Emergence of Colistin Resistance Gene mcr-8 and Its Variant in Raoultella ornithinolytica

Abstract

Recently, a novel mobile colistin resistance gene, <i>mcr-8</i>, was identified in <i>Klebsiella pneumoniae</i>. Here, we report the identification of <i>mcr-8</i> and its variant, <i>mcr-8.4</i>, in <i>Raoultella ornithinolytica</i> isolates which also belong to Enterobacteriaceae family. The <i>mcr-8</i> gene was located on transferrable plasmids with difference sizes. Notably, the transferability of <i>mcr-8</i>-carrying plasmids was enhanced once they entered into <i>Escherichia coli</i> hosts and multiple β-lactamase genes could co-transfer with <i>mcr-8</i>. These findings expand our knowledge of <i>mcr-8</i>-carrying bacterial species.