Prevalence, detection of virulence genes and antimicrobial susceptibility of Escherichia coli isolated from arbor acres broilers feeding cycle in China

The prevalence of antimicrobial resistance originating from animals presents a significant threat to the treatment of animal disease, public health, and food safety. Researchers have focused on antibiotic resistance in <i>Escherichia coli</i> (<i>E. coli</i>), yet there are few reports on the resistance change during the feeding cycle. The purpose of this study was to investigate the prevalence and antibiotic resistance changes of <i>E. coli</i> in animal, environmental, and human samples during the broiler feeding cycle. Epidemiological surveys were performed in a farm with feeding AA broilers in Yangzhou, Jiangsu Province, China. Results showed that during a 42-days feeding cycle, 128 <i>E. coli</i> isolates were obtained from the cloaca of white-feathered broilers (<i>n</i> = 140), with an isolation rate of 91.4%, 27 <i>E. coli</i> isolates were obtained from Feed (<i>n</i> = 70) and 35 <i>E. coli</i> isolates were obtained from cage swabs (<i>n</i> = 70). A workers' hands swabs sample isolation rate of 68.6% (24/35) was observed. Antibiotic susceptibility testing revealed that out of 214 <i>E. coli</i> isolates, varying degrees of resistance were observed against 14 antibiotics. Most strains were resistant to ampicillin, cephalothiophene, ciprofloxacin, tetracycline, sulfamisoxazole, sulfamethoxazole and florfenicol, with a resistance rate exceeding 80%. The resistant strains demonstrated relatively stable patterns in their resistance to various antibiotics. Of the six antibiotic resistance genes tested, the <i>floR</i> gene showed the highest detection rate (72.4%), followed by <i>qnrS</i> (43.0%), <i>mcr-1</i> (35.0%), <i>aadE-Sat4-aphA-3</i> (28.0%), <i>blaNDM</i> (8.4%), <i>aac(6')-lb</i> (3.7%), and <i>cfr</i> (0). The highest detection rate for virulence genes was <i>yijp</i>. In summary, the isolation rate of <i>E. coli</i> and antibiotic resistance profile in broiler chickens remained stable throughout their feeding cycle. These findings can serve as a reference for the rational use of antibiotics in clinical settings, they can guide the use of veterinary drugs in poultry breeding.