Surveillance and potential health risks of antibiotic-resistant shiga toxigenic Escherichia coli isolated from beef sold in Osogbo, Nigeria

Abstract

Shiga toxigenic Escherichia coli (STEC) has been implicated in foodborne infections across the globe. However, STEC's presence in beef samples has received little attention in many parts of Nigeria. In this study, we determined the incidence and evaluated the antimicrobial susceptibility profile of STEC in beef sold in the two (Olorunda and Osogbo) local government areas (LGAs) of Osogbo, Nigeria. Exactly 100 beef samples from 20 abattoirs and 80 retail shops were screened for coliform and STEC using MacConkey and Sorbitol-MacConkey agar respectively. The STEC were confirmed using polymerase chain reactions and 16S rRNA sequencing. The phylogenetic relatedness of the identified strains was investigated using MEGA X. STEC were further identified using Shiga toxin1 (stx1), Shiga toxin2 (stx2), haemolysin (hylA) and Intimin (eaeA) oligonucleotides. The Kirby-Bauer disk diffusion method was adopted to evaluate the antimicrobial susceptibility profile of the recovered STEC against 13 antibiotics. Cumulatively, abattoirs at Olorunda and Osogbo LGAs showed the highest (6.7 log CFU/g) and lowest (6.3 log CFU/g) coliform counts respectively. Among the 18 identified STEC, 14 encoded single genes (11 stx2 and three eaeA), two encoded the co-presence of stx2 and hlyA. None encoded stx1, co-presence of stx2 and eaeA, hlyA and eaeA, or the four genes. The STEC recovered from the beef were highly resistant to sulphamethoxazole/trimethoprim, aztreonam, cefoxitin, cefepime, ceftazidime/avibactam, ampicillin/sulbactam and doxycycline. Susceptibilities (≥ 50%) were observed in gentamicin and levofloxacin. Our study showed that beef contaminated by antibiotic-resistant STEC may pose impending risks to its consumers.