The emergence of plasmid-mediated colistin resistance genes (mcr), which is occurring in numerous countries, is a worldwide concern, primarily because colistin is a last-resort antibiotic. Compared to E. coli, prevalence of mcr genes in Salmonella is unclear in Japan. Here we screened for mcr-1–5 genes in our collection of Salmonella strains isolated from retail meat products collected in Japan from 2012 through 2016. We found that Salmonella Albany strain 27A-368 encodes mcr-5 and that mcr genes were undetectable among the remaining 202 isolates. The resistance plasmid p27A-368 was transferred by conjugation to S. Infantis and was stably retained as a transconjugant. Whole-genome sequencing revealed that mcr-5 resided on a 115 kb plasmid (p27A-368). The plasmid backbone of p27A-368 is more similar to that of pCOV27, an ESBL-encoding plasmid recovered from avian pathogenic E. coli, rather than pSE13-SA01718 of S. Paratyphi B that encodes mcr-5. Further, mcr-5 is located on a transposon, and its sequence is similar to that of pSE13-SA01718. A phylogenetic tree based on single nucleotide variants implies a relationship between 27A-368 and S. Albany isolated in Southeast Asian countries.

中文翻译：

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日本零售鸡肉中含有mcr-5的肠炎沙门氏菌血清型奥尔巴尼的分离和质粒表征。

质粒介导的大肠菌素抗性基因（mcr）的出现在许多国家都引起了全世界的关注，这主要是因为大肠菌素是一种最后的抗生素。与大肠杆菌相比，日本沙门氏菌中mcr基因的流行率尚不清楚。在这里，我们从2012年至2016年从日本零售肉类产品中分离出的沙门氏菌菌株中筛选了mcr-1–5基因。我们发现沙门氏菌奥尔巴尼菌株27A-368编码mcr-5，而mcr在其余的202个分离株中未检测到基因。电阻质粒p27A-368是通过接合转移到小号。Infantis并被稳定保留为转导结合剂。全基因组测序表明，mcr-5位于115 kb质粒（p27A-368）上。p27A-368的质粒骨架是更类似于pCOV27的，编码ESBL的质粒从禽类致病回收大肠杆菌，而不是pSE13-SA01718小号。乙型副伤寒编码MCR-5 。此外，mcr-5位于转座子上，其序列与pSE13-SA01718相似。基于单核苷酸变异的系统树暗示了27A-368和S之间的关系。奥尔巴尼在东南亚国家孤立。