Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, China.
Nantong Center for Disease Control and Prevention, Nantong 226007, China.
Microbiol Res. 2023 Sep;274:127441. doi: 10.1016/j.micres.2023.127441. Epub 2023 Jun 20.
Salmonella enterica serovar Typhimurium (S. Typhimurium) and S. 4,[5],12:i:- have become the most common serovars associated with human salmonellosis worldwide. Moreover, the emergence of mcr-carrying S. Typhimurium and S. 4,[5],12:i:- with multidrug resistance (MDR) patterns has posed a threat to public health. In this study, we retrospectively screened 2009-2022 laboratory-preserved strains for the presence of mcr genes. We obtained 16 mcr-1-positive S. Typhimurium and S. 4,[5],12:i:- strains with MDR that belonged to sequence type 34 (ST34). Whole-genome sequencing analysis revealed that the mcr-1 was located on the IncI2 or IncHI2 plasmids. The ISApl1 element downstream of mcr-1 was present in all pig-derived strains. Conjugation experiments confirmed that nine mcr-1-carrying IncHI2 plasmids could not be transferred to Escherichia coli due to loss of the conjugation region. Finally, core genome single nucleotide polymorphism (cgSNP) analyses of the 16 mcr-1-carrying strains and 77 mcr-carrying ST34-Salmonella genome sequences from the NCBI and ENA databases showed that five out of eight clusters contained strains from pig and pig products, revealing pigs and pig products as key reservoirs of mcr-1-positive ST34-Salmonella strains. The transmission of mcr-carrying ST34 Salmonella strains to humans via the pig food chain is a potential cause for public health concern in controlling human salmonellosis.
鼠伤寒沙门氏菌血清型 Typhimurium（S. Typhimurium）和 S. 4,[5],12:i:-已成为全球与人类沙门氏菌病相关的最常见血清型。此外，携带 mcr 基因的鼠伤寒沙门氏菌和 S. 4,[5],12:i:-出现了多药耐药（MDR）模式，这对公共卫生构成了威胁。在本研究中，我们回顾性筛选了 2009 年至 2022 年实验室保存的菌株，以检测 mcr 基因的存在。我们获得了 16 株携带 mcr-1 的 MDR 鼠伤寒沙门氏菌和 S. 4,[5],12:i:-菌株，它们属于序列型 34（ST34）。全基因组测序分析显示，mcr-1 位于 IncI2 或 IncHI2 质粒上。mcr-1 下游的 ISApl1 元件存在于所有猪源菌株中。接合实验证实，由于接合区丢失，无法将 9 株携带 mcr-1 的 IncHI2 质粒转移到大肠杆菌中。最后，对 16 株携带 mcr-1 的菌株和从 NCBI 和 ENA 数据库获得的 77 株携带 mcr 的 ST34-沙门氏菌基因组序列的核心基因组单核苷酸多态性（cgSNP）分析表明，8 个聚类中有 5 个聚类包含来自猪和猪产品的菌株，这表明猪和猪产品是 mcr-1 阳性 ST34-沙门氏菌菌株的关键储存库。mcr 携带的 ST34 沙门氏菌菌株通过猪食物链传播给人类，可能是控制人类沙门氏菌病的公共卫生关注的一个潜在原因。
