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Certain Strains (certain + strain)
Selected AbstractsThe diversity of Listeria monocytogenes strains from 10 Icelandic sheep farmsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2004K.B. Gudmundsdottir Abstract Aims:, The purpose of this study was to examine the diversity of Listeria monocytogenes strains from healthy sheep, winter feed and environment of sheep farms in Iceland. Methods and Results:, A total of 104 L. monocytogenes isolates from animals, winter feed and environment on 10 Icelandic sheep farms were compared by serotyping, ribotyping, and pulsed-field gel electrophoresis with ApaI and AscI. The isolates were divided into 24 genotypes, all identified as serovars 1/2a, 1/2b, or 4b. Nine genotypes were detected on more than one farm. On three of the farms there seemed to be a dominant strain of L. monocytogenes. Isolates from incidents of listeriosis in animals occurring on two of the farms belonged to the genotype most commonly found on the particular farm. Nine of the 24 genotypes found on the sheep farms have been associated with disease in animals and/or humans elsewhere in Iceland. Conclusions:, Certain strains of L. monocytogenes seem to be widely distributed on Icelandic sheep farms. On some farms there appears to be a dominant strain of L. monocytogenes. Incidents of listeriosis in animals may tend to be associated with strains commonly found on the farm. Significance and Impact of the Study:, This study demonstrates the diversity of L. monocytogenes present in healthy sheep and their environment. [source] Is contact allergy in man lifelong?CONTACT DERMATITIS, Issue 3 2001An overview of patch test follow-ups In contradistinction from certain strains of mice, contact allergy in man is hypothesized to be either lifelong or at least to last for years. We examined follow-up studies on contact allergy, as evaluated by patch testing, attempting to quantify its natural history. The allergens include colophonium, gold sodium thiosulfate, nickel, and cobalt. At present, due to technical limitations, we cannot state in quantitative terms whether contact allergy in man is lifelong and whether its clinical manifestations change. Thus, we list some criteria for future studies which may help resolve the above question. [source] The structures of Escherichia coli O-polysaccharide antigensFEMS MICROBIOLOGY REVIEWS, Issue 3 2006Roland Stenutz Abstract Escherichia coli is usually a non-pathogenic member of the human colonic flora. However, certain strains have acquired virulence factors and may cause a variety of infections in humans and in animals. There are three clinical syndromes caused by E. coli: (i) sepsis/meningitis; (ii) urinary tract infection and (iii) diarrhoea. Furthermore the E. coli causing diarrhoea is divided into different ,pathotypes' depending on the type of disease, i.e. (i) enterotoxigenic; (ii) enteropathogenic; (iii) enteroinvasive; (iv) enterohaemorrhagic; (v) enteroaggregative and (vi) diffusely adherent. The serotyping of E. coli based on the somatic (O), flagellar (H) and capsular polysaccharide antigens (K) is used in epidemiology. The different antigens may be unique for a particular serogroup or antigenic determinants may be shared, resulting in cross-reactions with other serogroups of E. coli or even with other members of the family Enterobacteriacea. To establish the uniqueness of a particular serogroup or to identify the presence of common epitopes, a database of the structures of O-antigenic polysaccharides has been created. The E. coli database (ECODAB) contains structures, nuclear magnetic resonance chemical shifts and to some extent cross-reactivity relationships. All fields are searchable. A ranking is produced based on similarity, which facilitates rapid identification of strains that are difficult to serotype (if known) based on classical agglutinating methods. In addition, results pertinent to the biosynthesis of the repeating units of O-antigens are discussed. The ECODAB is accessible to the scientific community at http://www.casper.organ.su.se/ECODAB/. [source] Exploiting the genetic and biochemical capacities of bacteria for the remediation of heavy metal pollutionFEMS MICROBIOLOGY REVIEWS, Issue 4 2002Marc Valls Abstract The threat of heavy metal pollution to public health and wildlife has led to an increased interest in developing systems