Prevalence and molecular characterization of sorbitol fermenting and non-fermenting Escherichia coli O157:H7+/H7– isolated from cattle at slaughterhouse and slaughterhouse wastewater

Abstract

The prevalence and seasonal distribution of E. colt 0157:H7(+)/H7(-) in an array of aged cattle at slaughter and its dissemination with slaughterhouse wastewater over a two year period in Turkey were investigated. For this purpose, a total of 720 samples (240 rectoanal mucosal swap [RAMS], 240 carcass sponge and 240 bile samples) of 240 cattle categorized according to age, gender, breed and sampling site were collected along with additional 24 wastewater samples and were subjected to immunomagnetic separation based cultivation technique to efficiently isolate E. coli 0157 from the background flora. Identification (rfbE(0157),fliC(h7)), detection of major virulence factors (sbc7, sU2, eaeA, hly, lpfA1-3 and espA), intimin variants (eae-alpha 1, eae-alpha 2, eae-beta 3, eae-beta 1, eae-beta 2, eae-gamma l and eae-gamma 2/0) and shiga toxin variants (stx70 stx(1d), stx(2c), stx(2d), stx(2e), stx(2f)and stx(2g)) of all the isolates were assessed by PCR. From 10(42%) of RAMS and 11(4.6%) of carcass sponge samples and 5 (20.8%) of slaughterhouse wastewater samples, a total of 102 colonies (99 sorbitol negative and 3 sorbitol positive) were isolated. Overall, 17 (7.1%) and 15 (6.3%) of 240 sampled cattle were shown to harbor E. coli 0157 and E. colt 0157:H7, respectively either in their RAMS or carcass sponge samples analyzed. Statistically significant differences between categories; season, age, gender and breed of cattle were not observed (p > 0.05). None of the isolated E. coli 0157:H7+/H7- strains harbored any of the investigated intimin types other than eaeyi or shiga toxin variants stx(1d), StX(2e), six(2f) or StX(2g) while all were lpfA1-3+ except 5 E. coli 0157:H7- strains. Intimin variant eaey, and shiga toxin 1 variant stx/c were detected from all of the eaeA+ (97/102, 95.1%) and stxt (32/102,313%) strains, respectively while from sbd" (80/102, 78.4%) isolates, both stx(2c) (68/80, 85.0%) and 5tx(2d) (12/80, 15.0%) variants were determined. In the last decade, prevalence of E. coli 0157:H7 has an increasing trend in cattle. Slaughterhouses are the significant sources of environmental contamination with E. coli 0157:H7. Isolation and molecular characterization of sorbitol fermenting E. coli 0157:H7 are a novel finding and may lead to a revision of reference isolation procedure of E. coli 0157:H7 in future. (C) 2014 Elsevier B.V. All rights reserved.