear stress. The biofilm structure in a 5:1 (width to height) aspect ratio rectangular flow cell was observed to consist mainly of a layer of bacterial cells with thicker biofilm formation observed in the flow cell corners. For square cross-section (1:1 aspect ratio) flow cells, generally thicker and more uniform surface coverage biofilms were observed. Mushroom shaped structures with hollow centers and wall breaks, indicative of 'seeding' dispersal structures, were found exclusively in the square cross-section tubes. Exposure of PAO1 biofilms grown in the flow cells to gentamicin revealed a difference in susceptibility. Biofilms grown in the rectangular flow cell overall exhibited a greater susceptibility to gentamicin compared to those grown in square flow cells. However, even within a given flow cell, differences in susceptibility were observed depending on location. This study demonstrates that the spanwise shear stress distribution within the flow cells has an important impact on the location of colonization and structure of the resultant biofilm. These differences in biofilm structure have a significant impact on the susceptibility of the biofilms grown within flow channels. The impact of flow modification due to flow cell geometry should be considered when designing flow cells for laboratory investigation of bacterial biofilms.

  2. Factors that influence women's dispositions toward science

    Science.gov (United States)

    Atria, Catherine Graczyk

    Females have been underrepresented in the study of science and science careers for decades although advancements have been made in closing this gender gap, the gap persists particularly in the physical sciences. Variables which influence a woman's desire to pursue and maintain a science course of study and career must be discovered. The United States lags behind other industrialized countries in the fields of science, math, and engineering. Females comprise an estimated half of the population; their potential contributions cannot be ignored or overlooked. This retrospective research study explores the personal experiences of ten women enrolled in science majors, with science related career plans. The goal of this study is to describe the factors that influence the participants' interest in science. The findings, the effect of science coursework, science teachers' personality and manner, other influential educational personnel, role models and mentors, external influences exclusive of school, parental influence, locus of control and positive attitudes toward science confirm what other researchers have found.

  3. Uncovering Factors Influencing Interpersonal Health Communication.

    Science.gov (United States)

    Donné, Lennie; Jansen, Carel; Hoeks, John

    2017-01-01

    Talking to friends, family, or peers about health issues might, among other things, increase knowledge of social norms and feelings of self-efficacy in adopting a healthier lifestyle. We often see interpersonal health communication as an important mediating factor in the effects of health campaigns on health behavior. No research has been done so far, however, on factors that influence whether and how people talk about health issues without being exposed to a health campaign first. In this exploratory study, we interviewed 12 participants about their communication behavior concerning six different health themes, like smoking and exercising. The results suggest that at least four types of interpersonal health communication can be distinguished, each influenced by different factors, like conversational partner and objective of the conversation. Future research should take this diversity of interpersonal health communication into account, and focus on designing health campaigns that aim to trigger dialogue within target populations.

  4. Theoretical difference between impact factor and influence factor

    Directory of Open Access Journals (Sweden)

    Đilda Pečarić

    2010-06-01

    Full Text Available Bibliometric constructions of "knowledge maps" and "cognitive structures of science" do not differentiate between impact and influence factors. The difference can be constructedaccording to different meaning and interpretation of the terms reference and citation. Reference is "acknowledgment which one author gives to another", whereas citation is "acknowledgment which one document receives from another". Development of Information Science according to period and subject area is analyzed on the corpus of citation literature retrieved from doctoral dissertations in Information Science from 1978 to 2007 at Croatian universities. The research aim is to indicate the difference between document impact factor and author's influence factor (i.e. reference ability to produce effects on actions, behavior, and opinions of authors of doctoral theses. The influence factor serves to distinguish the key role of cited authors in time and according to the duration of the influence (the average age for cited papers of dominant authors in different periods is between eight and ten years. The difference between linear and interactive communication seems vital for the interpretation of cited half-life, i.e. the attitude of one science community towards used information resources and cognitive heritage. The analyzed corpus of 22,210 citations can be divided into three communication phases according to influence factor criteria: in the phase of dialogue and interactive communication 25% of bibliographic units are cited in the first four years; in the second phase another 25% of units are cited from the fifth to the ninth year; after ten years, in the dominant linear communication phase, approximately 30% of units are cited.

  5. What Factors Influence Knowledge Sharing in Organizations?

    DEFF Research Database (Denmark)

    Razmerita, Liana; Kirchner, Kathrin; Nielsen, Pia

    2016-01-01

    Purpose: Enterprise social media platforms provide new ways of sharing knowledge and communicating within organizations to benefit from the social capital and valuable knowledge that employees have. Drawing on social dilemma and self-determination theory, the aim of the study is to understand what...... factors drive employees’ participation and what factors hamper their participation in enterprise social media. Design/methodology/approach: Based on a literature review, a unified research model is derived integrating demographic, individual, organizational and technological factors that influence...... knowledge sharing framework helps to understand what factors impact engagement on social media. Furthermore the article suggests different types of interventions to overcome the social dilemma of knowledge sharing. Originality/value: The study contributes to an understanding of factors leading...

  6. Investigating important factors influencing purchasing from chains

    Directory of Open Access Journals (Sweden)

    Naser Azad

    2012-04-01

    Full Text Available In this paper, we survey important factors, influencing customers to buy more from one of well known food market operating in capital city of Iran named Shahrvand. The survey studies the effects of six factors including customer's perception, persuasive factors, brand, customers' expectations, product's characteristics and special features of store on attracting more customers. We have distributed questionnaire among 196 customers who regularly visit stores and analyzed details of the data. The results indicate that customers' perception is the most important item, which includes eight components. Years of experience is the most important item in our survey followed by impact of color and working hours. Diversity of services is another factor, which plays the most important role followed by quality of services. Next, fidelity and brand are other most important factors and the name of store and risk are in lower degree of importance.

  7. Beneficial biofilms

    Directory of Open Access Journals (Sweden)

    Sara R Robertson

    2015-10-01

    Full Text Available Surface-adherent biofilm growth is a common trait of bacteria and other microorganisms in nature. Within biofilms, organisms are present in high density and are enmeshed in an organic matrix containing polysaccharides and other molecules. The close proximity of organisms within biofilms facilitates microbial interactions and signaling, including many metabolic processes in which consortia rather than individual organisms participate. Biofilm growth also enables microorganisms to withstand chemical and biological stresses. Here, we review some current literature and document representative beneficial aspects of biofilms using examples from wastewater treatment, microbial fuel cells, biological repair (biocementation of stonework, and biofilm protection against Candida albicans infections. Finally, we address a chemical ecology strategy whereby desired microbial succession and beneficial biofilm formation can be encouraged via manipulation of culture conditions and bacterial signaling.

  8. An Integrated Modeling and Experimental Approach to Study the Influence of Environmental Nutrients on Biofilm Formation of Pseudomonas aeruginosa.

    Science.gov (United States)

    Xu, Zhaobin; Islam, Sabina; Wood, Thomas K; Huang, Zuyi

    2015-01-01

    The availability of nutrient components in the environment was identified as a critical regulator of virulence and biofilm formation in Pseudomonas aeruginosa. This work proposes the first systems-biology approach to quantify microbial biofilm formation upon the change of nutrient availability in the environment. Specifically, the change of fluxes of metabolic reactions that were positively associated with P. aeruginosa biofilm formation was used to monitor the trend for P. aeruginosa to form a biofilm. The uptake rates of nutrient components were changed according to the change of the nutrient availability. We found that adding each of the eleven amino acids (Arg, Tyr, Phe, His, Iso, Orn, Pro, Glu, Leu, Val, and Asp) to minimal medium promoted P. aeruginosa biofilm formation. Both modeling and experimental approaches were further developed to quantify P. aeruginosa biofilm formation for four different availability levels for each of the three ions that include ferrous ions, sulfate, and phosphate. The developed modeling approach correctly predicted the amount of biofilm formation. By comparing reaction flux change upon the change of nutrient concentrations, metabolic reactions used by P. aeruginosa to regulate its biofilm formation are mainly involved in arginine metabolism, glutamate production, magnesium transport, acetate metabolism, and the TCA cycle.

  9. An Integrated Modeling and Experimental Approach to Study the Influence of Environmental Nutrients on Biofilm Formation of Pseudomonas aeruginosa

    Directory of Open Access Journals (Sweden)

    Zhaobin Xu

    2015-01-01

    Full Text Available The availability of nutrient components in the environment was identified as a critical regulator of virulence and biofilm formation in Pseudomonas aeruginosa. This work proposes the first systems-biology approach to quantify microbial biofilm formation upon the change of nutrient availability in the environment. Specifically, the change of fluxes of metabolic reactions that were positively associated with P. aeruginosa biofilm formation was used to monitor the trend for P. aeruginosa to form a biofilm. The uptake rates of nutrient components were changed according to the change of the nutrient availability. We found that adding each of the eleven amino acids (Arg, Tyr, Phe, His, Iso, Orn, Pro, Glu, Leu, Val, and Asp to minimal medium promoted P. aeruginosa biofilm formation. Both modeling and experimental approaches were further developed to quantify P. aeruginosa biofilm formation for four different availability levels for each of the three ions that include ferrous ions, sulfate, and phosphate. The developed modeling approach correctly predicted the amount of biofilm formation. By comparing reaction flux change upon the change of nutrient concentrations, metabolic reactions used by P. aeruginosa to regulate its biofilm formation are mainly involved in arginine metabolism, glutamate production, magnesium transport, acetate metabolism, and the TCA cycle.

  10. Biofilm formation and antibiotic production in Ruegeria mobilis are influenced by intracellular concentrations of cyclic dimeric guanosinmonophosphate

    DEFF Research Database (Denmark)

    D'Alvise, Paul; Magdenoska, Olivera; Melchiorsen, Jette

    2014-01-01

    formation and production of the potent antibiotic tropodithietic acid (TDA). An introduced phosphodiesterase gene decreased c-di-GMP and reduced biofilm formation and TDA production. tdaC, a key gene for TDA biosynthesis, was expressed only in attached or biofilm-forming cells, and expression was induced...

  11. Modeling biofilm dynamics and hydraulic properties in variably saturated soils using a channel network model

    Science.gov (United States)

    Rosenzweig, Ravid; Furman, Alex; Dosoretz, Carlos; Shavit, Uri

    2014-07-01

    Biofilm effects on water flow in unsaturated environments have largely been ignored in the past. However, intensive engineered systems that involve elevated organic loads such as wastewater irrigation, effluent recharge, and bioremediation processes make understanding how biofilms affect flow highly important. In the current work, we present a channel-network model that incorporates water flow, substrate transport, and biofilm dynamics to simulate the alteration of soil hydraulic properties, namely water retention and conductivity. The change in hydraulic properties due to biofilm growth is not trivial and depends highly on the spatial distribution of the biofilm development. Our results indicate that the substrate mass transfer coefficient across the water-biofilm interface dominates the spatiotemporal distribution of biofilm. High mass transfer coefficients lead to uncontrolled biofilm growth close to the substrate source, resulting in preferential clogging of the soil. Low mass transfer coefficients, on the other hand, lead to a more uniform biofilm distribution. The first scenario leads to a dramatic reduction of the hydraulic conductivity with almost no change in water retention, whereas the second scenario has a smaller effect on conductivity but a larger influence on retention. The current modeling approach identifies key factors that still need to be studied and opens the way for simulation and optimization of processes involving significant biological activity in unsaturated soils.

  12. Influence of organizational factors on safety

    Energy Technology Data Exchange (ETDEWEB)

    Haber, S.B.; Metlay, D.S.; Crouch, D.A.

    1990-01-01

    There is a need for a better understanding of exactly how organizational management factors at a nuclear power plant (NPP) affect plant safety performance, either directly or indirectly, and how these factors might be observed, measured, and evaluated. The purpose of this research project is to respond to that need by developing a general methodology for characterizing these organizational and management factors, systematically collecting information on their status and integrating that information into various types of evaluative activities. Research to date has included the development of the Nuclear Organization and Management Analysis Concept (NOMAC) of a NPP, the identification of key organizational and management factors, and the identification of the methods for systematically measuring and analyzing the influence of these factors on performance. Most recently, two field studies, one at a fossil fuel plant and the other at a NPP, were conducted using the developed methodology. Results are presented from both studies highlighting the acceptability, practicality, and usefulness of the methods used to assess the influence of various organizational and management factors including culture, communication, decision-making, standardization, and oversight. 6 refs., 3 figs., 1 tab.

  13. Factors Influencing Colorectal Cancer Screening Participation

    Directory of Open Access Journals (Sweden)

    Antonio Z. Gimeno García

    2012-01-01

    Full Text Available Colorectal cancer (CRC is a major health problem worldwide. Although population-based CRC screening is strongly recommended in average-risk population, compliance rates are still far from the desirable rates. High levels of screening uptake are necessary for the success of any screening program. Therefore, the investigation of factors influencing participation is crucial prior to design and launches a population-based organized screening campaign. Several studies have identified screening behaviour factors related to potential participants, providers, or health care system. These influencing factors can also be classified in non-modifiable (i.e., demographic factors, education, health insurance, or income and modifiable factors (i.e., knowledge about CRC and screening, patient and provider attitudes or structural barriers for screening. Modifiable determinants are of great interest as they are plausible targets for interventions. Interventions at different levels (patient, providers or health care system have been tested across the studies with different results. This paper analyzes factors related to CRC screening behaviour and potential interventions designed to improve screening uptake.

  14. Roles of Candida albicans Gat2, a GATA-type zinc finger transcription factor, in biofilm formation, filamentous growth and virulence.

    Science.gov (United States)

    Du, Han; Guan, Guobo; Xie, Jing; Sun, Yuan; Tong, Yaojun; Zhang, Lixin; Huang, Guanghua

    2012-01-01

    Candida albicans is the most common human fungal pathogen, causing not only superficial infections, but also life-threatening systemic disease. C. albicans can grow in several morphological forms including unicellular yeast-form, elongated hyphae and pseudohyphae. In certain natural environments, C. albicans also exists as biofilms, which are structured and surface-attached microbial communities. Transcription factors play a critical role in morphogenesis and biofilm development. In this study, we identified four adhesion-promoting transcription factors (Tec1, Cph1, Ume6 and Gat2) by screening a transcription factor overexpression library. Sequence analysis indicates that Gat2 is a GATA-type zinc finger transcription factor. Here we showed that the gat2/gat2 mutant failed to form biofilms on the plastic and silicone surfaces. Overexpression of GAT2 gene promoted filamentous and invasive growth on agar containing Lee's medium, while deletion of this gene had an opposite effect. However, inactivation of Gat2 had no obvious effect on N-acetyl-glucosamine (GlcNAc) induced hyphal development. In a mouse model of systemic infection, the gat2/gat2 mutant showed strongly attenuated virulence. Our results suggest that Gat2 plays a critical role in C. albicans biofilm formation, filamentous growth and virulence.

  15. Mutations in the rpoS gene are the major limiting factor for biofilm formation in Escherichia coli serotype O157:H7 clinical isolates

    Science.gov (United States)

    Background: Biofilm formation is a complex process that is highly regulated through a battery of transcriptional regulators, small regulatory RNAs, and environmental conditions. RpoS sigma factor along with MlrA protein directly regulate the expression of the curli key regulator CsgD. In most serot...

  16. Biofilm roughness determines Cryptosporidium parvum retention in environmental biofilms.

    Science.gov (United States)

    DiCesare, E A Wolyniak; Hargreaves, B R; Jellison, K L

    2012-06-01

    The genus Cryptosporidium is a group of waterborne protozoan parasites that have been implicated in significant outbreaks of gastrointestinal infections throughout the world. Biofilms trap these pathogens and can contaminate water supplies through subsequent release. Biofilm microbial assemblages were collected seasonally from three streams in eastern Pennsylvania and used to grow biofilms in laboratory microcosms. Daily oocyst counts in the influx and efflux flow allowed the calculation of daily oocyst retention in the biofilm. Following the removal of oocysts from the influx water, oocyst attachment to the biofilm declined to an equilibrium state within 5 days that was sustained for at least 25 days. Varying the oocyst loading rate for the system showed that biofilm retention could be saturated, suggesting that discrete binding sites determined the maximum number of oocysts retained. Oocyst retention varied seasonally but was consistent across all three sites; however, seasonal oocyst retention was not consistent across years at the same site. No correlation between oocyst attachment and any measured water quality parameter was found. However, oocyst retention was strongly correlated with biofilm surface roughness and roughness varied among seasons and across years. We hypothesize that biofilm roughness and oocyst retention are dependent on environmentally driven changes in the biofilm community rather than directly on water quality conditions. It is important to understand oocyst transport dynamics to reduce risks of human infection. Better understanding of factors controlling biofilm retention of oocysts should improve our understanding of oocyst transport at different scales.

  17. Factors influencing the feasibility of laparoscopy colectomy

    Institute of Scientific and Technical Information of China (English)

    He Zhiyun; Zhang Zhongtao

    2014-01-01

    Objective The objective was to review the factors affecting the feasibility of performing successful laparoscopic colectomy.Data sources The literatures about the risk factors closely related to the ability to perform laparoscopic colectomy on different surgical diseases of the colon cited in this review were obtained from PubMed published in English from 2006 to 2012.Study selection Original articles regarding the risk factors that affect the ability to perform laparoscopic colectomy were selected.Results Obesity,diabetes,inflammatory bowel diseases,advanced age,emergency operation,and pelvic anatomy are all important risk factors that increase the risk of developing serious complications such as hemorrhage,anastomotic leak,and skin and soft tissue infections following laparoscopic colectomy.These factors also increase the likelihood of conversion to an open operation.In this study,we reviewed the recent original articles about the relationship of laparoscopic colectomy with these risk factors.We also describe some strategies that limit the likelihood of these complications and the likelihood of conversion to an open operation.Conclusions Obesity,diabetes,inflammatory bowel diseases,age,emergency operation,and pelvic anatomy are all important risk factors that increase the risk of either serious complications or conversion to open operation with laparoscopic colectomy.Evaluation of these risk factors preoperatively should influence the decision to perform colectomy using laparoscopic techniques.

  18. Factors Influencing Tacit Knowledge in Construction

    Directory of Open Access Journals (Sweden)

    Jawahar Nesan

    2012-11-01

    Full Text Available Increased complexity of the construction business and consequentuse of new management concepts and technologies ledconstruction organisations to focus more on the transfer of explicitknowledge. However, it is the tacit knowledge that determinesthe construction companies’ competitiveness in a business thatis driven by turbulent market conditions and customers’ everincreasingdemands. This paper highlights the importance of tacitknowledge sharing in construction, explores the challenges andopportunities to efficiently share tacit knowledge, and based on theliterature review identifies some critical factors that influence tacitknowledge in construction. It is argued that employees’ knowledgesharing (learning behaviours are influenced by work practices thatare borne by respective organisational behaviours. Organisational,cultural, and project characteristics that facilitate knowledgesharing among construction employees are explored and thepractices that influence the construction employee behaviour insharing tacit knowledge are highlighted.

  19. Factors Influencing Tacit Knowledge in Construction

    Directory of Open Access Journals (Sweden)

    Jawahar Nesan

    2012-11-01

    Full Text Available Increased complexity of the construction business and consequentuse of new management concepts and technologies ledconstruction organisations to focus more on the transfer of explicitknowledge. However, it is the tacit knowledge that determinesthe construction companies’ competitiveness in a business thatis driven by turbulent market conditions and customers’ everincreasingdemands. This paper highlights the importance of tacitknowledge sharing in construction, explores the challenges andopportunities to efficiently share tacit knowledge, and based on theliterature review identifies some critical factors that influence tacitknowledge in construction. It is argued that employees’ knowledgesharing (learning behaviours are influenced by work practices thatare borne by respective organisational behaviours. Organisational,cultural, and project characteristics that facilitate knowledgesharing among construction employees are explored and thepractices that influence the construction employee behaviour insharing tacit knowledge are highlighted.

  20. Microencapsulation techniques, factors influencing encapsulation efficiency.

    Science.gov (United States)

    Jyothi, N Venkata Naga; Prasanna, P Muthu; Sakarkar, Suhas Narayan; Prabha, K Surya; Ramaiah, P Seetha; Srawan, G Y

    2010-05-01

    Microencapsulation is one of the quality preservation techniques of sensitive substances and a method for production of materials with new valuable properties. Microencapsulation is a process of enclosing micron-sized particles in a polymeric shell. There are different techniques available for the encapsulation of drug entities. The encapsulation efficiency of the microparticle or microsphere or microcapsule depends upon different factors like concentration of the polymer, solubility of polymer in solvent, rate of solvent removal, solubility of organic solvent in water, etc. The present article provides a literature review of different microencapsulation techniques and different factors influencing the encapsulation efficiency of the microencapsulation technique.

  1. Factors Influencing Consumer Behavior of Smartphone Users

    OpenAIRE

    Nagarkoti, Bishal

    2014-01-01

    The aim of the study is to know about the factors influencing consumer behavior of Smartphone users. Under this study, the main focus is to identify whether Smartphone users buy Smartphone because of their need or wish, reasons to buy expensive smart phones, how social and personal factors affect them to make purchasing decision, for what purposes they use Smartphone, where and how long a day, change in usage of com-puters due to Smartphone and how high is the phone bill after using Smartphon...

  2. FACTORS INFLUENCING BENDING RIGIDITY OF SUBMERGED VEGETATION

    Institute of Scientific and Technical Information of China (English)

    WU Long-hua; YANG Xiao-li

    2011-01-01

    The bending rigidity of submerged vegetation is closely related with vegetative drag force.This work aims at determining the effects of flow conditions and characteristics of vegetation on the bending rigidity of submerged vegetation.Based on the dimensional analysis method,the factors influencing the bending rigidity of individual submerged vegetation were analyzed.The relationship between the relative bending rigidity and its influencing factors was investigated by experimental observation,and a relative bending rigidity expression for submerged vegetation was obtained by means of multiple linear regression method.The results show that the submerged vegetation has three states under different inflow conditions,and the each critical relative bending rigidity of individual submerged vegetation was determined for the different states of submerged vegetation.

  3. Investigating different factors influencing on brand equity

    Directory of Open Access Journals (Sweden)

    Afsane Zamanimoghadam

    2014-07-01

    Full Text Available The purpose of this paper is to determine and prioritize factors influencing on brand equity in consumer’s point of view for a case study of Samsung appliance consumers in city of Tehran, Iran. The study investigates the effects of four factors in terms of the customer's perspective, price, advertisement, family and brand image, by dimensions of brand equity, perceived quality, brand awareness, brand association, brand loyalty, on brand equity. The research method is based on a descriptive-survey research. The questionnaire includes Samsung consumers in city of Tehran, Iran. To test the hypotheses, SPSS and LISREL software packages are used. For data analysis, descriptive statistics and inferential statistical tests including structural equation modeling and path analysis are used. The results of the survey have indicated that family and brand image influence positively on brand equity but the effects of advertisement and price on brand equity were not confirmed.

  4. Factors Influencing Impulse Buying in Retail Stores

    OpenAIRE

    Giorgadze, Nino

    2014-01-01

    Impulse buying is a widely pervasive phenomenon. Statistics shows that more and more shoppers are experiencing irresistible urge to purchase unplanned and in most cases unnecessary product. Existing researches fall short in identifying most suitable tools that marketers can adopt in order to promote impulsive sales. Therefore, this thesis provides deep analysis of those, controllable factors that influence impulse buying. Particularly four external cues are examined: product display, promotio...

  5. Major Factors influences the 2008 Stock Market

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ 2007 was an unusual year for China's stock market, as the index climbed from 2675 points up to 6124 by the end of the year, setting new records again and again throughout 2007. What will happen to the stock market in the coming 2008? Let's havea look at some of the main factors that will influence the stock market this year, perhaps we can find out if 2008 will be another memorable year full of surprises.

  6. Influence of the surface speciation on biofilm attachment to chalcopyrite by Acidithiobacillus thiooxidans.

    Science.gov (United States)

    Lara, René H; García-Meza, J Viridiana; González, Ignacio; Cruz, Roel

    2013-03-01

    Surfaces of massive chalcopyrite (CuFeS2) electrodes were modified by applying variable oxidation potential pulses under growth media in order to induce the formation of different secondary phases (e.g., copper-rich polysulfides, S n(2-); elemental sulfur, S(0); and covellite, CuS). The evolution of reactivity (oxidation capacity) of the resulting chalcopyrite surfaces considers a transition from passive or inactive (containing CuS and S n(2-)) to active (containing increasing amounts of S(0)) phases. Modified surfaces were incubated with cells of sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) for 24 h in a specific culture medium (pH 2). Abiotic control experiments were also performed to compare chemical and biological oxidation. After incubation, the density of cells attached to chalcopyrite surfaces, the structure of the formed biofilm, and their exopolysaccharides and nucleic acids were analyzed by confocal laser scanning microscopy (CLSM) and scanning electron microscopy coupled to dispersive X-ray analysis (SEM-EDS). Additionally, CuS and S n(2-)/S(0) speciation, as well as secondary phase evolution, was carried out on biooxidized and abiotic chalcopyrite surfaces using Raman spectroscopy and SEM-EDS. Our results indicate that oxidized chalcopyrite surfaces initially containing inactive S n(2-) and S n(2-)/CuS phases were less colonized by A. thiooxidans as compared with surfaces containing active phases (mainly S(0)). Furthermore, it was observed that cells were partially covered by CuS and S(0) phases during biooxidation, especially at highly oxidized chalcopyrite surfaces, suggesting the innocuous effect of CuS phases during A. thiooxidans performance. These results may contribute to understanding the effect of the concomitant formation of refractory secondary phases (as CuS and inactive S n(2-)) during the biooxidation of chalcopyrite by sulfur-oxidizing microorganisms in bioleaching systems.

  7. Antibiotic Resistance Genes in Freshwater Biofilms May Reflect Influences from High-Intensity Agriculture.

    Science.gov (United States)

    Winkworth-Lawrence, Cynthia; Lange, Katharina

    2016-11-01

    Antibiotic resistance is a major public health concern with growing evidence of environmental gene reservoirs, especially in freshwater. However, the presence of antibiotic resistance genes in freshwater, in addition to the wide spectrum of land use contaminants like nitrogen and phosphate, that waterways are subjected to is inconclusive. Using molecular analyses, freshwater benthic rock biofilms were screened for genes conferring resistance to antibiotics used in both humans and farmed animals (aacA-aphD to aminoglycosides; mecA to ß-lactams; ermA and ermB to macrolides; tetA, tetB, tetK, and tetM to tetracyclines; vanA and vanB to glycopeptides). We detected widespread low levels of antibiotic resistance genes from 20 waterways across southern New Zealand throughout the year (1.3 % overall detection rate; 480 samples from three rocks per site, 20 sites, eight occasions; July 2010-May 2011). Three of the ten genes, ermB, tetK, and tetM, were detected in 62 of the 4800 individual screens; representatives confirmed using Sanger sequencing. No distinction could be made between human and agricultural land use contamination sources based on gene presence distribution alone. However, land use pressures are suggested by moderate correlations between antibiotic resistance genes and high-intensity farming in winter. The detection of antibiotic resistance genes at several sites not subject to known agricultural pressures suggests human sources of resistance, like waterway contamination resulting from unsatisfactory toilet facilities at recreational sites.

  8. Factors influencing the eicosanoids synthesis in vivo.

    Science.gov (United States)

    Szefel, Jarosław; Kruszewski, Wiesław Janusz; Sobczak, Ewa

    2015-01-01

    External factors activate a sequence of reactions involving the reception, transduction, and transmission of signals to effector cells. There are two main phases of the body's reaction to harmful factors: the first aims to neutralize the harmful factor, while in the second the inflammatory process is reduced in size and resolved. Secondary messengers such as eicosanoids are active in both phases. The discovery of lipoxins and epi-lipoxins demonstrated that not all arachidonic acid (AA) derivatives have proinflammatory activity. It was also revealed that metabolites of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) such as resolvins, protectins, and maresins also take part in the resolution of inflammation. Knowledge of the above properties has stimulated several clinical trials on the influence of EPA and DHA supplementation on various diseases. However, the equivocal results of those trials prevent the formulation of guidelines on EPA and DHA supplementation. Prescription drugs are among the substances with the strongest influence on the profile and quantity of the synthesized eicosanoids. The lack of knowledge about their influence on the conversion of EPA and DHA into eicosanoids may lead to erroneous conclusions from clinical trials.

  9. An ecological perspective of Listeria monocytogenes biofilms in food processing facilities.

    Science.gov (United States)

    Valderrama, Wladir B; Cutter, Catherine N

    2013-01-01

    Listeria monocytogenes can enter the food chain at virtually any point. However, food processing environments seem to be of particular importance. From an ecological point of view, food processing facilities are microbial habitats that are constantly disturbed by cleaning and sanitizing procedures. Although L. monocytogenes is considered ubiquitous in nature, it is important to recognize that not all L. monocytogenes strains appear to be equally distributed; the distribution of the organism seems to be related to certain habitats. Currently, no direct evidence exists that L. monocytogenes-associated biofilms have played a role in food contamination or foodborne outbreaks, likely because biofilm isolation and identification are not part of an outbreak investigation, or the definition of biofilm is unclear. Because L. monocytogenes is known to colonize surfaces, we suggest that contamination patterns may be studied in the context of how biofilm formation is influenced by the environment within food processing facilities. In this review, direct and indirect epidemiological and phenotypic evidence of lineage-related biofilm formation capacity to specific ecological niches will be discussed. A critical view on the development of the biofilm concept, focused on the practical implications, strengths, and weaknesses of the current definitions also is discussed. The idea that biofilm formation may be an alternative surrogate for microbial fitness is proposed. Furthermore, current research on the influence of environmental factors on biofilm formation is discussed.

  10. Biofilm structures (EPS and bacterial communities) in drinking water distribution systems are conditioned by hydraulics and influence discolouration.

    Science.gov (United States)

    Fish, K; Osborn, A M; Boxall, J B

    2017-03-27

    High-quality drinking water from treatment works is degraded during transport to customer taps through the Drinking Water Distribution System (DWDS). Interactions occurring at the pipe wall-water interface are central to this degradation and are often dominated by complex microbial biofilms that are not well understood. This study uses novel application of confocal microscopy techniques to quantify the composition of extracellular polymeric substances (EPS) and cells of DWDS biofilms together with concurrent evaluation of the bacterial community. An internationally unique, full-scale, experimental DWDS facility was used to investigate the impact of three different hydraulic patterns upon biofilms and subsequently assess their response to increases in shear stress, linking biofilms to water quality impacts such as discolouration. Greater flow variation during growth was associated with increased cell quantity but was inversely related to EPS-to-cell volume ratios and bacterial diversity. Discolouration was caused and EPS was mobilised during flushing of all conditions. Ultimately, biofilms developed under low-varied flow conditions had lowest amounts of biomass, the greatest EPS volumes per cell and the lowest discolouration response. This research shows that the interactions between hydraulics and biofilm physical and community structures are complex but critical to managing biofilms within ageing DWDS infrastructure to limit water quality degradation and protect public health.

  11. A Review of Factors Influencing Health Inequalities

    Directory of Open Access Journals (Sweden)

    Hassan Almaspoor Khanghah

    2016-01-01

    Full Text Available ​Background and Objectives : Inequity in health is a universal term which is used for showing current differences, variations and inequalities of people in accessing to health services. The current study aimed to assess the factors influencing health inequalities to present the results to the researchers and health care professionals. Material and Methods : In this review, several databases including PubMed, Proquest, Scopus, Google Scholar search engine, SID and IranDoc were searched within 2000-2014 period. We found 746 articles and refined them step by step according to the aim of the study by reviewing the titles, abstracts and full texts. Finally, 16 articles were selected for further study Results: In the present study, identified determinants in health inequalities were as follows: 1- Economic and income factors 2- Political factors, social and public policy 3- Cultural and social values 4- social and demographic factors 5- Behavioral, psychological and biological factors. Although, other factors like governmental, international, social cohesion, incidents and even the health system itself were involved in health inequalities, but the listed determinants were among the most important determinants in health inequalities in the conducted studies. Conclusion : Given the importance of people's health and inequalities in health, the approach should focus on reducing the inequalities in all policies and development programs and the role of these factors should be taken into consideration by managers and policy-makers

  12. Exposure of Escherichia coli ATCC 12806 to sublethal concentrations of food-grade biocides influences its ability to form biofilm, resistance to antimicrobials, and ultrastructure.

    Science.gov (United States)

    Capita, Rosa; Riesco-Peláez, Félix; Alonso-Hernando, Alicia; Alonso-Calleja, Carlos

    2014-02-01

    Escherichia coli ATCC 12806 was exposed to increasing subinhibitory concentrations of three biocides widely used in food industry facilities: trisodium phosphate (TSP), sodium nitrite (SNI), and sodium hypochlorite (SHY). The cultures exhibited an acquired tolerance to biocides (especially to SNI and SHY) after exposure to such compounds. E. coli produced biofilms (as observed by confocal laser scanning microscopy) on polystyrene microtiter plates. Previous adaptation to SNI or SHY enhanced the formation of biofilms (with an increase in biovolume and surface coverage) both in the absence and in the presence (MIC/2) of such compounds. TSP reduced the ability of E. coli to produce biofilms. The concentration of suspended cells in the culture broth in contact with the polystyrene surfaces did not influence the biofilm structure. The increase in cell surface hydrophobicity (assessed by a test of microbial adhesion to solvents) after contact with SNI or SHY appeared to be associated with a strong capacity to form biofilms. Cultures exposed to biocides displayed a stable reduced susceptibility to a range of antibiotics (mainly aminoglycosides, cephalosporins, and quinolones) compared with cultures that were not exposed. SNI caused the greatest increase in resistances (14 antibiotics [48.3% of the total tested]) compared with TSP (1 antibiotic [3.4%]) and SHY (3 antibiotics [10.3%]). Adaptation to SHY involved changes in cell morphology (as observed by scanning electron microscopy) and ultrastructure (as observed by transmission electron microscopy) which allowed this bacterium to persist in the presence of severe SHY challenges. The findings of the present study suggest that the use of biocides at subinhibitory concentrations could represent a public health risk.

  13. Biofilm Infections

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Jensen, Peter Østrup; Moser, Claus Ernst

    A still increasing interest and emphasis on the sessile bacterial lifestyle biofilms has been seen since it was realized that the vast majority of the total microbial biomass exists as biofilms. Aggregation of bacteria was first described by Leeuwenhoek in 1677, but only recently recognized...... as being important in chronic infection. In 1993 the American Society for Microbiology (ASM) recognized that the biofilm mode of growth was relevant to microbiology. This book covers both the evidence for biofilms in many chronic bacterial infections as well as the problems facing these infections...... such as diagnostics, pathogenesis, treatment regimes and in vitro and in vivo models for studying biofilms. This is the first scientific book on biofilm infections, chapters written by the world leading scientist and clinicians. The intended audience of this book is scientists, teachers at university level as well...

  14. Electron transfer mediators accelerated the microbiologically influence corrosion against carbon steel by nitrate reducing Pseudomonas aeruginosa biofilm.

    Science.gov (United States)

    Jia, Ru; Yang, Dongqing; Xu, Dake; Gu, Tingyue

    2017-12-01

    Electron transfer is a rate-limiting step in microbiologically influenced corrosion (MIC) caused by microbes that utilize extracellular electrons. Cross-cell wall electron transfer is necessary to transport the electrons released from extracellular iron oxidation into the cytoplasm of cells. Electron transfer mediators were found to accelerate the MIC caused by sulfate reducing bacteria. However, there is no publication in the literature showing the effect of electron transfer mediators on MIC caused by nitrate reducing bacteria (NRB). This work demonstrated that the corrosion of anaerobic Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was enhanced by two electron transfer mediators, riboflavin and flavin adenine dinucleotide (FAD) separately during a 7-day incubation period. The addition of either 10ppm (w/w) (26.6μM) riboflavin or 10ppm (12.7μM) FAD did not increase planktonic cell counts, but they increased the maximum pit depth on carbon steel coupons considerably from 17.5μm to 24.4μm and 25.0μm, respectively. Riboflavin and FAD also increased the specific weight loss of carbon steel from 2.06mg/cm(2) to 2.34mg/cm(2) and 2.61mg/cm(2), respectively. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization curves all corroborated the pitting and weight loss data. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. CREDIT LEVEL INFLUENCING FACTORS AT HUNGARIAN FARMS

    Directory of Open Access Journals (Sweden)

    Toth Jozsef

    2012-12-01

    Full Text Available In this paper we estimate the impact of different factors on creditability of agricultural farms. According to the literature the collateral (tangible assets, the farm size, productivity, and subsidies should have significant effects on farm loans. We use data from the Hungarian Farm Accountancy Data Network to test our two hypotheses and theoretical assumptions for the period 2001-2010. Because of using panel data, we do our estimations using fixed effects econometrics model to test our assumptions. The results indicate that the chosen factors have significant influence on total liabilities and short- and long-term loans as well. With specially interest of subsidies the growing level of supports decrease the need of other financial tools. At output factors (inclusive farm size have significant and positive effect, same as collateral (tangible assets.

  16. Factors Affecting Biofilm of Membrane-Aerated Biofilm Reactor (MABR)%膜曝气生物膜反应器生物膜影响因素分析

    Institute of Scientific and Technical Information of China (English)

    何秋阳

    2012-01-01

    The membrane-aerated biofilm reactor (MABR) is a novel wastewater treatment process which uses penneatable membrane for aeration to realize nitrification and denitrification simultaneously. In the paper, the principle and characteristics of MABR are introduced; the rearch achievements in this field are summerized; especially the factors affecting the biofilm performance such as C/N, oxygen pressure, air flow velocity, biofilm thickness, temperature and pH are analyzed.%膜曝气生物膜反应器(MABR)是一种利用透气膜进行曝气,可以实现同步硝化反硝化的污水生物处理新工艺。本文阐述了膜曝气生物反应器生物膜的原理和特点,总结了国内外在该领域的研究成果,重点介绍了C/N、氧气压力、流速、生物膜厚度、温度和pH对生物膜性能的影响。

  17. Effects of nutritional and environmental conditions on planktonic growth and biofilm formation of Citrobacter werkmanii BF-6.

    Science.gov (United States)

    Zhou, Gang; Li, Long-jie; Shi, Qing-shan; Ouyang, You-sheng; Chen, Yi-ben; Hu, Wen-feng

    2013-12-01

    Citrobacter sp. is a cause of significant opportunistic nosocomial infection and is frequently found in human and animal feces, soil, and sewage water, and even in industrial waste or putrefaction. Biofilm formation is an important virulence trait of Citrobacter sp. pathogens but the process and characteristics of this formation are unclear. Therefore, we employed in vitro assays to study the nutritional and environmental parameters that might influence biofilm formation of C. werkmanii BF-6 using 96-well microtiter plates. In addition, we detected the relative transcript levels of biofilm formation genes by RT-PCR. Our results indicated that the capacity of C. werkmanii BF-6 to form biofilms was affected by culture temperature, media, time, pH, and the osmotic agents glucose, sucrose, NaCl, and KCl. Confocal laser scanning microscopy results illustrated that the structure of biofilms and extracellular polysaccharide was influenced by 100 mM NaCl or 100 mM KCl. In addition, nine biofilm formation genes (bsmA, bssR, bssS, csgD, csgE, csgF, mrkA, mrkB, and mrkE) were found to contribute to planktonic and biofilm growth. Our data suggest that biofilm formation by C. werkmanii BF-6 is affected by nutritional and environmental factors, which could pave the way to the prevention and elimination of biofilm formation using proper strategies.

  18. Understanding Biofilms in Chronic Sinusitis.

    Science.gov (United States)

    Tajudeen, Bobby A; Schwartz, Joseph S; Palmer, James N

    2016-02-01

    Chronic sinusitis is a burdensome disease that has substantial individual and societal impact. Although great advances in medical and surgical therapies have been made, some patients continue to have recalcitrant infections. Microbial biofilms have been implicated as a cause of recalcitrant chronic sinusitis, and recent studies have tried to better understand the pathogenesis of chronic sinusitis as it relates to microbial biofilms. Here, we provide an overview of biofilms in chronic sinusitis with emphasis on pathogenesis, treatment, and future directions. In addition, recent evidence is presented, elucidating the role of bitter taste receptors as a possible key factor leading to biofilm formation.

  19. Internal factors influencing the knowledge continuity ensuring

    Directory of Open Access Journals (Sweden)

    Hana Urbancová

    2012-01-01

    Full Text Available The aim of the systematic ensuring of knowledge continuity is the continuity of an organisation’s development, the quality of managerial positions and the continuity of decision-making. By ensuring knowledge continuity, organisations may gain a performance-enhancing factor. The objective of the article is to identify the level of impact of decisive internal factors determining knowledge continuity ensuring and contributing to the efficiency of the organisations. Knowledge continuity ensuring as an internal force, however, can together with the right employees, help adapt more quickly to external conditions that organisations can hardly control. Monitoring and ensuring knowledge continuity can contribute to a higher quality of processes in general, in particular processes exploiting knowledge, and thus help improve the level of management. The first part of the article presents theoretical views on the aspects of knowledge continuity ensuring in organisations while the second part analyses the findings of the surveys carried out among managers in organisations in the Czech Republic. Based on the summary of the outcomes obtained it is possible to say that internal factors influence knowledge continuity ensuring in organisations, however, the level of impact of individual factors is determined by their size. The findings regarding the impact of each of the factors show that the most significant barriers to knowledge continuity ensuring are those associated with the human factor.

  20. Chamaecyparis obtusa Essential Oil Inhibits Methicillin-Resistant Staphylococcus aureus Biofilm Formation and Expression of Virulence Factors.

    Science.gov (United States)

    Kim, Eun-Sook; Kang, Sun-Young; Kim, Young-Hoi; Lee, Young-Eun; Choi, Na-Young; You, Yong-Ouk; Kim, Kang-Ju

    2015-07-01

    The emergence of antibiotic-resistant bacteria has caused difficulty in treating infectious diseases. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most commonly recognized antibiotic-resistant bacteria. Novel antibiotics are urgently required to treat these bacteria. Raw materials derived from natural sources can be used for the development of novel antibiotics, such as Chamaecyparis obtusa (C. obtusa), which has been traditionally used in treating asthmatic disease. In this study, the antibacterial activity of the essential oil (EO) extracted from C. obtusa leaves against MRSA was investigated. MRSA growth and acid production from glucose metabolism were inhibited at concentrations greater than 0.1 mg/mL C. obtusa EO. MRSA biofilm formation was observed using scanning electron microscopy and safranin staining. C. obtusa EO inhibited MRSA biofilm formation at concentrations greater than 0.1 mg/mL. Using real-time polymerase chain reaction, mRNA expression of virulence factor genes, sea, agrA, and sarA, was observed. agrA expression was inhibited with C. obtusa EO concentrations greater than 0.2 mg/mL, whereas inhibition of sea and sarA expression was also observed at a concentration of 0.3 mg/mL. C. obtusa EO was analyzed by gas chromatography (GC) and GC coupled for mass spectrometry, which identified 59 constituents, accounting to 98.99% of the total EO. These findings suggest that C. obtusa EO has antibacterial effects against MRSA, which might be associated with the major components of C. obtusa EO, such as sabinene (19.06%), α-terpinyl acetate (16.99%), bornyl acetate (10.48%), limonene (8.54%), elemol (7.47%), myrcene (5.86%), γ-terpinene (4.04%), and hibaene (3.01%).

  1. Anti-quorum Sensing and Anti-biofilm Activity of Delftia tsuruhatensis Extract by Attenuating the Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa.

    Science.gov (United States)

    Singh, Vijay K; Mishra, Avinash; Jha, Bhavanath

    2017-01-01

    Multidrug-resistance bacteria commonly use cell-to-cell communication that leads to biofilm formation as one of the mechanisms for developing resistance. Quorum sensing inhibition (QSI) is an effective approach for the prevention of biofilm formation. A Gram-negative bacterium, Delftia tsuruhatensis SJ01, was isolated from the rhizosphere of a species of sedge (Cyperus laevigatus) grown along the coastal-saline area. The isolate SJ01 culture and bacterial crude extract showed QSI activity in the biosensor plate containing the reference strain Chromobacterium violaceum CV026. A decrease in the violacein production of approximately 98% was detected with the reference strain C. violaceum CV026. The bacterial extract (strain SJ01) exhibited anti-quorum sensing activity and inhibited the biofilm formation of clinical isolates wild-type Pseudomonas aeruginosa PAO1 and P. aeruginosa PAH. A non-toxic effect of the bacterial extract (SJ01) was detected on the cell growth of the reference strains as P. aeruginosa viable cells were present within the biofilm. It is hypothesized that the extract (SJ01) may change the topography of the biofilm and thus prevent bacterial adherence on the biofilm surface. The extract also inhibits the motility, virulence factors (pyocyanin and rhamnolipid) and activity (elastase and protease) in P. aeruginosa treated with SJ01 extract. The potential active compound present was identified as 1,2-benzenedicarboxylic acid, diisooctyl ester. Microarray and transcript expression analysis unveiled differential expression of quorum sensing regulatory genes. The key regulatory genes, LasI, LasR, RhlI, and RhlR were down-regulated in the P. aeruginosa analyzed by quantitative RT-PCR. A hypothetical model was generated of the transcriptional regulatory mechanism inferred in P. aeruginosa for quorum sensing, which will provide useful insight to develop preventive strategies against the biofilm formation. The potential active compound identified, 1

  2. Environmental factors influencing the development of atherosclerosis

    Directory of Open Access Journals (Sweden)

    Andrzej Brodziak

    2013-12-01

    Full Text Available The aim of the paper is to present an overview of recent findings on the environmental and behavioral factors influencing the development of atherosclerosis. The authors primarily concentrated on deliberations of possibile main causes of the damage of the endothelium. At the same time the following pathogenic mechanisms as cellular dysfunction, inflammation and coagulation disorders have been enumerated. The links between the state of the vascular endothelium and life style have been emphasized. It is also important to note that the primary causes of the endothelial damage should be traced as originally suggested many years ago viewing such factors as anger, hostility, aggression, impulsiveness and depression but with a new approach. The authors supplement the comments, on the environmental factors influencing the development of atherosclerosis, with basic data on family predisposition to the development of this disease. They highlight that current genetic research have not determined genes responsible for atheroscelosis. According to the authors the considerations and conclusions presented in this overview are important for the educational purposes related to the most frequent disease process resulting in many diseases in medical disciplines.

  3. Discrimination of Four Marine Biofilm-Forming Bacteria by LC-MS Metabolomics and Influence of Culture Parameters.

    Science.gov (United States)

    Favre, Laurie; Ortalo-Magné, Annick; Greff, Stéphane; Pérez, Thierry; Thomas, Olivier P; Martin, Jean-Charles; Culioli, Gérald

    2017-04-12

    Most marine bacteria can form biofilms, and they are the main components of biofilms observed on marine surfaces. Biofilms constitute a widespread life strategy, as growing in such structures offers many important biological benefits. The molecular compounds expressed in biofilms and, more generally, the metabolomes of marine bacteria remain poorly studied. In this context, a nontargeted LC-MS metabolomics approach of marine biofilm-forming bacterial strains was developed. Four marine bacteria, Persicivirga (Nonlabens) mediterranea TC4 and TC7, Pseudoalteromonas lipolytica TC8, and Shewanella sp. TC11, were used as model organisms. The main objective was to search for some strain-specific bacterial metabolites and to determine how culture parameters (culture medium, growth phase, and mode of culture) may affect the cellular metabolism of each strain and thus the global interstrain metabolic discrimination. LC-MS profiling and statistical partial least-squares discriminant analyses showed that the four strains could be differentiated at the species level whatever the medium, the growth phase, or the mode of culture (planktonic vs biofilm). A MS/MS molecular network was subsequently built and allowed the identification of putative bacterial biomarkers. TC8 was discriminated by a series of ornithine lipids, while the P. mediterranea strains produced hydroxylated ornithine and glycine lipids. Among the P. mediterranea strains, TC7 extracts were distinguished by the occurrence of diamine derivatives, such as putrescine amides.

  4. Biofilm formation and antibiotic production in Ruegeria mobilis are influenced by intracellular concentrations of cyclic dimeric guanosinmonophosphate.

    Science.gov (United States)

    D'Alvise, Paul W; Magdenoska, Olivera; Melchiorsen, Jette; Nielsen, Kristian F; Gram, Lone

    2014-05-01

    In many species of the marine Roseobacter clade, periods of attached life, in association with phytoplankton or particles, are interspersed with planktonic phases. The purpose of this study was to determine whether shifts between motile and sessile life in the globally abundant Roseobacter clade species Ruegeria mobilis are associated with intracellular concentrations of the signal compound cyclic dimeric guanosinmonophosphate (c-di-GMP), which in bacteria regulates transitions between motile and sessile life stages. Genes for diguanylate cyclases and phosphodiesterases, which are involved in c-di-GMP signalling, were found in the genome of R. mobilis strain F1926. Ion pair chromatography-tandem mass spectrometry revealed 20-fold higher c-di-GMP concentrations per cell in biofilm-containing cultures than in planktonic cells. An introduced diguanylate cyclase gene increased c-di-GMP and enhanced biofilm formation and production of the potent antibiotic tropodithietic acid (TDA). An introduced phosphodiesterase gene decreased c-di-GMP and reduced biofilm formation and TDA production. tdaC, a key gene for TDA biosynthesis, was expressed only in attached or biofilm-forming cells, and expression was induced immediately after initial attachment. In conclusion, c-di-GMP signalling controls biofilm formation and biofilm-associated traits in R. mobilis and, as suggested by presence of GGDEF and EAL domain protein genes, also in other Roseobacter clade species. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

  5. Contextual factors influencing research use in nursing.

    Science.gov (United States)

    French, Beverley

    2005-01-01

    Contextual factors are perceived to be significant barriers to research-utilisation-related activity, but little is known about how context impacts on specific research-based decisions, or how the individual interacts with the organisation in the requirement for research-based change. This study describes the impact of contextual factors on the practical reasoning of nurse specialists in the construction of policy for practice. Three groups of clinical nurse specialists were observed during a series of meetings convened to construct evidence-based guidelines for nursing practice. Transcripts of the meetings were analysed to identify and categorise the physical, social, political, and economic influences on 31 nursing issues. Multiple contextual factors influenced each decision made, with decisions about nursing practice bounded by setting and system considerations, relationships with others in the care team, and resource constraints. Practitioners were involved in weighing up alternative scenarios, contexts, and contingencies for each decision, requiring strategies to adapt and reconstruct the nature of care, to influence others, and to affect organisational decision-making processes. The practical accomplishment of evidence-based practice required diverse skills: translating between evidence and practice; mediating the values, preferences, and working practices of multiple stakeholders; negotiating organisational complexity and the management of boundaries; and coordinating inter-organisational and inter-agency working. Nurse specialists in this study had a significant role in instigating, fuelling, and coordinating policy review, predominantly by communication across professional and organisational boundaries. Clinical specialists acting as organisational boundary spanners require skills in the informal cultural work of organising, facilitating, and maintaining links across professional, team, and organisational boundaries. If their role in the negotiation of

  6. Influence of selected factors on induced syneresis

    Directory of Open Access Journals (Sweden)

    Jovanović Snežana T.

    2004-01-01

    Full Text Available Syneresis is the process of whey separation induced by gel contraction resulting in rearranging or restructuring of casein matrix formed during enzymatic coagulation. Numerous factors can influence the process of syneresis. The influences of pH, calcium concentration, temperature of coagulation of milk and applied heat treatment on the syneresis induced by different intensity of centrifugal force have been investigated. Coagulated samples were centrifuged at 1000, 2000 and 3000 rpm for 5 min, respectively. Reconstituted skim milk powder (control sample and reconstituted non-fat milk heat treated at 87ºC/10 min (experimental sample are coagulated at temperatures of 30ºC and 35ºC, at pH value of 5.8 and 6.2, and with the addition of 100, 200 and 400 mg/l of CaCl2, respectively. Centrifugation at 1000 rpm of both control and experimental samples didn’t recover any sera, regardless of the applied coagulation conditions. This indicates that the intensity of centrifugal force wasn’t strong enough to disrupt gel structure and cause syneresis. When the intensity of centrifugal force was increased up to 2000 rpm, the syneresis was induced, but the degree of syneresis depended on the applied factors of coagulation, primary on the applied heat treatments and temperature of coagulation. The amount of added CaCl2 didn’t have a significant influence on the induced syneresis at 2000 rpm. The induced syneresis was very significant for both control and experimental samples when the intensity of centrifugal force of 3000 rpm was applied. It was also noted that curd produced from heat treated milk in which milk protein coaggregates were formed, released less sera regardless of the applied coagulation factors.

  7. Factors influencing aircraft ground handling performance

    Science.gov (United States)

    Yager, T. J.

    1983-01-01

    Problems associated with aircraft ground handling operations on wet runways are discussed and major factors which influence tire/runway braking and cornering traction capability are identified including runway characteristics, tire hydroplaning, brake system anomalies, and pilot inputs. Research results from tests with instrumented ground vehicles and aircraft, and aircraft wet runway accident investigation are summarized to indicate the effects of different aircraft, tire, and runway parameters. Several promising means are described for improving tire/runway water drainage capability, brake system efficiency, and pilot training to help optimize aircraft traction performance on wet runways.

  8. Factors influencing the cardiac MIBG accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Takatsu, Hisato; Fujiwara, Hisayoshi [Gifu Univ. (Japan). School of Medicine

    1997-02-01

    Following factors possibly influencing the cardiac MIBG accumulation were examined mainly in mice. 1. The specific activity of the MIBG (meta-iodo-benzyl guanidine) on the neuronal and non-neuronal fractions. 2. Motor restriction stress on MIBG accumulation and washout. 3. Loading and restriction of sodium chloride on the accumulation and effect of suppression of renin-angiotensin system. 4. Examinations in Dahl rats. 125I- or 131I-MIBG was intravenously administered to mice at 74 kBq. At 30 min or 4 hr after administration, mice were sacrificed and their left ventricles were dissected out for measurement of radioactivity in a liquid scintillation counter. Salt-sensitive and -resistant Dahl rats were given with 37 MBq of 123I-MIBG and cardiac radioactivity was measured externally for calculation of washout. Factors examined were found highly correlated with the accumulation of MIBG and measurement of its washout was considered useful for evaluating sympathetic activity. (K.H.)

  9. A survey on factors influencing city branding

    Directory of Open Access Journals (Sweden)

    Seyed Mohsen Mahmoudzadeh

    2014-10-01

    Full Text Available Nowadays, the issue of “globalization” is entering to all areas in the world. In addition to products and companies, cities and countries also have the opportunity to see themselves as important actors in international arena. Places define their positions in different fields like business, leisure and recreation, educational opportunities, living, etc. This paper presents an empirical study to introduce city branding as one of the solutions to join globalization process. The method of this research is based on the “descriptive-analytic” and utilize the available literature and experts’ opinions to prioritize the influencing factors of city branding. We use Delphi consensus methods and technique of analytical hierarchy process to evaluate the factors. Finally, the results of the study indicate that security, transportation and mental creativity are the weakest fields and business and shopping facilities are strong fields of city branding in metropolitan of Tehran.

  10. Microbial Biofilm Community Variation in Flowing Habitats: Potential Utility as Bioindicators of Postmortem Submersion Intervals.

    Science.gov (United States)

    Lang, Jennifer M; Erb, Racheal; Pechal, Jennifer L; Wallace, John R; McEwan, Ryan W; Benbow, Mark Eric

    2016-01-04

    Biofilms are a ubiquitous formation of microbial communities found on surfaces in aqueous environments. These structures have been investigated as biomonitoring indicators for stream heath, and here were used for the potential use in forensic sciences. Biofilm successional development has been proposed as a method to determine the postmortem submersion interval (PMSI) of remains because there are no standard methods for estimating the PMSI and biofilms are ubiquitous in aquatic habitats. We sought to compare the development of epinecrotic (biofilms on Sus scrofa domesticus carcasses) and epilithic (biofilms on unglazed ceramic tiles) communities in two small streams using bacterial automated ribosomal intergenic spacer analysis. Epinecrotic communities were significantly different from epilithic communities even though environmental factors associated with each stream location also had a significant influence on biofilm structure. All communities at both locations exhibited significant succession suggesting that changing communities throughout time is a general characteristic of stream biofilm communities. The implications resulting from this work are that epinecrotic communities have distinctive shifts at the first and second weeks, and therefore the potential to be used in forensic applications by associating successional changes with submersion time to estimate a PMSI. The influence of environmental factors, however, indicates the lack of a successional pattern with the same organisms and a focus on functional diversity may be more applicable in a forensic context.

  11. Microbial Biofilm Community Variation in Flowing Habitats: Potential Utility as Bioindicators of Postmortem Submersion Intervals

    Directory of Open Access Journals (Sweden)

    Jennifer M. Lang

    2016-01-01

    Full Text Available Biofilms are a ubiquitous formation of microbial communities found on surfaces in aqueous environments. These structures have been investigated as biomonitoring indicators for stream heath, and here were used for the potential use in forensic sciences. Biofilm successional development has been proposed as a method to determine the postmortem submersion interval (PMSI of remains because there are no standard methods for estimating the PMSI and biofilms are ubiquitous in aquatic habitats. We sought to compare the development of epinecrotic (biofilms on Sus scrofa domesticus carcasses and epilithic (biofilms on unglazed ceramic tiles communities in two small streams using bacterial automated ribosomal intergenic spacer analysis. Epinecrotic communities were significantly different from epilithic communities even though environmental factors associated with each stream location also had a significant influence on biofilm structure. All communities at both locations exhibited significant succession suggesting that changing communities throughout time is a general characteristic of stream biofilm communities. The implications resulting from this work are that epinecrotic communities have distinctive shifts at the first and second weeks, and therefore the potential to be used in forensic applications by associating successional changes with submersion time to estimate a PMSI. The influence of environmental factors, however, indicates the lack of a successional pattern with the same organisms and a focus on functional diversity may be more applicable in a forensic context.

  12. A study of factors influencing advanced puberty

    Directory of Open Access Journals (Sweden)

    Yong Jun Park

    2010-02-01

    Full Text Available Purpose : The purpose of this study was to evaluate the timing of puberty and the factors inducing advanced puberty in elemental school students of low grades. Methods : The 1st, 2nd, and 3rd grade elemental students from the Goyang province were randomly selected, and their sexual maturation rate was assessed by physical examination. After obtaining an informed consent, a questionnaire was administered to the parents; eating habits, lifestyle, use of growth-inducing medication, and present illness of the students were evaluated to determine the factors that induced advanced puberty. The data were statistically analyzed. Results : We selected 170 children and the girls:boys sex ratio was 1.2:1. Two 9-year-old boys were in genital stage 2. Two (14.3% 6-year-old girls, 6 (19.4% 7-year-old girls, 15 (39.6% 8-year-old girls, and 4 (57.1% 9-year-old girls were in breast stage 2. The average pubertal timing predicted for girls was 9.11¡?#?.86; years. The main factors influencing pubertal timing were obesity scale, frequency of eating fast food, and the use of growth-inducing medication. A high rating on the obesity scale and high frequency of eating fast food indicated advanced stage of puberty. Growth-inducing medication induced puberty through obesity. Conclusion : We proposed that predictive average pubertal timing in girls was 9.11¡?#?.86; years, which was consistent with the previously reported findings from abroad. The significant influencing factors in advanced puberty were obesity scale and frequency of fast food.

  13. The Role of Efflux and Physiological Adaptation in Biofilm Tolerance and Resistance.

    Science.gov (United States)

    Van Acker, Heleen; Coenye, Tom

    2016-06-10

    Microbial biofilms demonstrate a decreased susceptibility to antimicrobial agents. Various mechanisms have been proposed to be involved in this recalcitrance. We focus on two of these factors. Firstly, the ability of sessile cells to actively mediate efflux of antimicrobial compounds has a profound impact on resistance and tolerance, and several studies point to the existence of biofilm-specific efflux systems. Secondly, biofilm-specific stress responses have a marked influence on cellular physiology, and contribute to the occurrence of persister cells. We provide an overview of the data that demonstrate that both processes are important for survival following exposure to antimicrobial agents.

  14. Carbon isotope fractionation in developing natural phototrophic biofilms

    Science.gov (United States)

    Staal, M.; Thar, R.; Kühl, M.; van Loosdrecht, M. C. M.; Wolf, G.; de Brouwer, J. F. C.; Rijstenbil, J. W.

    2007-01-01

    Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which are expected to lead to a limitation of light or mass transport. In this study it is shown that a variation of the availability of CO2 leads to a shift in fractionation, thereby affecting δ13C signatures during the successive developmental stages. For phototrophic freshwater biofilms it was found that the δ13C value became less negative with the thickening of the biofilm, while the opposite trend in δ13C values was found in marine biofilms. Modeling and pH profiling indicated that the change in the freshwater system was caused by an increase in CO2 limitation resulting in an increase of HCO3- as C-source. The opposite trend in the marine system could be explained by a higher heterotrophic biomass and activity causing a higher carbon recycling and thereby lower δ13C values. We conclude that δ13C was more related to the net areal photosynthesis rate and carbon recycling, rather than to the growth rate of the biofilms.

  15. Biofilm streamer formation in a microfluidic porous media mimic

    Science.gov (United States)

    Kumar, Aloke; Valiei, Amin; Mukherjee, Partha; Liu, Yang; Thundat, Thomas

    2013-03-01

    Biofilm formation in porous media is of significant importance in many environmental and industrial processes such as bioremediation, oil recovery, and wastewater treatment. Among different biological and environmental factors, hydrodynamics is considered an important determinant of the dynamics of biofilm formation. In the present study, we fabricated a microfluidic porous media mimic and investigated how fluid flow influences the formation of filamentous structures, known as streamers, between porous media structures. Streamers are viscoelastic materials composed of extracellular polymeric substances (EPS) and bacterial cells, and these filamentous structures are typically tethered at either one of both ends to surfaces. We studied evolution of streamers in different flow rates and identified a tangible link between hydrodynamic conditions and development of these filamentous structures. Our results show that hydrodynamic conditions not only determine the limit of the streamers formation, but also influence both temporal evolution and spatial organization of biofilm streamers.

  16. Factors influencing seed germination in Cerrado grasses

    Directory of Open Access Journals (Sweden)

    Rosana Marta Kolb

    2016-03-01

    Full Text Available Few studies address the ecology of herbs of Cerrado grasslands, which are ecosystems where the long dry season, high temperatures, insolation, fire and invasive grasses greatly influencing germination and the establishment of plants. We assessed germination of 13 species of Poaceae from Cerrado grasslands under nursery conditions or in germination chambers, the latter with i recently collected seeds and seeds after six months storage, ii under constant and alternating temperatures, and iii in the presence and absence of light. Germinability, mean germination time (MGT and required light were quantified to elucidate factors involved in successful germination. Germinability was low for most grasses, probably because of low seed viability. For most species, germinability and MGT were not altered by seed storage. Germination percentages were higher at alternating temperatures and in the presence of light, factors that are more similar to natural environmental situations compared with constant temperature or the absence of light. Our findings indicate that alternating temperatures and light incidence are key factors for germination of species of Poaceae. The maintenance of these environmental factors, which are crucial for the conservation of Cerrado grasslands, depends on appropriate management interventions, such as fire management and the control of biological invasion.

  17. Factors Influencing Acceptance Of Contraceptive Methods

    Directory of Open Access Journals (Sweden)

    Anita Gupta

    1997-04-01

    Full Text Available Research Problem: What are the factors influencing acceptance of contraceptive methods.Objective: To study the determinants influencing contra­ceptive acceptance.Study design: Population based cross - sectional study.Setting: Rural area of East DelhiParticipants: Married women in the reproductive age group.Sample:Stratified sampling technique was used to draw the sample.Sample Size: 328 married women of reproductive age group.Study Variables: Socio-economic status, Type of contraceptive, Family size, Male child.Outcome Variables: Acceptance of contraceptivesStatistical Analysis: By proportions.Result: Prevalence of use of contraception at the time of data collection was 40.5%. Tubectomy and vasectomy were most commonly used methods. (59.4%, n - 133. Educational status of the women positively influenced the contraceptive acceptance but income did not. Desire for more children was single most important deterrent for accepting contraception.Recommendations:(i             Traditional method of contraception should be given more attention.(ii            Couplesshould be brought in the contraceptive use net at the early stage of marriage.

  18. Landslide forecasting and factors influencing predictability

    Science.gov (United States)

    Intrieri, Emanuele; Gigli, Giovanni

    2016-11-01

    Forecasting a catastrophic collapse is a key element in landslide risk reduction, but it is also a very difficult task owing to the scientific difficulties in predicting a complex natural event and also to the severe social repercussions caused by a false or missed alarm. A prediction is always affected by a certain error; however, when this error can imply evacuations or other severe consequences a high reliability in the forecast is, at least, desirable. In order to increase the confidence of predictions, a new methodology is presented here. In contrast to traditional approaches, this methodology iteratively applies several forecasting methods based on displacement data and, thanks to an innovative data representation, gives a valuation of the reliability of the prediction. This approach has been employed to back-analyse 15 landslide collapses. By introducing a predictability index, this study also contributes to the understanding of how geology and other factors influence the possibility of forecasting a slope failure. The results showed how kinematics, and all the factors influencing it, such as geomechanics, rainfall and other external agents, are key concerning landslide predictability.

  19. Macromolecular fingerprinting of sulfolobus species in biofilm: a transcriptomic and proteomic approach combined with spectroscopic analysis.

    Science.gov (United States)

    Koerdt, Andrea; Orell, Alvaro; Pham, Trong Khoa; Mukherjee, Joy; Wlodkowski, Alexander; Karunakaran, Esther; Biggs, Catherine A; Wright, Phillip C; Albers, Sonja-Verena

    2011-09-02

    Microorganisms in nature often live in surface-associated sessile communities, encased in a self-produced matrix, referred to as biofilms. Biofilms have been well studied in bacteria but in a limited way for archaea. We have recently characterized biofilm formation in three closely related hyperthermophilic crenarchaeotes: Sulfolobus acidocaldarius, S. solfataricus, and S. tokodaii. These strains form different communities ranging from simple carpet structures in S. solfataricus to high density tower-like structures in S. acidocaldarius under static condition. Here, we combine spectroscopic, proteomic, and transcriptomic analyses to describe physiological and regulatory features associated with biofilms. Spectroscopic analysis reveals that in comparison to planktonic life-style, biofilm life-style has distinctive influence on the physiology of each Sulfolobus spp. Proteomic and transcriptomic data show that biofilm-forming life-style is strain specific (eg ca. 15% of the S. acidocaldarius genes were differently expressed, S. solfataricus and S. tokodaii had ~3.4 and ~1%, respectively). The -omic data showed that regulated ORFs were widely distributed in basic cellular functions, including surface modifications. Several regulated genes are common to biofilm-forming cells in all three species. One of the most striking common response genes include putative Lrs14-like transcriptional regulators, indicating their possible roles as a key regulatory factor in biofilm development.

  20. Bacteriophage inspired antibiotics discovery against infection involved biofilm.

    Science.gov (United States)

    Fan, Xiangyu; Li, Wu; Zheng, Fei; Xie, Jianping

    2013-01-01

    Bacterial biofilm profoundly influences the fate of bacteria within and the outcome of related infection, and is closely associated with antibiotics resistance and bacterial persistence. Bacteriophages represent a new promising alternative to combat biofilm-related infection. The interplay between phages and biofilms is complex. Some phages or their components can inhibit the host bacteria biofilm via diverse mechanisms, while other phages can facilitate the host biofilm formation through phage-mediated lysis and extracellular DNA release. In this paper, we summarize the role of bacteriophages in the biofilm formation, and the application of phages to the control of bacterial persisters and infectious biofilms, in particular, the phage-inspired antibiotics discovery.

  1. Intrinsic and extrinsic factors influencing large African herbivore movements

    NARCIS (Netherlands)

    Venter, J.A.; Prins, H.H.T.; Mashanova, A.; Boer, de W.F.; Slotow, R.

    2015-01-01

    Understanding environmental as well as anthropogenic factors that influence large herbivore ecological patterns and processes should underpin their conservation and management. We assessed the influence of intrinsic, extrinsic environmental and extrinsic anthropogenic factors on movement behaviour o

  2. Transcription Factors Efg1 and Bcr1 Regulate Biofilm Formation and Virulence during Candida albicans-Associated Denture Stomatitis.

    Science.gov (United States)

    Yano, Junko; Yu, Alika; Fidel, Paul L; Noverr, Mairi C

    2016-01-01

    Denture stomatitis (DS) is characterized by inflammation of the oral mucosa in direct contact with dentures and affects a significant number of otherwise healthy denture wearers. The disease is caused by Candida albicans, which readily colonizes and form biofilms on denture materials. While evidence for biofilms on abiotic and biotic surfaces initiating Candida infections is accumulating, a role for biofilms in DS remains unclear. Using an established model of DS in immunocompetent animals, the purpose of this study was to determine the role of biofilm formation in mucosal damage during pathogenesis using C. albicans or mutants defective in morphogenesis (efg1-/-) or biofilm formation (bcr1-/-). For in vivo analyses, rats fitted with custom dentures, consisting of fixed and removable parts, were inoculated with wild-type C. albicans, mutants or reconstituted strains and monitored weekly for fungal burden (denture and palate), body weight and tissue damage (LDH) for up to 8 weeks. C. albicans wild-type and reconstituted mutants formed biofilms on dentures and palatal tissues under in vitro, ex vivo and in vivo conditions as indicated by microscopy demonstrating robust biofilm architecture and extracellular matrix (ECM). In contrast, both efg1-/- and bcr1-/- mutants exhibited poor biofilm growth with little to no ECM. In addition, quantification of fungal burden showed reduced colonization throughout the infection period on dentures and palates of rats inoculated with efg1-/-, but not bcr1-/-, compared to controls. Finally, rats inoculated with efg1-/- and bcr1-/- mutants had minimal palatal tissue damage/weight loss while those inoculated with wild-type or reconstituted mutants showed evidence of tissue damage and exhibited stunted weight gain. These data suggest that biofilm formation is associated with tissue damage during DS and that Efg1 and Bcr1, both central regulators of virulence in C. albicans, have pivotal roles in pathogenesis of DS.

  3. Transcription Factors Efg1 and Bcr1 Regulate Biofilm Formation and Virulence during Candida albicans-Associated Denture Stomatitis.

    Directory of Open Access Journals (Sweden)

    Junko Yano

    Full Text Available Denture stomatitis (DS is characterized by inflammation of the oral mucosa in direct contact with dentures and affects a significant number of otherwise healthy denture wearers. The disease is caused by Candida albicans, which readily colonizes and form biofilms on denture materials. While evidence for biofilms on abiotic and biotic surfaces initiating Candida infections is accumulating, a role for biofilms in DS remains unclear. Using an established model of DS in immunocompetent animals, the purpose of this study was to determine the role of biofilm formation in mucosal damage during pathogenesis using C. albicans or mutants defective in morphogenesis (efg1-/- or biofilm formation (bcr1-/-. For in vivo analyses, rats fitted with custom dentures, consisting of fixed and removable parts, were inoculated with wild-type C. albicans, mutants or reconstituted strains and monitored weekly for fungal burden (denture and palate, body weight and tissue damage (LDH for up to 8 weeks. C. albicans wild-type and reconstituted mutants formed biofilms on dentures and palatal tissues under in vitro, ex vivo and in vivo conditions as indicated by microscopy demonstrating robust biofilm architecture and extracellular matrix (ECM. In contrast, both efg1-/- and bcr1-/- mutants exhibited poor biofilm growth with little to no ECM. In addition, quantification of fungal burden showed reduced colonization throughout the infection period on dentures and palates of rats inoculated with efg1-/-, but not bcr1-/-, compared to controls. Finally, rats inoculated with efg1-/- and bcr1-/- mutants had minimal palatal tissue damage/weight loss while those inoculated with wild-type or reconstituted mutants showed evidence of tissue damage and exhibited stunted weight gain. These data suggest that biofilm formation is associated with tissue damage during DS and that Efg1 and Bcr1, both central regulators of virulence in C. albicans, have pivotal roles in pathogenesis of DS.

  4. Enhanced Biofilm Formation and Increased Resistance to Antimicrobial Agents and Bacterial Invasion Are Caused by Synergistic Interactions in Multispecies Biofilms

    DEFF Research Database (Denmark)

    Burmølle, Mette; Webb, J.S.; Rao, D.

    2006-01-01

    Most biofilms in their natural environments are likely to consist of consortia of species that influence each other in synergistic and antagonistic manners. However, few reports specifically address interactions within multispecies biofilms. In this study, 17 epiphytic bacterial strains, isolated...... specific interactions. In summary, our data strongly indicate that synergistic effects promote biofilm biomass and resistance of the biofilm to antimicrobial agents and bacterial invasion in multispecies biofilms....

  5. Examinations of factors influencing toe grip strength.

    Science.gov (United States)

    Soma, Masayuki; Murata, Shin; Kai, Yoshihiro; Nakae, Hideyuki; Satou, Yousuke; Murata, Jun; Miyazaki, Junya

    2016-11-01

    [Purpose] This study examined the relationship between toe grip strength and its associated factors by focusing on factors that were suggested to have a relationship with toe grip strength in previous studies, aiming to clarify the factors influencing the toe grip strength of healthy women. [Subjects and Methods] Twelve healthy young women were selected for this study. Their toe grip strength, angular changes in their ankle joint during toe grip, maximum voluntary contraction activities of the rectus femoris, biceps femoris, and tibialis anterior muscles, and the medial head of the gastrocnemius muscles were measured using electromyography. Their toe curl ability, foot-arch height ratio, and weight were also measured. [Results] Multiple regression analysis demonstrated that the predictors of toe grip strength in the resulting model were foot-arch height ratio and the percentage of integrated electromyography (%IEMG) of the tibialis anterior muscle, as the dependent variables. This reveals that women whose tibialis anterior muscle %IEMG values and foot-arch height ratio are high have greater %IEMG values have greater toe grip strength. [Conclusion] These findings suggest a significant relationship between foot-arch height ratio and toe grip strength, with a reciprocal interaction. These findings further indicate that the risk of falls by the elderly could be decreased if toe grip strength were enhanced, by increasing the height of a low foot-arch with the help of an inserted insole.

  6. Candida albicans biofilms and MMA surface treatment influence the adhesion of soft denture liners to PMMA resin.

    Science.gov (United States)

    Mendonça e Bertolini, Martinna de; Cavalcanti, Yuri Wanderley; Bordin, Dimorvan; Silva, Wander José da; Cury, Altair Antoninha Del Bel

    2014-01-01

    The effect of Candida albicans biofilms and methyl methacrylate (MMA) pretreatment on the bond strength between soft denture liners and polymethyl methacrylate (PMMA) resin was analyzed. Specimens were prepared and randomly divided with respect to PMMA pretreatment, soft liner type (silicone-based or PMMA-based), and presence or absence of a C. albicans biofilm. Samples were composed of a soft denture liner bonded between two PMMA bars. Specimens (n = 10) were incubated to produce a C. albicans biofilm or stored in sterile PBS for 12 days. The tensile bond strength test was performed and failure type was determined using a stereomicroscope. Surface roughness (SR) and scanning electron microscopy (SEM) analysis were performed on denture liners (n = 8). Highest bond strength was observed in samples containing a silicone-based soft liner and stored in PBS, regardless of pretreatment (p PMMA-based liners predominantly underwent cohesive failures. The silicone-based specimens SR decreased after 12 days of biofilm accumulation or PBS storage, while the SR of PMMA-based soft liners increased (p PMMA-based soft liners surfaces presented sharp valleys and depressions, while silicone-based specimens surfaces exhibited more gentle features. In vitro exposure to C. albicans biofilms reduced the adhesion of denture liners to PMMA resin, and MMA pretreatment is recommended during relining procedures.

  7. Candida albicans biofilms and MMA surface treatment influence the adhesion of soft denture liners to PMMA resin

    Directory of Open Access Journals (Sweden)

    Martinna de Mendonça e Bertolini

    2014-01-01

    Full Text Available The effect of Candida albicans biofilms and methyl methacrylate (MMA pretreatment on the bond strength between soft denture liners and polymethyl methacrylate (PMMA resin was analyzed. Specimens were prepared and randomly divided with respect to PMMA pretreatment, soft liner type (silicone-based or PMMA-based, and presence or absence of a C. albicans biofilm. Samples were composed of a soft denture liner bonded between two PMMA bars. Specimens (n = 10 were incubated to produce a C. albicans biofilm or stored in sterile PBS for 12 days. The tensile bond strength test was performed and failure type was determined using a stereomicroscope. Surface roughness (SR and scanning electron microscopy (SEM analysis were performed on denture liners (n = 8. Highest bond strength was observed in samples containing a silicone-based soft liner and stored in PBS, regardless of pretreatment (p < 0.01. Silicone-based specimens mostly underwent adhesive failures, while samples containing PMMA-based liners predominantly underwent cohesive failures. The silicone-based specimens SR decreased after 12 days of biofilm accumulation or PBS storage, while the SR of PMMA-based soft liners increased (p < 0.01. The PMMA-based soft liners surfaces presented sharp valleys and depressions, while silicone-based specimens surfaces exhibited more gentle features. In vitro exposure to C. albicans biofilms reduced the adhesion of denture liners to PMMA resin, and MMA pretreatment is recommended during relining procedures.

  8. [Relation between biofilm, caries activity and gingivitis in HIV + children].

    Science.gov (United States)

    Ribeiro, Apoena de Aguiar; Portela, Maristela; Souza, Ivete Pomarico de

    2002-01-01

    The utilization of medicines to treat HIV-infected children has been promoting a decrease in the prevalence of soft-tissue oral lesions, as years pass by. In contrast, it has been observed that the experience of caries and gingivitis is constant in this population, mostly because of the chronic influence of some factors involved in the HIV-infection process, such as the chronic utilization of sweetened liquid medicines and carbohydrate-enriched diet, as well as frequent episodes of hospitalization. So, the purpose of this study was to evaluate if the quality and quantity of biofilm are important factors in the activity of dental caries and gingivitis, also in this special group. After examination of the biofilm (biofilm index - Ribeiro23, 2000), the activity of caries and gingivitis was assessed in 56 children, aging from 0 to 14 years, who were patients with definitive diagnosis of HIV infection. It was observed that only 7 subjects (12.5%) did not present with clinically visible biofilm, and 33 (58.9%) presented with gingivitis, with the average of 4.44 bleeding sites. As to dental caries, 73.2% of the patients presented with active carious lesions. A strong correlation was verified between Biofilm Index, gingival status and active carious lesions (Spearman's correlation test, r s = +0.57 and r s = +0.49, respectively). It was concluded that, also in HIV-infected children, the quality and quantity of biofilm over the dental surfaces are important etiologic factors related to the activity of caries and gingivitis. Biofilm should, thus, be controlled in order to reestablish the oral health of HIV-infected children.

  9. Biofilm development

    DEFF Research Database (Denmark)

    Tolker-Nielsen, Tim

    2015-01-01

    During the past decade we have gained much knowledge about the molecular mechanisms that are involved in initiation and termination of biofilm formation. In many bacteria, these processes appear to occur in response to specific environmental cues and result in, respectively, induction or terminat......During the past decade we have gained much knowledge about the molecular mechanisms that are involved in initiation and termination of biofilm formation. In many bacteria, these processes appear to occur in response to specific environmental cues and result in, respectively, induction...... or termination of biofilm matrix production via the second messenger molecule c-di-GMP. In between initiation and termination of biofilm formation we have defined specific biofilm stages, but the currently available evidence suggests that these transitions are mainly governed by adaptive responses......, and not by specific genetic programs. It appears that biofilm formation can occur through multiple pathways and that the spatial structure of the biofilms is species dependent as well as dependent on environmental conditions. Bacterial subpopulations, e.g., motile and nonmotile subpopulations, can develop...

  10. Factors influencing career choice in anaesthesiology

    Directory of Open Access Journals (Sweden)

    Asha Tyagi

    2012-01-01

    Full Text Available Background: There is a shortage of anaesthesiologists in India. The factors that prompt medical students to opt for anaesthesiology as their career are not known; neither do we have any mechanism to know a student′s stress-bearing ability before he/she opts for a stressful career like anaesthesiology. We conducted an anonymous, questionnaire-based, cross-sectional survey among 200 post-graduate anaesthesiology students to know various factors that they considered while opting for this speciality, and also evaluated their stress-bearing ability using Antonovsky′s 13-point sense of coherence scale. Methods: Two-hundred anaesthesiology students were asked to complete a questionnaire regarding the factors they considered important while opting for anaesthesiology, also enumerated in order of importance the three most important factors that led to opting this career. Students also answered the questions in Antonovsky′s sense of coherence (SOC scale. Results: Economic security was considered by maximum number of students (67.7%, while intellectual stimulation/challenge offered by anaesthesiology was rated first in order of importance. Influence of doctor−patient relationship was not considered by large number of students. The weak SOC score (55 (25 th percentile was not greatly different than the mean SOC score (60 in the survey. Conclusion: Increasing the exposure of students to anaesthesiology at undergraduate level and building public awareness about the speciality will prompt more students to opt for the speciality, while career counselling with regard to specific needs of a speciality and ability of a student will help in opting the speciality that best suits the student′s personality.

  11. Factors influencing nurses' perceptions of occupational safety.

    Science.gov (United States)

    Samur, Menevse; Intepeler, Seyda Seren

    2017-01-02

    To determine nurses' perceptions of occupational safety and their work environment and examine the sociodemographic traits and job characteristics that influence their occupational safety, we studied a sample of 278 nurses. According to the nurses, the quality of their work environment is average, and occupational safety is insufficient. In the subdimensions of the work environment scale, it was determined that the nurses think "labor force and other resources" are insufficient. In the occupational safety subdimensions "occupational illnesses and complaints" and "administrative support and approaches," they considered occupational safety to be insufficient. "Doctor-nurse-colleague relationships," "exposure to violence," and "work unit" (eg, internal medicine, surgical, intensive care) are the main factors that affect occupational safety. This study determined that hospital administrations should develop and immediately implement plans to ameliorate communication and clinical precautions and to reduce exposure to violence.

  12. Factors Influencing Sulfinatodehalogenation Reactions of Perhalocarbons

    Institute of Scientific and Technical Information of China (English)

    WU,Kai(吴恺); CHEN,Qing-Yun(陈庆云)

    2004-01-01

    The study on the factors influencing sulfinatodehalogenation of perfluorohexyl chloride plus octene-1 by using Na2S2O4/NaHCO3 discovered that among the various solvents tested(e.g.Me2SO,NMP,DMAc,CH3CN,CH3CN/H2O)at different temperatures,Me2SO was found to be the most suitable solvent and the conversion of the chloride was very dependent on the reaction temperature.When Me2SO was used in the reaction of perfluoroalkyl iodides,the reaction temperature could be decreased by 20℃ as compared with that carried out in CH3CN/H2O to reach the comparable yields.

  13. Factors influencing presence in virtual worlds.

    Science.gov (United States)

    Chow, Meyrick C M

    2012-01-01

    Virtual worlds are showing potential as an effective platform for a variety of activities, including learning. The concept of presence (the sensation of "being there" in a mediated environment) has received substantial attention from the virtual reality community, and the effectiveness of virtual worlds has often been linked to the feelings of presence reported by their users. The present study examined the effects of attitude and perceived ease of use on sense of presence in Second Life, which is one of the most known and used virtual worlds. Based on data from a survey of 206 nursing students, hypotheses are empirically tested. Findings suggest that users' attitude toward using Second Life and their perceived ease of use of it have a positive effect on their sense of presence in the virtual environment. This study advances our understanding of factors influencing presence in virtual worlds.

  14. Factors influencing consumer dietary health preventative behaviours

    Directory of Open Access Journals (Sweden)

    Ritson Christopher

    2006-09-01

    Full Text Available Abstract Background The deterioration of the health status of the Romanian population during the economic transition from a centrally planned to a free market economy has been linked to lifestyles factors (e.g. diet regarded as a main determinants of the disparity in life expectancy between Eastern and Western Europe. Reforms in the health care system in this transition economy aim to focus on preventive action. The purpose of this study was to identify the factors that impact on the individual decision to engage in Dietary Health Preventive Behaviour (DHPB and investigate their influence in the context of an adapted health cognition model. Methods A population-based study recruited 485 adult respondents using random route sampling and face-to-face administered questionnaires. Results and discussion Respondents' health motivation, beliefs that diet can prevent disease, knowledge about nutrition, level of education attainment and age have a positive influence on DHPB. Perceived barriers to healthy eating have a negative impact on alcohol moderation. The information acquisition behaviour (frequency of reading food labels is negatively predicted by age and positively predicted by health motivation, education, self-reported knowledge about nutrition and household financial status. A significant segment of respondents believe they are not susceptible to the elicited diseases. Health promotion strategies should aim to change the judgments of health risk. Conclusion The adaptation of the Health Belief Model and the Theory of Health Preventive Behaviour represents a valid framework of predicting DHPB. The negative sign of perceived threat of disease on DHPB may suggest that, under an income constraint, consumers tend to trade off long-term health benefits for short-term benefits. This cautions against the use of negative messages in public health campaigns. Raising the awareness of diet-disease relationships, knowledge about nutrition (particularly

  15. Factors influencing women's decision making in hysterectomy.

    Science.gov (United States)

    Janda, Monika; Armfield, Nigel R; Page, Katie; Kerr, Gayle; Kurz, Suzanne; Jackson, Graeme; Currie, Jason; Weaver, Edward; Yazdani, Anusch; Obermair, Andreas

    2017-09-12

    To explore factors influencing how well-informed women felt about hysterectomy, influences on their decision making, and on them receiving a less-invasive alternative to open surgery. Online questionnaire, conducted in 2015-2016, of women who had received a hysterectomy in Australia, in the preceding two years. Questionnaires were completed by 2319/6000 women (39% response). Most women (n=2225; 96%) felt well-informed about hysterectomy. Women were more aware of the open abdominal approach (n=1798; 77%), than of less-invasive vaginal (n=1552; 67%), laparoscopic (n=1540; 66%), laparoscopic-assisted (n=1303; 56%), and robotic approaches (n=289; 12%). Most women (n=1435; 62%) reported their gynaecologist was the most influential information source. Women who received information about hysterectomy from a GP (OR=1.47; 95% CI 1.15-1.90), or from a gynaecologist (OR=1.3; 95% CI 1.06-1.58), were more likely to feel better informed (p<0.01). This study is important because it helps clinicians, researchers and health policy makers to understand why many women still receive an open abdominal approach despite many learned societies recommending to avoid it if possible. Additional information, or education about avoiding open abdominal approach where possible may lead to a greater number of women receiving less-invasive types of hysterectomy in the future. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

  16. Influence of anodic biofilm growth on bioelectricity production in single chambered mediatorless microbial fuel cell using mixed anaerobic consortia.

    Science.gov (United States)

    Venkata Mohan, S; Veer Raghavulu, S; Sarma, P N

    2008-09-15

    The effect of anodic biofilm growth and extent of its coverage on the anodic surface of a single chambered mediatorless microbial fuel cell (MFC) was evaluated for bioelectricity generation using designed synthetic wastewater (DSW) and chemical wastewater (CW) as substrates and anaerobic mixed consortia as biocatalyst. Three MFCs (plain graphite electrodes, air cathode, Nafion membrane) were operated separately with variable biofilm coverage [control; anode surface coverage (ASC), 0%], partially developed biofilm [PDB; ASC approximately 44%; 90 days] and fully developed biofilm [FDB; ASC approximately 96%; 180 days] under acidophilic conditions (pH 6) at room temperature. The study depicted the effectiveness of anodic biofilm formation in enhancing the extracellular electron transfer in the absence of mediators. Higher specific power production [29 mW/kg COD(R) (CW and DSW)], specific energy yield [100.46 J/kg VSS (CW)], specific power yield [0.245 W/kg VSS (DSW); 0.282 W/kg VSS (CW)] and substrate removal efficiency of 66.07% (substrate degradation rate, 0.903 kgCOD/m(3)-day) along with effective functioning fuel cell at relatively higher resistance [4.5 komega (DSW); 14.9 komega (CW)] correspond to sustainable power [0.008 mW (DSW); 0.021 mW (CW)] and effective electron discharge (at higher resistance) and recovery (Coulomb efficiency; 27.03%) were observed especially with FDB operation. Cyclic voltammetry analysis documented six-fold increment in energy output from control (1.812 mJ) to PDB (10.666 mJ) operations and about eight-fold increment in energy from PDB to FDB (86.856 mJ). Biofilm configured MFC was shown to have the potential to selectively support the growth of electrogenic bacteria with robust characteristics, capable of generating higher power yields along with substrate degradation especially operated with characteristically complex wastewaters as substrates.

  17. A small-molecule norspermidine and norspermidine-hosting polyelectrolyte coatings inhibit biofilm formation by multi-species wastewater culture.

    Science.gov (United States)

    Si, Xiurong; Quan, Xiangchun; Wu, Yachuan

    2015-12-01

    Norspermidine is a potent and non-bactericidal small-molecule inhibitor of biofilm growth. In this study, impacts of norspermidine on biofilm control and existing biofilm dispersal by a mixed culture from wastewater treatment systems were investigated. A surface-mediated releasing approach for prevention of bacterial biofilm formation was established via encapsulating norspermidine into polyelectrolyte multilayer coatings. Results showed that the presence of norspermidine (500-1000 μM) in medium remarkably prevented biofilm formation. Norspermidine was also effective in disassembling pre-formed biofilms. Norspermidine-containing multilayer coatings were successfully fabricated on glass slides via layer-by-layer deposition in polyethylenimine (PEI) and poly(acrylic acid) (PAA) solution. This coating exhibited a high anti-biofilm property against a mixed culture and three pure strains (Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli). The loading amount and space distribution of norspermidine in the multilayer coating were key factors influencing its anti-biofilm efficacy. The polymer coating with norspermidine loaded in each bilayer (each-layer-type) exhibited better anti-biofilm efficacy than the bottom-type and the top-type coating, which showed a stable biofilm inhibition rate of about 60 % even after 5-day leaching in aqueous solution. Norspermidine could retard bacterial adhesion and destruct biofilm matrix by reducing exopolysaccharides and extracellular DNA (eDNA) associated with bacteria instead of growth inhibition. Norspermidine and the norspermidine-hosting coatings in this study offer a great potential for the control of biofilms in the settings of water purification and wastewater treatment systems, which shows the advantage of broad spectrum and less risk of evolved bacterial resistance compared to conventional microbicidal agents (e.g., antibiotics).

  18. Factors Influencing Students’ Perceptions of Online Teamwork

    Directory of Open Access Journals (Sweden)

    Irina Falls

    2014-02-01

    Full Text Available The evolution of online teaching in higher education demands a change in the types of pedagogies used in those courses. An example of one of these important pedagogies includes online teamwork. Teamwork in this context is one in which the majority of the individual’s grade is dependent on the positive or negative group experiences. This study utilized the theoretical framework of social motivation and cohesion to identify the factors shaping students’ perceptions of teamwork in online college courses. In these courses, the pedagogical approach known as the Five Pillars of effective collaborative work was applied. An Online Teamwork Learning Survey was developed based on these principles and completed by 62 undergraduate students enrolled in semester-long online courses required in their early childhood education program of study. Using a comparison between pre–postsurveys and regression analysis, the results showed that although the students’ perceptions of teamwork did not significantly change, the factors influencing their responses during the posttest doubled in number. The results showed that through carefully designed virtual teamwork activities, students learned that essential team characteristics such as promotive interaction, individual accountability, and positive interdependence are an integral part of effective collaboration and strong predictors of teamwork perception.

  19. Influence of biofilms on migration of uranium, americium and europium in the environment; Einfluss von Biofilmen auf das Migrationsverhalten von Uran, Americium und Europium in der Umwelt

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, Nils; Zirnstein, Isabel; Arnold, Thuro

    2015-07-01

    The report on the influence of biofilms on migration of uranium, americium and europium in the environment deals with the contamination problems of uranium mines such as SDAG WISMUT in Saxonia and Thuringia. In mine waters microorganisms form a complex microbiological biocoenosis in spite of low pH values and high heavy metal concentrations including high uranium concentrations. The analyses used microbiological methods like confocal laser scanning microscopy and molecular-biological techniques. The interactions of microorganism with fluorescent radioactive heavy metal ions were performed with TRLFS (time resolved laser-induced fluorescence spectroscopy).

  20. Preoperative factors influencing success in pterygium surgery

    Directory of Open Access Journals (Sweden)

    Torres-Gimeno Ana

    2012-08-01

    Full Text Available Abstract Background To identify preoperative, perioperative and postoperative risk factors that influence the success of pterygium surgery. Methods This is a prospective study of thirty-six patients with primary or recurrent pterygia. A detailed anamnesis and an ophthalmological examination were performed looking for the following factors: age, race, latitude and altitude of the main place of residence, hours of exposure to the sun, use of protective measures against UV-radiation, classification of pterygium, width of the pterygium at limbus, surgical technique (conjunctival autograft plus suturing versus tissue glue, graft alterations (misapposition, granuloma, haemorrhage, oedema, retraction or necrosis, and postoperative symptoms (foreign-body sensation, pain. The examinations were performed 2 and 7 days and 2, 6 and 12 months after surgery. In addition, recurrence was defined as any growth of conjunctiva into the cornea. Results A logistic regression and a survival analysis have been used to perform data analysis. A total number of 36 patients completed a one year follow-up. A total of 13 patients were born and lived in Spain, and 26 came from other countries, mostly Latin America. A total number of 8 males (no women presented a recurrence, mainly between 2 and 6 months. The hours of sun exposure through their life was independently related to surgical success. Pterygia of less than 5 mm of base width showed a weak positive correlation with recurrence. None of the other factors considered were significantly related to recurrence. Conclusions Male gender and high sun exposure are strongly and independently related to surgical success after the removal of pterygia.

  1. Biogenesis of Enterococcis faecium biofilms

    NARCIS (Netherlands)

    Paganelli, F.L.

    2015-01-01

    Nosocomial infections caused by Enterococcus faecium have rapidly increased worldwide and treatment options become more limited. The presence of antibiotic resistance genes and virulence factors in pathogenic E. faecium contribute to difficult-to-treat infections, frequently biofilm mediated, such

  2. Remarks on the physical factor influencing the individual language learners

    Institute of Scientific and Technical Information of China (English)

    刘晨君

    2015-01-01

    individual language learner as a subject of learning can be influenced by many factors such as physical factor,cognitive factor,and affective factor.All of which play an important role in language learning.These three factors are worthy of our research and physical factor will be discussed in this essay.

  3. Streptococcus oligofermentans Inhibits Streptococcus mutans in Biofilms at Both Neutral pH and Cariogenic Conditions.

    Directory of Open Access Journals (Sweden)

    Xudong Bao

    Full Text Available Homeostasis of oral microbiota can be maintained through microbial interactions. Previous studies showed that Streptococcus oligofermentans, a non-mutans streptococci frequently isolated from caries-free subjects, inhibited the cariogenic Streptococcus mutans by the production of hydrogen peroxide (HP. Since pH is a critical factor in caries formation, we aimed to study the influence of pH on the competition between S. oligofermentans and S. mutans in biofilms. To this end, S. mutans and S. oligofermentans were inoculated alone or mixed at 1:1 ratio in buffered biofilm medium in a 96-well active attachment model. The single- and dual-species biofilms were grown under either constantly neutral pH or pH-cycling conditions. The latter includes two cycles of 8 h neutral pH and 16 h pH 5.5, used to mimic cariogenic condition. The 48 h biofilms were analysed for the viable cell counts, lactate and HP production. The last two measurements were carried out after incubating the 48 h biofilms in buffers supplemented with 1% glucose (pH 7.0 for 4 h. The results showed that S. oligofermentans inhibited the growth of S. mutans in dual-species biofilms under both tested pH conditions. The lactic acid production of dual-species biofilms was significantly lower than that of single-species S. mutans biofilms. Moreover, dual-species and single-species S. oligofermentans biofilms grown under pH-cycling conditions (with a 16 h low pH period produced a significantly higher amount of HP than those grown under constantly neutral pH. In conclusion, S. oligofermentans inhibited S. mutans in biofilms not only under neutral pH, but also under pH-cycling conditions, likely through HP production. S. oligofermentans may be a compelling probiotic candidate against caries.

  4. Biofilm Morphotypes and Population Structure among Staphylococcus epidermidis from Commensal and Clinical Samples.

    Directory of Open Access Journals (Sweden)

    Llinos G Harris

    Full Text Available Bacterial species comprise related genotypes that can display divergent phenotypes with important clinical implications. Staphylococcus epidermidis is a common cause of nosocomial infections and, critical to its pathogenesis, is its ability to adhere and form biofilms on surfaces, thereby moderating the effect of the host's immune response and antibiotics. Commensal S. epidermidis populations are thought to differ from those associated with disease in factors involved in adhesion and biofilm accumulation. We quantified the differences in biofilm formation in 98 S. epidermidis isolates from various sources, and investigated population structure based on ribosomal multilocus typing (rMLST and the presence/absence of genes involved in adhesion and biofilm formation. All isolates were able to adhere and form biofilms in in vitro growth assays and confocal microscopy allowed classification into 5 biofilm morphotypes based on their thickness, biovolume and roughness. Phylogenetic reconstruction grouped isolates into three separate clades, with the isolates in the main disease associated clade displaying diversity in morphotype. Of the biofilm morphology characteristics, only biofilm thickness had a significant association with clade distribution. The distribution of some known adhesion-associated genes (aap and sesE among isolates showed a significant association with the species clonal frame. These data challenge the assumption that biofilm-associated genes, such as those on the ica operon, are genetic markers for less invasive S. epidermidis isolates, and suggest that phenotypic characteristics, such as adhesion and biofilm formation, are not fixed by clonal descent but are influenced by the presence of various genes that are mobile among lineages.

  5. Hydrolysis kinetics of atrazine and influence factors

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrolysis kinetics of atrazine in distilled water and leaching water from soil, and their influence factors were studied by incubation at 35℃ and HPLC analysis method in this paper. The kinetic process of atrazine hydrolysis can be described by the first-order reaction law. The results showed that the hydrolysis rate constants k in leaching water and distilled water were 1.606x10-3/d and 1.055x10-3/d, respectively; the half-life of atrazine hydrolysis in distilled water at pH 3, pH 4.5 and pH 8 were 373 days, 522 days and 657 days respectively. The results also showed that the proton in reaction solution can catalyze the atrazine hydrolysis; humic acid and NH4+ etc. substances in aqueous solution can facilitate atrazine hydrolysis; rate constants of atrazine hydrolysis with humic acid and NH4NO3 were 2.431x10-3/d and 1.498x10-3/d respectively which were 2.3 and 1.42 times of control(1.055x10-3/d); anion NO3- can inhibit catalysis of humic acid to atrazine hydrolysis.

