Molecular and functional characterization of a novel efflux pump, AmvA, mediating antimicrobial and disinfectant resistance in Acinetobacter baumannii.
OBJECTIVE
Acinetobacter baumannii has emerged as an important nosocomial pathogen in hospitalized patients, and causes a multitude of infections with significant morbidity and mortality. The aim of this study was to elucidate the role of a novel efflux pump in A. baumannii.


METHODS
The open reading frame ABAYE1518, annotated as a putative Methyl Viologen resistance protein in the genome of strain A. baumannii AYE, exhibits >50% similarity with members of the major facilitator superfamily (MFS) multidrug efflux pumps. The antimicrobial susceptibility profiles of Escherichia coli KAM32 cells carrying the putative efflux pump were monitored by broth dilution method. Different efflux pump inhibitors were used for fluorimetric efflux assays. The functions of the putative efflux pump were confirmed in A. baumannii by insertional inactivation and complementation. Its expression in clinical isolates was analysed by reverse transcriptase-PCR.


RESULTS
E. coli cells carrying the pump had decreased susceptibility to some antibiotics, disinfectants, dyes and detergents, with enhanced efflux activity. The pump was inactivated in a clinical isolate of A. baumannii AC0037 and further characterization confirmed its role in antimicrobial resistance by active efflux. We found increased expression of the pump in clinical isolates that also exhibited elevated tolerance to antibacterial agents.


CONCLUSIONS
This report describes the functions of a novel resistance determinant, a member of the MFS efflux pumps, for the first time in A. baumannii.
Rajamohan
Govindan
G
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, Columbus, OH, USA.
Srinivasan
Vijaya Bharathi
VB
Gebreyes
Wondwossen A
WA
D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism*; D040981:Acinetobacter baumannii / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D003001:Cloning, Molecular; D004202:Disinfectants / Q000378:metabolism / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D017353:Gene Deletion; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018528:ATP-Binding Cassette Transporters; D000900:Anti-Bacterial Agents; D004202:Disinfectants