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Sample records for bacteriolysis

  1. Listeria monocytogenes triggers AIM2-mediated pyroptosis upon infrequent bacteriolysis in the macrophage cytosol.

    Science.gov (United States)

    Sauer, John-Demian; Witte, Chelsea E; Zemansky, Jason; Hanson, Bill; Lauer, Peter; Portnoy, Daniel A

    2010-05-20

    A host defense strategy against pathogens is the induction of cell death, thereby eliminating the pathogen's intracellular niche. Pyroptosis, one such form of cell death, is dependent on inflammasome activation. In a genetic screen to identify Listeria monocytogenes mutants that induced altered levels of host cell death, we identified a mutation in lmo2473 that caused hyperstimulation of IL-1beta secretion and pyroptosis following bacteriolysis in the macrophage cytosol. In addition, strains engineered to lyse in the cytosol by expression of both bacteriophage holin and lysin or induced to lyse by treatment with ampicillin stimulated pyroptosis. Pyroptosis was independent of the Nlrp3 and Nlrc4 inflammasome receptors but dependent on the inflammasome adaptor ASC and the cytosolic DNA sensor AIM2. Importantly, wild-type L. monocytogenes were also found to lyse, albeit at low levels, and trigger AIM2-dependent pyroptosis. These data suggested that pyroptosis is triggered by bacterial DNA released during cytosolic lysis.

  2. Production and characterization of chicken origin Shigella dysenteriae ghosts with double bacteriolysis plasmids%双重溶菌质粒制备鸡痢疾志贺菌菌壳的研究

    Institute of Scientific and Technical Information of China (English)

    蒋大伟; 刘军; 张瑞安; 夏力亮; 孙洋; 祝令伟; 冯书章; 许兰菊

    2013-01-01

    In order to improve lysis rate and stability of chicken origin Shigella dysenteriae ghosts,recombinant strain of Shigella with double bacteriolytic plasmids was constructed and its characteristics was studied. Two recombinant bacteriolysis plasmid pBV220: :E and pBBR IMCS-E were co-transformed into the Shigella strain isolated from chicken to produce recombinant strain Sd(pBV220::E /pBBRIMCS-E). The recombinant strain Sd(pBV220::E /pBBRIMCS-E) was grown at 28℃ with shaking until mid log-phase,followed by incubation at 42℃ to induce the expression of gene E and produce Shigella dysenteriae ghosts. The D600 value of bacterial cultures was monitored over 20 h at 30 min intervals. The morphology of chicken origin Shigella dysenteriae ghosts was observed by electron microscope. The recombinant strains Sd(pBV220 : : E/pB-BRIMCS-E) generated chicken origin Shigella dysenteriae ghosts after inducing at 42℃. The ghosts retained basic cell morphology,with the lysis rate of 99. 999 9%. The chicken origin Shigella dysenteriae ghosts were generated successfully with double bacteriolysis plasmids, which laid foundation for future development of bacterial ghost vaccine against Shigella infection in chicken.%通过将2种不同的重组溶菌质粒转化至鸡痢疾志贺菌中,构建含有双重溶菌质粒的志贺菌重组菌株,以提高该菌菌壳制备的裂解率和稳定性,并对其特性进行研究.用重组溶菌质粒pBV220::E和pBBRIMCS-E共同转化到鸡痢疾志贺菌,构建志贺菌重组菌株Sd(pBV220::E/pBBRI MCS-E),重组菌株于28 C培养至D600值为0.5时升至42℃继续培养,间隔30 min检测菌液D600值,进行重组菌株的溶菌裂解动力学比较试验,绘制裂解曲线图并计算出裂解率,制备菌壳并对其形态进行电镜观察.重组菌株Sd(pBV220::E/pBBRIMCS-E)经42℃诱导后可形成菌壳且保留了基本的细胞形态,裂解率达到了99.999 9%.本研究成功制备出鸡痢疾志贺菌菌壳,为研究利用该

  3. Perforin enhances the granulysin-induced lysis of Listeria innocua in human dendritic cells

    Directory of Open Access Journals (Sweden)

