ABSTRACT Since the initial discovery of mcr-1 in an Escherichia coli isolate from China, the gene has also been detected in Klebsiella pneumoniae and Salmonella enterica but is rarely reported in other Enterobacteriaceae . Here, we report the isolation and identification of a Shigella flexneri strain harboring mcr-1 from stool samples in a pig farm in China from 2009. The MIC of colistin for the isolate is 4 μg/ml. Conjugation assays showed that the donor S. flexneri strain has functional and transferable colistin resistance. Sequencing revealed that mcr-1 was present on a putative composite transposon flanked by inverted repeats of IS Apl1 . IMPORTANCE There are four species of Shigella , and Shigella flexneri is the most frequently isolated species in low- and middle-income countries (LMICs). In this study, we report a functional, transferable, plasmid-mediated mcr-1 gene in S. flexneri . We have shown that mcr-1 is located on a novel composite transposon which is flanked by inverted repeats of IS Apl1 . The host strain is multidrug resistant, and this multidrug resistance is also transferable. The finding of a functional mcr-1 gene in S. flexneri , a human-associated Enterobacteriaceae family member, is a cause for concern as infections due to S. flexneri are the main Shigella infections in most low- and middle-income countries.
【저자키워드】 Multidrug resistance, plasmid transfer, ISApl1, Tn6390, composite transposon,