[Diagnostic bacteriophage V32 as a tool for the rapid identification of Escherichia coli serogroup O157.]

Bacteriophage V32, a representative of bacterial viruses of the Myoviridae family Ounavirinae subfamily, is proposed for search and identification of E. coli O157 serogroup, including Shiga-toxin producing E. coli O157:H7 (STEC O157:H7), among cultures of enterobacteria from the primary seeding of the material studied. Phage genome containes a linear double-stranded DNA of 87875 base pairs with G/C-content of 38.9% and includes 132 open reading frames (ORF). In the genome, there are no determinants of antibiotic resistance, virulence genes of STEC and other well-known pathogroups of E. coli. It has been established that phage V32 has lytic activity against all studied cultures of E. coli O157 serogroup (n=183) isolated from people and farm animals in various regions of the Russian Federation, as well as in Japan and Italy. At the same time, the phage lyses only 6 of 182 strains (3.3%) of E. coli not belonging to the O157 serogroup and is not active against strains of other enterobacteria. That is, the phage has a high specificity. The use of bacteriophage V32 as a diagnostic tool is a highly efficient, fast, cheap and simple method for identifying E. coli serogroup O157, including the serotype E. coli O157: H7, in any bacteriological laboratory without special equipment and special training of performers.

A small-scale experiment of using phage-based probiotic dietary supplement for prevention of E. coli traveler's diarrhea.

Traveler's diarrhea (TD) is caused by Escherichia coli in 30% of cases. We have developed a phage cocktail for prophylaxis of TD caused by E.coli, Shigella flexneri, Shigella sonnei, Salmonella enterica, Listeria monocytogenes or Staphylococcus aureus, and investigated its effectiveness against infection caused by the non-pathogenic Lac (-) strain of E.coli K12 C600 in animal and human trials. On the 6th day of both animal and human trials E. coli K12 C600 strain was detected in titer of 104 CFU/g of mice feces and 106 CFU/g of human feces in the control (untreated) groups, while it was not detected in the samples of either of the study (phage-treated) groups. These results have great significance because the original coliphages included in the cocktail have a broad host-range including ETEC, EAEC and EHEC strains which cause severe cases of TD.

[Corynebacterium diphtheriae nontoxigenic strain carrying the gene of diphtheria toxin]. / Kharakteristika netoksigennykh shtammov Corynebacterium diphtheriae, nesushchikh gen difteriinogo toksina.

Among 828 C. diphtheriae nontoxigenic cultures isolated in different region of Russia in 1994-2002, 114 cultures (13.8%) had the gene of diphtheria toxin (gene tox) and were thus called nontoxigenic tox-carrying (NTTC) strains. All NTTC strains were found to belong to biovar mitis and formed neither normal, nor "defective" diphtheria toxin. The most of NTTC strains (94%) belonged to ribotype "Moskva", not occurring among C. diphtheriae toxigenic strains. The incapacity of NNTC strains of forming diphtheria toxin was caused by mutation: the deletion of one nucleotide which led to the shift of the open reading frame and to the formation of the stop codon. The results of these studies are indicative of the fact that a sufficiently homogeneous and isolated group of C. diphtheriae nontoxigenic strains is spread in Russia. These strains carry the nonexpressing gene of diphtheria toxin and are of no epidemic importance in diphtheria infection.

[Effect of TRA-system of plasmids RP4 and R68.45 on pseudomonas mallei virulence]. / Vliianie Tra-sistemy plazmid RP4 i R68.45 na virulentnost' vozbuditelia sapa.

In Pseudomonas mallei, spontaneous mutants (Tra- mutants) of the plasmids RP4 and R68.45, losing the ability to transfer at conjugation are formed. The plasmids RP4 and R68.45 with Tra(+)-phenotype caused a decrease in P. mallei virulence for laboratory animals. At the same time, Tra- mutants of these plasmids do not affect P. mallei virulence. The insertion of DNA fragment of about 1900 bp into the plasmid transfer gene regions (tra-2-tra-3) gave rise to RP4 and R68.45 tra mutations detectable on examination.