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Pathogenic Organisms (pathogenic + organism)
Selected AbstractsFood Safety Objective (FSO) and Performance Objective/Heat Resistance of Pathogenic OrganismsINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 1 2006Alan G Williams No abstract is available for this article. [source] Nocardiosis in large yellow croaker, Larimichthys crocea (Richardson)JOURNAL OF FISH DISEASES, Issue 6 2005G-L Wang Abstract An epizootic in seawater-cage reared large yellow croaker, Larimichthys crocea, in China was caused by a Nocardia sp. from August to October 2003. The cumulative mortality rate was 15% and the diseased fish were 16 months old with individual length varying from 25 to 30 cm. Multiple, white nodules, 0.1,0.2 cm in diameter, were scattered on the heart, spleen and kidney. The morphology of isolated bacteria from Lowenstein,Jensen medium and tryptic soy agar was bead-like or long, slender, filamentous rods. Experimental infection indicated that the isolated bacterium was the pathogen responsible for the mortalities. A partial sequence of the 16S rRNA gene of the organism and the type strain of Nocardia seriolae JCM 3360T (Z36925) formed a monophyletic clade with a high sequence similarity of 99.9%. Based on the morphological, physiological, biological properties and the phylogenetic analysis, the pathogenic organism was identified as N. seriolae. This is the first report on N. seriolae -infected large yellow croaker in aquaculture. [source] DOES THE CYTOSKELETON OF INTESTINAL EPITHHELIAL CELLS FUNCTION AS A CELLULAR ALARM TO IDENTIFY THE E. COLI INFECTIONJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 2001Zhe Li Intestinal epithelial cells play an important role in regulating host immunity in response to intestinal infection. Pathogenic bacteria (EPEC and EHEC) cause profound cytoskeletal rearrangement in intestinal epithelial cells during attachment or invasion. Rearrangement of cytoskeletal proteins could be a signal to up-regulate host defence response. Aims, To determine the role of actin cytoskeleton and microtubles in IL-8 mRNA response to E. coli infection. Methods, T84 cell monolayers in 6-well plates were infected with HB101, EPEC and EHEC (105 CFU/well) and compared with uninfected control at 3, 6 and 12 h post infection. Control and infected monolayers were treated with nocodazole (Noc, microtubule disrupter, 30 mm), taxol (Tax, microtubule stabiliser, 10 mm), cytochalasin D (CytoD, actin depolymeriser, 100 nm) and Jasplakinolide (Jasp, actin polymeriser, stabilise actin filaments, 1 mm) and studied 6 h post infection. IL-8 gene expression was measured by semiquantitative RT,PCR in control and uninfected monolayers with and without drug treatment and IL8 protein secretion by ELISA. The morphology of F-actin and ,-tubulin was examined by FITC-phaloidin staining (FAS), immunohistochemistry and confocal microscopy. Results, IL-8 mRNA and IL-8 were increased by infection with all bacterial strains at 3 and 6 h but both IL-8 mRNA and IL-8 in EHEC and EPEC infection were decreased compared with control and HB101 at 12 h. Disruption of microfilaments by Noc increased IL-8 (2.7 fold) while preservation of microfilaments by Tax inhibited IL8 response (0.5 fold) to HB101 infection only. CytoD decreased (0.1,0.5 fold) IL8 expression at all time points in all infections while stabilising actin by Jasp markedly increased the IL8 response (2,6 fold) in control, HB101, EHEC and EPEC at 3 and 6 h. CytoD inhibited Noc-induced IL8 gene expression. Confocal microscopy demonstrated that CytoD and Noc caused major morphological damage to the actin and ,-tubulin by 6 h. Similar changes were also observed in EPEC and EHEC infection at 12 h but not HB101. Jasp preserved actin stress filaments in both EPEC and EHEC. Conclusions, Disruption of microtubules and exogenous rearrangement of actin by pathogenic organism may be primary stimuli to up-regulate proinflammatory cytokine gene expression. Preservation of actin filaments is required for this response and may be necessary for signal transduction to the nucleus. [source] Factors influencing the challenges of modelling and treating fecal indicator bacteria in surface watersECOHYDROLOGY, Issue 4 2009Cristiane Q. Surbeck Abstract In the United States, thousands of creeks, rivers, and coastal zones are listed as impaired in the Clean Water Act's 303(d) list. The number one general cause of impairments is denoted as ,pathogens', which