    Wagner Carsten A

    2007-08-01

    Full Text Available Abstract Background Cytotoxic T lymphocytes (CTL and natural killer (NK cells play an essential role in the host defence against intracellular pathogens such as Listeria, and Mycobacteria. The key mediator of bacteria-directed cytotoxicity is granulysin, a 9 kDa protein stored in cytolytic granules together with perforin and granzymes. Granulysin binds to cell membranes and is subsequently taken up via a lipid raft-associated mechanism. In dendritic cells (DC granulysin is further transferred via early endosomes to L. innocua-containing phagosomes were bacteriolysis is induced. In the present study we analysed the role of perforin in granulysin-induced intracellular bacteriolysis in DC. Results We found granulysin-induced lysis of intracellular Listeria significantly increased when perforin was simultaneously present. In pulse-chase experiments enhanced bacteriolysis was observed when perforin was added up to 25 minutes after loading the cells with granulysin demonstrating no ultimate need for simultaneous uptake of granulysin and perforin. The perforin concentration sufficient to enhance granulysin-induced intracellular bacteriolysis did not cause permanent membrane pores in Listeria-challenged DC as shown by dye exclusion test and LDH release. This was in contrast to non challenged DC that were more susceptible to perforin lysis. For Listeria-challenged DC, there was clear evidence for an Ca2+ influx in response to sublytic perforin demonstrating a short-lived change in the plasma membrane permeability. Perforin treatment did not affect granulysin binding, initial uptake or intracellular trafficking to early endosomes. However, enhanced colocalization of granulysin with listerial DNA in presence of perforin was found by confocal laser scanning microscopy. Conclusion The results provide evidence that perforin increases granulysin-mediated killing of intracellular Listeria by enhanced phagosome-endosome fusion triggered by a transient Ca2+ flux.

  4. A defect in cell wall recycling triggers autolysis during the stationary growth phase of Escherichia coli.

    OpenAIRE

    Templin, M F; Ursinus, A; Höltje, J V

    1999-01-01

    The first gene of a family of prokaryotic proteases with a specificity for L,D-configured peptide bonds has been identified in Escherichia coli. The gene named ldcA encodes a cytoplasmic L, D-carboxypeptidase, which releases the terminal D-alanine from L-alanyl-D-glutamyl-meso-diaminopimelyl-D-alanine containing turnover products of the cell wall polymer murein. This reaction turned out to be essential for survival, since disruption of the gene results in bacteriolysis during the stationary g...

  5. Listeria monocytogenes that lyse in the macrophage cytosol trigger AIM2-mediated pyroptosis

    Science.gov (United States)

    Sauer, John-Demian; Witte, Chelsea E.; Zemansky, Jason; Hanson, Bill; Lauer, Peter; Portnoy, Daniel A.

    2010-01-01

    Summary To gain insight into the mechanisms by which host cells detect cytosolic invasion by intracellular pathogens, a genetic screen was performed to identify Listeria monocytogenes mutants that induced altered levels of host cell death. A mutation in lmo2473 resulted in hyper-stimulation of host cell death and IL-1β secretion (pyroptosis) following bacteriolysis in the macrophage cytosol. In addition, strains engineered to lyse in the cytosol by expression of both bacteriophage holin and lysin or induced to lyse by treatment with ampicillin stimulated pyroptosis. Pyroptosis was independent of the Nlrp3 and Nlrc4 receptors, but dependent on ASC and AIM2. Importantly, wild type L. monocytogenes were also found to lyse, albeit at low levels, and trigger AIM2-dependent pyroptosis. Since AIM2 is activated by DNA, these data suggested that pyroptosis is triggered by bacterial DNA released during lysis. PMID:20417169

  6. Immunization with Brucella VirB proteins reduces organ colonization in mice through a Th1-type immune response and elicits a similar immune response in dogs.

