Acquisition of cephalosporin resistance genes blaCTX‐M‐55, blaCTX‐M‐65, and blaCMY‐2 leads to quinolone resistance in colistin‐resistant Escherichia coli harboring mcr‐1 gene

Abstract

AbstractFood contamination with plasmid‐mediated antibiotic‐resistant Escherichia coli has not been thoroughly investigated. This study aimed to clarify the prevalence of colistin‐resistant AmpC/extended‐spectrum β‐lactamase (ESBL)‐producing E. coli harbouring mcr (COL‐ESBL‐EC) and to determine antibiotic resistance by comparison with AmpC/ESBL‐producing E. coli (ESBL‐EC) and colistin‐resistant E. coli harbouring mcr (COL‐EC). Sixty chicken meats were tested for COL‐ESBL‐EC contamination. The result showed that 64 COL‐ESBL‐EC were isolated from 66.7% of the samples, and compared with ESBL‐EC and COL‐EC were isolated before. The genotypes of the COL‐ESBL‐EC showed blaCTX‐M‐55/TEM, blaCTX‐M‐55, blaCMY‐2, and blaCTX‐M‐65 were predominant. The COL‐ESBL‐EC results showed a similar trend for blaCTX‐M identification to that of ESBL‐EC. The mcr was investigated, and mcr‐1 was detected in COL‐ESBL‐EC and COL‐EC. Antibiotic susceptibility testing revealed that many strains of COL‐ESBL‐EC and ESBL‐EC were resistant to quinolones, and fosfomycin (FOS). These results suggest that COL‐ESBL‐EC has simultaneously acquired AmpC/ESBL‐related, quinolone, and FOS resistance genes in COL‐EC.