Abstract
Atypical enteropathogenic E. coli (aEPEC) is a group of diarrhoeagenic Escherichia coli with high diversity of serogroups, which lack the bundle-forming pili (BFP) and genes encoding for shiga toxins. The aim of this study was to isolate, identify and determine virulence and antibiotic resistance profiles of aEPEC O177 strains from cattle feces. A total of 780 samples were collected from beef and dairy cattle and analyzed for the presence of E. coli O177. One thousand two hundred and seventy-two (1272) presumptive isolates were obtained and 915 were confirmed as E. coli species. Three hundred and seventy-six isolates were positively confirmed as E. coli O177 through amplification of rmlB and wzy gene sequences using multiplex PCR. None of these isolates harbored bfpA gene. A larger proportion (12.74%) of the isolates harbored hlyA gene while 11.20, 9.07, 7.25, 2.60, and 0.63% possessed stx2, stx1, eaeA, stx2a, and stx2d, respectively. Most of E. coli O177 isolates carried stx2/hlyA (9.74%). Furthermore, 7.40% of the isolates harbored stx1/stx2 while 7.09% possessed stx1/stx2/hlyA genes. Only one isolate harbored stx1/stx2/hly/eaeA/stx2a/stx2d while 5.11% of the isolates harbored all the four major virulence genes stx1/stx2/hlyA/eaeA, simultaneously. Further analysis revealed that the isolates displayed varied antimicrobial resistance to erythromycin (63.84%), ampicillin (21.54%), tetracycline (13.37%), streptomycin (17.01%), kanamycin (2.42%), chloramphenicol (1.97%), and norfloxacin (1.40%). Moreover, 20.7% of the isolates exhibited different phenotypic multi-drug resistance patterns. All 73 isolates harbored at least one antimicrobial resistance gene. The aadA, streA, streB, erm, and tetA resistance genes were detected separately and/or concurrently. In conclusion, our findings indicate that environmental isolates of aEPEC O177 strains obtained from cattle in South Africa harbored virulence and antimicrobial resistance gene determinants similar to those reported in other shiga-toxin producing E. coli strains and suggest that these determinants may contribute to the virulence of the isolates.
Highlights
Enteropathogenic E. coli (EPEC) is a group of diarrhoeagenic E. coli that is reported to cause high morbidity and mortality in humans, especially in immune-compromised subjects, elderly individuals and young children
Based on the presence or absence of the EPEC adherence factor (EAF) plasmid, EPEC is subdivided into two groups that include typical Enteropathogenic E. coli and atypical Enteropathogenic E. coli (Trabulsi et al, 2002; Alonso et al, 2017)
A total of 780 cattle fecal samples were analyzed for the presence of E. coli O177 using Rainbow agarO157 and a total of 1,272 non-repetitive presumptive isolates were obtained
Summary
Enteropathogenic E. coli (EPEC) is a group of diarrhoeagenic E. coli that is reported to cause high morbidity and mortality in humans, especially in immune-compromised subjects, elderly individuals and young children. Despite the fact that tEPEC have been most often associated disease complications in humans, it is only recently that aEPEC been reported to cause diseases in both animals and humans (Malik et al, 2017) This may account for the reason why previous studies that have been documented worldwide and in the study area have focused on EHEC, especially E. coli O157 and non-O157 strains that received great attention due to its high pathogenicity (Ateba and Bezuidenhout, 2008; Ateba and Mbewe, 2011; Iwu et al, 2016; Jajarmi et al, 2017; Toro et al, 2018). This was motivated from the fact that cattle are the primary reservoir of both EHEC (stx+) and aEPEC (stx−) strains, providing opportunities for horizontal transfer of virulence and antibiotic resistant genes between species and/or strains living in the same ecological niches (Bibbal et al, 2017)
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