can include known pathogenic organisms or, more commonly, fecal indicator bacteria (FIB), such as fecal coliform bacteria, Escherichia coli, and enterococci bacteria. Despite efforts by water quality managers to reduce FIB in surface waters via treatment, successful and significant reduction of FIB has been difficult to achieve to meet water quality standards. In addition, current efforts to numerically model FIB concentrations in surface waters do not consider many complexities associated with FIB as a pollutant. Reasons for the challenge of treating and modelling FIB are their varied sources and mechanisms of survival and decay in the environment. This technical note addresses this challenge by discussing the nature of FIB, their sources, and their fate and transport mechanisms. Sources of FIB to surface waters include wastewater, stormwater and dry-weather runoff, and animals. Mechanisms of pathogen indicator occurrence in surface waters are transport in stormwater, ecological proliferation, and interaction with sediments. Copyright © 2009 John Wiley & Sons, Ltd. [source] d -Alanyl ester depletion of teichoic acids in Lactobacillus reuteri 100-23 results in impaired colonization of the mouse gastrointestinal tractENVIRONMENTAL MICROBIOLOGY, Issue 7 2007Jens Walter Summary The dlt operon of Gram-positive bacteria encodes proteins required for the incorporation of d -alanine esters into cell wall-associated teichoic acids (TA). d -Alanylation of TA has been shown to be important for acid tolerance, resistance to antimicrobial peptides, adhesion, biofilm formation, and virulence of a variety of pathogenic organisms. The aim of this study was to determine the importance of d -alanylation for colonization of the gastrointestinal tract by Lactobacillus reuteri 100-23. Insertional inactivation of the dltA gene resulted in complete depletion of d -alanine substitution of lipoteichoic acids. The dlt mutant had similar growth characteristics as the wild type under standard in vitro conditions, but formed lower population sizes in the gastrointestinal tract of ex- Lactobacillus -free mice, and was almost eliminated from the habitat in competition experiments with the parental strain. In contrast to the wild type, the dlt mutant was unable to form a biofilm on the forestomach epithelium during gut colonization. Transmission electron microscope observations showed evidence of cell wall damage of mutant bacteria present in the forestomach. The dlt mutant had impaired growth under acidic culture conditions and increased susceptibility to the cationic peptide nisin relative to the wild type. Ex vivo adherence of the dlt mutant to the forestomach epithelium was not impaired. This study showed that d -alanylation is an important cell function of L. reuteri that seems to protect this commensal organism against the hostile conditions prevailing in the murine forestomach. [source] Penicillin Binding Proteins: key players in bacterial cell cycle and drug resistance processesFEMS MICROBIOLOGY REVIEWS, Issue 5 2006Pauline Macheboeuf Abstract Bacterial cell division and daughter cell formation are complex mechanisms whose details are orchestrated by at least a dozen different proteins. Penicillin-binding proteins (PBPs), membrane-associated macromolecules which play key roles in the cell wall synthesis process, have been exploited for over 70 years as the targets of the highly successful ,-lactam antibiotics. The increasing incidence of ,-lactam resistant microorganisms, coupled to progress made in genomics, genetics and immunofluorescence microscopy techniques, have encouraged the intensive study of PBPs from a variety of bacterial species. In addition, the recent publication of high-resolution structures of PBPs from pathogenic organisms have shed light on the complex intertwining of drug resistance and cell division processes. In this review, we discuss structural, functional and biological features of such enzymes which, albeit having initially been identified several decades ago, are now being aggressively pursued as highly attractive targets for the development of novel antibiotherapies. [source] X-ray crystallographic analysis of the complexes of enoyl acyl carrier protein reductase of Plasmodium falciparum with triclosan variants to elucidate the importance of different functional groups in enzyme inhibitionIUBMB LIFE, Issue 6 2010Koustav Maity Abstract Triclosan, a well-known inhibitor of Enoyl Acyl Carrier Protein Reductase (ENR) from several pathogenic organisms, is a promising lead compound to design effective drugs. We have solved the X-ray crystal structures of Plasmodium falciparum ENR in complex with triclosan variants having different substituted and unsubstituted groups at different key functional locations. The structures revealed that 4 and 2, substituted compounds have more interactions with the protein, cofactor, and solvents when compared with triclosan. New water molecules were found to interact with some of these inhibitors. Substitution at the 2, position of triclosan caused the relocation of a conserved water molecule, leading to an additional hydrogen bond with the inhibitor. This observation can help in conserved water-based inhibitor design. 2, and 4, unsubstituted compounds showed a movement away from the hydrophobic pocket to compensate for the interactions made by the halogen groups of triclosan. This compound also makes additional interactions with the protein and cofactor which compensate for the lost interactions due to the unsubstitution at 2, and 4,. In cell culture, this inhibitor shows less potency, which indicates that the chlorines at 2, and 4, positions increase the ability of the inhibitor to cross multilayered membranes. This knowledge helps us to modify the different functional groups of triclosan to get more potent inhibitors. © 2010 IUBMB IUBMB Life, 467,476, 2010 [source] Phage-mediated transfer of virulence genesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2001Jon R Saunders Abstract Bacteriophages as accessory genetic elements play a crucial role in the dissemination of genes and the promotion of genetic diversity within bacterial populations. Such horizontal transfer of DNA is critical in the emergence of new pathogenic organisms, through the dissemination of genes encoding virulence factors such as toxins, adhesins and agressins. Phages can transfer genes that are not necessary for bacteriophage persistence and are generally recognised by their ability to convert their host bacteria to new phenotypes. This phenomenon is known as phage conversion. If such converting genes encode for virulence factors, the consequences of phage infection may include increased virulence of the host bacteria, and the conversion of a non-pathogenic strain to a potentially dangerous pathogen. A number of virulence factors in bacteria causing diseases in plants, animals and humans are encoded by converting phages, the vast majority of which are temperate as opposed to lytic in nature. © 2001 Society of Chemical Industry [source] Real-time PCR for the detection and quantitative analysis of IHNV in salmonidsJOURNAL OF FISH DISEASES, Issue 6 2001K Overturf The rapid identification and quantification of virus in diseased fish is a goal both conservationists and commercial aquaculturists have struggled to attain. Recently a technique for the detection of viral mRNA particles that uses fluorescent tagging and amplification has been developed. Utilizing primers and fluorescent labelled probes generated for the specific identification of the nucleocapsid (N) and glycoprotein (G) genes of infectious haematopoietic necrosis virus (IHNV), and an instrument that measures cyclic emittance of fluorescence, the presence or absence of virus can be easily and rapidly confirmed. This method is not only useful in confirming viral presence but is effective in measuring the relative or absolute quantity of virus present within the sample. This allows for the determination of the health status of a carrier fish by measuring the quantity of viral genomes or transcribed viral genes present. Because this method is based on sequence detection, instead of virus isolation in cell culture, it is also effective in determining the presence of pathogenic organisms from water, fish feeds, or other potential reservoirs of infection. [source] Active Packaging of Fresh Chicken Breast, with Allyl Isothiocyanate (AITC) in Combination with Modified Atmosphere Packaging (MAP) to Control the Growth of PathogensJOURNAL OF FOOD SCIENCE, Issue 2 2010Joongmin Shin ABSTRACT:,Listeria monocytogenes,and,Salmonella typhimurium,are major bacterial pathogens associated with poultry products. Ally isothiocyanate (AITC), a natural antimicrobial compound, is reportedly effective against these pathogenic organisms. A device was designed for the controlled release of AITC with modified atmosphere packaging (MAP), and then evaluated for its ability to control the growth