Characterization of the MexC-MexD-OprJ multidrug efflux system in DeltamexA-mexB-oprM mutants of Pseudomonas aeruginosa.
Expression of the multidrug efflux system MexC-MexD-OprJ in nfxB mutants of Pseudomonas aeruginosa contributes to resistance to fluoroquinolones and the "fourth-generation" cephems (cefpirome and cefozopran), but not to most beta-lactams, including the ordinary cephems (ceftazidime and cefoperazone). nfxB mutants also express a second multidrug efflux system, MexA-MexB-OprM, due to incomplete transcriptional repression of this operon by the mexR gene product. To characterize the contribution of the MexC-MexD-OprJ system to drug resistance in P. aeruginosa, a site-specific deletion method was employed to remove the mexA-mexB-oprM region from the chromosome of wild-type and nfxB strains of P. aeruginosa. Characterization of mutants lacking the mexA-mexB-oprM region clearly indicated that the MexC-MexD-OprJ efflux system is involved in resistance to the ordinary cephems as well as fluoroquinolones and the fourth-generation cephems but not to carbenicillin and aztreonam. Rabbit polyclonal antisera and murine monoclonal antibody against the components of the MexA-MexB-OprM system were prepared and used to demonstrate the reduced production of this efflux system in the nfxB mutants. Consistent with this, transcription of the mexA-mexB-oprM operon decreased in an nfxB mutant. This reduction appears to explain the hypersusceptibility of the nfxB mutant to beta-lactams, including ordinary cephems.
Department of Microbiology, Kyoto Pharmaceutical University, Yamashina, Kyoto 607-8414, Japan. ngotoh@mb.kyoto-phu.ac.jp
N
N
Gotoh
H
H
Tsujimoto
M
M
Tsuda
K
K
Okamoto
A
A
Nomura
T
T
Wada
M
M
Nakahashi
T
T
Nishino
D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D024841:Fluoroquinolones; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D009876:Operon; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D013379:Substrate Specificity
D000890:Anti-Infective Agents; D002511:Cephalosporins; D024841:Fluoroquinolones