Department of Microbiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Department of Clinical Microbiology and Applied Technology, Faculty of Medical Technology, Mahidol University, Nakhon Pathom, Thailand.
Sci Rep. 2021 Jul 8;11(1):14170. doi: 10.1038/s41598-021-93529-6.
Nontyphoidal Salmonella, an important zoonotic pathogen and a major cause of foodborne illnesses, could be a potential reservoir of plasmids harbouring mobile colistin resistance gene (mcr). This study reported, for the first time, a high rate of mcr-carrying Salmonella clinical isolates (3.3%, 24/724) in Thailand, associated with mcr-3 gene (3.0%, 22/724) in S. 4,[5],12:i:-(15.4%, 4/26), S. Typhimurium (8.8%, 5/57), and S. Choleraesuis (5.6%, 13/231). Remarkably, the increasing trends of colistin and extended-spectrum cephalosporin resistances have displayed a high agreement over the years, with a dramatic rise in the mcr-carrying Salmonella from 1.1% (6/563) during 2005-2007 to 11.2% (18/161) during 2014-2018 when CTX-M-55 became abundant. Clonal and plasmid analysis revealed that the self-transferable IncA/C and a novel hybrid IncA/C-FIIs MDR plasmids were the major vehicles to disseminate both mcr-3 and bla genes among diverse Salmonella strains, from as early as 2007. To our knowledge the occurrence of mcr-3 and the co-existence of it with bla in S. Choleraesuis are reported here for the first time, leading to clinical concern over the treatment of the invasive salmonellosis. This study provides evidence of the potential reservoirs and vectors in the dissemination of the mcr and highlights the co-selection by colistin and/or cephalosporins.
非伤寒沙门氏菌是一种重要的人畜共患病原体和食源性疾病的主要原因，可能是携带移动多粘菌素耐药基因（mcr）的质粒的潜在储库。本研究首次报告了泰国沙门氏菌临床分离株中 mcr 携带率较高（3.3%，24/724），与 mcr-3 基因（3.0%，22/724）相关，存在于 S. 4,[5],12:i:-(15.4%，4/26)、鼠伤寒沙门氏菌（8.8%，5/57）和猪霍乱沙门氏菌（5.6%，13/231）中。值得注意的是，多年来，多粘菌素和扩展谱头孢菌素耐药性的上升趋势高度一致，2005-2007 年 mcr 携带沙门氏菌从 1.1%（6/563）急剧上升到 2014-2018 年 CTX-M-55 大量出现时的 11.2%（18/161）。克隆和质粒分析表明，可自我转移的 IncA/C 和新型混合 IncA/C-FIIs MDR 质粒是在不同沙门氏菌菌株中传播 mcr-3 和 bla 基因的主要载体，早在 2007 年就已经存在。据我们所知，mcr-3 的出现及其与 bla 在猪霍乱沙门氏菌中的共存，首次引起了人们对侵袭性沙门氏菌病治疗的关注。本研究提供了 mcr 传播的潜在储库和载体的证据，并强调了多粘菌素和/或头孢菌素的共同选择。
