Molecular characteristics and antimicrobial susceptibility of Shiga toxin-producing Escherichia coli O157:H7 from beef cattle feces and carcasses in municipal abattoirs in Central Ethiopia

Pathogenic Escherichia coli O157:H7 has been reported to occur on beef carcasses in Ethiopia which can pose a significant public health risk. This study was conducted to assess the occurrence, potential source of contamination and the antimicrobial susceptibility of E. coli O157:H7 on bovine carcasses from three municipal abattoirs from Central Ethiopia. A total of 216 fecal and hide samples each, 540 carcass swabs, 18 water samples, and 18 swabs each from workers’ hands and knives were collected. The study revealed a 1.4% and 1.1% prevalence of E. coli O157:H7 in feces and on carcasses, respectively. E. coli O157:H7 was not detected (0%) in the remaining samples including water, hides, workers’ hands and knives. A whole-genome-sequencing-based core genome multilocus sequence typing (cgMLST) analysis of the E. coli O157:H7 isolates from the same municipal abattoir showed clonal relatedness, i.e. clustering together with no allele differences (AD) in the cgMLST scheme. However, genetic diversity was observed between isolates originating from different abattoirs, with allelic differences ranging from 140 to 226 AD. All strains carried virulence genes encoding adherence factors ( eae , iha , and tir ), type III secretion system translocated proteins ( espA , espB , espJ , espP , etpD , nleA , nleB , and nleC ), outer membrane proteins ( chuA , ompT , and traT ), toxins ( astA , ehxA , and toxB ), and other pathogenicity-related factors ( gad , iss , katP , and terC ). All strains carried the stx2 gene subtype stx2c . All isolates were susceptible to the antimicrobials for which valid clinical breakpoints were available and displayed wild-type MIC distributions for most antimicrobials evaluated using available EUCAST ECOFFs. Neither acquired antimicrobial resistance genes nor known resistance-associated chromosomal mutations were detected. The study findings suggest that contact with fecal material during evisceration is a possible source for contaminating the carcasses with E. coli O157:H7. Therefore, strict hygienic practice should be followed during carcass processing.