that can remove or neutralise its toxic effects in soil, sediments and wastewater. Unlike organic contaminants, which can be degraded to harmless chemical species, heavy metals cannot be destroyed. Remediating the pollution they cause can therefore only be envisioned as their immobilisation in a non-bioavailable form, or their re-speciation into less toxic forms. While these approaches do not solve the problem altogether, they do help to protect afflicted sites from noxious effects and isolate the contaminants as a contained and sometimes recyclable residue. This review outlines the most important bacterial phenotypes and properties that are (or could be) instrumental in heavy metal bioremediation, along with what is known of their genetic and biochemical background. A variety of instances are discussed in which valuable properties already present in certain strains can be combined or improved through state-of-the-art genetic engineering. In other cases, knowledge of metal-related reactions catalysed by some bacteria allows optimisation of the desired process by altering the physicochemical conditions of the contaminated area. The combination of genetic engineering of the bacterial catalysts with judicious eco-engineering of the polluted sites will be of paramount importance in future bioremediation strategies. [source] Nisin Z inhibits the growth of Candida albicans and its transition from blastospore to hyphal formJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2008C. Le Lay Abstract Aims:, To investigate the efficacy of nisin Z, an antimicrobial peptide produced by certain strains of Lactococcus lactis against Candida albicans growth and transition. Methods and Results:,Candida albicans was cultured in the presence of various concentrations of nisin Z (1000, 500, and 100 ,g ml,1) for different time points. Candida albicans growth was determined using the Alamar Blue assay. The yeast's transition from blastospore to hyphal form was assessed through optical microscope observations. The effect of nisin Z on C. albicans ultrastructure was followed by scanning and transmission electron microscopy. Our results show that nisin Z inhibited C. albicans growth beginning at 500 ,g ml,1. This inhibition was both time- and dose-dependent. Nisin Z was also active against C. albicans transition by significantly inhibiting the transformation of C. albicans from the blastospore to hyphal form. Treatments with nisin Z lead to ultrastructural disturbances of C. albicans. Conclusion:, Our findings indicate that nisin Z significantly reduced C. albicans growth and transition. These effects may have occurred through ultrastructural modifications of this yeast. Significance and Impact of the Study:, For the first time, effect of nisin Z on C. albicans was investigated. These results therefore suggest that nisin Z may have antifungal properties, and could be used as an antifungal molecule. [source] An in vitro study of the pH-lowering potential of salivary lactobacilli associated with dental cariesJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2001M.C. Badet M.C. BADET, B. RICHARD AND G. DORIGNAC. 2001. Aims: Lactobacilli are known to produce acids from sucrose or glucose. This acid production can cause a drop in pH which is sufficiently significant to demineralize the hard tissues of the teeth. Some authors have demonstrated the benefits of substituting sorbitol or xylitol for sucrose. The aim of this work was to study the acid production of salivary lactobacilli with one test sugar (glucose) and two polyols (sorbitol and xylitol). Methods and Results: The pH-lowering potential of three strains of oral lactobacilli was recorded with glucose or one of the polyols at three different concentrations. The results showed that polyols were broken down by certain strains of lactobacilli. When this degradation took place, the pH dropped to values sufficiently low to demineralize the hard tissues of the teeth. Conclusions: Further studies must be carried out on the metabolism of polyols before encouraging their widespread substitution for sucrose. [source] Antagonistic Activity of Spent Culture Supernatants of Lactic Acid Bacteria against,Helicobacter Pylori,Growth and Infection in Human Gastric Epithelial AGS CellsJOURNAL OF FOOD SCIENCE, Issue 6 2009Wen-Hsin Lin ABSTRACT:, We investigated the bactericidal activity and exclusion effect of 10 strains of