title: The BpeAB-OprB efflux pump of Burkholderia pseudomallei 1026b does not play a role in quorum sensing, virulence factor production, or extrusion of aminoglycosides but is a broad-spectrum drug efflux system.
abstract: Most Burkholderia pseudomallei strains are intrinsically aminoglycoside resistant, mainly due to AmrAB-OprA-mediated efflux. Rare naturally occurring or genetically engineered mutants lacking this pump are aminoglycoside susceptible despite the fact that they also encode and express BpeAB-OprB, which was reported to mediate efflux of aminoglycosides in the Singapore strain KHW. To reassess the role of BpeAB-OprB in B. pseudomallei aminoglycoside resistance, we used mutants overexpressing or lacking this pump in either AmrAB-OprA-proficient or -deficient strain 1026b backgrounds. Our data show that BpeAB-OprB does not mediate efflux of aminoglycosides but is a multidrug efflux system which extrudes macrolides, fluoroquinolones, tetracyclines, acriflavine, and, to a lesser extent, chloramphenicol. Phylogenetically, BpeAB-OprB is closely related to Pseudomonas aeruginosa MexAB-OprM, which has a similar substrate spectrum. AmrAB-OprA is most closely related to MexXY, the only P. aeruginosa efflux pump known to extrude aminoglycosides. Since BpeAB-OprB in strain KHW was also implicated in playing a major role in export of acylated homoserine lactone (AHL) quorum-sensing molecules and in expression of diverse virulence factors, we explored whether this was also true in the strain 1026b background. The results showed that BpeAB-OprB was not required for AHL export, and mutants lacking this efflux system exhibited normal swimming motility and siderophore production, which were severely impaired in KHW bpeAB-oprB mutants. Biofilm formation was impaired in 1026b Delta(amrRAB-oprA) and Delta(amrRAB-oprA) Delta(bpeAB-oprB) mutants. At present, we do not know why our BpeAB-OprB susceptibility and virulence factor expression results with 1026b and its derivatives are different from those previously published for Singapore strain KHW.
authors.affiliation: Department of Microbiology, Immunology and Pathology, Colorado State University, IDRC at Foothills Campus, Campus Delivery 2025, Fort Collins, CO 80523-2025, USA.
authors.forename: Takehiko
authors.initials: T
authors.lastname: Mima
authors.forename: Herbert P
authors.initials: HP
authors.lastname: Schweizer
mesh_terms: D000617:Aminoglycosides / Q000378:metabolism / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016957:Burkholderia pseudomallei / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D003470:Culture Media; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D033903:Periplasmic Proteins / Q000235:genetics / Q000378:metabolism*; D053038:Quorum Sensing; D012846:Singapore; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; C485375:BpeA protein, Burkholderia pseudomallei; C485376:BpeB protein, Burkholderia pseudomallei; D003470:Culture Media; D026901:Membrane Transport Proteins; C485377:OprB protein, Burkholderia pseudomallei; D033903:Periplasmic Proteins; D037521:Virulence Factors