of,L. monocytogenes,and,S. typhimurium,on raw chicken breast during refrigerated storage. In order to obtain controlled release during the test period, a glass vial was filled with AITC and triglyceride. It was then sealed using high-density polyethylene film. The release of AITC was controlled by the concentration (mole fraction) of AITC in the triglyceride and by the AITC vapor permeability through the film. The fresh chicken samples were inoculated with one or the other of the pathogens at 104 CFU/g, and the packages (with and without AITC-controlled release device) were flushed with ambient air or 30% CO2/70% N2 before sealing, and then stored at 4 °C for up to 21 d. The maximum reduction in MAP plus AITC (compared to MAP alone) was 0.77 log CFU/g for,L.,monocytogenes,and 1.3 log CFU/g for,S.,typhimurium. The color of the chicken breast meat was affected by the concentration of AITC. Overall, a release rate of 0.6 ,g/h of AITC was found to not affect the color, whereas at 1.2 ,g/h of AITC the surface of the chicken was discolored. [source] Introgressive hybridization of human and rodent schistosome parasites in western KenyaMOLECULAR ECOLOGY, Issue 23 2008MICHELLE L. STEINAUER Abstract Hybridization and introgression can have important consequences for the evolution, ecology and epidemiology of pathogenic organisms. We examined the dynamics of hybridization between a trematode parasite of humans, Schistosoma mansoni, and its sister species, S. rodhaini, a rodent parasite, in a natural hybrid zone in western Kenya. Using microsatellite markers, rDNA and mtDNA, we showed that hybrids between the two species occur in nature, are fertile and produce viable offspring through backcrosses with S. mansoni. Averaged across collection sites, individuals of hybrid ancestry comprised 7.2% of all schistosomes collected, which is a large proportion given that one of the parental species, S. rodhaini, comprised only 9.1% of the specimens. No F1 individuals were collected and all hybrids represented backcrosses with S. mansoni that were of the first or successive generations. The direction of introgression appears highly asymmetric, causing unidirectional gene flow from the rodent parasite, S. rodhaini, to the human parasite, S. mansoni. Hybrid occurrence was seasonal and most hybrids were collected during the month of September over a 2-year period, a time when S. rodhaini was also abundant. We also examined the sex ratios and phenotypic differences between the hybrids and parental species, including the number of infective stages produced in the snail host and the time of day the infective stages emerge. No statistical differences were found in any of these characteristics, and most of the hybrids showed an emergence pattern similar to that of S. mansoni. One individual, however, showed a bimodal emergence pattern that was characteristic of both parental species. In conclusion, these species maintain their identity despite hybridization, although introgression may cause important alterations of the biology and epidemiology of schistosomiasis in this region. [source] Functional analysis of NsrR, a nitric oxide-sensing Rrf2 repressor in Neisseria gonorrhoeaeMOLECULAR MICROBIOLOGY, Issue 1 2009Vincent M. Isabella Summary Nitric oxide (NO) has been shown to be an important component of the human immune response, and as such, it is important to understand how pathogenic organisms respond to its presence. In Neisseria gonorrhoeae, recent work has revealed that NsrR, an Rrf2-type transcriptional repressor, can sense NO and control the expression of genes responsible for NO metabolism. A highly pure extract of epitope-tagged NsrR was isolated and mass spectroscopic analysis suggested that the protein contained a [2Fe,2S] cluster. NsrR/DNA interactions were thoroughly analysed in vitro. Using EMSA analysis, NsrR::FLAG was shown to interact with predicted operators in the norB, aniA and nsrR upstream regions with a Kd of 7, 19 and 35 nM respectively. DNase I footprint analysis was performed on the upstream regions of norB and nsrR, where NsrR was shown to protect the predicted 29 bp binding sites. The presence of exogenously added NO inhibited DNA binding by NsrR. Alanine substitution of C90, C97 or C103 in NsrR abrogated repression of norB::lacZ and inhibited DNA binding, consistent with their presumed role in co-ordination of a NO-sensitive Fe,S centre required for DNA binding. [source] Unravelling a histone code for malaria