Open AccessNagZ Inactivation Prevents and Reverts β-Lactam Resistance, Driven by AmpD and PBP 4 Mutations, in Pseudomonas aeruginosa
Author(s) -
Laura Zamorano,
Thomas M. Reeve,
Liwei Deng,
Carlos Juan,
Bartolomé Moyá,
Gabriel Cabot,
David J. Vocadlo,
Brian L. Mark,
Antonio Oliver
Publication year - 2010
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.00385-10
Subject(s) - pseudomonas aeruginosa , mutant , microbiology and biotechnology , ceftazidime , biology , cephalosporin , mutation , antibacterial agent , wild type , penicillin binding proteins , pseudomonadales , pseudomonadaceae , penicillin , antibiotics , bacteria , genetics , gene
AmpC hyperproduction is the most frequent mechanism of resistance to penicillins and cephalosporins inPseudomonas aeruginosa and is driven byampD mutations or the recently described inactivation ofdacB , which encodes the nonessential penicillin-binding protein (PBP) PBP 4. Recent work showed thatnagZ inactivation attenuates β-lactam resistance inampD mutants. Here we explored whether the same could be true for thedacB mutants withdacB mutations alone or in combination withampD mutations. The inactivation ofnagZ restored the wild-type β-lactam MICs andampC expression of PAO1dacB andampD mutants and dramatically reduced the MICs (for example, the MIC for ceftazidime dropped from 96 to 4 μg/ml) and the level ofampC expression (from ca. 1,000-fold to ca. 50-fold higher than that for PAO1) in thedacB -ampD double mutant. On the other hand,nagZ inactivation had little effect on the inducibility of AmpC. The NagZ inhibitorO -(2-acetamido-2-deoxy-d -glucopyranosylidene)amino-N -phenylcarbamate attenuated the β-lactam resistance of the AmpC-hyperproducing strains, showing a greater effect on thedacB mutant (reducing the ceftazidime MICs from 24 to 6 μg/ml) than theampD mutant (reducing the MICs from 8 to 4 μg/ml). Additionally,nagZ inactivation in thedacB mutant blocked the overexpression ofcreD (blrD ), which is a marker of the activation of the CreBC (BlrAB) regulator involved in the resistance phenotype. Finally, through population analysis, we show that the inactivation ofnagZ dramatically reduces the capacity ofP. aeruginosa to develop ceftazidime resistance, since spontaneous mutants were not obtained at concentrations ≥8 μg/ml (the susceptibility breakpoint) for thenagZ mutant but were obtained with wild-type PAO1. Therefore, NagZ is envisaged to be a candidate target for preventing and reverting β-lactam resistance inP. aeruginosa .