  6. Factors influencing competitive anxiety in Brazilian athletes

    Directory of Open Access Journals (Sweden)

    Marcos Gimenes Fernandes

    2013-09-01

    Full Text Available The study of factors influencing competitive anxiety, according to a multidimensional perspective and supported by valid instruments, is scarce among Brazilian athletes of different sports. The present study aims to: i investigate the theoretical relationship between the different dimensions of the multidimensional theory of anxiety (i.e., cognitive anxiety, somatic anxiety and self-confidence; and ii investigate the effects of gender, type of sport (individual or collective and competitive experience levels on cognitive anxiety, somatic anxiety and self-confidence. A total of 303 athletes (233 males and 70 females, from different sports, aged between 18 and 40 years (M =24.22, SD = 5.07 completed a shortened version of CSAI-2 (i.e., CSAI-2R, about one hour before the start of competitions. Results revealed significant correlations between cognitive anxiety, somatic anxiety and self-confidence dimensions, in accordance with the assumptions of the multidimensional theory. Additionally, comparative analyses indicated that female athletes and athletes from collective sports showed higher levels of cognitive anxiety, while male athletes and athletes with high competitive experience reported higher levels of self-confidence. These results were discussed taking into account the theoretical and practical implications of these findings for planning interventions of sport psychology in Brazil with athletes of different contexts.

  7. Factors That Influence Primary Cilium Length

    Directory of Open Access Journals (Sweden)

    Miyoshi,Ko

    2011-10-01

    Full Text Available Almost all mammalian cells carry one primary cilium that functions as a biosensor for chemical and mechanical stimuli. Genetic damages that compromise cilia formation or function cause a spectrum of disorders referred to as ciliapathies. Recent studies have demonstrated that some pharmacological agents and extracellular environmental changes can alter primary cilium length. Renal injury is a well-known example of an environmental insult that triggers cilia length modification. Lithium treatment causes primary cilia to extend in several cell types including neuronal cells;this phenomenon is likely independent of glycogen synthase kinase-3β inhibition. In renal epithelial cell lines, deflection of the primary cilia by fluid shear shortens them by reducing the intracellular cyclic AMP level, leading to a subsequent decrease in mechanosensitivity to fluid shear. Primary cilium length is also influenced by the dynamics of actin filaments and microtubules through the levels of soluble tubulin in the cytosol available for primary cilia extension. Thus, mammalian cells can adapt to the extracellular environment by modulating the primary cilium length, and this feedback system utilizing primary cilia might exist throughout the mammalian body. Further investigation is required concerning the precise molecular mechanisms underlying the control of primary cilium length in response to environmental factors.

  8. Wound biofilms: lessons learned from oral biofilms.

    Science.gov (United States)

    Mancl, Kimberly A; Kirsner, Robert S; Ajdic, Dragana

    2013-01-01

    Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque, are a primary cause of oral diseases including caries, gingivitis, and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible; thus, biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well elucidated. In contrast, wound research has relatively recently directed attention to the role biofilms have in chronic wounds. This review discusses the biofilms in periodontal disease and chronic wounds with comparisons focusing on biofilm detection, biofilm formation, the immune response to biofilms, bacterial interaction, and quorum sensing. Current treatment modalities used by both fields and future therapies are also discussed.

  9. Urban water consumption and its influencing factors in China

    NARCIS (Netherlands)

    Fan, Liangxin; Gai, Lingtong; Tong, Yan; Li, Ruihua

    2017-01-01

    Factors that affect water consumption should be identified to develop effective public policies. However, factors influencing domestic water consumption in cities in China, particularly on a national scale, are unclear. In this study, urban water consumption and its influencing factors in 286

  10. What Factors Influence a Teacher's Commitment to Student Learning?

    Science.gov (United States)

    Dannetta, Vincent

    2002-01-01

    Study of the personal, organizational, student-related factors influencing teacher commitment to student learning. Finds, for example, that among personal factors intrinsic rewards are more important than extrinsic rewards, that among organization factors collegiality is an important influence on commitment to student learning, and that among…

  11. A Comparison of Factors that Influence the Lyophilization Process

    OpenAIRE

    Dumitru Mnerie; Gabriela-victoria Anghel; Alin Vasile Mnerie; Constantin Cheveresan

    2007-01-01

    The lyophilization (or freeze drying) process for agro-foods products depends on a series of technological factors that are in an inter-dependence with the process performance. This paper presents an expert method and its application. This method characterizes the influence factors of the lyophilization process, after the importance level of some factors in correlation with other factors, is defined. Only the most important factors were considered; influence considerations were made in relati...

  12. Factors Influencing Food Choice in the Elderly Mauritian Population ...

    African Journals Online (AJOL)

    Factors Influencing Food Choice in the Elderly Mauritian Population. ... in influencing food choices and thus food intake of the elderly people in Mauritius. A cross-sectional nutritional survey was carried out in different regions around the island ...

  13. Potentially pathogenic Escherichia coli can form a biofilm under conditions relevant to the food production chain.

    Science.gov (United States)

    Nesse, Live L; Sekse, Camilla; Berg, Kristin; Johannesen, Karianne C S; Solheim, Heidi; Vestby, Lene K; Urdahl, Anne Margrete

    2014-04-01

    The biofilm-producing abilities of potentially human-pathogenic serotypes of Escherichia coli from the ovine reservoir were studied at different temperatures and on different surfaces. A possible influence of the hydrophobicity of the bacterial cells, as well as the presence of two virulence factors, the Shiga toxin-encoding (Stx) bacteriophage and the eae gene, was also studied. A total of 99 E. coli isolates of serotypes O26:H11, O103:H2, and O103:H25 isolated from sheep feces were included. The results show that isolates of all three E. coli serotypes investigated can produce biofilm on stainless steel, glass, and polystyrene at 12, 20, and 37°C. There was a good general correlation between the results obtained on the different surfaces. E. coli O103:H2 isolates produced much more biofilm than those of the other two serotypes at all three temperatures. In addition, isolates of serotype O26:H11 produced more biofilm than those of O103:H25 at 37°C. The hydrophobicity of the isolates varied between serotypes and was also influenced by temperature. The results strongly indicated that hydrophobicity influenced the attachment of the bacteria rather than their ability to form biofilm once attached. Isolates with the eae gene produced less biofilm at 37°C than isolates without this gene. The presence of a Stx bacteriophage did not influence biofilm production. In conclusion, our results show that potentially human-pathogenic E. coli from the ovine reservoir can form biofilm on various surfaces and at several temperatures relevant for food production and handling.

  14. Roles of a novel Crp/Fnr family transcription factor Lmo0753 in soil survival, biofilm production and surface attachment to fresh produce of Listeria monocytogenes.

    Directory of Open Access Journals (Sweden)

    Joelle K Salazar

    Full Text Available Listeria monocytogenes is a foodborne bacterial pathogen and the causative agent of an infectious disease, listeriosis. L. monocytogenes is ubiquitous in nature and has the ability to persist in food processing environments for extended periods of time by forming biofilms and resisting industrial sanitization. Human listeriosis outbreaks are commonly linked to contaminated dairy products, ready-to-eat meats, and in recent years, fresh produce such as lettuce and cantaloupes. We identified a putative Crp/Fnr family transcription factor Lmo0753 that is highly specific to human-associated genetic lineages of L. monocytogenes. Lmo0753 possesses two conserved functional domains similar to the major virulence regulator PrfA in L. monocytogenes. To determine if Lmo0753 is involved in environmental persistence-related mechanisms, we compared lmo0753 deletion mutants with respective wild type and complementation mutants of two fully sequenced L. monocytogenes genetic lineage II strains 10403S and EGDe for the relative ability of growth under different nutrient availability and temperatures, soil survival, biofilm productivity and attachment to select fresh produce surfaces including romaine lettuce leaves and cantaloupe rinds. Our results collectively suggested that Lmo0753 plays an important role in L. monocytogenes biofilm production and attachment to fresh produce, which may contribute to the environmental persistence and recent emergence of this pathogen in human listeriosis outbreaks linked to fresh produce.

  15. Factors of Influence on Receivables and Payables and Their Classification

    OpenAIRE

    Kuzmin Oleg Ye.; Volovich Yelena B.

    2013-01-01

    The approaches to classification factors of receivables and payables are analyzed in the article. In order to develop effective methods of receivables and payables management, its factors of influence are proposed to divide into three groups - macro factors, the factors of enterprises immediate environment and micro factors.

  16. The composition and compression of biofilms developed on ultrafiltration membranes determine hydraulic biofilm resistance.

    Science.gov (United States)

    Derlon, Nicolas; Grütter, Alexander; Brandenberger, Fabienne; Sutter, Anja; Kuhlicke, Ute; Neu, Thomas R; Morgenroth, Eberhard

    2016-10-01

    This study aimed at identifying how to improve the level of permeate flux stabilisation during gravity-driven membrane filtration without control of biofilm formation. The focus was therefore on understanding (i) how the different fractions of the biofilms (inorganics particles, bacterial cells, EPS matrix) influence its hydraulic resistance and (ii) how the compression of biofilms impacts its hydraulic resistance, i.e., can water head be increased to increase the level of permeate flux stabilisation. Biofilms were developed on ultrafiltration membranes at 88 and 284 cm water heads with dead-end filtration for around 50 days. A larger water head resulted in a smaller biofilm permeability (150 and 50 L m(-2) h(-1) bar(-1) for biofilms grown at 88 cm and 284 cm water head, respectively). Biofilms were mainly composed of EPS (>90% in volume). The comparison of the hydraulic resistances of biofilms to model fouling layers indicated that most of the hydraulic resistance is due to the EPS matrix. The compressibility of the biofilm was also evaluated by subjecting the biofilms to short-term (few minutes) and long-term variations of transmembrane pressures (TMP). A sudden change of TMP resulted in an instantaneous and reversible change of biofilm hydraulic resistance. A long-term change of TMP induced a slow change in the biofilm hydraulic resistance. Our results demonstrate that the response of biofilms to a TMP change has two components: an immediate variation of resistance (due to compression/relaxation) and a long-term response (linked to biofilm adaptation/growth). Our results provide relevant information about the relationship between the operating conditions in terms of TMP, the biofilm structure and composition and the resulting biofilm hydraulic resistance. These findings have practical implications for a broad range of membrane systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Membrane-aerated biofilms for high rate biotreatment: performance appraisal, engineering principles, scale-up, and development requirements.

    Science.gov (United States)

    Syron, Eoin; Casey, Eoin

    2008-03-15

    Diffusion of the electron acceptor is the rate controlling step in virtually all biofilm reactors employed for aerobic wastewater treatment. The membrane-aerated biofilm reactor (MABR) is a technology that can deliver oxygen at high rates and transfer efficiencies, thereby enhancing the biofilm activity. This paper provides a comparative performance rate analysis of the MABR in terms of its application for carbonaceous pollutant removal, nitrification/denitrification and xenobiotic biotreatment. We also describe the mechanisms influencing process performance in the MABR and the inter-relationships between these factors. The challenges involved in scaling-up the process are discussed with recommendations for prioritization of research needs.

  18. Influence of carrier filling ratio on the performance of moving bed biofilm reactor in treating coking wastewater.

    Science.gov (United States)

    Gu, Qiyuan; Sun, Tichang; Wu, Gen; Li, Mingyue; Qiu, Wei

    2014-08-01

    This study aims to evaluate the effect of carrier filling ratio on the performance of a moving bed biofilm reactor in degrading chemical oxygen demand, phenol, thiocyanate, and ammonia from coking wastewater at 20h of hydraulic retention time. The operational experiments under different carrier filling ratios ranging from 20% to 60% were investigated. The maximum removal efficiency of 89%, 99% and 99% for COD, phenol and thiocyanate, and minimum sensitivity to the increasing contaminants concentration in the influent were achieved at 50% carrier filling ratio. The Haldane competitive substrate inhibition kinetics model was used to describe the relationship between the oxygen uptake rate of ammonium oxidizers and the concentration of free ammonium. The highest biofilm microbial community functional diversity (Shannon's diversity index, H') and evenness (Shannon's evenness index, E') were obtained at 50% carrier filling ratio in all runs using a Biolog ECO microplate.

  19. Biofilm formation by Staphylococcus aureus isolates from a dental clinic in Konya, Turkey.

    Science.gov (United States)

    Torlak, Emrah; Korkut, Emre; Uncu, Ali T; Şener, Yağmur

    2017-02-14

    The ability of Staphylococcus aureus to form biofilm is considered to be a major virulence factor influencing its survival and persistence in both the environment and the host. Biofilm formation in S. aureus is most frequently associated with production of polysaccharide intercellular adhesion by ica operon-encoded enzymes. The present work aimed at evaluating the in vitro biofilm production and presence of the icaA and icaD genes in S. aureus isolates from a dental clinic in Konya, Turkey. The surfaces of inanimate objects were sampled over a period of six months. S. aureus isolates were subjected to Congo Red Agar (CRA) and crystal violet (CV) staining assays to evaluate their ability of biofilm production, while the presence of the icaA and icaD genes was determined by polymerase chain reaction. S. aureus contamination was detected in 13.2% of the environmental samples. All the 32 isolates were observed to be positive for both the icaA and icaD genes. Phenotypic evaluations revealed that CV staining assay is a more reliable alternative to CRA assay to determine biofilm formation ability. A high percentage of agreement (91%) was observed between the results from CV staining and ica genes' detection assays. Phenotypic and genotypic evaluations should be combined to detect biofilm formation in S. aureus. Our findings indicate that dental clinic environments should be considered as potential reservoir for biofilm-producing S. aureus and thus cross contamination.

  20. The Role of Biofilms and Curli in Salmonella Transport Through Porous Media

    Science.gov (United States)

    Salvucci, A. E.; Zhang, W.; Morales, V. L.; Cakmak, M. E.; Hay, A. G.; Steenhuis, T. S.

    2008-12-01

    Microbial pathogens, such as Salmonella and E. coli, are continually deposited in the environment and have been shown to contaminate the groundwater by leaching through the vadose zone. Therefore, understanding the mechanisms controlling the transport of these microbial pathogens through porous media is critical to protecting drinking water supplies. As previous research has shown, retention of microbial pathogens in porous media can be influenced by numerous biological factors. Consequently, this experiment specifically investigated the role of biofilm formation and curli production on the transport of environmental Salmonella through porous media. Environmental Salmonella strains used in the experiment were isolated from tile drains on dairy farms. In addition, two well-characterized E. coli strains with known high and low biofilm and curli producing capabilities were tested as controls alongside the Salmonella isolates throughout the experiment. The isolates were first assayed for their ability to form biofilms and produce curli, and then a subset of these isolates, representing range of high and low biofilm and curli formation capabilities, were simultaneously examined for transport characteristics through packed sand columns. Transport characteristics were tested for correlation with biofilm and curli-forming capabilities. Unlike the E. coli strains in which column retention correlated with biofilm formation and curli production, no obvious correlation between Salmonella phenotypes was observed. The results indicate that while transport of well-characterized laboratory E. coli strains can often be hindered by the presence of curli and biofilms, such assumptions are not fully representative of the behavior exhibited by environmental isolates of Salmonella.

  1. Different carbon isotope fractionation patterns during the development of phototrophic freshwater and marine biofilms

    Directory of Open Access Journals (Sweden)

    M. Staal

    2007-08-01

    Full Text Available Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which is expected to lead to a limitation of light or mass transport. This study shows that variation in CO2(aq availability leads to a fractionation shift and thereby affects δ13C signatures during biofilm development. For phototrophic freshwater biofilms it was found that the δ13C value became less negative with the thickening of the biofilm, while the opposite trend was found in marine biofilms. Modeling and pH profiling indicated that the trend in the freshwater system was caused by an increase in CO2(aq limitation resulting in an increase of HCO3 as C-source. The opposite trend in the marine system could be explained by a higher heterotrophic biomass and activity causing a higher carbon recycling and thereby lower δ13C values. We conclude that δ13C was more related to the net areal photosynthesis rate and carbon recycling, rather than to the growth rate of the biofilms.

  2. Different carbon isotope fractionation patterns during the development of phototrophic freshwater and marine biofilms

    Science.gov (United States)

    Staal, M.; Thar, R.; Kühl, M.; van Loosdrecht, M. C. M.; Wolf, G.; de Brouwer, J. F. C.; Rijstenbil, J. W.

    2007-08-01

    Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which is expected to lead to a limitation of light or mass transport. This study shows that variation in CO2(aq) availability leads to a fractionation shift and thereby affects δ13C signatures during biofilm development. For phototrophic freshwater biofilms it was found that the δ13C value became less negative with the thickening of the biofilm, while the opposite trend was found in marine biofilms. Modeling and pH profiling indicated that the trend in the freshwater system was caused by an increase in CO2(aq) limitation resulting in an increase of HCO3- as C-source. The opposite trend in the marine system could be explained by a higher heterotrophic biomass and activity causing a higher carbon recycling and thereby lower δ13C values. We conclude that δ13C was more related to the net areal photosynthesis rate and carbon recycling, rather than to the growth rate of the biofilms.

  3. Does reactor staging influence microbial structure and functions in biofilm systems? The case of pre-denitrifying MBBRs

    OpenAIRE

    Polesel, Fabio; Torresi, Elena; Jensen, Marlene Mark; Fowler, Jane; Escola Casas, Monica; Barth F. Smets; Christensson, Magnus; Bester, Kai; Plósz, Benedek G.

    2016-01-01

    To date, a number of treatment technologies and configurations have been tested to improve the elimination of conventional and trace (e.g., pharmaceutical residues) pollutants via biological wastewater treatment. Bioreactor staging and the moving bed biofilm reactor (MBBR) technology have emerged as promising bioengineered solutions (Plósz et al., 2010) for this purpose. In this study, we combined the two solutions and investigated microbial functions (heterotrophic denitrification, pharmaceu...

  4. Antifouling Coatings Influence both Abundance and Community Structure of Colonizing Biofilms: a Case Study in the Northwestern Mediterranean Sea

    OpenAIRE

    Camps, Mercedes; Barani, Aude; Gregori, Gerald; Bouchez, Agnes; Le Berre, Brigitte; Bressy , Christine; Blache, Yves

    2014-01-01

    When immersed in seawater, substrates are rapidly colonized by both micro- and macroorganisms. This process is responsible for important economic and ecological prejudices, particularly when related to ship hulls or aquaculture nets. Commercial antifouling coatings are supposed to reduce biofouling, i.e., micro- and macrofoulers. In this study, biofilms that primarily settled on seven different coatings (polyvinyl chloride [PVC], a fouling release coating [FRC], and five self-polishing copoly...

  5. Influence of exudates of the kelp Laminaria digitata on biofilm formation of associated and exogenous bacterial epiphytes.

    Science.gov (United States)

    Salaün, Stéphanie; La Barre, Stéphane; Dos Santos-Goncalvez, Marina; Potin, Philippe; Haras, Dominique; Bazire, Alexis

    2012-08-01

    Wild populations of brown marine algae (Phaeophyta) provide extensive surfaces to bacteria and epiphytic eukaryotes for colonization. On one hand, various strategies allow kelps prevent frond surface fouling which would retard growth by reducing photosynthesis and increasing pathogenesis. On the other hand, production and release of organic exudates of high energy value, sometimes in association with more or less selective control of settlement of epiphytic strains, allow bacteria to establish surface consortia not leading to macrofouling. Here, we present the analysis of adhesion and biofilm formation of bacterial isolates from the kelp Laminaria digitata and of characterized and referenced marine isolates. When they were grown in flow cell under standard nutrient regimes, all used bacteria, except one, were able to adhere on glass and then develop as biofilms, with different architecture. Then, we evaluated the effect of extracts from undisturbed young Laminaria thalli and from young thalli subjected to oxidative stress elicitation; this latter condition induced the production of defense molecules. We observed increasing or decreasing adhesion depending on the referenced strains, but no effects were observed against strains isolated from L. digitata. Such effects were less observed on biofilms. Our results suggested that L. digitata is able to modulate its bacterial colonization. Finally, mannitol, a regular surface active component of Laminaria exudates was tested individually, and it showed a pronounced increased on one biofilm strain. Results of these experiments are original and can be usefully linked to what we already know on the oxidative halogen metabolism peculiar to Laminaria. Hopefully, we will be able to understand more about the unique relationship that bacteria have been sharing with Laminaria for an estimated one billion years.

  6. The influence of antimicrobial peptides and mucolytics on the integrity of biofilms consisting of bacteria and yeasts as affecting voice prosthetic air flow resistances

    NARCIS (Netherlands)

    Oosterhof, JJH; Elving, GJ; Stokroos, [No Value; Amerongen, AV; van der Mei, HC; Busscher, HJ; van Weissenbruch, R; Albers, FWJ

    2003-01-01

    The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary p

  7. The influence of antimicrobial peptides and mucolytics on the integrity of biofilms consisting of bacteria and yeasts as affecting voice prosthetic air flow resistances

    NARCIS (Netherlands)

    Oosterhof, JJH; Elving, GJ; Stokroos, [No Value; Amerongen, AV; van der Mei, HC; Busscher, HJ; van Weissenbruch, R; Albers, FWJ

    2003-01-01

    The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary

  8. Naturally Ocurring Polyphosphate-accumulating Bacteria in Benthic Biofilms

    Science.gov (United States)

    Locke, N. A.; Saia, S. M.; Walter, M. T.; Carrick, H. J.; Buda, A. R.; Regan, J. M.

    2014-12-01

    Polyphosphate accumulating organisms (PAOs), known to store excess phosphorus (P) as polyphosphate (poly-P), influence P transport in the environment. Enhanced biological phosphorus removal (EBPR) from wastewater has long served as a basis to study bacterial PAOs, yet little research has genetically identified similar organisms in natural settings. Aerobic/anaerobic cycles, used to select for PAOs in EBPR, can result from changing environmental conditions such as night/day cycles for benthic biofilms. Benthic biofilms from eight Pennsylvanian streams were studied for naturally-occurring bacterial PAOs similar to those typically found in EBPR systems. PAOs were confirmed in the benthic biofilms by a characteristic yellow fluorescent emission from DAPI staining. Cells containing yellow fluorescence were separated from the rest of the sample using a flow cytometer, resulting in a physically enriched culture of PAOs from the benthic biofilms. Amplicon-based metagenomic sequencing will reveal the phylogeny of bacteria responsible for poly-P accumulation in these benthic biofilms. Sequencing data will be used to develop fluorescent in-situ hybridization (FISH) probes, and hybridizations will be performed on DAPI-stained cells to confirm poly-P accumulation by targeted phylotypes. Identifying PAOs in natural settings is a critical step towards studying environments that support high concentrations of PAOs, serving as significant factors in the P cycle. PAOs can then be connected to P transport models to help understand and mitigate P pollution in agricultural watersheds.

  9. Physical solutions to the public goods dilemma in bacterial biofilms

    Science.gov (United States)

    Drescher, Knut; Nadell, Carey; Stone, Howard; Wingreen, Ned; Bassler, Bonnie

    2013-11-01

    Bacteria frequently live in densely populated surface-bound communities, termed biofilms. Biofilm-dwelling cells rely on secretion of extracellular substances to construct their communities and to capture nutrients from the environment. Some secreted factors behave as cooperative public goods: they can be exploited by non-producing cells. The means by which public good producing bacteria avert exploitation in biofilm environments are largely unknown. Using experiments with Vibrio cholerae, which secretes extracellular enzymes to digest its primary food source, the solid polymer chitin, we show that the public goods dilemma may be solved by two dramatically different, physical mechanisms: cells can produce thick biofilms that confine the goods to producers, or fluid flow can remove soluble products of chitin digestion, denying access to non-producers. Both processes limit the distance over which enzyme-secreting cells provide a benefit to neighbors, resulting in preferential benefit to nearby clonemates. Our results demonstrate how bacterial physiology and environmental conditions can interact with social phenotypes to influence the evolutionary dynamics of cooperation within biofilms.

  10. Biofilm responses to marine fish farm wastes

    Energy Technology Data Exchange (ETDEWEB)

    Sanz-Lazaro, Carlos, E-mail: carsanz@um.es [Departamento de Ecologia e Hidrologia, Facultad de Biologia, Universidad de Murcia, 30100 Murcia (Spain); Navarrete-Mier, Francisco; Marin, Arnaldo [Departamento de Ecologia e Hidrologia, Facultad de Biologia, Universidad de Murcia, 30100 Murcia (Spain)

    2011-03-15

    The changes in the biofilm community due to organic matter enrichment, eutrophication and metal contamination derived from fish farming were studied. The biofilm biomass, polysaccharide content, trophic niche and element accumulation were quantified along an environmental gradient of fish farm wastes in two seasons. Biofilm structure and trophic diversity was influenced by seasonality as well as by the fish farm waste load. Fish farming enhanced the accumulation of organic carbon, nutrients, selenium and metals by the biofilm community. The accumulation pattern of these elements was similar regardless of the structure and trophic niche of the community. This suggests that the biofilm communities can be considered a reliable tool for assessing dissolved aquaculture wastes. Due to the ubiquity of biofilms and its wide range of consumers, its role as a sink of dissolved wastes may have important implications for the transfer of aquaculture wastes to higher trophic levels in coastal systems. - Research highlights: > Biofilms can act as a trophic pathway of fish farm dissolved wastes. > Biofilms are reliable tools for monitoring fish farm dissolved wastes. > The influence of the fish farm dissolved wastes can be detected 120-350 m from farm. - Under the influence of fish farming biofilm accumulates organic carbon, nutrients, selenium and metals, regardless of the structure and trophic niche of the community.

  11. Evaluation of biofilm performance as a protective barrier against biocorrosion using an enzyme electrode.

    Science.gov (United States)

    Soleimani, S; Ormeci, B; Isgor, O B; Papavinasam, S

    2011-01-01

    Sulfide is known to be an important factor in microbiologically influenced corrosion (MIC) of metals and concrete deterioration in wastewater treatment structures and sewer pipelines. A sulfide biosensor was used to determine the effectiveness of Escherichia coli DH5 alpha biofilm as a protective barrier against MIC. The biofilm was shown to be effective in protecting surfaces from sulfide and helping to reduce MIC using amperometric measurements. The results also indicated that the growth conditions of E. coli DH5 alpha may have an impact on the performance of the biofilm as a sulfide barrier. The simple method provided in this work enables the comparison of several microbial biofilms and selection of the ones with potential to prevent MIC in a relatively short time.

  12. A multivariate approach to correlate bacterial surface properties to biofilm formation by lipopolysaccharide mutants of Pseudomonas aeruginosa.

    Science.gov (United States)

    Ruhal, Rohit; Antti, Henrik; Rzhepishevska, Olena; Boulanger, Nicolas; Barbero, David R; Wai, Sun Nyunt; Uhlin, Bernt Eric; Ramstedt, Madeleine

    2015-03-01

    Bacterial biofilms are involved in various medical infections and for this reason it is of great importance to better understand the process of biofilm formation in order to eradicate or mitigate it. It is a very complex process and a large range of variables have been suggested to influence biofilm formation. However, their internal importance is still not well understood. In the present study, a range of surface properties of Pseudomonas aeruginosa lipopolysaccharide mutants were studied in relation to biofilm formation measured in different kinds of multi-well plates and growth conditions in order to better understand the complexity of biofilm formation. Multivariate analysis was used to simultaneously evaluate the role of a range of physiochemical parameters under different conditions. Our results suggest the presence of serum inhibited biofilm formation due to changes in twitching motility. From the multivariate analysis it was observed that the most important parameters, positively correlated to biofilm formation on two types of plates, were high hydrophobicity, near neutral zeta potential and motility. Negative correlation was observed with cell aggregation, as well as formation of outer membrane vesicles and exopolysaccharides. This work shows that the complexity of biofilm formation can be better understood using a multivariate approach that can interpret and rank the importance of different factors being present simultaneously under several different environmental conditions, enabling a better understanding of this complex process.

  13. Inhibition of Quorum Sensing-Controlled Virulence Factors and Biofilm Formation in Pseudomonas aeruginosa by Culture Extract from Novel Bacterial Species of Paenibacillus Using a Rat Model of Chronic Lung Infection

    Directory of Open Access Journals (Sweden)

    Saad Musbah Alasil

    2015-01-01

    Full Text Available Quorum sensing (QS is a key regulator of virulence factors and biofilm formation in Gram-negative bacteria such as Pseudomonas aeruginosa. Microorganisms that inhabit soil are of strategic importance in the discovery of compounds with anti-QS properties. The objective of the study was to test the culture extract of a taxonomically novel species of Paenibacillus strain 139SI for its inhibitory effects on the QS-controlled virulence factors and biofilm formation of Pseudomonas aeruginosa both in vitro and in vivo. The Paenibacillus sp. culture extract was used to test its anti-QS effects on the LasA protease, LasB elastase, pyoverdin production, and biofilm formation of P. aeruginosa as well as evaluate its therapeutic effects on lung bacteriology, pathology, hematological profile, and serum antibody responses of experimental animals in a rat model of chronic lung infection. Results showed significant decrease in the activities of QS-controlled LasA protease, LasB elastase pyoverdin, and biofilm formation of P. aeruginosa caused by the culture extract. Moreover, the extract significantly prolonged the survival times of rats and facilitated the clearance of biofilm infections from infected lungs. In conclusion, the antiquorum sensing effects of culture extract from a novel species of Paenibacillus provide new insights to combat biofilm-associated infections.

  14. Understanding the influence of biofilm accumulation on the hydraulic properties of soils: a mechanistic approach based on experimental data

    Science.gov (United States)

    Carles Brangarí, Albert; Sanchez-Vila, Xavier; Freixa, Anna; Romaní, Anna M.; Fernàndez-Garcia, Daniel

    2017-04-01

    The distribution, amount, and characteristics of biofilms and its components govern the capacity of soils to let water through, to transport solutes, and the reactions occurring. Therefore, unraveling the relationship between microbial dynamics and the hydraulic properties of soils is of concern for the management of natural systems and many technological applications. However, the increased complexity of both the microbial communities and the geochemical processes entailed by them causes that the phenomenon of bioclogging remains poorly understood. This highlights the need for a better understanding of the microbial components such as live and dead bacteria and extracellular polymeric substances (EPS), as well as of their spatial distribution. This work tries to shed some light on these issues, providing experimental data and a new mechanistic model that predicts the variably saturated hydraulic properties of bio-amended soils based on these data. We first present a long-term laboratory infiltration experiment that aims at studying the temporal variation of selected biogeochemical parameters along the infiltration path. The setup consists of a 120-cm-high soil tank instrumented with an array of sensors plus soil and liquid samplers. Sensors measured a wide range of parameters in continuous, such as volumetric water content, electrical conductivity, temperature, water pressure, soil suction, dissolved oxygen, and pH. Samples were kept for chemical and biological analyses. Results indicate that: i) biofilm is present at all depths, denoting the potential for deep bioclogging, ii) the redox conditions profile shows different stages, indicating that the community was adapted to changing redox conditions, iii) bacterial activity, richness and diversity also exhibit zonation with depth, and iv) the hydraulic properties of the soil experienced significant changes as biofilm proliferated. Based on experimental evidences, we propose a tool to predict changes in the

  15. Factors Influencing the Adoption of Minimally Invasive Surgery

    African Journals Online (AJOL)

    of institutional, patient and surgeon-related factors ... Surgical site infections ... Factors influencing choice of open procedures over MIS are summarized in Table 1. The main .... written with pharmaceutical products in mind (25). ... JAMA Intern.

  16. External factors influencing the environmental performance of South African firms

    CSIR Research Space (South Africa)

    Peart, R

    2001-01-01

    Full Text Available This article reviews the external factors that influence environmental performance of companies in South Africa, drawing on international and local literature. After considering factors within the natural, social, economic and institutional...

