Characterization of antimicrobial resistant Escherichia coli isolated from processed bison carcasses

Aims: To determine the phenotypic and genotypic antimicrobial susceptibility profiles of Escherichia coli from bison carcasses. Methods and Materials: The antimicrobial resistance of 138 E. coli isolates recovered from processed bison carcasses was determined by using the National Antimicrobial Resistance Monitoring System panels, polymerase chain reaction assays, plasmid analysis and conjugation studies. Results: Resistance to 14 of the 16 antimicrobials was observed. Twenty-three (16.7%) isolates displayed resistance to at least one antimicrobial agent. The most prevalent resistances were to tetracycline (13.0%), sulfamethoxazole (7.9%) and streptomycin (5.8%). No resistance was observed to amikacin and ciprofloxacin. Further analysis of 23 antimicrobial-resistant E. coli isolates showed the presence of resistance genes corresponding to their phenotypic profiles. Results of conjugation studies carried out showed most isolates tested were able to transfer their resistance to recipients. Conclusion: This study indicated that multidrug-resistant E. coli isolates are present in bison. However, the resistance rate is lower than that reported in other meat species. Significance and Impact of the Study: The beneficial effects of antimicrobial-free feeding practice in bison may be promoting a reduction in the prevalence of antimicrobial resistance in commensal flora of bison.