Assignment of the Substrate-Selective Subunits of the MexEF-OprN Multidrug Efflux Pump of Pseudomonas aeruginosa

AUTOR(ES)

Maseda, Hideaki

FONTE

American Society for Microbiology

RESUMO

Pseudomonas aeruginosa expresses a low level of the MexAB-OprM efflux pump and shows natural resistance to many structurally and functionally diverse antibiotics. The mutation that has been referred to previously as nfxC expresses an additional efflux pump, MexEF-OprN, exhibiting resistance to fluoroquinolones, imipenem, and chloramphenicol and hypersusceptibility to β-lactam antibiotics. To address the antibiotic specificity of the MexEF-OprN efflux pump, we introduced a plasmid carrying the mexEF-oprN operon into P. aeruginosa lacking the mexAB-oprM operon. The transformants exhibited resistance to fluoroquinolones, trimethoprim, and chloramphenicol but, unlike most nfxC-type mutants, did not show β-lactam hypersusceptibility. The transformants exhibited additional resistance to tetracycline. In the next experiment, we analyzed the MexEF-OprN pump subunit(s) responsible for substrate selectivity by expressing MexE, MexF, OprN, and MexEF in strains lacking MexA, MexB, OprM, and MexAB, respectively. The MexEF-OprM/ΔMexAB transformants exhibited MexEF-OprN-type pump function that rendered the strains resistant to fluoroquinolones and chloramphenicol but did not change susceptibility to β-lactam antibiotics compared with the host strain. The MexAB-OprN/ΔOprM, MexAF-OprM/ΔMexB, and MexEB-OprM/ΔMexA mutants exhibited antibiotic susceptibility indistinguishable from that in the mutant lacking both types of efflux pumps. The results imply that the MexEF-OprM pump selects substrates by a MexEF functional unit. Interestingly, OprN did not link functionally with the MexAB complex, despite the fact that OprM interacted functionally with MexEF.

Documentos Relacionados

• Overexpression of the MexEF-OprN Multidrug Efflux System Affects Cell-to-Cell Signaling in Pseudomonas aeruginosa
• Overexpression of the Multidrug Efflux Pumps MexCD-OprJ and MexEF-OprN Is Associated with a Reduction of Type III Secretion in Pseudomonas aeruginosa
• Enhancement of the mexAB-oprM Efflux Pump Expression by a Quorum-Sensing Autoinducer and Its Cancellation by a Regulator, MexT, of the mexEF-oprN Efflux Pump Operon in Pseudomonas aeruginosa
• Mutations in PA2491 (mexS) Promote MexT-Dependent mexEF-oprN Expression and Multidrug Resistance in a Clinical Strain of Pseudomonas aeruginosa
• Differential Impact of MexB Mutations on Substrate Selectivity of the MexAB-OprM Multidrug Efflux Pump of Pseudomonas aeruginosa