Antimicrobial susceptibility of Escherichia coli and Shiga-toxin-producing Escherichia coli strains isolated from the slaughtered cattle and ground meat sold in retail markets in Dakar, Senegal

This study aimed to determine the phenotypic resistance profile and compare the antibiotic resistance patterns of Escherichia coli carrying virulence genes associated with Shiga toxin-producing E. coli (STEC) and commensal E. coli (non-virulent). In total, 75 strains from 199 cattle carcasses and 99 ground meat samples were tested. The Kirby-Bauer agar diffusion method was used to test fifteen different antibiotics on 54 non-virulent E. coli strains isolated from ground meat. Additionally, 21 E. coli strains carrying the stx and/or eae virulence genes, identified by PCR, were also evaluated. Among these, 15 strains were isolated from cattle carcasses and 6 from ground meat. The zones of inhibition were read and interpreted according to the antibiogram committee of the French society of microbiology, veterinary recommendations 2019. The results showed that resistance to tetracycline (41%), ampicillin (20%), and amoxicillin + clavulanic acid (13%) was most common among non-virulent E. coli strains. However, E. coli carrying virulence genes were resistant to cephalothin (100%), streptomycin (50%), and tetracycline (14%). The resistance of non-virulent E. coli to antibiotics was 71% compared with 50% of strains harbouring virulence genes. This suggests that the non-virulent E. coli strains were more resistant than the E. coli carrying stx/eae genes. Multidrug resistance (MDR) phenotypes were observed among the tested E. coli in this study. The findings confirm the possible risks of transmission of resistant bacteria to humans via foodstuffs of animal origin. Key words: Cattle carcasses, ground meat, Escherichia coli, stx/eae, antimicrobial resistance, Senegal.