Molecular Characterization of Escherichia coli Strains Isolated from Different Food Sources

Marija Trkov¹, Tatjana Rupel², Darja Žgur-Bertok³, Sara Trontelj³, Gorazd Avguštin⁴ and Jerneja Ambrožič Avguštin<sup>3*

1</sup>National Institute of Public Health of the Republic of Slovenia, Center for Laboratory Activities, Department of Medical Microbiology, Trubarjeva 2, SI-1000 Ljubljana, Slovenia
²Institute of Public Health Maribor, Department of Sanitary Microbiology, Unit Ljubljana, Prvomajska 1, SI-2000 Maribor, Slovenija
³Department of Biology, Biotehnical Faculty, University of Ljubljana, Ve~na pot 111, SI-1000 Ljubljana, Slovenia
⁴Department of Animal Science, Biotehnical Faculty, University of Ljubljana, Groblje 3, SI-1230 Dom`ale, Slovenia

Article history:
Received December 3, 2013
Accepted April 28, 2014

Key words:
Escherichia coli, food, virulence genes, phylogenetic groups, plasmid-mediated quinolone resistance genes

Summary:
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 phylogenetic 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.

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