    Science.gov (United States)

    Pollak, Cora N; Wanke, María Magdalena; Estein, Silvia M; Delpino, M Victoria; Monachesi, Norma E; Comercio, Elida A; Fossati, Carlos A; Baldi, Pablo C

    2015-03-01

    VirB proteins from Brucella spp. constitute the type IV secretion system, a key virulence factor mediating the intracellular survival of these bacteria. Here, we assessed whether a Th1-type immune response against VirB proteins may protect mice from Brucella infection and whether this response can be induced in the dog, a natural host for Brucella. Splenocytes from mice immunized with VirB7 or VirB9 responded to their respective antigens with significant and specific production of gamma interferon (IFN-γ), whereas interleukin-4 (IL-4) was not detected. Thirty days after an intraperitoneal challenge with live Brucella abortus, the spleen load of bacteria was almost 1 log lower in mice immunized with VirB proteins than in unvaccinated animals. As colonization reduction seemed to correlate with a Th1-type immune response against VirB proteins, we decided to assess whether such a response could be elicited in the dog. Peripheral blood mononuclear cells (PBMCs) from dogs immunized with VirB proteins (three subcutaneous doses in QuilA adjuvant) produced significantly higher levels of IFN-γ than cells from control animals upon in vitro stimulation with VirB proteins. A skin test to assess specific delayed-type hypersensitivity was positive in 4 out of 5 dogs immunized with either VirB7 or VirB9. As both proteins are predicted to locate in the outer membrane of Brucella organisms, the ability of anti-VirB antibodies to mediate complement-dependent bacteriolysis of B. canis was assessed in vitro. Sera from dogs immunized with either VirB7 or VirB9, but not from those receiving phosphate-buffered saline (PBS), produced significant bacteriolysis. These results suggest that VirB-specific responses that reduce organ colonization by Brucella in mice can be also elicited in dogs.

  7. Immunization with Brucella VirB proteins reduces organ colonization in mice through a Th1-type immune response and elicits a similar immune response in dogs.

    Science.gov (United States)

    Pollak, Cora N; Wanke, María Magdalena; Estein, Silvia M; Delpino, M Victoria; Monachesi, Norma E; Comercio, Elida A; Fossati, Carlos A; Baldi, Pablo C

    2015-03-01

    VirB proteins from Brucella spp. constitute the type IV secretion system, a key virulence factor mediating the intracellular survival of these bacteria. Here, we assessed whether a Th1-type immune response against VirB proteins may protect mice from Brucella infection and whether this response can be induced in the dog, a natural host for Brucella. Splenocytes from mice immunized with VirB7 or VirB9 responded to their respective antigens with significant and specific production of gamma interferon (IFN-γ), whereas interleukin-4 (IL-4) was not detected. Thirty days after an intraperitoneal challenge with live Brucella abortus, the spleen load of bacteria was almost 1 log lower in mice immunized with VirB proteins than in unvaccinated animals. As colonization reduction seemed to correlate with a Th1-type immune response against VirB proteins, we decided to assess whether such a response could be elicited in the dog. Peripheral blood mononuclear cells (PBMCs) from dogs immunized with VirB proteins (three subcutaneous doses in QuilA adjuvant) produced significantly higher levels of IFN-γ than cells from control animals upon in vitro stimulation with VirB proteins. A skin test to assess specific delayed-type hypersensitivity was positive in 4 out of 5 dogs immunized with either VirB7 or VirB9. As both proteins are predicted to locate in the outer membrane of Brucella organisms, the ability of anti-VirB antibodies to mediate complement-dependent bacteriolysis of B. canis was assessed in vitro. Sera from dogs immunized with either VirB7 or VirB9, but not from those receiving phosphate-buffered saline (PBS), produced significant bacteriolysis. These results suggest that VirB-specific responses that reduce organ colonization by Brucella in mice can be also elicited in dogs. PMID:25540276

  8. 南美白对虾保鲜剂研究进展%Research Progress on Penaeus vannamei Preservation

    Institute of Scientific and Technical Information of China (English)

    胡冬梅; 孙涛; 谢晶

    2011-01-01

    Several preservatives commonly used for Penaeus vannamei are briefly introduced in this paper,and the recent research of biological preservatives such as bacteriolysis enzyme,nisin,phytic acid and chitosan is elaborated in detail.The biological preservatives may obtain more advantages for further development in P.vannamei preservation due to their safety and high-efficiency.%介绍常用的几种南美白对虾保鲜剂,对溶菌酶、乳酸链球菌素、植酸及壳聚糖这几种生物保鲜剂在南美白对虾保鲜中的研究进展进行较为详尽的阐述。其中,生物保鲜剂因其具有安全、高效的作用而在南美白对虾保鲜方面具有较大的发展前景。

