Molecular Characterization of Escherichia coli Strains Isolated from Different Food Sources

Since food represents a possible source of pathogenic and antibiotic-resistant Escherichia coli strains, we analyzed 84 isolates from food samples identified in 2007 and 2008 at the National Institute of Public Health in Slovenia. Using polymerase chain reaction (PCR), the isolates were classified into phylogenetic groups and subgroups following the Clermont method. Forty-two (50 %) and thirty (35.7 %) isolates were classified into commensal gut phylogenefic groups A and B1, respectively. Only ten (11.9 %) and two (2.4 %) isolates were assigned to the phylogenetic groups D and B2, which include mainly extraintestinal pathogenic E. coli strains. The strains were further analyzed for the presence of various virulence genes and plasmid-mediated quinolone resistance qnr genes. Virulence genes stx1, stx2, both stx1 and stx2, ehxA and eae associated with Shiga-toxin-producing E. coli were detected in one (1.2 %), five (6 %), five (6 %), eight (9.5 %) and three (3.7 %) isolates, respectively. Seventy-four (88.1 %) isolates carried the gene fimH, whereas virulence genes characteristic of extraintestinal pathogenic E. coli, hra, ompT(APEC) and iha, were detected in nine (11 %), eight (9.5 %) and six (7 %) isolates, respectively. Genes kpsMTII, sfa, usp and vat were discovered in single isolates, whereas hlyA, bmaE, cnf, hbp and sat, as well as plasmid-mediated quinolone resistance genes qnr, were not detected in the analyzed strains. Our results show that various food items are indeed a source of intestinal and, albeit to a lesser extent, of extraintestinal pathogenic E. coli strains.