Study of the mechanisms of colistin heteroresistance in a strain of Enterobacter cloacae by random mutagenesis

Abstract

Objective: The Enterobacter cloacae complex belongs to a group in which colistin resistance is not well documented due to their frequent heteroresistance. Methods: We investigated the molecular basis of colistin heteroresistance using genome analysis and random mutagenesis in a strain of E. cloacae. Results: The arnA gene was truncated in the six colistin susceptible mutants we obtained. However, the mcr-9 gene was present in these mutants suggesting this gene is not responsible for colistin resistance. Conclusions: Previous studies have highlighted the role of the two-component system PhoPQ and its negative regulator mgrB or the arnBCADTEF operon. Our results confirm the crucial role of this operon.

Keywords

• Colistin resistance
• Enterobacter cloacae complex
• Heteroresistance
• Random mutagenesis