  9. An evaluation of the bacteriolytic and biochemical properties of ceftiolene (42980RP).

    Science.gov (United States)

    Williamson, R; Gutmann, L; Kitzis, M D; Acar, J F

    1984-12-01

    Ceftiolene (42980RP) is a new cephalosporin with a broad antibacterial spectrum similar to cefotaxime or ceftriaxone. The characteristics of ceftiolene have been tested in a variety of assays involving various biochemical aspects of the mode of action of beta-lactam antibiotics. The affinities of ceftiolene for penicillin-binding proteins were very comparable with those of ceftriaxone and cefotaxime for Escherichia coli, and generally greater than those of latamoxef (moxalactam) for the higher molecular weight PBPs of E. coli. Enterobacter cloacae. Proteus mirabilis and Pseudomonas aeruginosa. The affinity of ceftiolene for PBP1 of Staphylococcus aureus was greater than those of cefotaxime or latamoxef, but comparable with these antibiotics for PBP3. The bacteriolytic activity of ceftiolene at defined concentrations against Gram-negative organisms was similar to that of ceftriaxone, and significantly better than that of the other third-generation cephalosporins tested. Introduction of plasmid-encoded beta-lactamases into E. coli reduced the wide variation in bacteriolytic effect of the different cephalosporins, and a significant inoculum effect was observed for the bacteriolysis. Chloramphenicol was less antagonistic against ceftiolene- or ceftriaxone-induced lysis than was observed for cefotaxime or latamoxef. Growth of Staph. aureus at low concentrations of ceftiolene caused the bacteria to become more sensitive to lysis by lysostaphin than organisms grown with cefotaxime or latamoxef under the same conditions. These observations confirm the necessity to use techniques other than routine MIC determinations to distinguish between antibiotics which would otherwise appear very similar.

  10. Host-parasite interactions in closed and open microbial cultivation system

    Science.gov (United States)

    Pisman, T. I.; Pechurkin, N. S.

    We studied interaction between bacteria and phages within a host-parasite system the members of the system being continuously and closely cultivated The objects of our research were auxotrophic strain Brevibacterium 22L and bacteriophage Brevibacterium sp strain A discovered in the soil of the Soviet Union Republic of Latvia using enrichment method 1 Closed system We investigated the dependence of bacteriolysis time upon the multiplicity of phage infection It was shown that reduction of phage amount by one bacterium leads to increase of marked lysis Another important factor determining cytolysis in fluid medium is the physiological state of bacterial population Specific growth rate of bacteria at the moment of phage infection was chosen as the index of the physiological state of bacteria It was revealed that the shortest latent period and the maximal phage burst is observed when the bacteria located in a favorable nutrient medium are in the logarithmic phase If the bacterial population has already passed from the logarithmic phase to the stationary one the cells become a bad host for phage reproduction and lysis occurs very slowly or even never starts at all 2 Open system In the process of continuous cultivation the members of the host-parasite system showed an ability to coexist over a long period of time After phage infection there were variations in the size of both populations and then the density of the host population reached the level close to that of the uninfected culture In this situation the phage population

  11. [Soft contactlenses in general practice (author's transl)].

    Science.gov (United States)

    Miller, B

    1975-07-01

    In contrast to the hard lenses the soft lens has enough permeability for oxygen and water-soluble substances, whereas high molecular substances, bacteria and virus cannot penetrate the soft lenses, so long as their surfaces are intact. The two principal production methods, the spin cast method and the lathe-turned method are compared. The duration of wearing of the soft lens depends on the deposits of proteins from the tears on the surface of the lens and the desinfection method. The daily boiling of the lenses shortens their useful life, while chemical desinfection causes besides bacteriolysis, damage of the corneal cell protein. The new cleaners on the base of proteolytic plant enzymes promise good results. For the optical correction of astigmatism with more than 1 cyl, soft lenses with conic outer surface are used or combinations of a soft and a hard lens (Duosystem). The therapeutic use of soft lenses has as aim: protection of the cornea against mechanical irritation, release of pain, protracted administration output of medicaments. Further indications for use: aseptic corneal inflammation and corneal defects.

