title: Multiple antibiotic resistance in Pseudomonas aeruginosa: evidence for involvement of an efflux operon.
abstract: An outer membrane protein of 50 kDa (OprK) was overproduced in a siderophore-deficient mutant of Pseudomonas aeruginosa capable of growth on iron-deficient minimal medium containing 2,2'-dipyridyl (0.5 mM). The expression of OprK in the mutant (strain K385) was associated with enhanced resistance to a number of antimicrobial agents, including ciprofloxacin, nalidixic acid, tetracycline, chloramphenicol, and streptonigrin. OprK was inducible in the parent strain by growth under severe iron limitation, as provided, for example, by the addition of dipyridyl or ZnSO4 to the growth medium. The gene encoding OprK (previously identified as ORFC) forms part of an operon composed of three genes (ORFABC) implicated in the secretion of the siderophore pyoverdine. Mutants defective in ORFA, ORFB, or ORFC exhibited enhanced susceptibility to tetracycline, chloramphenicol, ciprofloxacin, streptonigrin, and dipyridyl, consistent with a role for the ORFABC operon in multiple antibiotic resistance in P. aeruginosa. Sequence analysis of ORFC (oprK) revealed that its product is homologous to a class of outer membrane proteins involved in export. Similarly, the products of ORFA and ORFB exhibit homology to previously described bacterial export proteins located in the cytoplasmic membrane. These data suggest that ORFA-ORFB-oprK (ORFC)-dependent drug efflux contributes to multiple antibiotic resistance in P. aeruginosa. We propose, therefore, the designation mexAB (multiple efflux) for ORFAB.
authors.affiliation: Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Poole
authors.forename: K
authors.initials: K
authors.lastname: Krebes
authors.forename: C
authors.initials: C
authors.lastname: McNally
authors.forename: S
authors.initials: S
authors.lastname: Neshat
mesh_terms: D015082:2,2'-Dipyridyl / Q000633:toxicity; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D001425:Bacterial Outer Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D026901:Membrane Transport Proteins; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016296:Mutagenesis; D016366:Open Reading Frames; D009876:Operon; D010957:Plasmids; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics*; D015183:Restriction Mapping
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; C118597:MexB protein, Pseudomonas aeruginosa; D015082:2,2'-Dipyridyl