  17. Dynamic interactions of neutrophils and biofilms

    Directory of Open Access Journals (Sweden)

    Josefine Hirschfeld

    2014-12-01

    Full Text Available Background: The majority of microbial infections in humans are biofilm-associated and difficult to treat, as biofilms are highly resistant to antimicrobial agents and protect themselves from external threats in various ways. Biofilms are tenaciously attached to surfaces and impede the ability of host defense molecules and cells to penetrate them. On the other hand, some biofilms are beneficial for the host and contain protective microorganisms. Microbes in biofilms express pathogen-associated molecular patterns and epitopes that can be recognized by innate immune cells and opsonins, leading to activation of neutrophils and other leukocytes. Neutrophils are part of the first line of defense and have multiple antimicrobial strategies allowing them to attack pathogenic biofilms. Objective/design: In this paper, interaction modes of neutrophils with biofilms are reviewed. Antimicrobial strategies of neutrophils and the counteractions of the biofilm communities, with special attention to oral biofilms, are presented. Moreover, possible adverse effects of neutrophil activity and their biofilm-promoting side effects are discussed. Results/conclusion: Biofilms are partially, but not entirely, protected against neutrophil assault, which include the processes of phagocytosis, degranulation, and formation of neutrophil extracellular traps. However, virulence factors of microorganisms, microbial composition, and properties of the extracellular matrix determine whether a biofilm and subsequent microbial spread can be controlled by neutrophils and other host defense factors. Besides, neutrophils may inadvertently contribute to the physical and ecological stability of biofilms by promoting selection of more resistant strains. Moreover, neutrophil enzymes can degrade collagen and other proteins and, as a result, cause harm to the host tissues. These parameters could be crucial factors in the onset of periodontal inflammation and the subsequent tissue breakdown.

  18. Factors influencing knowledge and practice of exclusive ...

    African Journals Online (AJOL)

    The independent variables were maternal education, marital status, both ... maternal employment status, health factors (place of delivery and maternal chronic illness) ... It was evident that family support is a key factor in the success of EBF with ...

  19. Exploration of fluid dynamic indicators/causative factors in the formation of tower structures in staphylococci bacteria bio-films

    Science.gov (United States)

    Sherman, Erica; Derek, Moormeier; Bayles, Kenneth; Wei, Timothy

    2015-11-01

    Staphylococcus aureus bacteria form biofilms with distinct structures that facilitate their ability to tolerate treatment and to spread within the body. As such, staph infections represent one of the greatest threats to post-surgery patients. It has been found that flow conditions play a significant role in the developmental and dispersal activity of a biofilm. The coupling between the growing biofilm and surrounding flow, however, is not well understood. Indeed, little is know why bacteria form tower structures under certain conditions but not in a predictable way. μ-PTV measurements were made in a microchannel to try to identify fluid dynamic indicators for the formation of towers in biofilm growth. Preliminary experiments indicated changes in the near wall flow up to five hours before a tower formed. The reason for that is the target of this investigation. Staphylococcus aureus bacteria were cultured in the Bioflux Fluxion channel and subjected to a steady shear rate of 0.5 dynes. In addition to μ-PTV measurement, nuclease production and cell number density counts were observed prior to and during tower development. These were compared against measurements made under the same nominal flow conditions where a tower did not form.

  20. Biofilm and mercury availability as key factors for mercury accumulation in fish (Curimata cyprinoides) from a disturbed Amazonian freshwater system.

    Science.gov (United States)

    Dominique, Yannick; Maury-Brachet, Régine; Muresan, Bogdan; Vigouroux, Régis; Richard, Sandrine; Cossa, Daniel; Mariotti, André; Boudou, Alain

    2007-01-01

    The Petit-Saut hydroelectric reservoir was filled in 1994 on the Sinnamary River in French Guiana (Amazonian basin). Flooding of the equatorial rain forest led to anoxia in most of the water column and enhanced mercury methylation in the reservoir hypolimnion. We selected the benthivorous/omnivorous fish species Curimata cyprinoides to investigate total mercury and methylmercury (MeHg) bioavailability and bioaccumulation capacities in the reservoir and downstream in the Sinnamary River. Mercury concentrations in the dorsal skeletal muscle were 10-fold higher in fish from the downstream zone. Stomach contents and stable nitrogen and carbon isotope ratios showed that biofilms and the associated invertebrate communities represented important food sources at the two sites. The delta 13C measurements indicated that biofilms in the flooded forest zone of the reservoir consist of endogenous primary producers; downstream, they are based on exogenous organic matter and microorganisms, mainly from the anoxic layers of the reservoir. Total mercury and MeHg concentrations in the biofilms and associated invertebrates were much higher at the downstream site compared to concentrations at the reservoir. Our results clearly show the importance of MeHg export from the anoxic layers of this tropical reservoir. We conclude that differences between biofilm composition and MeHg concentrations in the ingested food could explain the marked differences observed between mercury levels in fish.

  1. In vitro biofilm formation of commensal and pathogenic Escherichia coli strains: impact of environmental and genetic factors

    DEFF Research Database (Denmark)

    Reisner, A.; Krogfelt, Karen; Klein, B.M.

    2006-01-01

    Our understanding of Escherichia coli biofilm formation in vitro is based on studies of laboratory K-12 strains grown in standard media. However, pathogenic E. coli isolates differ substantially in their genetic repertoire from E. coli K-12 and are subject to heterogeneous environmental condition...

  2. Factors influencing electric utility expansion. Volume II

    Energy Technology Data Exchange (ETDEWEB)

    Masud, E. [ed.

    1977-01-01

    This report, Vol. 2, submitted by the General Electric Co., identifies factors that should be considered in planning interconnected systems and discusses how these factors relate to one another. The objective is to identify all the factors and classify them by their use and importance in arriving at a decision. Chapter 2 discusses the utility system and its system behavior characteristics, emphasizing behavior that affects the planning of the bulk-power generation and transmission system. Chapter 3 introduces interconnection planning by discussing the new system characteristics brought to operation and planning. Forty-two factors associated with cost, reliability, constraints, and coordination are related to each other by factor trees. Factor trees display the relationship of one factor such as reliability to more-detailed factors which in turn are further related to individual characteristics of facilities. These factor trees provide a structure to the presentation. A questionnaire including the 42 factors was completed by 52 system planners from utility companies and government authorities. The results of these questionnaires are tabulated and presented with pertinent discussion of each factor. Chapter 4 deals with generation planning, recognizing the existence of interconnections. Chapter 5 addresses transmission planning, questions related to reliability and cost measures and constraints, and factors related to both analytical techniques and planning procedures. The chapter ends with a discussion of combined generation-transmission planning. (MCW)

  3. SaeRS Is Responsive to Cellular Respiratory Status and Regulates Fermentative Biofilm Formation in Staphylococcus aureus.

    Science.gov (United States)

    Mashruwala, Ameya A; Gries, Casey M; Scherr, Tyler D; Kielian, Tammy; Boyd, Jeffrey M

    2017-08-01

    Biofilms are multicellular communities of microorganisms living as a quorum rather than as individual cells. The bacterial human pathogen Staphylococcus aureus uses oxygen as a terminal electron acceptor during respiration. Infected human tissues are hypoxic or anoxic. We recently reported that impaired respiration elicits a programmed cell lysis (PCL) phenomenon in S. aureus leading to the release of cellular polymers that are utilized to form biofilms. PCL is dependent upon the AtlA murein hydrolase and is regulated, in part, by the SrrAB two-component regulatory system (TCRS). In the current study, we report that the SaeRS TCRS also governs fermentative biofilm formation by positively influencing AtlA activity. The SaeRS-modulated factor fibronectin-binding protein A (FnBPA) also contributed to the fermentative biofilm formation phenotype. SaeRS-dependent biofilm formation occurred in response to changes in cellular respiratory status. Genetic evidence presented suggests that a high cellular titer of phosphorylated SaeR is required for biofilm formation. Epistasis analyses found that SaeRS and SrrAB influence biofilm formation independently of one another. Analyses using a mouse model of orthopedic implant-associated biofilm formation found that both SaeRS and SrrAB govern host colonization. Of these two TCRSs, SrrAB was the dominant system driving biofilm formation in vivo We propose a model wherein impaired cellular respiration stimulates SaeRS via an as yet undefined signal molecule(s), resulting in increasing expression of AtlA and FnBPA and biofilm formation. Copyright © 2017 American Society for Microbiology.

  4. Community Factors Influencing Birth Spacing among Married ...

    African Journals Online (AJOL)

    AJRH Managing Editor

    outcomes. This study investigates community-level influences on birth spacing outcomes among women aged 15-49 in Uganda ...... childhood stunting in nigeria: A multilevel analysis. ... Equity monitoring for social marketing: Use of wealth.

  5. Dermal factors influencing measurement of skin autofluorescence

    NARCIS (Netherlands)

    Noordzij, Margaretha J.; Lefrandt, Johan; Graaff, Reindert; Smit, Andries J.

    Background: Skin autofluorescence (SAF) is a noninvasive marker of accumulation of advanced glycation end products. It predicts cardiovascular complications and mortality in diabetes and renal failure. We assessed the influence of potential common confounders in SAF measurement, by determining the

  6. A mucosal model to study microbial biofilm development and anti-biofilm therapeutics

    Science.gov (United States)

    Anderson, Michele J.; Parks, Patrick J.; Peterson, Marnie L.

    2013-01-01

    Biofilms are a sessile colony of bacteria which adhere to and persist on surfaces. The ability of bacteria to form biofilms is considered a virulence factor, and in fact is central to the pathogenesis of some organisms. Biofilms are inherently resistant to chemotherapy and host immune responses. Clinically, biofilms are considered a primary cause of a majority of infections, such as otitis media, pneumonia in cystic fibrosis patients and endocarditis. However, the vast majority of the data on biofilm formation comes from traditional microtiter-based or flow displacement assays with no consideration given to host factors. These assays, which have been a valuable tool in high-throughput screening for biofilm-related factors, do not mimic a host-pathogen interaction and may contribute to an inappropriate estimation of the role of some factors in clinical biofilm formation. We describe the development of a novel ex vivo model of biofilm formation on a mucosal surface by an important mucosal pathogen, methicillin resistant S. aureus (MRSA). This model is being used for the identification of microbial virulence factors important in mucosal biofilm formation and novel anti-biofilm therapies. PMID:23246911

  7. Socio-economic, cultural and livelihood factors influencing local ...

    African Journals Online (AJOL)

    Socio-economic, cultural and livelihood factors influencing local people ... The social and economic circumstances prevailing in Tanzania today have made ... sociocultural and livelihood factors that influence community participation in ... Increased capacity for conservation skills was the most important driver of community ...

  8. Analysis of Factors Influencing Farmers’ Identification of Entrepreneurial Opportunity

    Institute of Scientific and Technical Information of China (English)

    Jing; GAO; Fang; YANG

    2013-01-01

    Based on the survey data of entrepreneurship concerning farmers in China,this article uses the multivariate adjustment regression analysis method,to analyze the factors influencing farmers’ identification of entrepreneurial opportunity and the mechanism. The results show that demographic characteristics are still an important factor influencing farmers’ identification of entrepreneurial opportunity,but the extent of its influence is weaker than entrepreneurs’ trait. The new trait theory is verified in farmers’ entrepreneurship opportunity behavior; entrepreneurship environment is becoming an important factor influencing entrepreneurial opportunity identification,whose regulation effect on entrepreneurs’ social network and previous experience is stronger than the regulation effect on entrepreneurs’ psychological trait.

  9. Effect of Negative Pressure on Proliferation, Virulence Factor Secretion, Biofilm Formation, and Virulence-Regulated Gene Expression of Pseudomonas aeruginosa In Vitro

    Directory of Open Access Journals (Sweden)

    Guo-Qi Wang

    2016-01-01

    Full Text Available Objective. To investigate the effect of negative pressure conditions induced by NPWT on P. aeruginosa. Methods. P. aeruginosa was cultured in a Luria–Bertani medium at negative pressure of −125 mmHg for 24 h in the experimental group and at atmospheric pressure in the control group. The diameters of the colonies of P. aeruginosa were measured after 24 h. ELISA kit, orcinol method, and elastin-Congo red assay were used to quantify the virulence factors. Biofilm formation was observed by staining with Alexa Fluor® 647 conjugate of concanavalin A (Con A. Virulence-regulated genes were determined by quantitative RT-PCR. Results. As compared with the control group, growth of P. aeruginosa was inhibited by negative pressure. The colony size under negative pressure was significantly smaller in the experimental group than that in the controls (p<0.01. Besides, reductions in the total amount of virulence factors were observed in the negative pressure group, including exotoxin A, rhamnolipid, and elastase. RT-PCR results revealed a significant inhibition in the expression level of virulence-regulated genes. Conclusion. Negative pressure could significantly inhibit the growth of P. aeruginosa. It led to a decrease in the virulence factor secretion, biofilm formation, and a reduction in the expression level of virulence-regulated genes.

  10. Fremmedlegemeinfektioner--nyt om biofilm og quorum sensing

    DEFF Research Database (Denmark)

    Høiby, Niels; Johansen, Helle Krogh; Ciofu, Oana

    2007-01-01

    Biofilms are structured consortia of bacteria embedded in self-produced polymer matrix. Biofilms are resistant to antibiotics, disinfectives and phagocytosis. The persistence of foreign body infections is due to biofilms. Chronic P. aeruginosa lung infection in cystic fibrosis patients is a biofilm....... Bacteria in biofilms communicate by means of quorum sensing which activates genes for virulence factors. Biofilms can be prevented by antibiotic prophylaxis or early therapy or by quorum sensing inhibitors which make them susceptible to antibiotics and phagocytosis. Udgivelsesdato: 2007-Nov-26...

  11. FACTORS INFLUENCING FRICTION OF PHOSPHATE COATINGS,

    Science.gov (United States)

    surface roughness, crystalline structure , and velocity. The coefficients of friction for manganese phosphate coatings did not differ to any practical...The coefficient of friction was independent of the applied load. Velocity during dynamic testing, surface finish, and crystalline structure influenced

  12. Dermal factors influencing measurement of skin autofluorescence

    NARCIS (Netherlands)

    Noordzij, Margaretha J.; Lefrandt, Johan; Graaff, Reindert; Smit, Andries J.

    2011-01-01

    Background: Skin autofluorescence (SAF) is a noninvasive marker of accumulation of advanced glycation end products. It predicts cardiovascular complications and mortality in diabetes and renal failure. We assessed the influence of potential common confounders in SAF measurement, by determining the e

  13. Biofilm characteristics of Staphylococcus epidermidis isolates associated with device-related meningitis.

    LENUS (Irish Health Repository)

    Stevens, Niall T

    2009-07-01

    Staphylococcus epidermidis biofilm causes device-related meningitis in neurosurgical patients. This study assessed the contribution of polysaccharide and protein to the development of a strong biofilm-positive phenotype in four S. epidermidis isolates associated with probable device-related meningitis, under varying environmental conditions. RT-PCR analysis of the intercellular adhesion operon (icaADBC) and assessment of polysaccharide intercellular adhesin (PIA) production indicated a correlation between increased icaA transcription and PIA production in ica(+) isolates grown in medium with 4 % ethanol and 4 % NaCl. Treatment of biofilm with sodium metaperiodate caused dispersion of adhered cells (P <0.0001), indicating involvement of PIA. Transcriptional levels of protein factors revealed that atlE transcription levels were similar in all isolates, whilst aap levels were variable, with induction being seen in two isolates following growth in the presence of alcohol or salt. Transcription of agr did not influence protein expression and RNAIII transcription varied among the strains. Although aap transcription was induced, the treatment of biofilm with proteinase K did not always disperse the biofilm. Our data suggest that, among the three ica(+) S. epidermidis isolates clinically associated with meningitis that were studied, PIA contributed to the strong biofilm-positive phenotype, whereas protein factors appeared to have a secondary role.

  14. Estudo dos fatores de virulência associados à formação de biofilme e agrupamento filogenético em Escherichia coli isoladas de pacientes com cistite Study on virulence factors associated with biofilm formation and phylogenetic groupings in Escherichia coli strains isolated from patients with cystitis

    Directory of Open Access Journals (Sweden)

    Monique Ribeiro Tiba

    2009-02-01

    Full Text Available Amostras de Escherichia coli, isoladas de pacientes do sexo feminino com quadro clínico de cistite, foram caracterizadas quanto à presença de fatores de virulência associados à formação de biofilme e ao agrupamento filogenético. Os resultados da reação em cadeia da polimerase demonstraram que todas as amostras foram positivas para o gene fimH (fímbria do tipo1, 91 amostras foram positivas para o gene fliC (flagelina 50 amostras positivas para o gene papC (fímbria P, 44 amostras positivas para o gene kpsMTII (cápsula e 36 amostras positivas para o gene flu (antígeno 43. Os resultados dos ensaios de quantificação da formação de biofilme demonstraram que 44 amostras formaram biofilme em microplacas de poliestireno e 56 amostras apresentaram resultado ausente/fraco. Também confirmamos a incidência das amostras de Escherichia coli no grupo filogenético B2 e D.Escherichia coli samples isolated from female patients with cystitis were characterized with regard to the presence of virulence factors associated with biofilm formation and phylogenetic groupings. Polymerase chain reaction results demonstrated that all the samples were positive for the gene fimH (type 1 fimbriae, 91 for fliC (flagellins, 50 for papC (P fimbriae, 44 for kpsMTII (capsules and 36 for flu (antigen 43. The results from assays to quantify the biofilm formation demonstrated that 44 samples produced biofilm on polystyrene microplates and 56 samples produced weak or no biofilm. We also confirmed that Escherichia coli samples were present in phylogenetic groups B2 and D.

  15. Factors influencing societal response of nanotechnology : an expert stakeholder analysis

    OpenAIRE

    2012-01-01

    Nanotechnology can be described as an emerging technology and, as has been the case with other emerging technologies such as genetic modification, different socio-psychological factors will potentially influence societal responses to its development and application. These factors will play an important role in how nanotechnology is developed and commercialised. This article aims to identify expert opinion on factors influencing societal response to applications of nanotechnology. Structured i...

  16. Factors Influencing Job Satisfaction among Army Chaplains

    Science.gov (United States)

    1976-05-20

    supported by Maslow’s need hierarchy, it is not substantiated by Herzberg’s Two Factor Theory. Still another approach is that of Leon Festinger’s...Herzberg, Vroom, McGregor, Lawler and Festinger provide a basic JWM » -, —_—^ . foundation and starting point for examining the factors of chaplain...identity, and autonomy, which are examined in this section. Further, Leon Festinger’s work on "cognitive dissonance" points toward the

  17. Factors influencing consumer dietary health preventative behaviours

    OpenAIRE

    Petrovici, Dan A.; Ritson, Christopher

    2006-01-01

    Background The deterioration of the health status of the Romanian population during the economic transition from a centrally planned to a free market economy has been linked to lifestyles factors (e.g. diet) regarded as a main determinants of the disparity in life expectancy between Eastern and Western Europe. Reforms in the health care system in this transition economy aim to focus on preventive action. The purpose of this study was to identify the factors that impact on the individual decis...

  18. Bifidobacterium spp. influences the production of autoinducer-2 and biofilm formation by Escherichia coli O157:H7.

    Science.gov (United States)

    Kim, Younghoon; Lee, Jae Won; Kang, Seo-Gu; Oh, Sejong; Griffiths, Mansel W

    2012-10-01

    The effect of Bifidobacterium spp. on the production of quorum-sensing (QS) signals and biofilm formation by enterohemorrhagic Escherichia coli (EHEC) O157:H7 was investigated. In an AI-2 bioassay, cell extracts of Bifidobacterium longum ATCC 15707 resulted in a 98-fold reduction in AI-2 activity in EHEC O157:H7 as well as in the Vibrio harveyi reporter strain, even though they did not inhibit the growth of EHEC O157:H7. In addition, they resulted in a 36% reduction in biofilm formation by the organism. Consistently, the virulence of EHEC O157:H7 was significantly attenuated by the presence of cell extracts of B. longum ATCC 15707 in the Caenorhabditis elegans nematode in vivo model. By a proteome analysis using two dimensional electrophoresis (2-DE), we determined that seven proteins including formation of iron-sulfur protein (NifU), thiol:disulfide interchange protein (DsbA), and flagellar P-ring protein (FlgI) were differentially regulated in the EHEC O157:H7 when supplemented with cell extracts of B. longum ATCC 15707. Taken together, these findings propose a novel function of a dairy adjunct in repressing the virulence of EHEC O157:H7.

  19. Antifouling Coatings Influence both Abundance and Community Structure of Colonizing Biofilms: a Case Study in the Northwestern Mediterranean Sea

    Science.gov (United States)

    Camps, Mercedes; Barani, Aude; Gregori, Gérald; Bouchez, Agnès; Le Berre, Brigitte; Bressy, Christine; Blache, Yves

    2014-01-01

    When immersed in seawater, substrates are rapidly colonized by both micro- and macroorganisms. This process is responsible for important economic and ecological prejudices, particularly when related to ship hulls or aquaculture nets. Commercial antifouling coatings are supposed to reduce biofouling, i.e., micro- and macrofoulers. In this study, biofilms that primarily settled on seven different coatings (polyvinyl chloride [PVC], a fouling release coating [FRC], and five self-polishing copolymer coatings [SPC], including four commercial ones) were quantitatively studied, after 1 month of immersion in summer in the Toulon Bay (Northwestern Mediterranean Sea, France), by using flow cytometry (FCM), microscopy, and denaturing gradient gel electrophoresis. FCM was used after a pretreatment to separate cells from the biofilm matrix, in order to determine densities of heterotrophic bacteria, picocyanobacteria, and pico- and nanoeukaryotes on these coatings. Among diatoms, the only microphytobenthic class identified by microscopy, Licmophora, Navicula, and Nitzschia were determined to be the dominant taxa. Overall, biocide-free coatings showed higher densities than all other coatings, except for one biocidal coating, whatever the group of microorganisms. Heterotrophic bacteria always showed the highest densities, and diatoms showed the lowest, but the relative abundances of these groups varied depending on the coating. In particular, the copper-free SPC failed to prevent diatom settlement, whereas the pyrithione-free SPC exhibited high picocyanobacterial density. These results highlight the interest in FCM for antifouling coating assessment as well as specific selection among microbial communities by antifouling coatings. PMID:24907329

  20. Influence of Nutritional Factors on Lipid Metabolism.

    Science.gov (United States)

    1980-12-01

    conditions of chronic high level fat oxidation such as exercise, Askew et al. (121) fed exercising rats diets supplemented with 0.5Z L- carnitine . Although...exercise increased adipose tissue fatty acid turnover, supplemental dietary carnitine neither increased skeletal muscle in vitro fatty acid oxidation...some investigators believe the relative activities of the sn-glycerolphosphate acyltransferase and carnitine palmttyltrans- ferase may influence the

  1. Dermal factors influencing measurement of skin autofluorescence.

    Science.gov (United States)

    Noordzij, Margaretha J; Lefrandt, Joop D; Graaff, Reindert; Smit, Andries J

    2011-02-01

    Skin autofluorescence (SAF) is a noninvasive marker of accumulation of advanced glycation end products. It predicts cardiovascular complications and mortality in diabetes and renal failure. We assessed the influence of potential common confounders in SAF measurement, by determining the effects of endogenous and exogenous local dermal changes by body creams, hyperemia, vasoconstriction, and hydration. SAF was measured before and after local administration of body lotion, day cream, sunscreen, or self-browning cream and after attempts to remove these effects with alcohol swabs and washing. SAF was measured before and during three hyperemia maneuvers: vasoconstriction and on a dry and wet skin. The body lotion increased SAF by 18%. Day cream, sunscreen, and self-browning cream gave an increase of >100%. Except for body lotion, subsequent cleaning with alcohol swabs and washing with soap did not return SAF to baseline values. The effect of self-browning cream persisted for 2 weeks and that of sunscreen for 4 days. Hyperemia caused by a hot bath, capsicum cream, or postocclusive reactive hyperemia gave a decrease in SAF of, respectively, 18%, 22%, and 2.3%. Vasoconstriction caused by immersing the arm in cold water gave a 10% increase. Hydration state did not influence SAF. Measurement of SAF is strongly affected by several skin creams. This effect was often not fully corrected by alcohol swabs and washing with soap and may persist for many days. Marked hyperemia and vasoconstriction also influence SAF. We advise avoiding these potential error sources.

  2. Choice of treatment with antidepressants: influencing factors.

    Science.gov (United States)

    Himmerich, Hubertus; Wranik, Dominika W

    2012-01-01

    Depressive disorders place a large burden on patients and on society. Although efficacious treatment options for unipolar depressive disorders exist, substantial gaps in care remain. In part, the challenge lies in the matching of individual patients with appropriate care. This is complicated by the steady increases in the variety of antidepressants available in the market. The goal of this study is to highlight the decision processes in the selection of antidepressants by clinicians, given that most treatments have similar clinical effectiveness profiles. We conducted a systematic literature review of studies that referred to the decisions surrounding treatment with antidepressants for the treatment of non-psychotic unipolar depression. Our analysis of the literature reveals that the choice of treatment is based on a variety of factors, of which clinical evidence is only one. These factors can be categorized into clinical factors such as illness and treatment characteristics, individual factors such as patient and physician characteristics, and contextual factors such as setting characteristics, decision supports and pharmacoeconomic aspects. Illness characteristics are defined by the type and severity of depression. Treatment characteristics include drug properties, efficacy, effectiveness and favorable as well as unintended adverse effects of the drug. Examples for patient characteristics are co-morbidities and individual preferences, and physician characteristics include knowledge, experience, values and beliefs, and the relationship with the patient. Treatment guidelines, algorithms, and most recently, computational supports and biological markers serve as decision supports.

  3. Innovative Strategies to Overcome Biofilm Resistance

    Directory of Open Access Journals (Sweden)

    Aleksandra Taraszkiewicz

    2013-01-01

    Full Text Available We review the recent literature concerning the efficiency of antimicrobial photodynamic inactivation toward various microbial species in planktonic and biofilm cultures. The review is mainly focused on biofilm-growing microrganisms because this form of growth poses a threat to chronically infected or immunocompromised patients and is difficult to eradicate from medical devices. We discuss the biofilm formation process and mechanisms of its increased resistance to various antimicrobials. We present, based on data in the literature, strategies for overcoming the problem of biofilm resistance. Factors that have potential for use in increasing the efficiency of the killing of biofilm-forming bacteria include plant extracts, enzymes that disturb the biofilm structure, and other nonenzymatic molecules. We propose combining antimicrobial photodynamic therapy with various antimicrobial and antibiofilm approaches to obtain a synergistic effect to permit efficient microbial growth control at low photosensitizer doses.

  4. Effects of low arsenic concentration exposure on freshwater fish in the presence of fluvial biofilms.

    Science.gov (United States)

    Tuulaikhuu, Baigal-Amar; Bonet, Berta; Guasch, Helena

    2016-02-15

    Arsenic (As) is a highly toxic element and its carcinogenic effect on living organisms is well known. However, predicting real effects in the environment requires an ecological approach since toxicity is influenced by many environmental and biological factors. The purpose of this paper was to evaluate if environmentally-realistic arsenic exposure causes toxicity to fish. An experiment with four different treatments (control (C), biofilm (B), arsenic (+As) and biofilm with arsenic (B+As)) was conducted and each one included sediment to enhance environmental realism, allowing the testing of the interactive effects of biofilm and arsenic on the toxicity to fish. Average arsenic exposure to Eastern mosquitofish (Gambusia holbrooki) was 40.5 ± 7.5 μg/L for +As treatment and 34.4 ± 1.4 μg/L for B+As treatment for 56 days. Fish were affected directly and indirectly by this low arsenic concentration since exposure did not only affect fish but also the function of periphytic biofilms. Arsenic effects on the superoxide dismutase (SOD) and glutathione reductase (GR) activities in the liver of mosquitofish were ameliorated in the presence of biofilms at the beginning of exposure (day 9). Moreover, fish weight gaining was only affected in the treatment without biofilm. After longer exposure (56 days), effects of exposure were clearly seen. Fish showed a marked increase in the catalase (CAT) activity in the liver but the interactive influence of biofilms was not further observed since the arsenic-affected biofilm had lost its role in water purification. Our results highlight the interest and application of incorporating some of the complexity of natural systems in ecotoxicology and support the use of criterion continuous concentration (CCC) for arsenic lower than 150 μg/L and closer to the water quality criteria to protect aquatic life recommended by the Canadian government which is 5 μg As/L.

  5. Factors influencing quality of life in asthmatics

    DEFF Research Database (Denmark)

    Al-kalemji, Abir; Petersen, Karin Dam; Sørensen, Jan

    2013-01-01

    INTRODUCTION: The quality of life (QOL) in persons with asthma is reduced and different factors such as demography, asthma severity and psychiatric comorbidity play an influential role. However, little is known about the interplay of these factors. OBJECTIVE: To describe QOL in relation to asthma...... and analyse for the relative impact of asthma severity, psychiatric comorbidity, lifestyle (smoking and obesity) and demographic determinants on QOL in persons with asthma. METHODS: One thousand one hundred sixty-one subjects from an earlier cohort with and without asthma were sent an asthma screening...... gender and smoking were associated with reduced QOL, suggesting that these factors play an independent role on lowering QOL. Depression did not inflate the relationship between asthma severity and worse QOL, suggesting that asthma severity plays an independent role on everyday life regardless...

  6. Sodium Lactate Negatively Regulates Shewanella putrefaciens CN32 Biofilm Formation via a Three-Component Regulatory System (LrbS-LrbA-LrbR).

    Science.gov (United States)

    Liu, Cong; Yang, Jinshui; Liu, Liang; Li, Baozhen; Yuan, Hongli; Liu, Weijie

    2017-07-15

    The capability of biofilm formation has a major impact on the industrial and biotechnological applications of Shewanella putrefaciens CN32. However, the detailed regulatory mechanisms underlying biofilm formation in this strain remain largely unknown. In the present report, we describe a three-component regulatory system which negatively regulates the biofilm formation of S. putrefaciens CN32. This system consists of a histidine kinase LrbS (Sputcn32_0303) and two cognate response regulators, including a transcription factor, LrbA (Sputcn32_0304), and a phosphodiesterase, LrbR (Sputcn32_0305). LrbS responds to the signal of the carbon source sodium lactate and subsequently activates LrbA. The activated LrbA then promotes the expression of lrbR, the gene for the other response regulator. The bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) phosphodiesterase LrbR, containing an EAL domain, decreases the concentration of intracellular c-di-GMP, thereby negatively regulating biofilm formation. In summary, the carbon source sodium lactate acts as a signal molecule that regulates biofilm formation via a three-component regulatory system (LrbS-LrbA-LrbR) in S. putrefaciens CN32.IMPORTANCE Biofilm formation is a significant capability used by some bacteria to survive in adverse environments. Numerous environmental factors can affect biofilm formation through different signal transduction pathways. Carbon sources are critical nutrients for bacterial growth, and their concentrations and types significantly influence the biomass and structure of biofilms. However, knowledge about the underlying mechanism of biofilm formation regulation by carbon source is still limited. This work elucidates a modulation pattern of biofilm formation negatively regulated by sodium lactate as a carbon source via a three-component regulatory system in S. putrefaciens CN32, which may serve as a good example for studying how the carbon sources impact biofilm development in other bacteria. Copyright

  7. Factors influencing nurses' participation in clinical research.

    Science.gov (United States)

    Jacobson, Ann F; Warner, Andrea M; Fleming, Eileen; Schmidt, Bruce

    2008-01-01

    Clinical research is necessary for developing nursing's body of knowledge and improving the quality of gastroenterology nursing care. The support and participation of nursing staff are crucial to conducting interventional research. Identification of characteristics of nurses and their work settings that facilitate or impede participation in research is needed. The purpose of this descriptive correlational study was to examine the effect of personal and professional characteristics and attitudes about nursing research on staff nurses' participation in a clinical nursing research project. A questionnaire measuring nurses' attitudes, perceptions of availability of support, and research use was distributed to staff nurses working on an endoscopy lab and two same-day surgery units where a nursing research study had recently been conducted. Investigator-developed items measured nurses' attitudes about the utility and feasibility of the interventions tested in the original study. A total of 36 usable questionnaires comprised the sample. Factor analysis of the two questionnaires resulted in three-factor (Importance of Research, Interest in Research, and Environment Support of Research) and two-factor (Value of Cognitive-Behavioral Interventions [CBIs] and Participation in Study) solutions, respectively. There were no statistically significant differences in mean scores for the five factors between nurses who did (n = 19) and those who did not (n = 17) participate in the original study. The Participation in Research Factor was significantly negatively correlated with years in nursing (r = -.336, p body of knowledge about factors that facilitate or impede staff nurses' involvement in research. This knowledge will be useful for nurse researchers planning intervention studies to forecast and foster staff nurse involvement in their projects. Findings may also be useful to nurse managers, nurse educators, and staff development personnel in assessing and promoting staff nurses

  8. Influencing factors of infrared surveying in roadway

    Institute of Scientific and Technical Information of China (English)

    CAI Kang-xu; GUO Da

    2006-01-01

    The main factors that affect infrared surveying in roadway include that property of rock, electromechanical equipments running, environmental temperature, hydrogeology and support material etc. This paper sums up the expression features of these disturbing factor through theoretical analysis and actual measurement contrasts and considers that some tunnel section does not suit to go on infrared survey, for instance, soft rock meets water to expanse, and surround rock has obviously pouring water. The basic methods had made evading disturbing of electromechanical equipments, environmental temperature and protect material etc to become possible. It is helpful that offers infrared surveying technical service for production safety better in roadway.

  9. Emergency department crowding: Factors influencing flow

    NARCIS (Netherlands)

    van der Linden, M.C.