  12. PREPARATION OF ANTI-IDIOTYPIC ANTIBODIES SPECIFIC FOR ANTI- HEL AND ANALYSIS OF THEIR FUNCTIONAL MIMICRY

    Institute of Scientific and Technical Information of China (English)

    李明远; 肖玉; 肖丽英; 李虹; 蒋中华; 牟家琬; 王道若

    2000-01-01

    Objective. This study is to investigate the functional mimicry by using anfi-idiotypic antibodies of enzymes. Methods. Monoclonal anti-idiotypic antibodies against anfi-HEL(hen egg-white lysozyme, HEL) antibodies were obtained by fusion of Sp2/0 myeloma ceils with spleen ceils of syngeneic mice immunized with monoclonal anti-HEL antibodies against HEL's different antigenic epitopes. Then bacteriolysis of the anti-idiotypic antibodies were ohserved. Results. Eight hybridomas strains secreting anti-idiotypic antibodies were observed and characterized. It was shown that two of eight anti-idiotypic antibodies secreted by two hybridomas( 1A10C9 and 2AllC1B3) could mimic HEL catalytic activity to lyse Micrococcus lysodeikticus and that the catalytic effect of mixed anti-idiotypic antibodies of 1A10 G9 and 2A11C1B3 was stronger than that of one of them, but less than HEL. Conclusion. The results demonstrated that the anti-idiotypic antibodies that could mimic enzyme activity existed in the idiotype network during anti-enzymatic immune response.

  13. 大肠杆菌病的噬菌体治疗进展%Progress of Phage Therapy of Colibacillosis

    Institute of Scientific and Technical Information of China (English)

    马艳香; 王元超; 任慧英

    2012-01-01

    近年来,由于抗生素的滥用,致使耐药菌株越来越多,新的抗生素的研制又存在周期长、花费高、使用后细菌很快产生耐药性等问题,严重限制了抗生素在细菌病治疗中的应用.噬菌体作为天然抗菌剂,可抵制细菌感染,无论是裂解来自人类、动物体中的细菌,抑或消除食品及公共环境领域的污染,噬菌体均扮演着重要的角色.本研究以大肠杆菌感染的噬菌体治疗为例,介绍噬菌体临床治疗方面的研究进展.%In recent years, the resistant bacteria increased dramatically due to the abuse of antibiotics. The researches on new antibiotics faced many problems, such as prolonged development process, high cost, resistance of the bacteria appeared quickly after antibiotics coming into markets and so on, which have seriously limited the application of antibiotics in the treatment of the bacterial diseases. As a kind of natural antiseptic, phages play an important role in the bacteriolysis to the bacteria from human, animal, food or environment. This paper was reviewed on the issue of phage therapy of colibacillosis.

  14. In vitro antibacterial analysis of phenoloxidase reaction products from the sea cucumber Apostichopus japonicus.

    Science.gov (United States)

    Jiang, Jingwei; Zhou, Zunchun; Dong, Ying; Cong, Cong; Guan, Xiaoyan; Wang, Bai; Chen, Zhong; Jiang, Bei; Yang, Aifu; Gao, Shan; Sun, Hongjuan

    2014-08-01

    Three phenoloxidases (POs) of Apostichopus japonicus, AjPOs (AjPO1, AjPO2 and AjPO3), were partially purified from the coelomocytes with an electrophoretic method, and then employed for the in vitro antibacterial analysis. Using L-3,4-dihydroxyphenylalanine (L-DOPA) as a substrate, AjPO1 and AjPO2-derived compounds inhibited the growth of Vibrio splendidus and Staphylococcus aureus, while AjPO3-derived compounds only inhibited the growth of V. splendidus. When dopamine was used as a substrate, AjPO1 and AjPO3-derived compounds inhibited the growth of V. splendidus and Vibrio harveyi, while AjPO2-derived compounds only inhibited the growth of V. splendidus. Moreover, AjPO1-derived compounds showed stronger inhibition in V. harveyi than AjPO3-derived compounds did. However, all of the three AjPO reaction products showed no inhibitions on the growth of Pseudoalteromonas nigrifaciens, Shewanella baltica, Micrococcus lysodeikticus, Streptococcus dysgalactiae and Nocardiopsis sp. with L-DOPA or dopamine as a substrate. Scanning electron microscope (SEM) observation of V. harveyi treated by AjPOs and dopamine showed that AjPO1-derived compounds resulted in massive bacteriolysis, AjPO2-derived compounds caused no obvious alteration on bacterial morphology, and AjPO3-derived compounds increased the ratio of spheroidal bacteria. All these results suggested that AjPO reaction products derived by L-DOPA and dopamine had different but limited antibacterial spectrum, and the different antibacterial effects observed among three AjPOs resulted from the different reaction products generated by AjPOs with the same substrate. PMID:24931626

