The presence of the plasmid-mediated colistin resistance encoding mcr gene family in the Enterobacteriaceae is one of the crucial global concerns. The use of colistin in livestock rearing is believed to be the cause of mcr gene spreading and is of impact to public health. The objective of this research was to detect the frequency and virulent genes of mcr-positive Escherichia coli (MCRPE) in fecal samples from healthy pigs in a contract farming system across Thailand. A total of 696 pooled samples were derived from 80 farms, located in 49 provinces across six regions of Thailand. The colistin-resistant E. coli were identified by MALDI-TOF mass spectrometry and antimicrobial susceptibility testing by broth microdilution. The antibiogram was determined using an automated susceptibility machine, and the genetic characteristics were investigated for mcr-1–5 genes, phylogenetic group, replicon types, and virulent genes. In total, 31 of 696 samples were positive, with E. coli containing mcr-1 or combination of mcr-1 and mcr-3 with incidence of 4.45 and 0.43%. Phylogenetic groups A and B1 and the IncF and IncFIB replicon types were predominantly found in the MCRPE located in the central area, with multidrug-resistant traits against 3–14 types of antimicrobials. Additionally, 19 of 31 isolates identified as enterotoxigenic E. coli were with the stap and stb (enterotoxin-encoding genes). In conclusion, a low carriage rate of mcr-positive E. coli was detected in the large-scale farming of healthy pigs. The association between multidrug-resistant MCRPE and their pathogenic potential should be of concern.

质粒介导的大肠菌素抗性编码 核磁共振 基因家族 肠杆菌科是全球关注的关键问题之一。据信大肠菌素在牲畜饲养中的使用是导致核磁共振基因传播，对公共卫生有影响。这项研究的目的是检测频率和有毒力的基因mcr-正 大肠杆菌（MCRPE）在整个合同制养殖系统中从健康猪的粪便样本中提取。来自泰国六个地区49个省的80个农场共采集了696个汇总样本。大肠杆菌抵抗大肠杆菌通过MALDI-TOF质谱进行鉴定，并通过肉汤微稀释进行抗菌药敏试验。用自动药敏仪测定抗菌素，并研究其遗传特性。mcr-1–5基因，系统发生族，复制子类型和有毒基因。总共696个样本中有31个呈阳性，其中大肠杆菌 包含 mcr-1 或 mcr-1 和 mcr-3发生率分别为4.45和0.43％。系统发育组A和B1以及IncF和IncFIB复制子类型主要位于中部地区的MCRPE中，具有针对3-14种抗微生物剂的多药耐药性。此外，在31株被鉴定为产肠毒素的菌株中，有19株大肠杆菌 与 装订 和 机顶盒（肠毒素编码基因）。总之，较低的运输速度mcr-正 大肠杆菌在健康猪的大规模养殖中被发现。多药耐药性MCRPE与它们的致病性之间的关联应受到关注。