    2015-01-01

    This thesis focuses on emergency department (ED) crowding. In the first part (ED crowding in the Netherlands) the current state of EDs regarding patients’ length of stay and ED managers’ experiences of crowding are described. Part two (input factors) contains three studies which describe the case lo

  10. Biofilm and siderophore effects on secondary waste water disinfection.

    Science.gov (United States)

    Saidi, N; Kouki, S; Mehri, I; Ben Rejeb, A; Belila, A; Hassen, A; Ouzari, H

    2011-10-01

    The efficiency of ultraviolet (UV) light disinfection of wastewater effluent using a large-scale pilot system was studied. The relationship between biofilm and siderophore production and UV doses received by Pseudomonas aeruginosa strain ATCC 15442 was determined. UV decreased pyoverdine production and enhanced biofilm production. Consequently external factors conditioned by both pyoverdine and biofilm may affect the UV effect on bacterial disinfection.

  11. [Factors that influence student ratings of instruction].

    Science.gov (United States)

    Chae, Su Jin; Choung, Yun Hoon; Chung, Yoon Sok

    2015-03-01

    The purpose of this study was to examine the validity of student ratings of instruction by analyzing their relationships with several variables, including gender, academic rank, specialty, teaching time, and teaching method, at a medical school. This study analyzed the student ratings of 297 courses at Ajou University School of Medicine in 2013. SPSS version 12.0 was used to analyze the data and statistics by t-test, analysis of variance, and Scheffe test. There were no statistically significant differences in student ratings between gender, rank, and specialty. However, student ratings were significantly influenced by teaching times and methods (pStudent ratings were high for teaching times of 10 hours or more and small-group learning, compared with lectures. There was relatively mean differences in students ratings by teaching times, specialty and rank, although the difference in ratings was not statistically significant. Student ratings can be classified by teaching time and method for summative purposes. To apply student ratings to the evaluation of the performance of faculty, further studies are needed to analyze the variables that influence student ratings.

  12. A Candida albicans early stage biofilm detachment event in rich medium

    Directory of Open Access Journals (Sweden)

    Nantel Andre

    2009-02-01

    Full Text Available Abstract Background Dispersal from Candida albicans biofilms that colonize catheters is implicated as a primary factor in the link between contaminated catheters and life threatening blood stream infections (BSI. Appropriate in vitro C. albicans biofilm models are needed to probe factors that induce detachment events. Results Using a flow through system to culture C. albicans biofilms we characterized a detachment process which culminates in dissociation of an entire early stage biofilm from a silicone elastomer surface. We analyzed the transcriptome response at time points that bracketed an abrupt transition in which a strong adhesive association with the surface is weakened in the initial stages of the process, and also compared batch and biofilm cultures at relevant time points. K means analysis of the time course array data revealed categories of genes with similar patterns of expression that were associated with adhesion, biofilm formation and glycoprotein biosynthesis. Compared to batch cultures the biofilm showed a pattern of expression of metabolic genes that was similar to the C. albicans response to hypoxia. However, the loss of strong adhesion was not obviously influenced by either the availability of oxygen in the medium or at the silicone elastomer surface. The detachment phenotype of mutant strains in which selected genes were either deleted or overexpressed was characterized. The microarray data indicated that changes associated with the detachment process were complex and, consistent with this assessment, we were unable to demonstrate that transcriptional regulation of any single gene was essential for loss of the strong adhesive association. Conclusion The massive dispersal of the early stage biofilm from a biomaterial surface that we observed is not orchestrated at the level of transcriptional regulation in an obvious manner, or is only regulated at this level by a small subpopulation of cells that mediate adhesion to the

  13. Aspartate inhibits Staphylococcus aureus biofilm formation.

    Science.gov (United States)

    Yang, Hang; Wang, Mengyue; Yu, Junping; Wei, Hongping

    2015-04-01

    Biofilm formation renders Staphylococcus aureus highly resistant to conventional antibiotics and host defenses. Four D-amino acids (D-Leu, D-Met, D-Trp and D-Tyr) have been reported to be able to inhibit biofilm formation and disassemble established S. aureus biofilms. We report here for the first time that both D- and L-isoforms of aspartate (Asp) inhibited S. aureus biofilm formation on tissue culture plates. Similar biofilm inhibition effects were also observed against other staphylococcal strains, including S. saprophyticus, S. equorum, S. chromogenes and S. haemolyticus. It was found that Asp at high concentrations (>10 mM) inhibited the growth of planktonic N315 cells, but at subinhibitory concentrations decreased the cellular metabolic activity without influencing cell growth. The decreased cellular metabolic activity might be the reason for the production of less protein and DNA in the matrix of the biofilms formed in the presence of Asp. However, varied inhibition efficacies of Asp were observed for biofilms formed by clinical staphylococcal isolates. There might be mechanisms other than decreasing the metabolic activity, e.g. the biofilm phenotypes, affecting biofilm formation in the presence of Asp.

  14. Focus on the physics of biofilms

    Science.gov (United States)

    Lecuyer, Sigolene; Stocker, Roman; Rusconi, Roberto

    2015-03-01

    Bacteria are the smallest and most abundant form of life. They have traditionally been considered as primarily planktonic organisms, swimming or floating in a liquid medium, and this view has shaped many of the approaches to microbial processes, including for example the design of most antibiotics. However, over the last few decades it has become clear that many bacteria often adopt a sessile, surface-associated lifestyle, forming complex multicellular communities called biofilms. Bacterial biofilms are found in a vast range of environments and have major consequences on human health and industrial processes, from biofouling of surfaces to the spread of diseases. Although the study of biofilms has been biologists’ territory for a long time, a multitude of phenomena in the formation and development of biofilms hinges on physical processes. We are pleased to present a collection of research papers that discuss some of the latest developments in many of the areas to which physicists can contribute a deeper understanding of biofilms, both experimentally and theoretically. The topics covered range from the influence of physical environmental parameters on cell attachment and subsequent biofilm growth, to the use of local probes and imaging techniques to investigate biofilm structure, to the development of biofilms in complex environments and the modeling of colony morphogenesis. The results presented contribute to addressing some of the major challenges in microbiology today, including the prevention of surface contamination, the optimization of biofilm disruption methods and the effectiveness of antibiotic treatments.

  15. Factors influencing women's attitudes towards midwifery: Tool validation.

    Science.gov (United States)

    Al-Rajabi, Omaymah; Al-Hadid, Lourance; Subih, Maha

    2015-10-01

    The purpose of this study was to validate a tool that explores the factors influencing women's opinion of and attitudes towards midwifery. A descriptive, cross-sectional design was used. The sample consisted of 526 Jordanian women. Cluster sampling was used to ensure a representative sample; then, convenience sampling was performed. The instrument asked non-identifying demographic questions and covered factors reported in literature to influence women's attitudes towards and views of the profession. The resulting instrument consisted of five factors explained by 29 items. These factors were women's general view of midwives, midwife duties, professional ethics, media influence and demotivating factors associated with working as a midwife. Although the instrument is valid and reliable, it needs further testing in other studies. Taking the factors reported on by the present study into account in public policy-making could promote better understanding of midwifery and improve its status in the community. © 2014 Wiley Publishing Asia Pty Ltd.

  16. Factors influencing medication label viewing in Malaysia.

    Science.gov (United States)

    Cheah, Yong Kang; Chong, Yen Wan

    2016-07-12

    The misuse of medicine is a serious public health issue worldwide. An important factor that contributes to the misuse of medicine is the lack of medication label viewing by consumers. The objective of the present study is to examine the socio-economic, demographic and lifestyle factors associated with medication label viewing among Malaysian adults. The empirical analysis is based on a nationally representative data set of 30,992 respondents. An ordered probit model is used to examine different types of medication label viewers. The results of this study suggest that socio-economic (i.e. age, income level, education level, location of residence), demographic (i.e. gender, ethnicity, marital status) and lifestyle factors (i.e. physical activity, smoking) have significant effects on medication label viewing. It is found that age, low-income and low-education level reduce the likelihood of viewing medication label. Based on these findings, several policy implications are suggested. The present study provides policy makers with baseline information regarding which cohorts of individuals to focus on in efforts to increase the frequency of medication label viewing.

  17. Factors influencing early survival after liver transplantation.

    Science.gov (United States)

    Stock, P G; Estrin, J A; Fryd, D S; Payne, W D; Belani, K G; Elick, B A; Najarian, J S; Ascher, N L

    1989-02-01

    The purpose of this study was to analyze data from all adult and pediatric liver transplants performed between January 1, 1983 and January 15, 1986 at the University of Minnesota Hospital and identify perioperative variables that predict patient survival and could aid in patient selection. Charts, intraoperative anesthesia records, blood bank records, flow sheets, outpatient records, and autopsy reports were examined in 45 pediatric and 15 adult patients who underwent primary orthotopic liver transplantation. Analysis of the data can be summarized as follows: (1) Pediatric patients whose coagulation parameters could not be corrected prior to operation and who consequently required preoperative exchange transfusion had poorer outcomes than those not requiring an exchange to correct coagulation parameters. (2) The rapid infusion technique for massive blood transfusion resulted in significantly decreased blood loss and intraoperative blood product replacement. (3) Twenty-four hour postoperative factor V levels were good predictors of survival. Patients with poor factor V levels required rigorous replacement of coagulation factors. (4) Pediatric patients with uncorrectable coagulopathies requiring immediate postoperative exchange transfusion had extremely high mortality.

  18. Factors influencing recognition of interrupted speech.

    Science.gov (United States)

    Wang, Xin; Humes, Larry E

    2010-10-01

    This study examined the effect of interruption parameters (e.g., interruption rate, on-duration and proportion), linguistic factors, and other general factors, on the recognition of interrupted consonant-vowel-consonant (CVC) words in quiet. Sixty-two young adults with normal-hearing were randomly assigned to one of three test groups, "male65," "female65" and "male85," that differed in talker (male/female) and presentation level (65/85 dB SPL), with about 20 subjects per group. A total of 13 stimulus conditions, representing different interruption patterns within the words (i.e., various combinations of three interruption parameters), in combination with two values (easy and hard) of lexical difficulty were examined (i.e., 13×2=26 test conditions) within each group. Results showed that, overall, the proportion of speech and lexical difficulty had major effects on the integration and recognition of interrupted CVC words, while the other variables had small effects. Interactions between interruption parameters and linguistic factors were observed: to reach the same degree of word-recognition performance, less acoustic information was required for lexically easy words than hard words. Implications of the findings of the current study for models of the temporal integration of speech are discussed.

  19. Clinically important factors influencing endothelial function.

    Science.gov (United States)

    Vapaatalo, H; Mervaala, E

    2001-01-01

    The endothelium, a continuous cellular monolayer lining the blood vessels, has an enormous range of important homeostatic roles. It serves and participates in highly active metabolic and regulatory functions including control of primary hemostasis, blood coagulation and fibrinolysis, platelet and leukocyte interactions with the vessel wall, interaction with lipoprotein metabolism, presentation of histocompatibility antigens, regulation of vascular tone and growth and further of blood pressure. Many crucial vasoactive endogenous compounds like prostacyclin, thromboxane, nitric oxide, endothelin, angiotensin, endothelium derived hyperpolarizing factor, free radicals and bradykinin are formed in the endothelial cells to control the functions of vascular smooth muscle cells and of circulating blood cells. These versatile and complex systems and cellular interactions are extremely vulnerable. The balances may be disturbed by numerous endogenous and exogenous factors including psychological and physical stress, disease states characterized by vasospasm, inflammation, leukocyte and platelet adhesion and aggregation, thrombosis, abnormal vascular proliferation, atherosclerosis and hypertension. The endothelial cells are also the site of action of many drugs and exogenous toxic substances (e.g. smoking, alcohol). As markers and assays for endothelial dysfunction, direct measurement of nitric oxide, its metabolites from plasma and urine, functional measurement of vascular nitric oxide dependent responses and assay of different circulating markers have been used. In numerous pathological conditions (e.g. atherosclerosis, hypertension, congestive heart failure, hyperhomocysteinemia, diabetes, renal failure, transplantation, liver cirrhosis) endothelial dysfunction has been described to exist. Some of them, as well as hormonal and nutritional factors and drug treatment will be discussed in this short review.

  20. FocVel1 influences asexual production, filamentous growth, biofilm formation, and virulence in Fusarium oxysporum f. sp. cucumerinum

    Directory of Open Access Journals (Sweden)

    Li ePeiqian

    2015-05-01

    Full Text Available Velvet genes play critical roles in the regulation of diverse cellular processes. In current study, we identified the gene FocVel1, a homolog of Fusarium graminearum VelA, in the plant pathogenic fungus F. oxysporum f. sp. cucumerinum. This pathogen causes the destructive disease called cucumber Fusarium wilt, which severely affects the production and marketing of this vegetable worldwide. Transcript analyses revealed high expression of FocVel1 during conidiophore development. Disruption of the FocVel1 gene led to several phenotypic defects, including reduction in aerial hyphal formation and conidial production. The deletion mutant ⊿FocVel1 showed increased resistance to both osmotic stress and cell wall-damaging agents, but increased sensitivity to iprodione and prochloraz fungicides, which may be related to changes in cell wall components. In the process of biofilm formation in vitro, the mutant strain ⊿FocVel1 displayed not only a reduction in spore aggregation but also a delay in conidial germination on the polystyrene surface, which may result in defects in biofilm formation. Moreover, pathogenicity assays showed that the mutant ⊿FocVel1 exhibited impaired virulence in cucumber seedlings. And the genetic complementation of the mutant with the wild-type FocVel1 gene restored all the defects of the ⊿FocVel1. Taken together, the results of this study indicated that FocVel1 played a critical role in the regulation of various cellular processes and pathogenicity in F. oxysporum f. sp. cucumerinum.

  1. Factors Influencing the Performance of Coal Briquettes

    Directory of Open Access Journals (Sweden)

    Unsia HABIB

    2014-01-01

    Full Text Available The continuous supply of energy resources is essential for the development of any nation. The economic and social life of any nation depends enormously on the energy resources. Over the past few years the energy crisis is becoming a major issue in developing countries as Pakistan. Oil, Natural gas and hydro are the three major energy resources of the Pakistan. These conventional energy resources were being exploited in the past leading to an issue of energy crisis in the country. Replacing expensive imported energy resources with coal briquettes made from indigenous coal reserves can provide fuel for the local residential and commercial markets. Coal briquettes formation is a process to convert coal powder into a specific shape with the help of a binder. An external force is applied to the coal binder mixture to make a firm body of desired shape. The briquettes formed this way will not disintegrate under normal conditions of transportation and use. Coal briquettes are preferred over raw coal because they are a smokeless, strong and low emissive fuel that can be used in numerous domestic and commercial applications. The performance of coal briquettes formed is dependent largely upon its thermal properties and the mechanical strength. Nowadays an environmentally safe briquettes formation process is also included in the performance criteria of coal briquettes. The mechanical strength of coal briquettes affects its storage and transportation to the intended market. The studies on coal briquettes show that coal briquettes quality depends on many factors like the type of binder, quantity of binder, grade of coal, moisture level, coal particle size and its distribution etc. These factors along with some of the factors as time of compaction, compaction temperature, and compaction pressure and moisture level are discussed in this paper to evaluate the performance of briquetting technology in future.

  2. Organizational Culture Factors that Can Influence Knowledge Transfer

    Directory of Open Access Journals (Sweden)

    Ioan Pastor

    2011-05-01

    Full Text Available The paper tries to establish the correlation that exists between the types of organizational culture and the factors that influence knowledge transfer. We started from the hypothesis that organizations which have high scores for cultural factors of openness to change and innovation as well as for task-oriented organizational growth will have the tendency of being favourable to knowledge transfer. Moreover, we started from the hypothesis that organizations that have high scores for bureaucracy and competition factors will have the tendency of being unfavourable to knowledge transfer. The research reached the conclusion that there seems to be a correlation between organizational culture and the factors that influence knowledge transfer.

  3. Factors influencing condom use among Nigerian undergraduates: A ...

    African Journals Online (AJOL)

    Factors influencing condom use among Nigerian undergraduates: A mixed method study. ... PROMOTING ACCESS TO AFRICAN RESEARCH ... group discussions) and quantitative (cross-sectional survey) methods were utilised for this study.

  4. Social and economic factors influencing the patronage and use of ...

    African Journals Online (AJOL)

    Social and economic factors influencing the patronage and use of complementary and alternative medicine in Enugu. ... Journal of Pharmacy & Bioresources ... approaches to medical treatment that are outside of mainstream medical training.

  5. Personal and Socio-Economic Factors Influencing Female Choice of ...

    African Journals Online (AJOL)

    Personal and Socio-Economic Factors Influencing Female Choice of Courses in ... Female students in six (Arts, Education, Pharmacy, Science, Social Sciences and ... services to secondary school students in the choice of courses and career.

  6. Factors Influencing the Development of Practical Skills of Interns ...

    African Journals Online (AJOL)

    Factors Influencing the Development of Practical Skills of Interns Working in ... It starts with a good theoretical preparation and some practical experience at university. ... The relationship between intern and senior doctor was important when it ...

  7. Factors influencing the job satisfaction of academics in higher ...

    African Journals Online (AJOL)

    Factors influencing the job satisfaction of academics in higher education. ... 94 respondents from similar departments at a residential and a distance education institution. A questionnaire focused on teaching, research, community service, ...

  8. Assessment of risk factors that influence pregnancy outcomes in ...

    African Journals Online (AJOL)

    Keywords: Pregnancy outcome, low birth weight, Apgar score, maternal age, Tanzania ... (2006) reported that, several risk factors influence neonatal mortality. ..... which is the lowest cut off point for the classification of normal blood pressure.

  9. 'Mum never loved me.' How structural factors influence adolescent ...

    African Journals Online (AJOL)

    How structural factors influence adolescent sexual and reproductive health ... Research in high income countries shows parent–child connectedness to be ... to young people's low self-esteem and risky sexual behaviour while unplanned ...

  10. Analysis of Socio-Economic Factors Influencing Farmers' Adoption ...

    African Journals Online (AJOL)

    Analysis of Socio-Economic Factors Influencing Farmers' Adoption of Rice ... Farming experience, household size, farm size and extension contact ... gender, market availability, education, extension contact, labour availability and farm size.

  11. Factors Influencing Farmer Output in the International Fund for ...

    African Journals Online (AJOL)

    kim

    Department of Rural Sociology and Extension. Michael Okpara ... This study analysed factors influencing International Fund for Agricultural. Development ..... farmers (50.9%) acquired secondary education as against Cross River IFAD farmers.

  12. Factors Influencing the Consumption of Pulses in Rural and Urban ...

    African Journals Online (AJOL)

    Factors Influencing the Consumption of Pulses in Rural and Urban Areas of Tanzania. ... Model results revealed that household sizes and education levels of the ... To increase the market share of pulses, traders should devise effective ...

  13. Characteristics and factors influencing fast food intake of young ...

    African Journals Online (AJOL)

    Characteristics and factors influencing fast food intake of young adult consumers in Johannesburg, South Africa. ... their reasons for and frequency of fast food consumption, their specific fast food choices, and their attitudes towards health.

  14. LITERATURE REVIEW ON FACTORS INFLUENCING MILK PURCHASE BEHAVIOUR

    National Research Council Canada - National Science Library

    Klaudia Kurajdova; Janka Taborecka-Petrovicova

    2015-01-01

    In today’s highly informed, competitive and saturated market, a key to success of any business depends on knowing consumer and his consumption patterns and recognizing and understanding factors influencing...

  15. Socio-Demographic Factors Influencing Work-Role Salience Among ...

    African Journals Online (AJOL)

    Socio-Demographic Factors Influencing Work-Role Salience Among ... The findings showed that students from lower socio-economic status homes and those ... The need to involve the students\\' parents in career education programmes and ...

  16. Factors Influencing Food Choice in the Elderly Mauritian Population

    African Journals Online (AJOL)

    admpather

    Only the factor of taste influencing food choice was significantly different between the two ..... available through the media, promotions, and advertising may confuse consumers and cause ... Predictors of self-initiated, healthful dietary change.

  17. Factors Influencing the Consumption of Pulses in Rural and Urban ...

    African Journals Online (AJOL)

    factors that influenced the extent of consumption in urban areas. In summary, the model .... model to control for self-selection bias because some potential consumers may ... accommodate consumer's zero value of purchase as an outcome of a ...

  18. Factors influencing eating attitudes in secondary-school girls in ...

    African Journals Online (AJOL)

    Factors influencing eating attitudes in secondary-school girls in South Africa - a preliminary stud. ... PROMOTING ACCESS TO AFRICAN RESEARCH. AFRICAN JOURNALS ONLINE (AJOL) ... South African Medical Journal. Journal Home ...

  19. Factors influencing utilization of Natural Family Planning among ...

    African Journals Online (AJOL)

    Factors influencing utilization of Natural Family Planning among Child Bearing Women in Chilonga ... Medical Journal of Zambia ... The literature review was mainly obtained from studies conducted globally, regionally and Zambia inclusively.

  20. Factors influencing choice of paediatrics as a career among medical ...

    African Journals Online (AJOL)

    female students (30%) considered gender distribution to be a factor influencing their career choice (p=0.046). ... role models in the specialty, job opportunities and financial .... of non-responder bias, although the relatively high response.

  1. Prevalence Of Early Childhood Malnutrition And Influencing Factors ...

    African Journals Online (AJOL)

    therefore, to asses the prevalence of malnutrition and the factors influencing the ... childhood malnutrition in Kabarole District and other areas in Uganda, and ..... Jitta JJ, Migadde M and J Mudusu Determinants of Malnutrition in under-fives.

  2. INFLUENCING FACTORS OF PRICE AND ASSOCIATED STRATEGIES

    OpenAIRE

    Liviu NEAMTU; NEAMTU Adina Claudia

    2012-01-01

    The price is an important element in product position; it is a means of sending signals to consumers about the nature and quality of the product. When, for a certain business environment, the demand curve is known in relation to market (competition) costs and prices, the firm can choose a pricing policy simultaneously with business strategy. This study synthesizes the key-factors occurring in choosing a business strategy and the game of price and cost on the market As an approach to pricing p...

  3. Emotional Factors Influencing Students’ English Writing Competence

    Institute of Scientific and Technical Information of China (English)

    聂勇伟

    2015-01-01

    As an international common language,English becomes more and more important.Students try their best to improve their English writing competence,especially as the social’s requirements for their English writing become higher and higher.However,students’English writing is very poor,fewer and fewer of them can write fluent English.Through the study of this topic,the author hopes it can remove students’emotional obstacles of English writing learning,master the direction of emotional factor,arouse students’interesting in learning oral English,make them practice English writing positively and obtain a better teaching effect

  4. Treatment Factors That Influence Mortality in Acromegaly.

    Science.gov (United States)

    McCabe, John; Ayuk, John; Sherlock, Mark

    2016-01-01

    Acromegaly is a rare condition characterized by excessive secretion of growth hormone (GH), which is almost always due to a pituitary adenoma. Acromegaly is associated with significant morbidity such as hypertension, type 2 diabetes, cardiomyopathy, obstructive sleep apnoea, malignancy and musculoskeletal abnormalities. Acromegaly has also been associated with increased mortality in several retrospective studies. This review will focus on the epidemiological data relating to mortality rates in acromegaly, the relationship between acromegaly and malignancy, the role of GH and insulin-like growth factor-I in assessing the risk of future mortality, and the impact of radiotherapy and hypopituitarism on mortality.

  5. Biofilm and Dental Biomaterials

    Directory of Open Access Journals (Sweden)

    Marit Øilo

    2015-05-01

    Full Text Available All treatment involving the use of biomaterials in the body can affect the host in positive or negative ways. The microbiological environment in the oral cavity is affected by the composition and shape of the biomaterials used for oral restorations. This may impair the patients’ oral health and sometimes their general health as well. Many factors determine the composition of the microbiota and the formation of biofilm in relation to biomaterials such as, surface roughness, surface energy and chemical composition, This paper aims to give an overview of the scientific literature regarding the association between the chemical, mechanical and physical properties of dental biomaterials and oral biofilm formation, with emphasis on current research and future perspectives.

  6. Factors influencing consumer satisfaction with health care.

    Science.gov (United States)

    Deshpande, Satish P; Deshpande, Samir S

    2014-01-01

    The purpose of this study was to examine factors that impact consumer satisfaction with health care. This is a secondary analysis of the Center for Studying Health System Change's 2010 Health Tracking Household Survey. Regression analysis was used to examine the impact of treatment issues, financial issues, family-related issues, sources of health care information, location, and demographics-related factors on satisfaction with health care. The study involved 12280 subjects, 56% of whom were very satisfied with their health care, whereas 66% were very satisfied with their primary care physician. Fourteen percent of the subjects had no health insurance; 34% of the subjects got their health care information from the Web. Satisfaction with primary care physician, general health status, promptness of visit to doctor, insurance type, medical cost per family, annual income, persons in family, health care information from friends, and age significantly impacted satisfaction with health care. The regression models accounted for 23% of the variance in health care satisfaction. Satisfaction with primary care physicians, health insurance, and general health status are the 3 most significant indicators of an individual's satisfaction with health care.

  7. Factors influencing the intention to watch online video advertising.

    Science.gov (United States)

    Lee, Joonghwa; Lee, Mira

    2011-10-01

    This study examines the factors influencing consumer intention to watch online video ads, by applying the theory of reasoned action. The attitude toward watching online video ads, the subjective norm, and prior frequency of watching online video ads positively influence the intention to watch online video ads. Further, beliefs held about entertainment and information outcomes from watching online video ads and subjective norm influence attitude toward watching these ads.

  8. FACTORS INFLUENCING BRAND EQUITY OF BALI AS A TOURISM DESTINATION

    OpenAIRE

    I Ketut Surya Diarta; I Gde Pitana; Nyoman Darma Putra; Agung Suryawan Wiranatha

    2016-01-01

    Globally, competition among tourism destinations is more stringent in getting foreign tourists, including Bali. One effort to win the competition is increasing destination brand equity through maintaining its influencing factors and gaining tourist positive behavior toward destination. This effort, in long run, will increase and stabilize destination revenue and sustainability. This research aims to analyze factors influencing brand equity of Bali as a tourism destination. This research was c...

  9. Plaque biofilms: the effect of chemical environment on natural human plaque biofilm architecture.

    Science.gov (United States)

    Robinson, C; Strafford, S; Rees, G; Brookes, S J; Kirkham, J; Shore, R C; Watson, P S; Wood, S

    2006-11-01

    The architecture of microbial biofilms especially the outer regions have an important influence on the interaction between biofilm and local environment particularly on the flux of materials into and out of biofilm compartments and as a consequence, biofilm metabolic behaviour. In the case of dental plaque biofilms, architecture will determine access of nutrients including acidogenic substrates and therapeutic materials to the microbial biomass and to the underlying tooth surface. Manipulation of this architecture may offer a means of altering mass transfer into the whole biofilm and biomass and raises the possibility of improving access of therapeutics. Plaque biofilms formed in vivo on human enamel were subjected to a number of different chemical conditions while under observation by confocal laser scanning microscopy in reflection mode. In this way the outer 50-100 microm or so of the biofilms was examined. Density and distribution of biomass were recorded as degree of reflectance. The amount and density of biofilm biomass increased from the plaque saliva interface towards the interior. Plaque biofilms were robust and little affected by mechanical manipulation, high ionic strength or low pH (2.5). Detergent (SLS), however, often appeared to either remove biomass and/or dramatically reduce its density.

  10. Factors Influencing the Disabled's Employment in the Competitive Labour Market.

    Science.gov (United States)

    Mannila, Simo

    1995-01-01

    Factors influencing the job search outcomes of 1,353 Finnish individuals with disabilities were studied, focusing on age, gender, domicile, basic education, vocational training, and type of disability. Results showed that age, education, and domicile influenced outcomes, and labor market status was to some extent gender specific. (JDD)

  11. STUDY ON FACTORS INFLUENCING INK ABSORPTION OF COATED PAPER

    Institute of Scientific and Technical Information of China (English)

    Yanxin Liu; Chuanshan Zhao; Shuxia Shang; Zhongwei Sun

    2004-01-01

    Ink absorption is one of the most important factors which influence printing properties. This article had discussed the influence of coating properties,technologies of heating and pressure etc. on ink absorption and showed that ink absorption can be adjusted and coating surface structure can be improved when technologies of heating and pressure change, pigment and adhesive altered.

  12. Linguistic Factors Influencing Speech Audiometric Assessment.

    Science.gov (United States)

    Coene, Martine; Krijger, Stefanie; Meeuws, Matthias; De Ceulaer, Geert; Govaerts, Paul J

    2016-01-01

    In speech audiometric testing, hearing performance is typically measured by calculating the number of correct repetitions of a speech stimulus. We investigate to what extent the repetition accuracy of Dutch speech stimuli presented against a background noise is influenced by nonauditory processes. We show that variation in verbal repetition accuracy is partially explained by morpholexical and syntactic features of the target language. Verbs, prepositions, conjunctions, determiners, and pronouns yield significantly lower correct repetitions than nouns, adjectives, or adverbs. The reduced repetition performance for verbs and function words is probably best explained by the similarities in the perceptual nature of verbal morphology and function words in Dutch. For sentences, an overall negative effect of syntactic complexity on speech repetition accuracy was found. The lowest number of correct repetitions was obtained with passive sentences, reflecting the cognitive cost of processing a noncanonical sentence structure. Taken together, these findings may have important implications for the audiological practice. In combination with hearing loss, linguistic complexity may increase the cognitive demands to process sentences in noise, leading to suboptimal functional hearing in day-to-day listening situations. Using test sentences with varying degrees of syntactic complexity may therefore provide useful information to measure functional hearing benefits.

  13. Physical factors influence for biologic systems

    Science.gov (United States)

    Piruzyan, L. A.

    2005-08-01

    Physical methods are widely spread in diagnostics and therapy of different pathologies, especially in oncology. The application of lasers occurred to be the perspective approach for combined methods application in medicine. Our work is devoted to investigation of thermal effect of focused laser beam in the model of Garding-Passi melanoma and also to the study of free radicals activity after the radiation with non-focused laser beam. The histologic alterations correlated with theoretical calculations of temperature distribution in irradiated tissue for energies 30-60 J attracted our interest. The values of maximal temperatures in depths of tissue for energies 30-60 J were carried out. In the model of permanent magnetic field (PMF) effect for mice ascites sarcoma 37 we have showed the linear dependence of tumor growth inhibition from the period of PMF treatment. Simultaneously we investigated PMF influence for free radical"s (FR) concentrations in mice organs and tissues and potentially appearing questions of PMF effect for biopotential in connection with FR formation. We have also studied the alterations of K, Na and Ca ions concentrations in ascetic fluids after animal"s PMF treatment. We revealed some reasons of biopotential generation and concluded that biopotential is not the result of specific ions gradient only but its generation can be followed by free radicals states appearance and occurrence of semi-conductivity in biostructures.

  14. Biofilm Growth and Turbulence Effects on Stream Ecosystem Respiration: Measurement by Resazurin

    Science.gov (United States)

    Haggerty, R.; Ribot, M.; Singer, G. A.; Martí, E.; Argerich, A.; Battin, T. J.; Agell, G.

    2011-12-01

    Stream ecosystem respiration was quantified via resazurin reduction in a series of 6 flume experiments, with the purpose of understanding how respiration is influenced by biofilms and presence of bedforms that resulted in increased turbulence intensity. Two streamside flumes (40 m x 0.4 m) with were constructed and operated in parallel. The first flume had no bedforms and the second had 10-cm bedforms built of impermeable material with a wavelength of 1.0 m. The bedforms were covered with a monolayer of gravel. Stream water was flushed through the flumes with a velocity of ~0.069 m/s. Ecosystem respiration was measured via resazurin transformation to resorufin. Three sets of experiments were conducted in each flume, one with minimal biofilms, one with 10 days of biofilm growth, and one with 30 days of biofilm growth. Velocity measurements were made throughout the flumes with acoustic Doppler velocimetry. Ecosystem respiration varied by a factor of 2.25 among the experiments. Respiration was nearly perfectly correlated (r2 = 0.99) to a combination of biofilm mass and turbulence intensity, with biofilm mass explaining 91% of the variation and turbulence intensity explaining the remainder of the variation.

  15. Exploring factors influencing smoking behaviour in Malaysia.

    Science.gov (United States)

    Cheah, Yong Kang; Naidu, Balkish Mahadir

    2012-01-01

    The objective of present study is to investigate the determinants of smoking behaviour among adults in Malaysia. Findings of the Third National Health and Morbidity Survey (NHMS-3) by the Ministry of Health, Malaysia, were used. The sample consisted of 34,539 observations. A logistic regression model was thus applied to estimate the probability to participate in smoking. Age, income, gender, marital status, ethnicity, employment status, residential area, education, lifestyle and health status were statistically significant in affecting the likelihood of smoking. Specifically, youngsters, low income earners, males, unmarried individuals, Malays, employed individuals, rural residents and primary educated individuals were more likely to smoke. In conclusion, socio-demographic, lifestyle and health factors have significant impacts on smoking participation in Malaysia. Based on these empirical findings, several policy implications are suggested.