virulenceMOLECULAR MICROBIOLOGY, Issue 6 2007Christy A. Comeaux Summary Epigenetic phenomena have been shown to play a role in the regulated expression of virulence genes in several pathogenic organisms, including the var gene family in Plasmodium falciparum. A better understanding of how P. falciparum can both maintain a single active var gene locus through many erythrocytic cycles and also achieve successive switching to different loci in order to evade the host immune system is greatly needed. Disruption of this tightly co-ordinated expression system presents an opportunity for increased clearance of the parasites by the immune system and, in turn, reduced mortality and morbidity. In the current issue of Molecular Microbiology, Lopez-Rubio and colleagues investigate the correlation of specific post-translational histone modifications with different transcriptional states of a single var gene, var2csa. Quantitative chromatin immunoprecipitation is used to demonstrate that different histone methylation marks are enriched at the 5, flanking and coding regions of active, poised or silenced var genes. They identify an increase of H3K4me2 and H3K4me3 in the 5, flanking region of an active var locus and expand on an earlier finding that H3K9me3 is enriched in the coding regions of silenced var genes. The authors also present evidence that H3K4me2 bookmarks the active var gene locus during later developmental stages for expression in the subsequent asexual cycle, hinting at a potential mechanism for transcriptional ,memory'. The stage is now set for work generating a complete catalogue of all histone modifications associated with var gene regulation as well as functional studies striving to uncover the precise mechanisms underlying these observations. [source] Are therapeutic ultrasound units a potential vector for nosocomial infection?PHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 2 2006Siobhan Schabrun Abstract Background and Purpose.,Nosocomial infections present a widespread problem in today's healthcare environment, with a significant number of patients acquiring an infection annually. With the contemporary transition of immunocompromised and high-risk patients to community-based care, therapeutic ultrasound has the potential to be a vector of infection in the physiotherapy setting. The purpose of the present study was to determine the degree of contamination on therapeutic ultrasound transducer heads and ultrasound gel after routine clinical use, and to evaluate the efficacy of recommended infection control procedures.,Method.,The study consisted of two phases. Using a prospective cross-sectional design, microbiological cultures were obtained from 44 transducer heads and 43 gels. Subjects were drawn from a variety of physiotherapy practice settings. All samples containing more than five colony forming units per cm2 were considered contaminated. Following these measurements, a repeated-measures design was used to re-evaluate the 44 transducer heads for the amount and type of bacteria present after cleaning with a 70% alcohol wipe.,Results.,Twenty-seven per cent of transducer heads and 28% of gels were contaminated. Transducer heads showed fairly low levels of contamination across the sample, with the majority of organisms isolated found in normal skin and environmental flora. Gels were heavily contaminated with opportunistic and potentially pathogenic organisms, including Stenotrophomonas maltophilia, Staphylococcus aureus, Acinetobacter baumannii and Rhodotorula mucilaginosa. No multi-resistant organisms were identified. Cleaning with 70% alcohol significantly reduced the level of contamination on transducer heads (p < 0.01).,Conclusions.,Therapeutic ultrasound equipment is a potential vector for nosocomial infection in physiotherapy patients. The risk of infection from transducer heads can be effectively removed by cleaning with 70% alcohol between patients. Further research into possible strategies to reduce the risk of infection from ultrasound gels is needed. Copyright © 2006 John Wiley & Sons, Ltd. [source] The 1.9,Å resolution structure of Mycobacterium tuberculosis 1-deoxy- d -xylulose 5-phosphate reductoisomerase, a potential drug targetACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2006Lena M. Henriksson 1-Deoxy- d -xylulose 5-phosphate reductoisomerase catalyzes the NADPH-dependent rearrangement and reduction of 1-deoxy- d -xylulose 5-phosphate to form 2- C -methyl- d -erythritol 4-phosphate, as the