lactic acid bacteria (LAB) isolated from different commercial food products and infant feces against,Helicobacter pylori,(H. pylori) in human gastric epithelial AGS cells. Antagonistic activity of spent culture supernatants (SCS) from LAB (LAB-SCS) was tested, and the content of organic acids in SCS was analyzed with high-performance liquid chromatography (HPLC). In addition, the bactericidal activities of LAB-SCS were estimated by a time-kill assay and by measuring the exclusion effect of LAB-SCS against,H. pylori,in AGS cells. The results showed that SCS from certain strains with higher concentrations of organic acids dramatically decreased the viability of,H. pylori. We also proved that the organic acids could inhibit,H. pylori,adhesion and invasion of AGS cells. Furthermore, the concentration and speciation of organic acids in SCS after fermentation of LAB are important factors in the inhibition of,H. pylori,infection. In addition, the,in vitro,methods used in this study might provide for the rapid screening of potential probiotics with anti- H. pylori,activity in the dairy industry. [source] Sensitivity of genera Porphyromonas and Prevotella to the bactericidal action of C-terminal domain of human CAP18 and its analoguesMOLECULAR ORAL MICROBIOLOGY, Issue 5 2003E. Isogai This paper reports the effect of the synthesized 27-amino acid sequence in the C-terminal domain of human CAP18 (hCAP18), a human cationic antibacterial protein or cathelicidin, on certain strains belonging to the genera Porophyromonas and Prevotella. The domain binds lipopolysaccharides (LPS) from Porophyromonas gingivalis and Porophyromonas circumdentaria as well as enterobacterial LPS. Two analogues of hCAP18, designated LL/CAP18 and FF/CAP18, were also tested to determine whether additional activity was obtained. The analogue peptides replaced with hydrophobic and cationic amino acid residues showed more potent bactericidal and LPS-binding activities than the original one. [source] Decrease in Langerhans Cells and Increase in Lymph Node Dendritic Cells Following Chronic Exposure of Mice to Suberythemal Doses of Solar Simulated RadiationPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2005Pauline McLoone ABSTRACT Exposure of certain strains of mice to ultraviolet radiation (UVR) causes suppression of some innate and adaptive immune responses. One such consequence of acute UVB exposure is a reduction in the number of Langerhans cells (LC) in the epidermis and an increase in dendritic cells (DC) in lymph nodes draining the irradiated skin sites. Exposure to chronic UVB irradiation also has effects on the immune system, but it is unknown what effects are caused by repeated doses of solar simulated radiation (SSR). Consequently, the main aims of the present study were to determine whether repeated exposure to low doses of SSR would lead to similar changes in these cell populations and whether chronic doses of SSR activate a protective photoadaptation mechanism. Groups of C3H/HeN mice were irradiated daily with 3.7 J/cm2 SSR from Cleo Natural lamps for 2, 10, 20, 30 or 60 days. Further groups of mice received an additional dose of 7.4 J/cm2 SSR on days 2, 10, 30 or 60 to test for photoadaptation. The numbers of LC in the epidermis and DC in the lymph nodes draining irradiated skin sites were counted 24 h after the final irradiation. With the exception of mice irradiated for only 2 days, LC were significantly reduced throughout the chronic irradiation protocol, and no recovery occurred. DC numbers were significantly increased in the draining lymph nodes of mice irradiated for 20 days and 60 days. [source] Placental macrophage contact induces complete replicative cycle of human immunodeficiency virus in latently infected syncytiotrophoblast cells: role of interleukine-6 and tumor necrosis factor-,AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 3 2002Ferenc D. Tóth The phenotypic mixing between human immunodeficiency virus type 1 (HIV-1) and vesicular stomatitis virus (VSV) has been exploited to assay the susceptibility of human term syncytiotrophoblast cells to penetration by various strains of HIV-1. VSV (HIV-1IIIB) and VSV (HIV-1Ba-L) pseudotypes were found to enter syncytiotrophoblasts. Infection of syncytiotrophoblasts was mediated by envelope glycoproteins of IIIB and Ba-L strains of HIV-1. Although certain strains of HIV-1 could enter syncytiotrophoblasts, the