  16. Factors influencing dependence on mobile phone

    Directory of Open Access Journals (Sweden)

    Mohammad-Hossein Biglu

    2016-08-01

    Full Text Available Introduction: The purpose of current study was to investigate the relationship between the problematic use of mobile phone and Big Five personality traits among students of Tabriz University of Medical Sciences in Tabriz, Iran. Methods: A total number of 120 students (80 females and 40 males were selected by applying proportional randomized classification sampling method from Tabriz University of Medical Sciences. The Mobile Phone Problematic Use Scale (MPPUS and demographic questionnaire were used to gather data. Data were analyzed using SPSS software. Results: Analysis of gathered data showed that gender, neuroticism, extraversion, and openness to experience had positive correlation with the problematic use of mobile phone, whereas conscientiousness and agreeableness were not correlated with the problematic use of mobile phone. Conclusion: The evaluation of Big Five personality traits would be a reliable factor for predicting the problematic use of mobile phone among students.

  17. Factors influencing citizen participation in community management

    Directory of Open Access Journals (Sweden)

    Ali Shamai

    2015-04-01

    Full Text Available The primary objective of this study is to assess the factors affecting citizen participation in community management in district 13 of Tehran Municipality. Measured variables are: social cohesion, profitable partnerships, social-economic agencies, trust among civilians, trust in municipality management, feelings of powerlessness and social anomie. The results of the implementation of Pearson correlation test show that all of these variables had significant relationships with community participation in neighborhood management. The results of multiple regression analysis showed that three variables of social cohesion, profitable partnerships and socio-economic status had explained 37% of changes in citizen participation in community management while the changing social cohesion maintained the highest impact.

  18. Factors influencing excessive daytime sleepiness in adolescents

    Directory of Open Access Journals (Sweden)

    Thiago de Souza Vilela

    2016-04-01

    Full Text Available Abstract Objective: Sleep deprivation in adolescents has lately become a health issue that tends to increase with higher stress prevalence, extenuating routines, and new technological devices that impair adolescents' bedtime. Therefore, this study aimed to assess the excessive sleepiness frequency and the factors that might be associated to it in this population. Methods: The cross-sectional study analyzed 531 adolescents aged 10–18 years old from two private schools and one public school. Five questionnaires were applied: the Cleveland Adolescent Sleepiness Questionnaire; the Sleep Disturbance Scale for Children; the Brazilian Economic Classification Criteria; the General Health and Sexual Maturation Questionnaire; and the Physical Activity Questionnaire. The statistical analyses were based on comparisons between schools and sleepiness and non-sleepiness groups, using linear correlation and logistic regression. Results: Sleep deprivation was present in 39% of the adolescents; sleep deficit was higher in private school adolescents (p < 0.001, and there was a positive correlation between age and sleep deficit (p < 0.001; r = 0.337. Logistic regression showed that older age (p = 0.002; PR: 1.21 [CI: 1.07–1.36] and higher score level for sleep hyperhidrosis in the sleep disturbance scale (p = 0.02; PR: 1.16 [CI: 1.02–1.32] were risk factors for worse degree of sleepiness. Conclusions: Sleep deficit appears to be a reality among adolescents; the results suggest a higher prevalence in students from private schools. Sleep deprivation is associated with older age in adolescents and possible presence of sleep disorders, such as sleep hyperhidrosis.

  19. Factors influencing weight gain after renal transplantation.

    Science.gov (United States)

    Johnson, C P; Gallagher-Lepak, S; Zhu, Y R; Porth, C; Kelber, S; Roza, A M; Adams, M B

    1993-10-01

    Weight gain following renal transplantation occurs frequently but has not been investigated quantitatively. A retrospective chart review of 115 adult renal transplant recipients was used to describe patterns of weight gain during the first 5 years after transplantation. Only 23 subjects (21%) were overweight before their transplant. Sixty-six subjects (57%) experienced a weight gain of greater than or equal to 10%, and 49 subjects (43%) were overweight according to Metropolitan relative weight criteria at 1 year after transplantation. There was an inverse correlation between advancing age and weight gain, with the youngest patients (18-29 years) having a 13.3% weight gain and the oldest patients (age greater than 50 years) having the lowest gain of 8.3% at 1 year (P = 0.047). Black recipients experienced a greater weight gain than whites during the first posttransplant year (14.6% vs. 9.0%; P = 0.043), and maintained or increased this difference over the 5-year period. Men and women experienced comparable weight gain during the first year (9.5% vs. 12.1%), but women continued to gain weight throughout the 5-year study (21.0% total weight gain). The men remained stable after the first year (10.8% total weight gain). Recipients who experienced at least a 10% weight gain also increased their serum cholesterol (mean 261 vs. 219) and triglyceride (mean 277 vs. 159) levels significantly, whereas those without weight gain did not. Weight gain did not correlate with cumulative steroid dose, donor source (living-related versus cadaver), rejection history, pre-existing obesity, the number of months on dialysis before transplantation, or posttransplant renal function. Posttransplant weight gain is related mainly to demographic factors, not to treatment factors associated with the transplant. The average weight gain during the first year after renal transplantation is approximately 10%. This increased weight, coupled with changes in lipid metabolism, may be significant in

  20. Factors influencing professional life satisfaction among neurologists.

    Science.gov (United States)

    Teixeira-Poit, Stephanie M; Halpern, Michael T; Kane, Heather L; Keating, Michael; Olmsted, Murrey

    2017-06-19

    Predicted shortages in the supply of neurologists may limit patients' access to and quality of care for neurological disorders. Retaining neurologists already in practice provides one opportunity to support the overall supply of practicing neurologists. Understanding factors associated with professional life satisfaction (and dissatisfaction) and implementing policies to enhance satisfaction may encourage neurologists to remain in clinical practice. In this paper, we present results from the first study examining factors associated with professional life satisfaction among a large sample of U.S, neurologists. We collaborated with the AAN to survey a sample of U.S. neurologists about their professional life satisfaction. Analyses examined the association of physician and practice characteristics with aspects of professional life satisfaction, including satisfaction with their career in medicine, medical specialty, current position, relationship with colleagues, relationship with patients, work/life balance, and pay. The study population consisted of 625 neurologists. In multivariate regression analyses, no single group or population stratum indicated high (or low) responses to all aspects of satisfaction. Older neurologists reported higher satisfaction with career, specialty, and relationship with patients than younger neurologists. Female neurologists had significantly lower satisfaction with pay than male neurologists. Neurologists who spent more time in research and teaching had greater satisfaction with specialty, relationship with colleagues, and relationship with patients than those spending no time in research. Neurologists who practiced in small cities/rural areas reported lower satisfaction across multiple dimensions than those practicing in large urban areas. Neurologists in solo practice had greater satisfaction with the relationship with their patients, but lower satisfaction with pay. Satisfaction is a multidimensional construct that is associated with

  1. Fish consumption preferences and factors influencing it

    Directory of Open Access Journals (Sweden)

    Mehmet Ferit Can

    2015-06-01

    Full Text Available Fish consumption preferences are affected by individuals’ socioeconomic characteristics. The aims of the present paper were (i to obtain information on fish consumption level and frequency; (ii to investigate the associations between the socioeconomic characteristics of consumers and their preferences; and (iii to examine the influence of determinants on fish consumption. Data were gathered through a questionnaire completed by a total of 127 randomly selected individuals from different socioeconomic backgrounds from the Antakya, Turkey. The average consumption was found to be 2.98 kg/person/year for fish. Anchovies, gilt-head sea bream, and sea bass were reported as the most consumed three species, respectively. Significant differences in fish consumption were found among age groups, gender groups, and education groups, as well as between marital statuses. A majority of the consumers eat fish once a month throughout the year or only during the winter months. Fish consumption level and frequency were significantly positively correlated with education (p<0.01, income (p<0.05 and total meat consumption (p<0.01. The stepwise multiple regression model explained 41.7% (p<0.01 of the total variance for fish consumption. The amount and frequency of the consumption in the region, which is very far below the world and Turkey average especially for lower socioeconomic groups and for less-consumed fish species, can be increased by certain policies, such as training, advertising and different marketing strategies. Moreover, consumption should be distributed equally throughout the year instead of consuming only in certain seasons.

  2. Impact of Environmental Factors on Biofilm Formation by Bifidobacterium Longium CICC6069%环境因素对长双歧杆菌CICC6069生物膜生成的影响

    Institute of Scientific and Technical Information of China (English)

    徐文生; 张艳艳; 黄漫青; 艾启俊; 王晓东; 张磊; 仝其根

    2012-01-01

    Objective: The impact of different environmental factor on biofilm formation by Bifidabacterium longium CICC 6069 was studied. Methods: The nutritional and environmental conditions of Bifidobacterium longium CICC 6069 culture were changed by systematically adding or removing the medium compounds from MRS or TSB, to determine the impact of different environmental conditions on biofilm formation by Bifidobacterium longium CICC 6069. Results: Biofilm assays indicated that in vitro biofilm formation by Bifidobacterium longium CICC 6069 was modulated by environmental conditions. Glucose, osmolarity and MgS04 increased in biofilm formation, while an inhibitory effect of EDTA, soy peptone and pH on biofilm formation could be observed. MnS04 on biofilm formation was shown to be medium dependent. Conclusion: The biofilm formation by Bifidubaclermm longium CICC 6069 was dependent on environment conditions. Different environmental factors had different impact on biofilm formation by Bifidobacterium longium CICC 6069, among them, glucose, NaCl and MgSO4 were significantly affected.%目的:研究不同环境因子对长双歧杆菌CICC6069生物膜生成能力的影响.方法:通过增添或删除培养基MRS和TSB的组成成分,改变双歧杆菌培养的营养和环境条件,测定不同条件对双歧杆菌生物膜生成的影响.结果:不同环境因子对双歧杆菌生物膜生成的影响不同,葡萄糖、MgSO4及渗透压可促进长双歧杆菌CICC6069生物膜的生成;EDTA、大豆蛋白胨及pH可抑制长双歧杆菌生物膜的生成;MnSO4对双歧杆菌生物膜生成的影响有培养基依赖性.结论:长双歧杆菌CICC6069生物膜的生成依赖环境条件,不同环境因子对长双歧杆菌生物膜的生成有不同的影响.其中,MgSO4、NaCl、葡萄糖对双歧杆菌生物膜生成的影响比较显著.

  3. The Biofilm Challenge

    DEFF Research Database (Denmark)

    Alhede, Maria; Alhede, Morten

    2014-01-01

    in wounds. However, the impact of biofilms is often debated, because infected wounds were also treated before the concept of biofilms was coined. In this short review, we will address the significance of biofilms and their role in wounds, and discuss the future tasks of the biofilm challenge....

  4. Factors influencing phototaxis in nocturnal migrating birds.

    Science.gov (United States)

    Zhao, Xuebing; Chen, Mingyan; Wu, Zhaolu; Wang, Zijiang

    2014-12-01

    Many migratory bird species fly during the night (nocturnal migrants) and have been shown to display some phototaxis to artificial light. During 2006 to 2009, we investigated phototaxis in nocturnal migrants at Jinshan Yakou in Xinping County (N23°56', E101°30'; 2400 m above sea-level), and at the Niaowang Mountain in Funing County (N23°30', E105°35'; 1400 m above sea-level), both in the Yunnan Province of Southwest China. A total of 5069 birds, representing 129 species, were captured by mist-netting and artificial light. The extent of phototaxis effect on bird migration was examined during all four seasons, three phases of the moon, and under two weather conditions (mist and wind). Data were statistically analyzed to determine the extent to which these factors may impact phototaxis of nocturnal migrants. The results point to phototaxis in birds migrating in the spring and autumn, especially in the autumn. Furthermore, migrating birds were more readily attracted to artificial lights during nights with little moonlight, mist, and a headwind. Regardless of the initial orientation in which birds flew, either following the wind or against the wind, birds would always fly against the wind when flying towards the light. This study broadens our understanding of the nocturnal bird migration, potentially resulting in improved bird ringing practices, increased awareness, and better policies regarding bird protection.

  5. Factors influencing riverine fish assemblages in Massachusetts

    Science.gov (United States)

    Armstrong, David S.; Richards, Todd A.; Levin, Sara B.

    2011-01-01

    The U.S. Geological Survey, in cooperation with the Massachusetts Department of Conservation and Recreation, Massachusetts Department of Environmental Protection, and the Massachusetts Department of Fish and Game, conducted an investigation of fish assemblages in small- to medium-sized Massachusetts streams. The objective of this study was to determine relations between fish-assemblage characteristics and anthropogenic factors, including impervious cover and estimated flow alteration, relative to the effects of environmental factors, including physical-basin characteristics and land use. The results of this investigation supersede those of a preliminary analysis published in 2010. Fish data were obtained for 669 fish-sampling sites from the Massachusetts Division of Fisheries and Wildlife fish-community database. A review of the literature was used to select fish metrics - species richness, abundance of individual species, and abundances of species grouped on life history traits - responsive to flow alteration. The contributing areas to the fish-sampling sites were delineated and used with a geographic information system to determine a set of environmental and anthropogenic factors that were tested for use as explanatory variables in regression models. Reported and estimated withdrawals and return flows were used together with simulated unaltered streamflows to estimate altered streamflows and indicators of flow alteration for each fish-sampling site. Altered streamflows and indicators of flow alteration were calculated on the basis of methods developed in a previous U.S. Geological Survey study in which unaltered daily streamflows were simulated for a 44-year period (water years 1961-2004), and streamflow alterations were estimated by use of water-withdrawal and wastewater-return data previously reported to the State for the 2000-04 period and estimated domestic-well withdrawals and septic-system discharges. A variable selection process, conducted using principal

  6. Selective reactivity of monochloramine with extracellular matrix components affects the disinfection of biofilm and detached clusters.

    Science.gov (United States)

    Xue, Zheng; Lee, Woo Hyoung; Coburn, Kimberly M; Seo, Youngwoo

    2014-04-01

    The efficiency of monochloramine disinfection was dependent on the quantity and composition of extracellular polymeric substances (EPS) in biofilms, as monochloramine has a selective reactivity with proteins over polysaccharides. Biofilms with protein-based (Pseudomonas putida) and polysaccharide based EPS (Pseudomonas aeruginosa), as well as biofilms with varied amount of polysaccharide EPS (wild-type and mutant P. aeruginosa), were compared. The different reactivity of EPS components with monochloramine influenced disinfectant penetration, biofilm inactivation, as well as the viability of detached clusters. Monochloramine transport profiling measured by a chloramine-sensitive microelectrode revealed a broader diffusion boundary layer between bulk and biofilm surface in the P. putida biofilm compared to those of P. aeruginosa biofilms. The reaction with proteins in P. putida EPS multiplied both the time and the monochloramine mass required to achieve a full biofilm penetration. Cell viability in biofilms was also spatially influenced by monochloramine diffusion and reaction within biofilms, showing a lower survival in the surface section and a higher persistence in the middle section of the P. putida biofilm compared to the P. aeruginosa biofilms. While polysaccharide EPS promoted biofilm cell viability by obstructing monochloramine reactive sites on bacterial cells, protein EPS hindered monochloramine penetration by reacting with monochloramine and reduced its concentration within biofilms. Furthermore, the persistence of bacterial cells detached from biofilm (over 70% for P. putida and ∼40% for polysaccharide producing P. aeruginosa) suggested that currently recommended monochloramine residual levels may underestimate the risk of water quality deterioration caused by biofilm detachment.

  7. Effect of Neovestitol-vestitol containing Brazilian red propolis on biofilm accumulation in vitro and dental caries development in vivo

    Science.gov (United States)

    Bueno-Silva, B; Koo, H; Falsetta, ML; Alencar, SM; Ikegaki, M; Rosalen, PL

    2013-01-01

    The present study examined the influences of the neovestitol-vestitol (NV) containing fraction isolated from Brazilian red propolis on biofilm development and expression of virulence factors by Streptococcus mutans using saliva-coated hydroxyapatite surfaces. In addition, NV was tested in a rodent model of dental caries to assess its potential effectiveness in vivo. Topical applications of NV (800μg/ml) significantly impaired the accumulation of S. mutans biofilms by largely disrupting the synthesis of glucosyltransferase-derived exopolysaccharides and the expression of genes associated with the adaptive stress response, such as copYAZ and sloA. Of even greater impact, NV was as effective as fluoride (positive control) in reducing the development of carious lesions in vivo. NV is a promising natural anti-biofilm agent that targets essential virulence traits in S. mutans, which are associated with cariogenic biofilm formation and the subsequent onset of dental caries disease. PMID:24099330

  8. Factors influencing ring closure through olefin metathesis - A perspective

    Indian Academy of Sciences (India)

    Subrata Ghosh; Sarita Ghosh; Niladri Sarkar

    2006-05-01

    Success of ring closure reactions of substrates having two terminal alkenes through olefin metathesis depends on a number of factors such as catalysts, nature and size of the rings to be formed and the substituents/functional groups present on the alkenes as well as at the allylic position. This article presents an overview of these influencing factors with illustrative examples.

  9. Professional Identity Development in Higher Education: Influencing Factors

    Science.gov (United States)

    Barbarà-i-Molinero, Alba; Cascón-Pereira, Rosalía; Hernández-Lara, Ana beatriz

    2017-01-01

    Purpose: In the last few years, the interest on professional identity development (PID) and the factors that influence PID has become central in higher education (HE) literature. However, the knowledge developed in this domain has focussed on a factor at a time and on a degree or discipline, thus being difficult to have a general picture of all…

  10. Influence of Psychological Factors on the Improvement of Spoken English

    Institute of Scientific and Technical Information of China (English)

    董宁

    2013-01-01

      From learner's innermost feelings,the author attempts to elaborate the influences of psychological factors on improving the spoken language. The study of spoken English is a very complex process, which is affected easily by learner's linguistic environment and character. We can draw a conclusion that psychological factors are an important problem and cannot be neglected.

  11. Factors influencing societal response of nanotechnology : an expert stakeholder analysis

    NARCIS (Netherlands)

    Gupta, N.; Fischer, A.R.H.; Lans, van der I.A.; Frewer, L.J.

    2012-01-01

    Nanotechnology can be described as an emerging technology and, as has been the case with other emerging technologies such as genetic modification, different socio-psychological factors will potentially influence societal responses to its development and application. These factors will play an import

  12. The influence of motivational factors on choice behaviour

    NARCIS (Netherlands)

    Van Amelsfort, D.H.; Steg, L.; Bliemer, M.C.J.; Schuitema, G.

    2010-01-01

    In this paper we investigate if and how motivational factors influence choice behaviour. We study four motivational factors: attitude towards car use, personal norm to reduce car use, car use habit, and perceived behavioural control to change car use to explain the choice behaviour of respondents in

  13. Using mixed methods to identify factors influencing patient flow.

    Science.gov (United States)

    Van Vaerenbergh, Cindy

    2009-11-01

    An effective method of identifying operational factors that influence patient flow can potentially lead to improvements and thus have huge benefits on the efficiency of hospital departments. This paper presents a new inductive mixed-method approach to identify operational factors that influence patient flow through an accident and emergency (A&E) department. Preliminary explorative observations were conducted, followed by semi-structured interviews with key stakeholders. A questionnaire survey of all medical, nursing, porter and clerical staff was then conducted. The observations provided factors for further exploration: skill-mix, long working hours, equipment availability, lack of orientation programmes, inefficient IT use and issues regarding communication structures. Interviewees highlighted several factors, including availability of medical supervision and senior nursing staff, nursing documentation issues, lack of morale due to overcrowding, personality differences and factors relating to the department layout. The questionnaire respondents strongly supported the importance of the previously identified factors. This paper demonstrates an effective mixed-method approach that can be replicated by other health-care managers to identify factors influencing patient flow. Further benefits include increased volume and quality of data, increased staff awareness for the influence of internal factors on patient flow and enhancing the evidence base for future decision making when prioritizing A&E projects.

  14. Psychosocial Factors Influencing Competency of Children's Statements on Sexual Trauma

    Science.gov (United States)

    Kim, Tae Kyung; Choi, Soul; Shin, Yee Jin

    2011-01-01

    Objectives: The objectives of this study are to assess children's competence to state their traumatic experience and to determine psychosocial factors influencing the competency of children's statements, such as emotional factors of children and parents and trauma-related variables, in Korean child sex abuse victims. Methods: We enrolled 214…

  15. Factors Influencing Technology Planning in Developing Countries: A Literature Review

    Science.gov (United States)

    Keengwe, Jared; Malapile, Sandy

    2014-01-01

    This article is a literature review concerning the factors that play an important role in the development of educational technology plans in the educational system of developing countries (DCs). Largely, the technology plans are influenced by factors that emanates from within the country (internal) and those outside of their borders (external).…

  16. Factors that Influence Students' Decision to Dropout of Online Courses

    Science.gov (United States)

    Willging, Pedro A.; Johnson, Scott D.

    2009-01-01

    Although there are many reasons why students dropout of college courses, those reasons may be unique for students who are enrolled in an online program. Issues of isolation, disconnectedness, and technological problems may be factors that influence a student to leave a course. To understand these factors, an online survey was developed to collect…

  17. Factors Influencing Psychological Help Seeking in Adults: A Qualitative Study

    Science.gov (United States)

    Topkaya, Nursel

    2015-01-01

    The aim of the current research is to identify which factors, and in what direction these factors influence adults' decisions to seek psychological help for their personal problems. The research was designed as a phenomenology model; the data was gathered through the semi-structured interview technique, which is mostly used in qualitative research…

  18. Raman imaging of biofilms using gold sputtered fiber optic probes

    Science.gov (United States)

    Christopher, Christina Grace Charlet; Manoharan, Hariharan; Subrahmanyam, Aryasomayajula; Sai, V. V. Raghavendra

    2016-12-01

    In this work we report characterization of bacterial biofilm using gold sputtered optical fiber probe as substrates for confocal Raman spectroscopy measurements. The chemical composition and the heterogeneity of biofilms in the extracellular polymeric substances (EPS) was evaluated. The spatial distribution of bacterial biofilm on the substrates during their growth phase was studied using Raman imaging. Further, the influence of substrate's surface on bacterial adhesion was investigated by studying growth of biofilms on surfaces with hydrophilic and hydrophobic coatings. This study validates the use of gold sputtered optical fiber probes as SERS substrates in confocal microscopic configuration to identify and characterize clinically relevant biofilms.

  19. The in vivo biofilm

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Alhede, Maria; Alhede, Morten

    2013-01-01

    Bacteria can grow and proliferate either as single, independent cells or organized in aggregates commonly referred to as biofilms. When bacteria succeed in forming a biofilm within the human host, the infection often becomes very resistant to treatment and can develop into a chronic state. Biofilms...... have been studied for decades using various in vitro models, but it remains debatable whether such in vitro biofilms actually resemble in vivo biofilms in chronic infections. In vivo biofilms share several structural characteristics that differ from most in vitro biofilms. Additionally, the in vivo...... experimental time span and presence of host defenses differ from chronic infections and the chemical microenvironment of both in vivo and in vitro biofilms is seldom taken into account. In this review, we discuss why the current in vitro models of biofilms might be limited for describing infectious biofilms...

  20. The Biofilm Challenge

    DEFF Research Database (Denmark)

    Alhede, Maria; Alhede, Morten

    2014-01-01

    The concept of biofilms has emerged in the clinical setting during the last decade. Infections involving biofilms have been documented in all parts of the human body, and it is currently believed that the presence of biofilm-forming bacteria is equivalent to chronic infection. A quick Pubmed search...... reveals the significance of biofilms, as evidenced by a dramatic increase in scientific publications on the topic, as well as in publications concerning wounds with biofilms, which reached 600 publications in 2013. Judged from the number of publications, it appears that biofilms play a significant role...... in wounds. However, the impact of biofilms is often debated, because infected wounds were also treated before the concept of biofilms was coined. In this short review, we will address the significance of biofilms and their role in wounds, and discuss the future tasks of the biofilm challenge....

  1. FACTORS INFLUENCING YIELD SPREADS OF THE MALAYSIAN BONDS

    Directory of Open Access Journals (Sweden)

    Norliza Ahmad

    2009-01-01

    Full Text Available Malaysian bond market is developing rapidly but not much is understood in terms of macroeconomic factors that could influence the yield spread of the Ringgit Malaysian denominated bonds. Based on a multifactor model, this paper examines the impact of four macroeconomic factors namely: Kuala Lumpur Composite Index (KLCI, Industry Production Index (IPI, Consumer Price Index (CPI and interest rates (IR on bond yield spread of the Malaysian Government Securities (MGS and Corporate Bonds (CBs for a period from January 2001 to December 2008. The findings support the expected hypotheses that CPI and IR are the major drivers that influence the changes in MGS yield spreads. However IPI and KLCI have weak and no influence on MGS yield spreads respectively Whilst IR, CPI and IPI have significant influence on the yield spreads of CB1, CB2 and CB3, KLCI has significant influence only on the CB1 yield spread but not on CB2 and CB3 yield spreads.

  2. Pseudomonas aeruginosa Biofilm Formation and Persistence, along with the Production of Quorum Sensing-Dependent Virulence Factors, Are Disrupted by a Triterpenoid Coumarate Ester Isolated from Dalbergia trichocarpa, a Tropical Legume

    Science.gov (United States)

    Pottier, Laurent; Huet, Joelle; Rabemanantsoa, Christian; Kiendrebeogo, Martin; Andriantsimahavandy, Abel; Rasamindrakotroka, Andry; Stévigny, Caroline; Duez, Pierre; El Jaziri, Mondher

    2015-01-01

    Recently, extracts of Dalbergia trichocarpa bark have been shown to disrupt P. aeruginosa PAO1 quorum sensing (QS) mechanisms, which are key regulators of virulence factor expression and implicated in biofilm formation. One of the active compounds has been isolated and identified as oleanolic aldehyde coumarate (OALC), a novel bioactive compound that inhibits the formation of P. aeruginosa PAO1 biofilm and its maintenance as well as the expression of the las and rhl QS systems. Consequently, the production of QS-controlled virulence factors including, rhamnolipids, pyocyanin, elastase and extracellular polysaccharides as well as twitching and swarming motilities is reduced. Native acylhomoserine lactones (AHLs) production is inhibited by OALC but exogenous supply of AHLs does not restore the production of virulence factors by OALC-treated cultures, indicating that OALC exerts its effect beyond AHLs synthesis in the QS pathways. Further experiments provided a significant inhibition of the global virulence factor activator gacA by OALC. OALC disorganizes established biofilm structure and improves the bactericidal activity of tobramycin against biofilm-encapsulated PAO1 cells. Finally, a significant reduction of Caenorhabditis elegans paralysis was recorded when the worms were infected with OALC-pre-treated P. aeruginosa. Taken together, these results show that triterpenoid coumarate esters are suitable chemical backbones to target P. aeruginosa virulence mechanisms. PMID:26186595

  3. Factors influencing nursing career choices and choice of study program.

    Science.gov (United States)

    Haron, Yafa; Reicher, Sima; Riba, Shoshana

    2014-01-01

    In advance of a recruitment campaign, Israeli first-year nursing students of all ethnicities were surveyed to elucidate what factors had influenced them to make nursing their career and what sort of training track they preferred. The responses made it clear that different factors influence different groups differently. There were noticeable differences by gender, age, and ethnicity. Overall, training institutions were chosen for their closeness to the student's home but other factors also operated among particular groups, such as institutional prestige and flexible entry criteria. There was a blatant preference for academic, particularly university-sited, programs over diploma programs.

  4. A Discussion on Motivation Factor Influencing Second Language Acquisition

    Institute of Scientific and Technical Information of China (English)

    盛芊芊

    2016-01-01

    Various characteristics can influence students'second language acquisition and language development, which in-cludes age, gender, personality, cognitive ability, motivation, learning strategies and so on. Among all these factors mentioned, motivation factor that is categorized into learner factors affects learner's learning effect to a great extent. In this paper, motiva-tion characteristic that influences second language learning are discussed. At last, some strategies on the real classroom teaching application are provided after the discussion, which aims at making contribution to the second language teaching process as well as students'language development.

  5. Nurturing Sport Expertise: Factors Influencing the Development of Elite Athlete

    Science.gov (United States)

    Baker, Joseph; Horton, Sean; Robertson-Wilson, Jennifer; Wall, Michael

    2003-01-01

    The development of expertise in sport is the result of successful interaction of biological, psychological, and sociological constraints. This review examines the training and environmental factors that influence the acquisition of sport expertise. Research examining the quality and quantity of training indicate that these two elements are crucial predictors of attainment. In addition, the possession of resources such as parental support and adequate coaching are essential. Social factors such as cultural influences and the relative age effect are also considered as determinants of sport expertise. Although it is evident that environmental factors are essential to the acquisition of high levels of sport development, further research is clearly required. PMID:24616603

  6. NURTURING SPORT EXPERTISE: FACTORS INFLUENCING THE DEVELOPMENT OF ELITE ATHLETE

    Directory of Open Access Journals (Sweden)

    Michael Wall

    2003-03-01

    Full Text Available The development of expertise in sport is the result of successful interaction of biological, psychological, and sociological constraints. This review examines the training and environmental factors that influence the acquisition of sport expertise. Research examining the quality and quantity of training indicate that these two elements are crucial predictors of attainment. In addition, the possession of resources such as parental support and adequate coaching are essential. Social factors such as cultural influences and the relative age effect are also considered as determinants of sport expertise. Although it is evident that environmental factors are essential to the acquisition of high levels of sport development, further research is clearly required

  7. Shewanella putrefaciens Adhesion and Biofilm Formation on Food Processing Surfaces

    Science.gov (United States)

    Bagge, Dorthe; Hjelm, Mette; Johansen, Charlotte; Huber, Ingrid; Gram, Lone

    2001-01-01

    Laboratory model systems were developed for studying Shewanella putrefaciens adhesion and biofilm formation under batch and flow conditions. S. putrefaciens plays a major role in food spoilage and may cause microbially induced corrosion on steel surfaces. S. putrefaciens bacteria suspended in buffer adhered readily to stainless steel surfaces. Maximum numbers of adherent bacteria per square centimeter were reached in 8 h at 25°C and reflected the cell density in suspension. Numbers of adhering bacteria from a suspension containing 108 CFU/ml were much lower in a laminar flow system (modified Robbins device) (reaching 102 CFU/cm2) than in a batch system (reaching 107 CFU/cm2), and maximum numbers were reached after 24 h. When nutrients were supplied, S. putrefaciens grew in biofilms with layers of bacteria. The rate of biofilm formation and the thickness of the film were not dependent on the availability of carbohydrate (lactate or glucose) or on iron starvation. The number of S. putrefaciens bacteria on the surface was partly influenced by the presence of other bacteria (Pseudomonas fluorescens) which reduced the numbers of S. putrefaciens bacteria in the biofilm. Numbers of bacteria on the surface must be quantified to evaluate the influence of environmental factors on adhesion and biofilm formation. We used a combination of fluorescence microscopy (4′,6′-diamidino-2-phenylindole staining and in situ hybridization, for mixed-culture studies), ultrasonic removal of bacteria from surfaces, and indirect conductometry and found this combination sufficient to quantify bacteria on surfaces. PMID:11319118

  8. Which factors influence women in the decision to breastfeed?

    Directory of Open Access Journals (Sweden)

    Cândida Canicali Primo

    Full Text Available Objective.Identify the factors that influence women in the decision to breastfeed. Methods. Integrative review. Information was gathered from original articles, case studies, theoretical studies, consensus and systematic reviews published between 2007-2013 in Spanish, Portuguese and English and recovered in the databases MEDLINE and LILACS. The descriptors used in this study were: breastfeeding, maternal behavior, risk factors, lactation and newborn. Results. Were included 30 articles, grouped into five categories. Factors influencing the decision of the breastfeeding woman are a convergence of breastfeeding's advantages, benefits and justifications, family, social and professional support, sociodemographic and clinical characteristics of women, personal experience and family tradition and personal choice. Conclusion. The decision to breastfeed by women is influenced by a convergence of factors. It is essential the role of nursing to encourage women in the decision to initiate and maintain breastfeeding her child.

  9. The ecology and biogeochemistry of stream biofilms.

    Science.gov (United States)

    Battin, Tom J; Besemer, Katharina; Bengtsson, Mia M; Romani, Anna M; Packmann, Aaron I

    2016-04-01

    Streams and rivers form dense networks, shape the Earth's surface and, in their sediments, provide an immensely large surface area for microbial growth. Biofilms dominate microbial life in streams and rivers, drive crucial ecosystem processes and contribute substantially to global biogeochemical fluxes. In turn, water flow and related deliveries of nutrients and organic matter to biofilms constitute major constraints on microbial life. In this Review, we describe the ecology and biogeochemistry of stream biofilms and highlight the influence of physical and ecological processes on their structure and function. Recent advances in the study of biofilm ecology may pave the way towards a mechanistic understanding of the effects of climate and environmental change on stream biofilms and the biogeochemistry of stream ecosystems.

