Prevalence and characterization of escherichia coli O157:H7 isolated from cattle

ABSTRACT
The objectives of this study were to determine the incidence of E. coli O157:H7 by immunomagnetic separation based selective enrichment technique in feces and/or colon tissue of cattle, to verify the isolates using PCR to detect fliC_h7 gene, and also other virulence genes as stx₁, stx₂, eae and hly by multiplex PCR technique, and to find out the genomic diversity using PFGE.
In the study, out of 282 feces and/or colon tissue of beef cattle samples, 11 (3.1 %) were found to be contaminated with E. coli O157:H7. According to the PCR analysis, fliC_h7, eae and hly genes were detected in all E. coli O157:H7 positive isolates (100.0 %). Isolates were also tested for the toxin genes and as a result, all isolates (100.0 %) were found to carry at least one toxin gene (stx₁ or stx₂ ). Six of the isolates (54.5 %) were positive for both of the shiga toxin 1 and 2 (stx₁ and stx₂), four of them (36.4 %) were only positive for stx₂, and one of them (9.1 %) was positive for stx₁.
According to the PFGE results, E. coli O157:H7 isolates were grouped into four different genomic characters (4 group). Two groups have only one isolate (9.1 %), one group has two (18.2 %) and, one group has 7 (63.6 %) isolates. Most of the isolates (72.7 %) were shown the same toxin profiles in the same genomic groups.