second step of the deoxyxylulose 5-phosphate/methylerythritol 4-phosphate pathway found in many bacteria and plants. The end product, isopentenyl diphosphate, is the precursor of various isoprenoids vital to all living organisms. The pathway is not found in humans; the mevalonate pathway is instead used for the formation of isopentenyl diphosphate. This difference, combined with its essentiality, makes the reductoisomerase an excellent drug target in a number of pathogenic organisms. The structure of 1-deoxy- d -xylulose 5-phosphate reductoisomerase from Mycobacterium tuberculosis (Rv2870c) was solved by molecular replacement and refined to a resolution of 1.9,Å. The enzyme exhibited an estimated kcat of 5.3,s,1 and Km and kcat/Km values of 7.2,µM and 7.4 × 105,M,1,s,1 for NADPH and 340,µM and 1.6 × 104,M,1,s,1 for 1-deoxy- d -xylulose 5-phosphate. In the structure, a sulfate is bound at the expected site of the phosphate moiety of the sugar substrate. The M. tuberculosis enzyme displays a similar fold to the previously published structures from Escherichia coli and Zymomonas mobilis. Comparisons offer suggestions for the design of specific drugs. Furthermore, the new structure represents an intermediate conformation between the open apo form and the closed holo form observed previously, giving insights into the conformational changes associated with catalysis. [source] Proteomics meets microbiology: technical advances in the global mapping of protein expression and functionCELLULAR MICROBIOLOGY, Issue 8 2005Carolyn I. Phillips Summary The availability of complete genome sequences for a large number of pathogenic organisms has opened the door for large-scale proteomic studies to dissect both protein expression/regulation and function. This review highlights key proteomic methods including two-dimensional gel electrophoresis, reference mapping, protein expression profiling and recent advances in gel-free separation techniques that have made a significant impact on the resolution of complex proteomes. In addition, we highlight recent developments in the field of chemical proteomics, a branch of proteomics aimed at functionally profiling a proteome. These techniques include the development of activity-based probes and activity-based protein profiling methods as well as the use of synthetic small molecule libraries to screen for pharmacological tools to perturb basic biological processes. This review will focus on the applications of these technologies to the field of microbiology. [source] Sequence-Based Identification of Specific Drug Target Regions in the Thymidylate Synthase Enzyme FamilyCHEMMEDCHEM, Issue 3 2008Stefania Ferrari Dr. Thymidylate synthases from pathogenic organisms: Sequence analysis and knowledge-based grouping have provided a step forward in the identification of potential drug target regions in thymidylate synthases. This provides a unique approach toward blocking the growth of pathogenic organisms. [source] Too clean, or not too clean: the Hygiene Hypothesis and home hygieneCLINICAL & EXPERIMENTAL ALLERGY, Issue 4 2006S. F. Bloomfield Summary The ,hygiene hypothesis' as originally formulated by Strachan, proposes that a cause of the recent rapid rise in atopic disorders could be a lower incidence of infection in early childhood, transmitted by unhygienic contact with older siblings. Use of the term ,hygiene hypothesis' has led to several interpretations, some of which are not supported by a broader survey of the evidence. The increase in allergic disorders does not correlate with the decrease in infection with pathogenic organisms, nor can it be explained by changes in domestic hygiene. A consensus is beginning to develop round the view that more fundamental changes in lifestyle have led to decreased exposure to certain microbial or other species, such as helminths, that are important for the development of immunoregulatory mechanisms. Although this review concludes that the relationship of the hypothesis to hygiene practice is not proven, it lends strong support to initiatives seeking to improve hygiene practice. It would however be helpful if the hypothesis were renamed, e.g. as the ,microbial exposure' hypothesis, or ,microbial deprivation' hypothesis, as proposed for instance by Bjorksten. Avoiding the term ,hygiene' would help focus attention on determining the true impact of microbes on atopic diseases, while minimizing risks of discouraging good hygiene practice. [source] | |||||||||||||||||||