T. Nakae et al., Resistance to beta-lactam antibiotics in Pseudomonas aeruginosa due to interplay between the MexAB-OprM efflux pump and beta-lactamase, ANTIM AG CH, 43(5), 1999, pp. 1301-1303
We evaluated the roles of the MexAB-OprM efflux pump and beta-lactamase in
beta-lactam resistance in Pseudomonas aeruginosa by constructing OprM-defic
ient, OprM basal level, and OprM fully expressed mutants from beta-lactamas
e-negative, -inducible, and -overexpressed strains. We conclude that, with
the notable exception of imipenem, the MexAB-OprM pump contributes signific
antly to beta-lactam resistance in both beta-lactamase-negative and beta-la
ctamase-inducible strains, while the contribution of the MexAB-OprM efflux
system is negligible in strains with overexpressed beta-lactamase. Overexpr
ession of the efflux pump alone contributes to the high level of beta-lacta
m resistance in the absence of beta-lactamase.