Transmission of carbapenem-resistant enterobacterales producing NDM-5 during the broiler breeding process in China

Abstract

This study conducted a four-month monitoring of carbapenem resistance in a broiler breeding farm in China. A total of 185 carbapenem-resistant bacterial isolates were obtained from 2298 cloacal swabs from broiler breeders and their offspring within a production cycle. The detection rate of carbapenem-resistant isolates was higher during the brooding period. Whole-genome sequencing (WGS) was performed on 133 isolates based on sampling stages, including 113 carbapenem-resistant Enterobacterales (CRE) isolates and 20 Stenotrophomonas pavanii isolates, which have intrinsic resistance to carbapenems. A total of 69 antibiotic resistance genes (ARGs), including blaNDM-1, mcr-1, and blaNDM-5, were identified among the sequenced CRE isolates. Notably, blaNDM-5 (92.0 %, 104/113) was the primary contributor to carbapenem resistance. CRE isolates from the same breeding stage exhibited close genomic relationships, and the blaNDM-5 genes were observed in similar genetic backgrounds, indicating the transmission of CRE strains and blaNDM-5 during the broiler breeding process. No CRE was isolated from 0 d broiler offspring, suggesting that broiler breeders were not the direct source of CRE in their offspring. Tracing the feeding process revealed that brooder and rearing houses were likely key factors in the cross-transmission of CRE between broiler breeders and their offspring. CRE pose a significant threat to public health and food safety. China is one of the world's leading poultry producing and consuming countries. This study provided insights into the epidemiological trends and key transmission nodes of carbapenem resistance and CRE within the broiler breeding process, which could help the control of antibiotic resistance and bacterial infections in the broiler industry.