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  • 1
    Electronic Resource
    Electronic Resource
    Structural characterization of lipo-oligosaccharide (LOS) from Yersinia pestis: regulation of LOS structure by the PhoPQ system (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 44 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The two-component regulatory system PhoPQ has been shown to regulate the expression of virulence factors in a number of bacterial species. For one such virulence factor, lipopolysaccharide (LPS), the PhoPQ system has been shown to regulate structural modifications in Salmonella enterica var Typhi-murium. In Yersinia pestis, which expresses lipo-oligosaccharide (LOS), a PhoPQ regulatory system has been identified and an isogenic mutant constructed. To investigate potential modifications to LOS from Y. pestis, which to date has not been fully characterized, purified LOS from wild-type plague and the phoP defective mutant were analysed by mass spectrometry. Here we report the structural characterization of LOS from Y. pestis and the direct comparison of LOS from a phoP mutant. Structural modifications to lipid A, the host signalling portion of LOS, were not detected but analysis of the core revealed the expression of two distinct molecular species in wild-type LOS, differing in terminal galactose or heptose. The phoP mutant was restricted to the expression of a single molecular species, containing terminal heptose. The minimum inhibitory concentration of cationic antimicrobial peptides for the two strains was determined and compared with the wild-type: the phoP mutant was highly sensitive to polymyxin. Thus, LOS modification is under the control of the PhoPQ regulatory system and the ability to alter LOS structure may be required for survival of Y. pestis within the mammalian and/or flea host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02990.x
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  • 2
    Electronic Resource
    Electronic Resource
    The nematode Panagrellus redivivus is susceptible to killing by human pathogens at 37 °C (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 250 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Caenorhabditis elegans has been used as a host for the study of bacteria that cause disease in mammals. However, a significant limitation of the model is that C. elegans is not viable at 37 °C. We report that the gonochoristic nematode Panagrellus redivivus survives at 37 °C and maintains its life cycle at temperatures up to and including 31.5 °C. The C. elegans pathogens Pseudomonas aeruginosa, Salmonella enterica, Staphylococcus aureus, but not Yersinia pseudotuberculosis, reduced P. redivivus lifespan. Of four strains of Burkholderia multivorans tested, one reduced P. redivivus lifespan at both temperatures, one was avirulent at both temperatures and two strains reduced P. redivivus lifespan only at 37 °C. The mechanism by which one of these strains killed P. redivivus at 37 °C, but not at 25 °C, was investigated further. Killing required viable bacteria, did not involve bacterial invasion of tissues, is unlikely to be due to a diffusible, bacterial toxin and was not associated with increased numbers of live bacteria within the intestine of the worm. We believe B. multivorans may kill P. redivivus by a temperature-regulated mechanism similar to B. pseudomallei killing of C. elegans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.06.046
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  • 3
    Electronic Resource
    Electronic Resource
    A dam mutant of Yersinia pestis is attenuated and induces protection against plague (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 252 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have constructed a dam mutant of Yersinia pestis GB. In BALB/c mice inoculated subcutaneously, the median lethal dose of the mutant was at least 2000-fold higher than the wild type. Mice inoculated with sub-lethal doses of the mutant were protected against a subsequent challenge with virulent Y. pestis. The effect of dam inactivation on gene expression was examined using a DNA microarray, which revealed increased expression of a number of genes associated with the SOS response. These results confirm the key role of Dam in the regulation of virulence, and its potential role as a target for the generation of attenuated strains of pathogenic bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.09.001
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  • 4
    Electronic Resource
    Electronic Resource
    Age influences resistance of Caenorhabditis elegans to killing by pathogenic bacteria (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 234 (2004), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Caenorhabditis elegans has previously been proposed as an alternative host for models of infectious disease caused by human pathogens. When exposed to some human pathogenic bacteria, the life span of nematodes is significantly reduced. We have shown that mutations in the age-1, and/or age-2 genes of C. elegans, that normally enhance life expectancy, can also increase resistance to killing by the bacterial pathogens Pseudomonas aeruginosa, Salmonella enterica var. Typhimurium, Burkholderia cepacia or Yersinia pseudotuberculosis. We also found that the rate at which wild-type C. elegans was killed by the bacterial pathogens tested increased as nematodes aged. In the case of P. aeruginosa infection, the difference in life span of wild type and age-1 mutants of C. elegans was not due to differences in the level of bacterial colonisation of the gut.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2004.tb09545.x
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  • 5
    Electronic Resource
    Electronic Resource
    The SCID/Beige mouse as a model to investigate protection against Yersinia pestis (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 23 (1999), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In this study, we have shown that severe combined immunodeficient/beige mice reconstituted with hyperimmune Balb/c lymphocytes can be used as a model to demonstrate adoptive and passive protection against plague infection. Reconstitution of severe combined immunodeficient/beige mice was successful in nine out of ten mice as demonstrated by spleen colonisation and sustained circulating immunoglobulin titres. Furthermore, an increase in antibody titre was evident after a booster immunisation of reconstituted mice. Presence of circulating antibody correlated with protection against a systemic plague challenge and indicated that in reconstituted mice adoptive transfer of a functional immune system had occurred. The severe combined immunodeficient/beige mouse was also used to demonstrate passive protection against inhaled and systemic plague infection. The reconstituted severe combined immunodeficient/beige mouse model demonstrating protective immunity against plague will be further developed to identify the immune cell subsets responsible for this protection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-695X.1999.tb01229.x
