Abstract
INTRODUCTION: The transmission of antimicrobial resistance (AMR), particularly the antimicrobial resistance gene in Enterobacteriaceae, presents a critical challenge to global public health. Sichuan province is the largest producer and consumer of rabbit meat in China. However, few studies have focused on AMR surveillance in rabbits. METHODS: Enterobacteriaceae strains were isolated and identified by MALDI-TOF. The minimum inhibitory concentration (MIC) was determined according to the Clinical and Laboratory Standards Institute. Whole-genome sequencing was performed using the Illumina and Oxford Nanopore Technologies (ONT) platforms. RESULTS AND DISCUSSION: A total of 73 Enterobacteriaceae strains were isolated, including Klebsiella pneumoniae, Salmonella enterica, Enterobacter hormaechei, and Escherichia coli. Resistance rates to tetracycline, ciprofloxacin, nalidixic acid, sulfamethoxazole-trimethoprim, and ampicillin exceeded 60%. For Escherichia coli isolates showed that ST328, ST22, and ST29 were the primary sequence types, with O178:H7 being the predominant serotype. Remarkably, 48% (35/73) of the isolates carried the mcr-1.1 gene, and among these, 82.9% (29/35) mcr-1.1-positive isolates contained the IncI2 plasmid replicon. The mcr-1.1 gene in Klebsiella pneumoniae, Salmonella enterica and Escherichia coli transferred to a recipient strain. Furthermore, the genetic environment of the mcr-1.1 gene showed that it was flanked by PAP2 and a relaxase. Comparative analysis indicated that the mcr-1.1-positive plasmid exhibited high sequence identity to plasmids from human, porcine, and bovine sources. Notably, a phylogenetic analysis based on core single nucleotide polymorphisms demonstrated that certain rabbit-derived mcr-1-positive Escherichia coli strains clustered within the same evolutionary branch as humanderived strains. These findings indicated that smaller-scale breeding operations, such as rabbit farming, could serve as underrecognized reservoirs of AMR determinants, particularly the mcr-1.1 gene, thus requiring systematic assessment.