Molecular Characterization of Escherichia coli Strains Isolated from Different Food Sources

Hrana predstavlja mogući izvor patogenih i na antibiotik otpornih sojeva bakterije Escherichia coli, pa je u radu analizirano 84 izolata iz uzoraka hrane identificiranih 2007. i 2008. godine na Nacionalnom institutu za javno zdravstvo u Sloveniji. Pomoću metode PCR (lančana reakcija polimeraze) prema Clermontu izolati su razvrstani u filogenetske skupine i podskupine. Četrdeset i dva (50 %) su izolata svrstana u filogenetsku skupinu A, a njih trideset (35,7 %) u skupinu B1. Te dvije skupine uglavnom obuhvaćaju komenzale crijevne mikroflore. Deset je izolata (11,9 %) svrstano u skupinu D, a samo njih dva (2,4 %) u skupinu B2. U tim se skupinama uglavnom nalaze ekstraintestinalni patogeni sojevi E. coli. Sojevi su zatim analizirani ne bi li se utvrdila prisutnost različitih virulentnih gena i plazmidnih gena otpornosti na kinolone (qnr). U jednom je izolatu (1,2 %) otkriven virulentni gen stx1, kod njih pet (6 %) gen stx2, a u sljedećih pet izolata (6 %) oba gena, stx1 i stx2. U osam je izolata (9,5 %) pronađen gen ehxA, a u njih tri (3,7 %) gen eae. Svi su ti geni karakteristični za patotip STEC, koji proizvodi Shiga toksin. Gen fimH pronađen je u sedamdeset i četiri (88,1 %) izolata. Od virulentnih gena tipičnih za ekstraintestinalne patogene sojeve E. coli, gen hra je pronađen u devet (11 %), gen ompTAPEC u osam (9,5 %), a gen iha u šest (7 %) izolata. U jednom su izolatu otkriveni geni kpsMTII, sfa, usp i vat, dok geni hlyA, bmaE, cnf, hpb, sat i plazmidni geni otpornosti na kinolone qnr nisu pronađeni u ispitanim izolatima. Rezultati pokazuju da razni prehrambeni proizvodi zaista predstavljaju izvor intestinalnih, te u manjoj mjeri ekstraintestinalnih patogenih sojeva E. coli.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, ompTAPEC 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