[Virulence markers of Escherichia coli O1 strains].

AIM: To detect virulence genes in clinical isolates of Escherichia coli O1 using polymerase chain reaction (PCR). MATERIALS AND METHODS: One hundred and twenty strains of E.coli O1 strains isolated from faeces of patients with acute diarrhea (n = 45) and healthy persons (n = 75) were studied. PCR with primers for rfb and fliC genes, which control synthesis of O- and H- antigens respectively, was used. Fourteen virulence genes (pap, aaf, sfa, afa, eaeA, bfpA, ial, hly, cnf, stx1, stx2, lt, st, and aer) were detected by PCR primers. K1-antigen was determined by Pastorex Meningo B/E. coli O1 kit (Bio-Rad). RESULTS: rfb gene controlling O-antigen synthesis in serogroup O1 as well as fliC gene controlling synthesis of H7 and K1 antigens were detected in all strains. Thus all E. coli strains had antigenic structure O1:K1 :H-:F7. Virulence genes aafl, sfa, afa, eaeA, bfpA, ial, hly, cnf, stx1, stx2, lt, and st were not detected. All strains owned pap and aer genes regardless of the presence of acute diarrhea symptoms. CONCLUSION: It was shown that E. coli O1:KI:H-:F7 strains do not have virulence genes which are characteristic for diarrhea-causing Escherichia. In accordance with the presence of pap and aer genes they could be attributed to uropathogenic Escherichia (UPEC) or avian-pathogenic Escherichia (APEC). It is necessary to detect virulence factors in order to determine E. coli as a cause of intestinal infection.

[Plasmids of antibiotic-resistant strains of Salmonella of varying origin, circulating the Saint-Petersburg and Leningrad region]. / Plazmidy antibiotikorezistentnykh shtammov sal'monell razlichnogo proiskhozhdeniia, tsirkuliruiushchikh v Sankt-Peterburge i Leningradskoi oblasti.

Two hundred and twenty Salmonella strains of various serovars isolated from different source in St. Petersburg and the Leningrad Region in 1984-1991 were investigated. It was shown that drug resistance in 39.3 per cent of the strains was determined by conjugative R plasmids with the molecular weights of 28 to 90 mD which transferred at a rate of 10(-4) to 10(-8). Thirteen detected types of the Salmonella conjugative R plasmids differing in the resistance markers, molecular weights and conjugative transfer rates most frequently contained the genes responsible for the resistance to tetracycline (97.7 per cent), chloramphenicol (92.0 per cent), streptomycin (83.0 per cent), kanamycin (76.1 per cent), monomycin (76.1 per cent) and neomycin (76.1 per cent). The conjugative R plasmids were mainly detected in S> typhimurium (92.9 per cent), especially in the isolates from humans (97.6 per cent). The most frequent plasmid type in the Salmonella strains of this serovar was that with the molecular weight of 90 mD carrying the genes of resistance to chloramphenicol, tetracycline, streptomycin, kanamycin, monomycin and neomycin.

[Sensitivity to antibacterial drugs of Salmonella isolated from various sources in Saint-Petersburg and Leningrad region]. / Chuvstvitel'nost' k antibakterial'nym preparatam sal'monell, vydelennykh iz razlichnykh istochnikov v Sankt-Peterburge i Leningradskoi oblasti.

The position of antibiotic resistant cultures among 1706 strains of 85 Salmonella serovars isolated from various sources in St. Petersburg and the Leningrad Region in 1984-1991 amounted to 16.4 per cent. The highest position of such cultures was among the isolates from humans (20.9 per cent). The positions of the isolates from animals, birds and environment were practically equal (13.8, 13.8 and 13.7 per cent respectively). Strains resistant to streptomycin (11.9 per cent), tetracycline (11.5 per cent) and chloramphenicol (11.2 per cent) were the most frequent Salmonella isolates from the different sources. Rifampicin, amikacin, thienamycin, nitroxolin, oxolinic acid, dioxidin, ciprofloxacin and pefloxacin proved to be highly active against the isolates. No significant difference in the antibiotic resistance spectra of the Salmonella strains circulating in different biotopes was detected. However, among the Salmonella isolates from humans there undoubtedly predominated polyresistant strains with the resistance spectra including 10 and 6 antibacterial drugs (42.4 and 28.8 per cent of the resistant strains respectively). Sometimes there was observed correlation between the serovars of the Salmonella strains (independent of the isolation source) and the most characteristic spectra of their antibiotic resistance. Thus, the antibiotic resistant spectra of 79 per cent of the S. typhimurium strains and 82.5 per cent of the S. haifa strains resistant to one and more antibacterial drugs were the following: CmTcSmKmMmNm and ApCbCmTcSmKmMmNmGmNal respectively.