ISEc69-Mediated Mobilization of the Colistin Resistance Gene mcr-2 in Escherichia coli

Abstract

ObjectivesThe emergence of mobile colistin resistance genes has compromised the efficacy of the last resort antibiotic, colistin, in clinical treatment. The mcr-2 gene was first identified in Belgium in association with the insertion sequence ISEc69. However, the molecular mechanisms of mcr-2 mobilization are not well understood.MethodsTo further explore the mobilization of mcr-2 gene via ISEc69, we constructed a conjugative plasmid that carries an intact composite transposon Tn7052. Transposition assays were performed by conjugation, the transposition sites were characterized by arbitrary primed PCR and DNA sequencing.ResultsIn this study, we experimentally demonstrated that mcr-2 could be mobilized as a composite transposon Tn7052 and its transposition generated 8-bp AT-rich duplications in the host genome.ConclusionThese results indicate that mcr-2 gene could be mobilized by ISEc69, the current investigations provide mechanistic insights in the transposition of mcr-2.