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of the nucleotide sequence and development of a PCR test for the epsilon toxin gene of Clostridium perfringens type B and type D (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 97 (1992), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The sequence of the epsilon toxin gene of Clostridium perfringens type D was determined and compared with that of the previously reported type B sequence. It showed two nucleotide changes in the open reading frame, giving rise to one amino acid substitution. The promoter sequences were not homologous, and different putative −35 and −10 regions have been identified in each. The sequence information was used to develop PCR primers which were specific for the epsilon toxin gene. The utility of this system for identifying type B or D strains of C. perfringens was demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb05443.x
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  • 7
    Electronic Resource
    Electronic Resource
    Macromolecular organisation of recombinant Yersinia pestis F1 antigen and the effect of structure on immunogenicity (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 21 (1998), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Yersinia pestis, the causative organism of plague, produces a capsular protein (fraction 1 or F1 antigen) that is one of the major virulence factors of the bacterium. We report here the production, structural and immunological characterisation of a recombinant F1 antigen (rF1). The rF1 was purified by ammonium sulfate fractionation followed by FPLC Superose gel filtration chromatography. Using FPLC gel filtration chromatography and capillary electrophoresis, we have demonstrated that rF1 antigen exists as a multimer of high molecular mass. This multimer dissociates after heating in the presence of SDS and reassociation occurs upon the removal of SDS. Using circular dichroism, we have monitored the reassociation of monomeric rF1 into a multimeric form. Mice immunised with monomeric or multimeric rF1 develop similar immune responses, but mice immunised with monomeric rF1 were significantly less well protected against a challenge of 1×106 cfu of Y. pestis than mice immunised with multimeric rF1 (1/7 compared with 5/7). The significance of this result in terms of the structure and the function of rF1 is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-695X.1998.tb01168.x
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  • 8
    Electronic Resource
    Electronic Resource
    A new improved sub-unit vaccine for plague: the basis of protection (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 12 (1995), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract In this study, we have determined the limit of protection achievable by immunisation with sub-units of Yersinia pestis against the development of plague in an experimental animal model. Co-immunisation with the purified culture-derived F1 and the recombinant V sub-units afforded a greater level of protection than with either sub-unit alone. The protection given by the combined sub-units was several orders of magnitude greater than that afforded by the whole cell killed (Cutter USP) vaccine and was equivalent to that achieved by vaccination with EV76, the live attenuated Y. pestis vaccine strain. However, the combined sub-unit vaccine has clear advantages over the live vaccine in terms of safety of use and absence of side-effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-695X.1995.tb00196.x
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  • 9
    Electronic Resource
    Electronic Resource
    The failure of different strains of Yersinia pestis to produce lipopolysaccharide O-antigen under different growth conditions is due to mutations in the O-antigen gene cluster (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 197 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The lipopolysaccharide (LPS) from eight strains of Yersinia pestis which had been cultured at 28°C appeared to be devoid of an O-antigen when analysed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. LPS isolated from three of these strains which had been cultured at 37°C also appeared to be devoid of an O-antigen. When the LPS from Y. pestis strain CO92 was purified and analysed by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry, the observed signals were in the mass range predicted for molecules containing lipid A plus the core oligosaccharide but lacking an O-antigen. The nucleotide sequence of Y. pestis strain CO92 revealed the presence of a putative O-antigen gene cluster. However, frame-shift mutations in the ddhB, gmd, fcl and ushA genes are likely to prevent expression of the O-antigen thus explaining the loss of phenotype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10608.x
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  • 10
    Electronic Resource
    Electronic Resource
    Salmonella vaccines for use in humans: present and future perspectives (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 26 (2002), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In recent years there has been significant progress in the development of attenuated Salmonella enterica serovar Typhi strains as candidate typhoid fever vaccines. In clinical trials these vaccines have been shown to be well tolerated and immunogenic. For example, the attenuated S. enterica var. Typhi strains CVD 908-htrA (aroC aroD htrA), Ty800 (phoPphoQ) and χ4073 (cya crp cdt) are all promising candidate typhoid vaccines. In addition, clinical trials have demonstrated that S. enterica var. Typhi vaccines expressing heterologous antigens, such as the tetanus toxin fragment C, can induce immunity to the expressed antigens in human volunteers. In many cases, the problems associated with expression of antigens in Salmonella have been successfully addressed and the future of Salmonella vaccine development is very promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.2002.tb00619.x
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