First Report of the Colistin Resistance Gene <i>mcr-10.1</i> Carried by Inc _pA1763-KPC Plasmid pSL12517-mcr10.1 in Enterobacter cloacae in Sierra Leone

Abstract

Mobile colistin resistance (<i>mcr</i>) gene <i>mcr-10.1</i> has been distributed widely since it was initially identified in 2020. The aim of this study was to report the first <i>mcr-10.1</i> in Africa and the first <i>mcr</i> in Sierra Leone; furthermore, we presented diverse modular structures of <i>mcr-10.1</i> loci. Here, the complete sequence of one <i>mcr-10.1</i>-carrying plasmid in one clinical Enterobacter cloacae isolate from Sierra Leone was determined. Detailed genetic dissection and comparison were applied to this plasmid, together with a homologous plasmid carrying <i>mcr-10.1</i> from GenBank. Moreover, a genetic comparison of 19 <i>mcr-10.1</i> loci was performed. In this study, <i>mcr-10.1</i> was carried by an Inc_pA1763-KPC plasmid from one Enterobacter cloacae isolate. A total of 19 <i>mcr-10.1</i> loci displayed diversification in modular structures through complex transposition and homologous recombination. A site-specific tyrosine recombinase XerC was located upstream of <i>mcr-10.1</i>, and at least one insertion sequence element was inserted adjacent to a conserved <i>xerC</i>-<i>mcr-10.1</i>-<i>orf336</i>-<i>orf177</i> region. Integration of <i>mcr-10.1</i> into a different gene context and carried by various Inc plasmids contributed to the wide distribution of <i>mcr-10.1</i> and enhanced the ability of bacteria to survive under colistin selection pressure. <b>IMPORTANCE</b> Colistin is used as one of the last available choices of antibiotics for patients infected by carbapenem-resistant bacterial strains, but the unrestricted use of colistin aggravated the acquisition and dissemination of mobile colistin resistance (<i>mcr</i>) genes. So far, 10 <i>mcr</i> genes have been reported in four continents around the world. This study presented one <i>mcr-10.1</i>-carrying Enterobacter cloacae isolate from Sierra Leone. The <i>mcr-10.1</i> gene was identified on an Inc_pA1763-KPC plasmid. According to the results of genetic comparison of 19 <i>mcr-10.1</i> loci, the <i>mcr-10.1</i> gene was found to be located in a conserved <i>xerC</i>-<i>mcr-10.1</i>-<i>orf336</i>-<i>orf177</i> region, and at least one insertion sequence element was inserted adjacent to this region. To our knowledge, this is the first report of identifying the <i>mcr-10.1</i> gene in Africa and the <i>mcr</i> gene in Sierra Leone.