  15. Lipoglycopeptide Antibacterial Agents in Gram-Positive Infections: A Comparative Review.

    Science.gov (United States)

    Van Bambeke, Françoise

    2015-12-01

    Oritavancin, telavancin, and dalbavancin are recently marketed lipoglycopeptides that exhibit remarkable differences to conventional molecules. While dalbavancin inhibits the late stages of peptidoglycan synthesis by mainly impairing transglycosylase activity, oritavancin and telavancin anchor in the bacterial membrane by the lipophilic side chain linked to their disaccharidic moiety, disrupting membrane integrity and causing bacteriolysis. Oritavancin keeps activity against vancomycin-resistant enterocococci, being a stronger inhibitor of transpeptidase than of transglycosylase activity. These molecules have potent activity against Gram-positive organisms, most notably staphylococci (including methicillin-resistant Staphylococcus aureus and to some extent vancomycin-intermediate S. aureus), streptococci (including multidrug-resistant pneumococci), and Clostridia. All agents are indicated for the treatment of acute bacterial skin and skin structure infections, and telavancin, for hospital-acquired and ventilator-associated bacterial pneumonia. While telavancin is administered daily at 10 mg/kg, the remarkably long half-lives of oritavancin and dalbavancin allow for infrequent dosing (single dose of 1200 mg for oritavancin and 1000 mg at day 1 followed by 500 mg at day 8 for dalbavancin), which could be exploited in the future for outpatient therapy. Among possible safety issues evidenced during clinical development were an increased risk of developing osteomyelitis with oritavancin; taste disturbance, nephrotoxicity, and risk of corrected QT interval prolongation (especially in the presence of at-risk co-medications) with telavancin; and elevation of hepatic enzymes with dalbavancin. Interference with coagulation tests has been reported with oritavancin and telavancin. These drugs proved non-inferior to conventional treatments in clinical trials but their advantages may be better evidenced upon future evaluation in more severe infections. PMID:26603874

  16. Cyclic di-AMP Is Critical for Listeria monocytogenes Growth, Cell Wall Homeostasis, and Establishment of Infection

    Science.gov (United States)

    Witte, Chelsea E.; Whiteley, Aaron T.; Burke, Thomas P.; Sauer, John-Demian; Portnoy, Daniel A.; Woodward, Joshua J.

    2013-01-01

    ABSTRACT Listeria monocytogenes infection leads to robust induction of an innate immune signaling pathway referred to as the cytosolic surveillance pathway (CSP), characterized by expression of beta interferon (IFN-β) and coregulated genes. We previously identified the IFN-β stimulatory ligand as secreted cyclic di-AMP. Synthesis of c-di-AMP in L. monocytogenes is catalyzed by the diadenylate cyclase DacA, and multidrug resistance transporters are necessary for secretion. To identify additional bacterial factors involved in L. monocytogenes detection by the CSP, we performed a forward genetic screen for mutants that induced altered levels of IFN-β. One mutant that stimulated elevated levels of IFN-β harbored a transposon insertion in the gene lmo0052. Lmo0052, renamed here PdeA, has homology to a cyclic di-AMP phosphodiesterase, GdpP (formerly YybT), of Bacillus subtilis and is able to degrade c-di-AMP to the linear dinucleotide pApA. Reduction of c-di-AMP levels by conditional depletion of the di-adenylate cyclase DacA or overexpression of PdeA led to marked decreases in growth rates, both in vitro and in macrophages. Additionally, mutants with altered levels of c-di-AMP had different susceptibilities to peptidoglycan-targeting antibiotics, suggesting that the molecule may be involved in regulating cell wall homeostasis. During intracellular infection, increases in c-di-AMP production led to hyperactivation of the CSP. Conditional depletion of dacA also led to increased IFN-β expression and a concomitant increase in host cell pyroptosis, a result of increased bacteriolysis and subsequent bacterial DNA release. These data suggest that c-di-AMP coordinates bacterial growth, cell wall stability, and responses to stress and plays a crucial role in the establishment of bacterial infection. PMID:23716572