cells did not exhibit permissiveness for HIV-1. The next studies tested the possibility that placental macrophages might induce replication of HIV-1 carried in syncytiotrophoblast cells and that infected syncytiotrophoblasts would be capable of transmitting virus into neighbouring macrophages. For this purpose, the macrophage-tropic Ba-L strain of HIV-1 was used. Interactions between syncytiotrophoblasts and macrophages activated HIV-1 from latency in syncytiotrophoblast cells, which delivered HIV-1 to cocultured macrophages. The stimulatory effect of coculture on HIV-1 gene expression was mediated by marked tumor necrosis factor-, and interleukin-6 release from macrophages, an effect caused by contact between the different placental cells. Results suggest an interactive role for the syncytiotrophoblast layer and placental macrophages in the dissemination of HIV-1 among placental tissue. [source] Structure of the d -alanylgriseoluteic acid biosynthetic protein EhpF, an atypical member of the ANL superfamily of adenylating enzymesACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2010Asim K. Bera The structure of EhpF, a 41,kDa protein that functions in the biosynthetic pathway leading to the broad-spectrum antimicrobial compound d -alanylgriseoluteic acid (AGA), is reported. A cluster of approximately 16 genes, including ehpF, located on a 200,kbp plasmid native to certain strains of Pantoea agglomerans encodes the proteins that are required for the conversion of chorismic acid to AGA. Phenazine-1,6-dicarboxylate has been identified as an intermediate in AGA biosynthesis and deletion of ehpF results in accumulation of this compound in vivo. The crystallographic data presented here reveal that EhpF is an atypical member of the acyl-CoA synthase or ANL superfamily of adenylating enzymes. These enzymes typically catalyze two-step reactions involving adenylation of a carboxylate substrate followed by transfer of the substrate from AMP to coenzyme A or another phosphopantetheine. EhpF is distinguished by the absence of the C-terminal domain that is characteristic of enzymes from this family and is involved in phosphopantetheine binding and in the second half of the canonical two-step reaction that is typically observed. Based on the structure of EhpF and a bioinformatic analysis, it is proposed that EhpF and EhpG convert phenazine-1,6-dicarboxylate to 6-formylphenazine-1-carboxylate via an adenylyl intermediate. [source] Thymus-leukemia antigen (TL) as a major histocompatibility complex (MHC) class Ib molecule and tumor-specific antigenCANCER SCIENCE, Issue 6 2004Kunio Tsujimura Mouse thymus-leukemia antigens (TL) belong to the family of major histocompatibility complex (MHC) class Ib antigens and have a unique mode of expression, i.e., in contrast to other MHC class Ib or la antigens, they are found restricted to the intestines in all mouse strains, but also in the thymus of certain strains (TL+ strains). Nevertheless, a proportion of T lymphomas/leukemias in strains that do not express TL in the thymus (TL, strains) feature TL as a tumor antigen. TL was originally defined serologically, but subsequently we have succeeded in generating T cell receptor (TCR) ,, and ,, cytotoxic T lymphocytes (CTL) recognizing TL. By use of TL tetramers free from peptides and transfectants expressing various TL/H-2 chimeric molecules, we have been able to show that TL-specific CTL recognize the ,1 /,2 domain of TL without any additional antigen molecules. We previously reported that one of TL's functions in the thymus is positive selection of TCR,, CTL. Recent studies with TL tetramers revealed that they can bind to normal intestinal intraepithelial lymphocytes (ilEL) and thymocytes in a CD8-dependent, but TCR/CD3-independent manner, while their binding to TL-specific CTL is TCR/CD3-and CDS-dependent. The possible significance of these findings in relation to the roles of TL in the intestines is discussed. We have long been interested in TL as a model tumor antigen which shares characteristics with human differentiation tumor antigens, and we have demonstrated that growth of TL+ lymphoma cells in vivo is suppressed by immunization with TL+ skin or dendritic cells (DC) from TL transgenic mice. In addition, anti-tumor effects against TL+ T lymphomas were obtained by adoptive transfer of TL tetramer strongly-positive TL-specific CTLs. [source] | ||||||||||||||||