A novel plasmid-encoded mcr-4.3 gene in a colistin-resistant Acinetobacter baumannii clinical strain.

ABSTRACT: OBJECTIVES:To identify the molecular mechanism of colistin resistance in an MDR Acinetobacter baumannii clinical strain isolated in 2008 from a meningitis case in Brazil. METHODS:Long- and short-read WGS was used to identify colistin resistance genes in A. baumannii strain 597A with a colistin MIC of 64?mg/L. MS was used to analyse lipid A content. mcr was cloned into pET-26b (+) and transformed into Escherichia coli BL21(?DE3)pLysS for analysis. RESULTS:A novel plasmid (pAb-MCR4.3) harbouring mcr-4.3 within a Tn3-like transposon was identified. The A. baumannii 597A lipid A MS spectra showed a main molecular ion peak at m/z=2034, which indicated the addition of phosphoethanolamine to the lipid A structure. E. coli BL21 transformed with pET-26b-mcr-4.3 gained colistin resistance with a colistin MIC of 8?mg/L. CONCLUSIONS:Colistin resistance in A. baumannii 597A was correlated with the presence of a novel plasmid-encoded mcr-4.3 gene.

SUBMITTER: Martins-Sorenson N 

PROVIDER: S-EPMC6910164 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature