Li Fangfang, Wang Haiyang, Shan Pengju, Wang Jingying, Hu Jiangang, Lian Liyan, Wang Zhihao, Saqib Nawaz, Bao Yinli, Han Xiangan, Wang Haidong
Serotyping identified O18 (28%) and O78 (20%) as the predominant serotypes, with no O1 detected. Phylogenetic analysis showed that phylogroup A was most prevalent (32.0%), followed by B2 (12.0%), D (12.0%), and B1 (10.0%); the remaining isolates (34.0%) were untypeable. All isolates were multidrug-resistant (resistant to ≥3 drug classes), with universal resistance to tetracycline and trimethoprim-sulfamethoxazole, and over 85% resistance to kanamycin, amoxicillin, florfenicol, and chloramphenicol. The resistance genes tetA, blaTEM, aphA, and sul2, as well as the virulence genes ibeB and ompA, were detected in all isolates (100%). Biofilm formation was observed in 96% of the isolates, though its correlation with individual resistance or virulence genes was weak.
INTRODUCTION: The emergence of mcr-1-harboring avian pathogenic Escherichia coli (APEC) poses a significant One Health challenge due to its zoonotic potential and adverse effects on poultry production.
METHODS: A total of 50 mcr-1-positive APEC isolates were recovered from diseased chickens in Shanxi Province, China, between 2021 and 2024. All isolates were subjected to serotyping, phylogenetic grouping, antimicrobial susceptibility testing, detection of resistance and virulence-associated genes, and biofilm formation assessment.
RESULTS: Serotyping identified O18 (28%) and O78 (20%) as the predominant serotypes, with no O1 detected. Phylogenetic analysis showed that phylogroup A was most prevalent (32.0%), followed by B2 (12.0%), D (12.0%), and B1 (10.0%); the remaining isolates (34.0%) were untypeable. All isolates were multidrug-resistant (resistant to ≥3 drug classes), with universal resistance to tetracycline and trimethoprim-sulfamethoxazole, and over 85% resistance to kanamycin, amoxicillin, florfenicol, and chloramphenicol. The resistance genes tetA, blaTEM, aphA, and sul2, as well as the virulence genes ibeB and ompA, were detected in all isolates (100%). Biofilm formation was observed in 96% of the isolates, though its correlation with individual resistance or virulence genes was weak.
DISCUSSION: The findings demonstrate that mcr-1-positive APEC isolates in Shanxi Province exhibit high-level multidrug resistance, widespread virulence gene carriage, and strong biofilm-forming capacity, underscoring their potential public health risk through animal-to-human transmission. These data provide a baseline for local surveillance and highlight the need for enhanced antimicrobial stewardship in poultry production.).