Prevalence, genetic characterization and virulence genes of sorbitol-fermenting Escherichia coli 0157:H- and E. coli 0157:H7 isolated from retail beef

Sorbitol-fermenting (SF) Escherichia coli 0157:H- strains have emerged as important pathogens and have been associated with a higher incidence of progression to hemolytic-uremic syndrome (HUS) than non-sorbitol fermenting (NSF) E. coli 0157:H7. The present study was carried out to determine the prevalence of SF E. coli 0157:H- and NSF E. coli 0157:H7 strains in retail beef products in Mansoura, Egypt. The contamination rates with rfbE(O157)-positive E. coli 0157 strains were 26.7% (8/30), 10% (3/30) and 3.7% (1/27) in ground beef, beef burger, and fresh beef samples, respectively with an overall mean of 13.8% (12/87) among all meat products tested. SF E. coli 0157:H- were the most dominant among the isolated 0157 strains. Of the fifteen 0157 strains isolated, 11(73.3%) were SF E. coli 0157:H-, while the remaining 4 (26.7%) were NSF E. coli 0157:H7. The 11 SF 0157H- strains were genetically positive for sfpA gene. Restriction fragment length polymorphism (RFLP) analysis for fliC gene demonstrated a similar pattern for both SF and NSF 0157 isolates. PCR assays verified the existence ofsUl gene in 7(46.7%) and stx2 gene in 13 (86.7%) of the 15 0157 strains isolated. Unexpectedly, two of the 15 0157 strains isolated were negative for Shiga toxin genes. The eae gene was identified in all of the 15 0157 strains except in one NSF 0157:H7 strain. EHEC-hlyA gene was detected in 14(93.3%) of the 15 0157 isolates, nonetheless only 11 strains showed enterohemolytic phenotype on blood agar. A combination of the four virulence genes, stx1, stx2, eae and EHEC-hlyA were detected in 7 (46.7%) strains, while six (40%) strains were positive for stx2, eae and hlyA genes. This is the first record for isolation of E. coli 0157: H- in Egypt as well as in the African continent. (C) 2013 Published by Elsevier B.V.