Emerging of a highly pathogenic and multi-drug resistant strain of Escherichia coli causing an outbreak of colibacillosis in chickens.

Extraintestinal pathogenic Escherichia coli (ExPEC) are important human pathogens responsible for urinary tract infection and meningitis. Therefore, infection of chickens by highly pathogenic E. coli with multi-drug resistance has become a major concern to food safety. In this study, we isolated a strain of E. coli (HB2016) from the oviduct of a diseased chicken with colibacillosis. Inoculation of chickens with 2 × 106  CFU of the isolate E. coli HB2016 by intraperitoneal injection successfully reproduced colibacillosis in chickens. We also found that E. coli HB2016 harbored four more virulence genes (tsh, trat, cvaC and cvaA/B) than E. coli reference strain CVCC1428. Importantly, E. coli HB2016 was resistant to cefuroxime, tobramycin, medemycin, cefazolin, cefoperazone, streptomycin and ampicillin, and carried multiple antibiotic resistance genes such as strA, strB, blaCMY-2 , blaCTX-M-19 , blaTEM-1B , fosA, mph(A), floR, sul2, tet(A) and tet(B). These findings suggest that the causative E. coli act as a potential zoonotic agent affecting human health.