  17. Differences in Shiga toxin and phage production among stx2g-positive STEC strains

    Directory of Open Access Journals (Sweden)

    Claudia Viviana Granobles Velandia

    2012-06-01

    Full Text Available Shigatoxigenic E. coli (STEC are characterized by the production of Shiga toxins (Stx encoded by temperate bacteriophages. Stx production is linked to the induction of the phage lytic cycle. Several stx variants have been described and differentially associated with the risk of developing severe illness.The variant named stx2g was first identified in a STEC strain isolated from the faeces of healthy cattle. Analysis of stx2g-positive strains isolated from humans, animals and environmental sources have shown that they have a close relationship. In this study, stx2g-positive STEC isolated from cattle were analyzed for phage and Stx production, with the aim to relate the results to differences observed in cytotoxicity.The presence of inducible phages was assessed by analyzing the bacterial growth/lysis curves and also by plaque assay. Bacterial growth curves in the absence of induction were similar for all isolates, however, notably differed among induced cultures. The two strains that clearly evidenced bacteriolysis under this condition also showed higher phage titers in plaque assays. However, only the phage plaques produced by one of these strains (FB 62 hybridized with a stx2-probe. Furthermore, the production of Stx was evaluated by EIA and Western immunoblotting in overnight supernatants. By EIA, we detected Stx only in supernatants of FB 62, with a higher signal with induced than in uninduced cultures. By immunoblotting, Stx2 could be detected after induction in all stx2g-positive isolates, but with lower amounts of Stx2B subunit in those supernatants where phages could not be detected.Taking into account all the results, several differences could be found among stx2g-positive strains. The strain with the highest cytotoxic titer showed higher levels of stx2-phages and toxin production by EIA, and the opposite was observed for strains that previously showed low cytotoxic titers, confirming that in stx2g-positive strains Stx production is

  18. The association between iron status and some immunological factors in the pregnancy

    Directory of Open Access Journals (Sweden)

    Nadereh Naderi

    2011-01-01

    (Hb levels, hematocrit (HCT, mean corpuscular volume (MCV, red blood cell distribution width (RDW, and mean corpuscular hemoglobin (MCH, serum iron (SI and total iron binding capacity (TIBC, concentration of ferritin, C3 and C4 complements and IgA, IgM and IgG subclasses of immunoglobulins were determined. Data was analyzed using SPSS version 11.5 using Student t-test, Pearson’s correlation test and Kolmogorov-Smirnov’s test of normal distribution.Ninety-two patients were studied. They were aged between 15 and 42 years (mean=25.69±6.2. According to our definition of IDA in pregnancy, 21 patients (22.8% had IDA.Our analysis of differences between the two groups in regard to immunologic markers showed that C4 levels are lower in the IDA group (p=0.009 and the levels of C3, IgM, IgG, IgA, IL-1, IL-6 and TNF-α were not statistically different in the two groups .Sobhani et al252 Iranian Journal of Reproductive Medicine Vol. 9. No. 3. pp: 251-252, Summer 20111We noticed that higher levels of serum iron are correlated with higher levels of C3, C4 and IgG1. Due to important properties of IgG1 like complement fixation and opsonic activity, this subclass is dominant antibody to pneumococcal capsular polysaccharides and its deficiency is associated with current infections (5. Taken together noticing key roles of C3, C4 in complement-mediated bacteriolysis, opsonization, facilitated ingestion immune adherence (6 and association of C3, C4 with Iron serum levels found in this study we suggest that decreased level of Iron increases susceptibility of pregnant women to infections like chronic bacterial respiratory infections and recurrent genital herpes (5. Analyzing immunologic parameters differences between the two groups of IDA and no IDA we found that C4 levels are lower in the IDA group but not the levels of C3, IgM, IgG, IgA, IL-1, IL-6 and TNF-α .Our findings about IgM, IgG, IgA are in contradiction to scanty studies in this field. Tang et al (2 about significantly lower