Structure and gene cluster of the O-polysaccharide of Yersinia rohdei H274-36/78.

A branched O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Yersinia rohdei H274-36/78 and found to contain d-rhamnose, d-mannose, and 3,6-dideoxy-4-C-[(S)-1-hydroxyethyl]-d-xylo-hexose called yersiniose A (Yer). Partial acid hydrolysis of the O-polysaccharide eliminated Yer residues to give a modified linear polysaccharide. Studies by sugar analysis and 1H and 13C NMR spectroscopy, including computational NMR analysis, enabled structure elucidation of a hexasaccharide repeating unit of the O-polysaccharide having two Yer residues attached as monosaccharide side chains. The O-antigen gene cluster of Y. rohdei H274-36/78 located between JUMPStart and galF genes contained putative genes for synthesis of precursors of two O-antigen constituents, GDP-d-Man and GDP-d-Rha, whereas genes responsible for synthesis of CDP-Yer were within the chromosome outside the O-antigen gene cluster. Glycosyltransferase genes and ABC 2 transporter genes were present in the O-antigen gene cluster, and hence the structure established is consistent with the polysaccharide synthesis gene content of the genome.

[The study of patterns of development of resistance of Staphylococcus aureus to triclosan].

The article presents the results of studying molecular genetic mechanisms of development of resistance to antiseptic Triclosan in strain Staphylococcus aureus АТСС25923. The modifcations of strain S. aureus АТСС25923 (Tr1, Tr2, Tr1С и Tr2С) are obtained resistant to 64 mg/l of Triclosan and stably preserving the given characteristic under cultivation in absence of selective pressure. The strain S. aureus Tr1was characterized by slightly delayed growth and the strain S. aureus Tr2 was characterized by growth velocity comparable with initial strain. In the Triclosan-resistant strains a mutation C284T in gene fabI was detected resulting in amino-acid replacement A95V in enzyme enoyl-acyl protein reductase FabI, triclosan target. Besides, in these strains a stably inheriting mutation was detected in genes associated with transport of substances in cell: hypothetical transport protein HlyC/CorC family transporter, protein-transporter of ions of Na+, K+, Li+ and alkali of Na+/H+ antiporter subunit F, membrane hypothetical protein and ATP-binding protein. It is demonstrated that resistance to triclosan in staphylococci is associated with acquirement of point mutations in genes of enoyl-acyl protein reductase and also in other genes related to transport of substances in bacterial cell.

[ON THE ORIGIN OF HYPERVIRULENCE OF THE CAUSATIVE AGENT OF PLAGUE].

The attempt to combine Yersinia pseudotuberculosis and Yersinia pestis into one species has been unsupported by microbiologists due to the specific features of the epidemiology and clinical presentations of their induced diseases and to basic differences in their virulence. Pseudotuberculosis is predominantly a relatively mild human intestinal infection transmitted through contaminated food and plague is an acute generalized disease with high mortality, which is most frequently transmitted by the bites of infected fleas. Y. pestis hypervirulence, the ability of single bacteria to ensure the development of predagonal bacteriemia in rodents, which is sufficient to contaminate the fleas, is one of the main events during pathogen adaptation to a new ecological niche. By analyzing the data of molecular typing of the representative kits of naturally occurring Y. pestis isolates, the authois consider the issues of formation of intraspecies groups with universal hypervirulence, as well as biovars that are highly virulent only to their major host. A strategy for searching for selective virulence factors, the potential molecular targets for vaccination and etiotropic treatment of plague, is discussed.

[Molecular-genetic characterization of shiga-toxin producing Escherichia coli isolated during a food-borne outbreak in St. Petersburg in 2013].

UNLABELLED: Shiga toxin-producing Escherichia coli (STEC) food-borne infections are reported worldwide and represent a serious problem for public healthcare. In the Russian Federation there is little information on epidemiology and etiology of STEC-infections as well as on molecular-genetic peculiarities of STEC pathogens. OBJECTIVE: Our aim was to describe a food-borne outbreak as hemorrhagic colitis (HC) along with hemolytic uremic syndrome (HUS), enterocolitis, and acute gastroenteritis in children in St. Petersburg in 2013. METHODS: Epidemiological, microbiological, molecular-genetic and bioinformatic methods were applied. RESULTS: Objects to study were clinical specimens, milk and food samples, as well as STEC strains isolated during the outbreak. The outbreak of food-borne infection was found to be caused by STEC-contaminated raw milk as confirmed by epidemiological analysis, detection of STEC DNA and isolation of relevant pathogens in milk and sick children fecal specimens. The whole-genome sequencing revealed two groups ofpathogens, E. coli O157:H7 and E. coli O101:H33 among collected strains. Group I strains were attributed to the previously known sequence type ST24, while group II strains belonged to the previously non-described sequence type ST145. In strain genomes of both groups there were identified nucleotide sequences of VT2-like prophage carrying stx2c gene, plasmid enterohemolysin gene, and gene of the STEC main adhesion factor intimin. Gene of intimin gamma was identified in E. coli O157:H7 strains and intimin iota 2 in E. coli O101:H33 strains. The latter previously was identified only in enteropathogenic E. coli (EPEC) strains. CONCLUSION: The additional knowledge of epidemiology and biology of STEC pathogens would assist clinicians and epidemiologists in diagnosing, treating and preventing hemorrhagic colitis.

[Vibrio cholerae strains certification].

AIM: Certification of V. cholerae strains stored at State collection of pathogenic microorganisms and cell cultures SCPM - Obolensk. MATERIALS AND METHODS: 50 V. cholerae strains were studied. Real-time PCR with primers to genes ctxA, ctxB, ace, zot, tcpA, toxR, hlyA, rtxC, rfbO1, ompU, ompW was used. RESULTS: Membership of the studied strains in V. cholerae species was confirmed by molecular-biological methods. 46 strains belong to O1 serogroup, 42 of those - E1 Tor toxigenic, having all the virulence genes and 4 non-toxigenic strains. A strain had ace, zot, tcpA, toxR, rtxC, hlyA, ompU genes. 2 strains had ace, toxR, rtxC, hlyA genes, a strain had only toxR gene which is a global regulatory gene. 2 of the 4 serogroup O1 strains were non-toxigenic and had all the virulence genes (ctxA, ctxB, ace, zot, tcpA, toxR, rtxC, hlyA, ompU). 1 non-toxigenic strain has ace, zot, toxR, hlyA, ompUgenes, and the other - toxR, hlyAgenes. CONCLUSION: Genome certificates of all the V. cholerae strains stored in State collection of pathogenic microorganisms and cell cultures SCPM - Obolensk were created. Markers of epidemic threat - ctxA, ctxB, tcpA, toxR and additional virulence genes were determined.