ABSTRACT
The purpose of the study was determination of the occurrence of E. coli O157 in faeces samples of healthy subjects and characterization of the isolated strains with respect to their potential pathogenicity. The study was carried out in two stages. In the first one in 5 sanitary-epidemiological stations samples were tested from healthy subjects after inoculation onto McConkey (MC) or/and McConkey with sorbitol (SMC) media and isolating from each culture 10 lactose-positive (on MC medium) or sorbitol-negative (on SMC) colonies. Then latex test was done with each isolate for E. coli O157 presence. In all, 1005 samples were studied, including 260 taken from children aged 0-2 years, 180 samples from children aged 3-10 years, and 565 samples from older children and adults. E. coli O157 rods were cultured from 6 adults (0.6%). In the second stage carried out at the Laboratory of Enterobacteriaceae, Bacteriology Department, National Institute of Hygiene strains obtained from territorial laboratories were studied determining their phenotypic and genotypic traits regarded as virulence markers of verotoxic E. coli O157 strains, such as inability to ferment sorbitol and MUG breakdown, and production of verotoxins and enterohaemolysin. By the PCR method fragments were sought of genes coding for production of verotoxins, intimin and enterohaemolysin. The results showed that no E. coli O157 strain obtained from healthy individuals produced verotoxins, but three studied strains contained the eae gene determining intimin production and they were regarded as enteropathogenic.
