Molecular cloning and functional characterization of two novel membrane fusion proteins in conferring antimicrobial resistance in Acinetobacter baumannii.

Objectives: The aim of this study was to elucidate the role of two novel membrane fusion proteins (MFPs) in the susceptibility of Acinetobacter baumannii to antimicrobial agents.

Methods: The genome sequence of A. baumannii ATCC 17978 contains two open reading frames (ORFs) annotated as AdeT in the NCBI genome database. Both the putative efflux genes display >30% similarity to known MFPs. The antimicrobial susceptibility profiles of Escherichia coli KAM32 cells carrying the genes were monitored by the broth dilution method. Different efflux pump inhibitors were used for fluorimetric efflux assays. The functions of putative ORFs were confirmed in A. baumannii by insertional inactivation and complementation.

Results: E. coli cells carrying the ORFs had decreased susceptibility to antibiotics, disinfectants, dyes and detergents, with enhanced efflux activity. Inactivation of the ORFs and further characterization in A. baumannii confirmed its role in antimicrobial resistance by active efflux.

Conclusions: This report describes the functions of novel resistance determinants, members of the MFP family, for the first time in A. baumannii.