  10. RISK FACTORS INFLUENCING CONSTRUCTION PROCUREMENT PERFORMANCE IN NIGERIA

    OpenAIRE

    Dahiru, A; Aminu, Muhammad Bashir

    2016-01-01

    One of the challenges facing construction procurement performance is the failure to determine the risk related factors limiting its success. These risk factors can cause a significant increase in the procurement cost leading to an increase in the overall project cost. The purpose of this study is to identify and evaluate the risk factors influencing construction procurement performance with a view to achieve the overall project performance. The objectives are to establish a relative significa...

  11. Environmental factors influencing asexual reproductive processes in echinoderms

    OpenAIRE

    Mladenov, Pv

    1996-01-01

    This review provides a brief update of the occurrence and adaptive significance of asexual reproduction in echinoderms. It then focuses on the state of knowledge of biotic and abiotic factors that influence asexual processes in this group, particularly factors that may play a role in regulating the expression and relative proportion of asexual versus sexual phenotypes within populations of species, as well as factors modulating and triggering asexual processes. The information presented in th...

  12. Biocorrosion: towards understanding interactions between biofilms and metals.

    Science.gov (United States)

    Beech, Iwona B; Sunner, Jan

    2004-06-01

    The term microbially influenced corrosion, or biocorrosion, refers to the accelerated deterioration of metals owing to the presence of biofilms on their surfaces. The detailed mechanisms of biocorrosion are still poorly understood. Recent investigations into biocorrosion have focused on the influence of biomineralization processes taking place on metallic surfaces and the impact of extracellular enzymes, active within the biofilm matrix, on electrochemical reactions at the biofilm-metal interface.

  13. Genetic and environmental factors influencing the Placental Growth Factor (PGF) variation in two populations

    DEFF Research Database (Denmark)

    Sorice, Rossella; Ruggiero, Daniela; Nutile, Teresa

    2012-01-01

    . However, to date, no information is available regarding the genetics of PGF variability. Furthermore, even though the effect of environmental factors (e.g.: cigarette smoking) on angiogenesis has been explored, no data on the influence of these factors on PGF levels have been reported so far. Here we have...... strongly replicated in the Danish sample. These results, for the first time, support the hypothesis of the presence of genetic and environmental factors influencing PGF plasma variability....

  14. The wills of older people: risk factors for undue influence.

    Science.gov (United States)

    Peisah, C; Finkel, S; Shulman, K; Melding, P; Luxenberg, J; Heinik, J; Jacoby, R; Reisberg, B; Stoppe, G; Barker, A; Firmino, H; Bennett, H

    2009-02-01

    As people live longer, there is increasing potential for mental disorders to interfere with testamentary distribution and render older people more vulnerable to "undue influence" when they are making a will. Accordingly, clinicians dealing with the mental disorders of older people will be called upon increasingly to advise the courts about a person's vulnerability to undue influence. A Subcommittee of the IPA Task Force on Testamentary Capacity and Undue Influence undertook to establish consensus on the definition of undue influence and the provision of guidelines for expert assessment of risk factors for undue influence. International jurisdictions differ in their approach to the notion of undue influence. Despite differences in legal systems, from a clinical perspective, the subcommittee identified some common "red flags" which might alert the expert to risk of undue influence. These include: (i) social or environmental risk factors such as dependency, isolation, family conflict and recent bereavement; (ii) psychological and physical risk factors such as physical disability, deathbed wills, sexual bargaining, personality disorders, substance abuse and mental disorders including dementia, delirium, mood and paranoid disorders; and (iii) legal risk factors such as unnatural provisions in a will, or provisions not in keeping with previous wishes of the person making the will, and the instigation or procurement of a will by a beneficiary. This review provides some guidance for experts who are requested by the courts to provide an opinion on the risk of undue influence. Whilst international jurisdictions require different thresholds of proof for a finding of undue influence, there is good international consensus on the clinical indicators for the concept.

  15. HD-GYP domain proteins regulate biofilm formation and virulence in Pseudomonas aeruginosa

    DEFF Research Database (Denmark)

    Ryan, Robert P.; Lucey, Jean; O'Donovan, Karen

    2009-01-01

    2572 had a negative influence on swarming that was cryptic and was revealed only after removal of an uncharacterized C-terminal domain. Mutation of PA4108, PA4781 and PA2572 had distinct effects on biofilm formation and architecture of P. aeruginosa. All three proteins contributed to virulence of P...... residues (YN-GYP). Here we have investigated the role of these proteins in biofilm formation, virulence factor synthesis and virulence of P. aeruginosa. Mutation of PA4108 and PA4781 led to an increase in the level of cyclic-di-GMP in P. aeruginosa, consistent with the predicted activity of the encoded...

  16. Dynamics of Biofilm Regrowth in Drinking Water Distribution Systems.

    Science.gov (United States)

    Douterelo, I; Husband, S; Loza, V; Boxall, J

    2016-07-15

    The majority of biomass within water distribution systems is in the form of attached biofilm. This is known to be central to drinking water quality degradation following treatment, yet little understanding of the dynamics of these highly heterogeneous communities exists. This paper presents original information on such dynamics, with findings demonstrating patterns of material accumulation, seasonality, and influential factors. Rigorous flushing operations repeated over a 1-year period on an operational chlorinated system in the United Kingdom are presented here. Intensive monitoring and sampling were undertaken, including time-series turbidity and detailed microbial analysis using 16S rRNA Illumina MiSeq sequencing. The results show that bacterial dynamics were influenced by differences in the supplied water and by the material remaining attached to the pipe wall following flushing. Turbidity, metals, and phosphate were the main factors correlated with the distribution of bacteria in the samples. Coupled with the lack of inhibition of biofilm development due to residual chlorine, this suggests that limiting inorganic nutrients, rather than organic carbon, might be a viable component in treatment strategies to manage biofilms. The research also showed that repeat flushing exerted beneficial selective pressure, giving another reason for flushing being a viable advantageous biofilm management option. This work advances our understanding of microbiological processes in drinking water distribution systems and helps inform strategies to optimize asset performance. This research provides novel information regarding the dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimize the performance of the distribution network and to guarantee safe and good-quality drinking water to consumers. Copyright © 2016 Douterelo et al.

  17. [Factors influencing research activity of Andalusian nurses and improvement strategies].

    Science.gov (United States)

    López Alonso, Sergio R; Gálvez González, María; Amezcua, Manuel

    2013-04-01

    To identify factors influencing research activity of Andalusian nurses and to find improvement strategies. Qualitative research using SWOT analysis (weaknesses, threats, strengths, opportunities). Nurses were selected deliberately in eight groups according to predetermined criteria. Analysis included categorization and relationship of factors and strategies. 81 participants were included in groups of 7-12 range. 45 categories were identified with 212 factors: 12 weaknesses (50 factors), 10 strengths (44 factors), 12 threats (68 factors) and 11 opportunities (50 factors). In addition, 32 categories were identified with 53 strategies: 14 categories of W-T strategies (42 strategies), 3 categories of S-T strategies (11 strategies), 5 categories of W-O strategies (13 strategies) and 10 categories of S-O strategies (41 strategies). Nurses identified numerous factors, mainly threats. The strategies are focused on W-T but they also suggest many but weak 5-0 strategies due to the low potential of the opportunities and strengths perceived.

  18. Factors influencing adherence among older people with osteoarthritis.

    Science.gov (United States)

    Loew, Laurianne; Brosseau, Lucie; Kenny, Glen P; Durand-Bush, Natalie; Poitras, Stéphane; De Angelis, Gino; Wells, George A

    2016-09-01

    This study aims to identify potential factors that could affect adherence and influence the implementation of an evidence-based structured walking program, among older adults diagnosed with knee osteoarthritis. A total of 69 participants with mild to moderate osteoarthritis of the knee fulfilled an online survey on potential factors that could affect their adherence to an evidence-based structured walking program. Adherence with regard to the influencing factors was explored using a logistic regression model. Results tend to show higher odds of adhering to the evidence-based walking program if the participants were supervised (more than 2.9 times as high), supported by family/friends (more than 3.7 times as high), and not influenced by emotional involvement (more than 11 times as high). The odds of adhering were 3.6 times lower for participants who indicated a change in their medication intake and 3.1 times lower for individuals who considered themselves as less physically active (95 % confidence interval (CI)). Our exploratory findings identified and defined potential adherence factors that could guide health professionals in their practice to better identify positive influences and obstacles to treatment adherence, which would lead to the adoption of a more patient-centered approach. A large-scale study is required to clearly delineate the key factors that would influence adherence. We addressed a new knowledge gap by identifying the main strategies to promote the long-term adherence of community-based walking program.

  19. Laboratory study on factors influencing nitrogen removal in marble chip biofilters incorporating nitritation and anammox.

    Science.gov (United States)

    Tao, Wendong; Wen, Jianfeng; Norton, Christopher

    2011-01-01

    It remains challenging to integrate nitritation and anammox in ecologically engineered treatment systems such as passive biofilters that are packed with natural materials and have low energy inputs. This study explored the factors influencing nitritation-anammox through parallel operation of two laboratory-scale biofilters packed with large and small marble chips respectively. Clean marble chips (mainly CaCO3) had an alkalinity dissolution rate of 130 mg CaCO3/kg marble d when water pH approached 6.5. Marble chips effectively increased water pH and provided sufficient alkalinity to support nitritation-anammox in the biofilters. Ammonium and total nitrogen removal decreased by 47 and 26%, respectively, when nutrients were not amended to influent. An influent nitrite concentration above 8.9 mg N/L could inhibit anammox in thin biofilms of biofilters. Nitritation-anammox was enhanced with a hydraulic retention time of 2 d relative to 7 d, likely due to enhanced air entrainment. Size of marble chips rarely made a significant difference in nitrogen removal, possibly due to sufficient surface area available for bacterial attachment and alkalinity dissolution.

  20. Pseudomonas biofilms: possibilities of their control.

    Science.gov (United States)

    Masák, Jan; Čejková, Alena; Schreiberová, Olga; Rezanka, Tomáš

    2014-07-01

    Genus Pseudomonas includes a large number of species that can be encountered in biotechnological processes as well as in the role of serious human or plant pathogens. Pseudomonads easily form biofilms on various types of surfaces. The biofilm phenotype is characterized by an increased resistance to environmental influences including resistance to antibiotics and other disinfectants, causing a number of problems in health care, food industry, and other areas. Considerable attention is therefore paid to the possibilities of eradication/destruction of pseudomonads biofilms both in terms of understanding the mechanisms of biofilm formation and at the level of finding suitable antibiofilm tools applicable in practice. The first part of this review is devoted to an overview of the regulatory mechanisms that are directly or indirectly involved in the formation of biofilm. The most effective approaches to suppressing the formation of biofilm that do not cause the development of resistance are based on the application of substances that interfere with the regulatory molecules or block the appropriate regulatory mechanisms involved in biofilm development by the cells. Pseudomonads biofilm formation is, similar to other microorganisms, a sophisticated process with many regulatory elements. The suppression of this process therefore also requires multiple antibiofilm tools.

  1. A survey on critical factors influencing organizational commitment

    Directory of Open Access Journals (Sweden)

    Hamidreza Kheirkhah

    2014-04-01

    Full Text Available Organizational commitment is an important issue and organization attitude has become an area of study among many researchers in the fields of organizational behavior. In fact, there are many studies on human resource management where the effects of organizational commitment on other issues have been investigated and the purpose of this research is to find critical factors influencing on organizational commitment. Based on an exploration of the literature review and interviews, the proposed study of this paper extracts 24 variables and using factor analysis, we select the most important factors, which are grouped in four categories. The implementation of our factor analysis has revealed Affective commitment, Continuous commitment, Moral commitment and Enduring commitment are the most important factors influencing organizational commitment.

  2. A survey on critical factors influencing agricultural insurance

    Directory of Open Access Journals (Sweden)

    Ali Valipour

    2013-01-01

    Full Text Available Agricultural business is a very high-risk job and an increase demand for agricultural products from one side and steady increase in production cost and weather changes, on the other side, have motivated many to use insurance for agricultural products. Insurance plays an important role in influencing crop production and insured satisfaction or farmers. The purpose of this research is to find critical components in agricultural insurance. Based on an exploration of the literature review and interviews, the proposed study of this paper extracts 24 variables and using factor analysis, we select the most important factors, which are grouped in seven categories. The implementation of our factor analysis has revealed uncertainty, moderator, market equilibrium, risky environment, empowering factor, education, training, structural hazards and natural ecosystems as the most important factors influencing agricultural industry.

  3. FACTORS INFLUENCING BRAND EQUITY OF BALI AS A TOURISM DESTINATION

    Directory of Open Access Journals (Sweden)

    I Ketut Surya Diarta

    2016-03-01

    Full Text Available Globally, competition among tourism destinations is more stringent in getting foreign tourists, including Bali. One effort to win the competition is increasing destination brand equity through maintaining its influencing factors and gaining tourist positive behavior toward destination. This effort, in long run, will increase and stabilize destination revenue and sustainability. This research aims to analyze factors influencing brand equity of Bali as a tourism destination. This research was conducted in Bali’s five major tourism objects. The 240 foreign tourists were chosen as respondents through convenience sampling technique. Data were analyzed using factor analysis. The results showed that factors that significantly influenced Bali brand equity were: symbolic and experiential benefit factor, direct and indirect destinations attributes, destination reliability and tangibility, assurance and empathy, brand destinations recognition and recall, destinations common psychological attributes, destination common functional attributes, unique functional attributes, behavioral loyalty, destination awareness, and attitudinal loyalty. Given the fluctuative nature of brand equity, Bali needs a consistent effort to maintain or to enhance brand equity of Bali as a tourism destination. Maintaining the dominant factors that influence the strength of brand equity can be used as a basis to develop destination branding strategy to expand market segment,  choose the right target market, and anchoring destination position in world market competition.

  4. Factors negatively influencing knowledge sharing in software development

    Directory of Open Access Journals (Sweden)

    Lucas T. Khoza

    2017-01-01

    Full Text Available Background: ‘Knowledge is power’ and software developing organisations are dependent on knowledge to achieve and maintain a competitive advantage. Subsequently, knowledge sharing is a key factor for modern software developing organisations to succeed in today’s competitive environment. For software developing organisations to reach their goals and objectives, knowledge sharing – and in particular the sharing of useful knowledge – needs to be targeted. To promote knowledge sharing, factors influencing knowledge sharing need to be identified and understood.Objective: This study seeks to identify factors that negatively influence knowledge sharing in software development in the developing country context.Method: Expert sampling as a subcategory of purposive sampling was employed to extract information, views and opinions from experts in the field of information and communication technology, more specifically from those who are involved in software development projects. Four Johannesburg-based software developing organisations listed on the Johannesburg Stock Exchange (JSE, South Africa, participated in this research study. Quantitative data were collected using an online questionnaire with closed-ended questions.Results: Findings of this research reveal that job security, motivation, time constraints, physiological factors, communication, resistance to change and rewards are core factors negatively influencing knowledge sharing in software developing organisations.Conclusions: Improved understanding of factors negatively influencing knowledge sharing is expected to assist software developing organisations in closing the gap for software development projects failing to meet the triple constraint of time, cost and scope.

  5. Influence of social factors on lead exposure and child development

    Energy Technology Data Exchange (ETDEWEB)

    Bornschein, R.L.

    1985-10-01

    A brief overview of current views of child development is provided, with particular attention given to the role the child's physical and social environment plays in influencing the developmental process. Examples from the recent literature are used to illustrate how these factors can influence lead exposure and most importantly how they might interact with lead to ameliorate or exacerbate possible lead effects. An example is provided which demonstrates that failure to control adequately and to adjust the data statistically to correct for the influence of these factors can lead one erroneously to attribute cognitive and behavioral changes to lead. Finally, data from the Cincinnati Prospective Lead Study are presented to illustrate the application of structural equation modeling as a means for unraveling the complex web of sociodemographic, environmental and behavioral influences on childhood lead exposure.

  6. ICT Interventions for Girls: Factors Influencing ICT Career Intentions

    Directory of Open Access Journals (Sweden)

    Elena Gorbacheva

    2014-11-01

    Full Text Available Intervention programs aimed at promoting study and work opportunities in the Information and Communications Technology (ICT field to schoolgirls have been encouraged to combat a decline in the interest among girls to study ICT at school. The goal of our study is to investigate the influence of such interventions on schoolgirls’ intentions to choose a career in the ICT field by analysing comprehensive survey data (n = 3577, collected during four interventions in Australia, using the Partial Least Squares method. Our study is also aimed at identifying other factors influencing ICT career intentions. We found that the attitude towards interventions has an indirect influence on ICT career intentions by affecting interest in ICT. Our results also challenge several existing theoretical studies by showing that factors that had previously been suggested as influencers were found to have little or no impact in this study, these being same-sex education and computer usage.

  7. Virulence gene expression by Staphylococcus epidermidis biofilm cells exposed to antibiotics.

    Science.gov (United States)

    Gomes, Fernanda; Teixeira, Pilar; Cerca, Nuno; Ceri, Howard; Oliveira, Rosário

    2011-06-01

    Staphylococcus epidermidis have become important causes of nosocomial infections, as its pathogenesis is correlated with the ability to form biofilms on polymeric surfaces. Production of poly-N-acetylglucosamine (PNAG) is crucial for S. epidermidis biofilm formation and is synthesized by the gene products of the icaADBC gene cluster. Production of PNAG/polysaccharide intercellular adhesin and biofilm formation are regulated by the alternative sigma factor, σ(B), and is influenced by a variety of environmental conditions including disinfectants and other antimicrobial substances. The susceptibility of five S. epidermidis strains to antibiotics alone and in double combination was previously tested. Our results demonstrated that some combinations are active and present a general broad spectrum against S. epidermidis biofilms, namely rifampicin-clindamycin and rifampicin-gentamicin. In the present study, it was investigated whether the combination of rifampicin with clindamycin and gentamicin and these antibiotics alone influence the expression of specific genes (icaA and rsbU) of S. epidermidis within biofilms using real-time polymerase chain reaction. The data showed that in most cases the expression of both genes tested significantly increased after exposure to antimicrobial agents alone and in combination. Besides having a similar antimicrobial effect, rifampicin combined with clindamycin and gentamicin induced a lower expression of biofilm-related genes relatively to rifampicin alone. Associated with the advantage of combinatorial therapy in avoiding the emergence of antibiotic resistance, this study demonstrated that it can also cause a lower genetic expression of icaA and rsbU genes, which are responsible for PNAG/polysaccharide intercellular adhesin production, and consequently reduce biofilm formation recidivism, relatively to rifampicin alone.

  8. Protein-based biofilm matrices in Staphylococci

    Directory of Open Access Journals (Sweden)

    Pietro eSpeziale

    2014-12-01

    Full Text Available Staphylococcus aureus and Staphylococcus epidermidis are the most important etiological agents of biofilm associated-infections on indwelling medical devices. Biofilm infections may also develop independently of indwelling devices, e.g. in native valve endocarditis, bone tissue and open wounds. After attachment to tissue or indwelling medical devices that have been conditioned with host plasma proteins, staphylococcal biofilms grow and produce a specific environment which provides the conditions for cell-cell interaction and formation of multicellular communities. Bacteria living in biofilms express a variety of macromolecules, including exopolysaccharides, proteins, extracellular eDNA and other polymers. The S. aureus surface protein C and G (SasC and SasG, clumping factor B (ClfB, serine aspartate repeat protein (SdrC, the biofilm-associated protein (Bap and the fibronectin/fibrinogen-binding proteins (FnBPA and FnBPB are individually implicated in biofilm matrix formation. In S. epidermidis, a protein named accumulation-associated protein (Aap contributes to both the primary attachment phase and the establishment of intercellular connections by forming fibrils on the cell surface. In S. epidermidis proteinaceous biofilm formation can also be mediated by the extracellular matrix binding protein (Embp and S. epidermidis surface protein C (SesC. Additionally, multifunctional proteins such as extracellular adherence protein (Eap and extracellular matrix protein binding protein (Emp of S. aureus and the iron-regulated surface determinant protein C (IsdC of S. lugdunensis can promote biofilm formation in iron-depleted conditions. This multitude of proteins intervene at different stages of biofilm formation with certain proteins contributing to biofilm accumulation and others mediating primary attachment to surfaces. This review examines the contribution of proteins to biofilm formation in staphylococci. The potential to develop vaccines to prevent

  9. A limited legacy effect of copper in marine biofilms.

    Science.gov (United States)

    McElroy, David J; Doblin, Martina A; Murphy, Richard J; Hochuli, Dieter F; Coleman, Ross A

    2016-08-15

    The effects of confounding by temporal factors remains understudied in pollution ecology. For example, there is little understanding of how disturbance history affects the development of assemblages. To begin addressing this gap in knowledge, marine biofilms were subjected to temporally-variable regimes of copper exposure and depuration. It was expected that the physical and biological structure of the biofilms would vary in response to copper regime. Biofilms were examined by inductively coupled plasma optical emission spectrometry, chlorophyll-a fluorescence and field spectrometry and it was found that (1) concentrations of copper were higher in those biofilms exposed to copper, (2) concentrations of copper remain high in biofilms after the source of copper is removed, and (3) exposure to and depuration from copper might have comparable effects on the photosynthetic microbial assemblages in biofilms. The persistence of copper in biofilms after depuration reinforces the need for consideration of temporal factors in ecology.

  10. Factors Influencing the Intended Likelihood of Exposing Sexual Infidelity.

    Science.gov (United States)

    Kruger, Daniel J; Fisher, Maryanne L; Fitzgerald, Carey J

    2015-08-01

    There is a considerable body of literature on infidelity within romantic relationships. However, there is a gap in the scientific literature on factors influencing the likelihood of uninvolved individuals exposing sexual infidelity. Therefore, we devised an exploratory study examining a wide range of potentially relevant factors. Based in part on evolutionary theory, we anticipated nine potential domains or types of influences on the likelihoods of exposing or protecting cheaters, including kinship, strong social alliances, financial support, previous relationship behaviors (including infidelity and abuse), potential relationship transitions, stronger sexual and emotional aspects of the extra-pair relationship, and disease risk. The pattern of results supported these predictions (N = 159 men, 328 women). In addition, there appeared to be a small positive bias for participants to report infidelity when provided with any additional information about the situation. Overall, this study contributes a broad initial description of factors influencing the predicted likelihood of exposing sexual infidelity and encourages further studies in this area.

  11. Empirical Analysis on Factors Influencing Distribution of Vegetal Production

    Institute of Scientific and Technical Information of China (English)

    Wenjie; WU

    2015-01-01

    Since the reform and opening-up,there has been a great change in spatial pattern of China’s vegetable production. This paper studied vegetable production in provinces of China in 1978- 2013. From the sequential characteristics,China’s vegetable production area is constantly growing and takes on stage characteristic. From the spatial distribution,China’s vegetable production takes on the trend of " going down the south" and " marching the west". In order to grasp rules of changes of vegetable production and the influence factors,this paper made theoretical and empirical analysis on factors possibly influencing distribution of vegetable production. Results show that major factors influencing distribution of China’s vegetable production include irrigation condition,non-agricultural employment,market demand,knowledge spillover,comparative effectiveness,rural road and government policies.

  12. MOTIVATIONS AND FACTORS INFLUENCING THE DECISION OF ONLINE TRADING

    Directory of Open Access Journals (Sweden)

    Ioana Ancuta IANCU

    2016-12-01

    Full Text Available In this study, using survey data, we explore motivations and factors that influence the Romanian investors to trade online even if they initially traded through a broker. To identify the factors we used secondary sources and for exploring the factors that influence the decision of trading online we used primary data. We find that investors decide to trade online especially because they spend less time, they have an easier access to information (due to the fact that most of the online trading platforms have notifications and alarms for news that can affect the stock market and they know how to use the internet. We discover that only a few investors are influenced by advertising and the fact that it is fashionable to trade online.

  13. Factors influencing the tolerance of flufenacet applications in winter rye

    OpenAIRE

    2016-01-01

    In winter rye which is grown mostly on locations with a lighter soil texture loose silky-bent grass (Apera spica-venti) is a dominate weed grass. Because of increasing herbicide resistance the control of A. spica-venti becomes more difficult. To manage resistant weed grass populations in winter rye flufenacet is a very important active substance. However, the application of flufenacet can lead to substantially culture damage. The influence of different factors influencing the tolerance of ...

  14. A new biofilm-associated colicin with increased efficiency against biofilm bacteria

    Science.gov (United States)

    Rendueles, Olaya; Beloin, Christophe; Latour-Lambert, Patricia; Ghigo, Jean-Marc

    2014-01-01

    Formation of bacterial biofilm communities leads to profound physiological modifications and increased physical and metabolic exchanges between bacteria. It was previously shown that bioactive molecules produced within the biofilm environment contribute to bacterial interactions. Here we describe new pore-forming colicin R, specifically produced in biofilms formed by the natural isolate Escherichia coli ROAR029 but that cannot be detected under planktonic culture conditions. We demonstrate that an increased SOS stress response within mature biofilms induces SOS-dependent colicin R expression. We provide evidence that colicin R displays increased activity against E. coli strains that have a reduced lipopolysaccharide length, such as the pathogenic enteroaggregative E. coli LF82 clinical isolate, therefore pointing to lipopolysaccharide size as an important determinant for resistance to colicins. We show that colicin R toxicity toward E. coli LF82 is increased under biofilm conditions compared with planktonic susceptibility and that release of colicin R confers a strong competitive advantage in mixed biofilms by rapidly outcompeting sensitive neighboring bacteria. This work identifies the first biofilm-associated colicin that preferentially targets biofilm bacteria. Furthermore, it indicates that the study of antagonistic molecules produced in biofilm and multispecies contexts could reveal unsuspected, ecologically relevant bacterial interactions influencing population dynamics in natural environments. PMID:24451204

  15. Inefficacy of vancomycin and teicoplanin in eradicating and killing Staphylococcus epidermidis biofilms in vitro.

    Science.gov (United States)

    Claessens, J; Roriz, M; Merckx, R; Baatsen, P; Van Mellaert, L; Van Eldere, J

    2015-04-01

    Biofilm-associated bacteria display a decreased susceptibility towards antibiotics. Routine assessment of antibiotic susceptibility of planktonic bacteria therefore offers an insufficient prediction of the biofilm response. In this study, in vitro biofilms of eight clinical Staphylococcus epidermidis strains were subjected to treatment with vancomycin, teicoplanin, oxacillin, rifampicin and gentamicin. In addition, the biofilms were subjected to combinations of an antibiotic with rifampicin. The effects on the biofilms were assessed by crystal violet staining to determine the total biofilm biomass, staining with XTT to determine bacterial cell viability, and microscopy. Combining these methods showed that treatment of S. epidermidis biofilms with glycopeptides increased the total biofilm biomass and that these antibiotics were not effective in killing bacteria embedded in biofilms. The decreased killing efficacy was more pronounced in biofilms produced by strains that were classified as 'strong' biofilm producers. Rifampicin, oxacillin and gentamicin effectively killed biofilm-associated bacteria of all tested strains. Combining antibiotics with rifampicin increased the killing efficacy without influencing the total biofilm biomass. When vancomycin or teicoplanin were combined with rifampicin, the increase in biofilm biomass was neutralised and also the killing efficacy was influenced in a positive way. We conclude that the combined methodology used in this study showed that glycopeptides were not effective in eradicating S. epidermidis biofilms but that combination with rifampicin improved the killing efficacy in vitro.

  16. Factors influencing consumer behaviour in market vegetables in Yemen

    Directory of Open Access Journals (Sweden)

    Tarish H. Al-Gahaifi

    2011-01-01

    Full Text Available The purpose of the research is to understand factors influencing consumer behaviour when buying vegetables in Republic of Yemen. Data collection was done by structured questionnaire administered through schools, universities, government offices, and markets from 13 provinces in 5 governorates. Random convenience sampling technique was used. Total sample comprised of 463 completed questionnaires which were used for analysis. The respondents were classified into five categories on the base of their monthly income, age, education, gender, and type of settlement. Authors present the factors that can influence significantly this behaviour, e.g. price, quality, the location of seller, habit, personal relationship between consumer and seller, occasions, discount, sorting, word-mouth, time of purchase, the way of products display, and recommendation of friends and families. From the obtained results, it is obvious that there was high influence on the behaviour of Yemeni consumer when buying vegetables for factors price, occasions, discontent, and time of purchase, while factors habit, display, sorting, and the location of seller suggests medium influence, and the influence was low for word-mouth.

  17. Oral biofilms: emerging concepts in microbial ecology.

    Science.gov (United States)

    Filoche, S; Wong, L; Sissons, C H

    2010-01-01

    Oral biofilms develop under a range of different conditions and different environments. This review will discuss emerging concepts in microbial ecology and how they relate to oral biofilm development and the treatment of oral diseases. Clues to how oral biofilms develop may lie in other complex systems, such as interactions between host and gut microbiota, and even in factors that affect biofilm development on leaf surfaces. Most of the conditions under which oral biofilms develop are tightly linked to the overall health and biology of the host. Advances in molecular techniques have led to a greater appreciation of the diversity of human microbiota, the extent of interactions with the human host, and how that relates to inter-individual variation. As a consequence, plaque development may no longer be thought of as a generic process, but rather as a highly individualized process, which has ramifications for the treatment of the diseases it causes.

  18. Psychosocial factors for influencing healthy aging in adults in Korea.

    Science.gov (United States)

    Han, KyungHun; Lee, YunJung; Gu, JaSung; Oh, Hee; Han, JongHee; Kim, KwuyBun

    2015-03-07

    Healthy aging includes physical, psychological, social, and spiritual well-being in later years. The purpose of this study is to identify the psychosocial factors influencing healthy aging and examining their socio-demographic characteristics. Perceived health status, depression, self-esteem, self-achievement, ego-integrity, participation in leisure activities, and loneliness were identified as influential factors in healthy aging. 171 Korean adults aged between 45 and 77 years-old participated in the study. Self-reporting questionnaires were used, followed by descriptive statistics and multiple regressions as inferential statistical analyses. There were significant differences between participants' general characteristics: age, education, religion, housing, hobby, and economic status. The factors related to healthy aging had positive correlation with perceived health status, self-esteem, self-achievements, and leisure activities, and negative correlation with depression and loneliness. The factors influencing healthy aging were depression, leisure activities, perceived health status, ego integrity, and self-achievements. These factors were able to explain 51.9%. According to the results, depression is the factor with the greatest influence on healthy aging. Perceived health status, ego integrity, self-achievement, self-esteem, participation of leisure activities were also influential on healthy aging as beneficial factors.

  19. Factors of influence and changes in the tourism consumer behaviour

    Directory of Open Access Journals (Sweden)

    Fratu, D.

    2011-01-01

    Full Text Available Consumer behaviour is a very important aspect to be studied in every marketing activity, therefore in tourism marketing as well. Defining and identifying the factors that influence consumers help in understanding individual needs and buying processes in their whole complexity. Consumers have changed their behaviour over the last two years due to the instability of the economic environment. The author describes in this article the factors which influence consumer behaviour and also presents how it has changed over the past two years.

  20. Anti-Biofilm and Immunomodulatory Activities of Peptides That Inhibit Biofilms Formed by Pathogens Isolated from Cystic Fibrosis Patients.

    Science.gov (United States)

    de la Fuente-Núñez, César; Mansour, Sarah C; Wang, Zhejun; Jiang, Lucy; Breidenstein, Elena B M; Elliott, Melissa; Reffuveille, Fany; Speert, David P; Reckseidler-Zenteno, Shauna L; Shen, Ya; Haapasalo, Markus; Hancock, Robert E W

    2014-01-01

    Cystic fibrosis (CF) patients often acquire chronic respiratory tract infections due to Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) species. In the CF lung, these bacteria grow as multicellular aggregates termed biofilms. Biofilms demonstrate increased (adaptive) resistance to conventional antibiotics, and there are currently no available biofilm-specific therapies. Using plastic adherent, hydroxyapatite and flow cell biofilm models coupled with confocal and scanning electron microscopy, it was demonstrated that an anti-biofilm peptide 1018 prevented biofilm formation, eradicated mature biofilms and killed biofilms formed by a wide range of P. aeruginosa and B. cenocepacia clinical isolates. New peptide derivatives were designed that, compared to their parent peptide 1018, showed similar or decreased anti-biofilm activity against P. aeruginosa biofilms, but increased activity against biofilms formed by the Gram-positive bacterium methicillin resistant Staphylococcus aureus. In addition, some of these new peptide derivatives retained the immunomodulatory activity of 1018 since they induced the production of the chemokine monocyte chemotactic protein-1 (MCP-1) and suppressed lipopolysaccharide-mediated tumor necrosis factor-α (TNF-α) production by human peripheral blood mononuclear cells (PBMC) and were non-toxic towards these cells. Peptide 1018 and its derivatives provide promising leads for the treatment of chronic biofilm infections and hyperinflammatory lung disease in CF patients.