Open AccessImipenem-induced resistance to antipseudomonal beta-lactams in Pseudomonas aeruginosa
Author(s) -
Francisca Tausk,
Martin E. Evans,
L S Patterson,
Charles F. Federspiel,
Charles W. Stratton
Publication year - 1985
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.28.1.41
Subject(s) - imipenem , pseudomonas aeruginosa , microbiology and biotechnology , antibiotics , antibacterial agent , biology , beta lactamase , pseudomonadaceae , pseudomonas , antimicrobial , chemistry , bacteria , antibiotic resistance , escherichia coli , biochemistry , genetics , gene
Using clinical isolates of Pseudomonas aeruginosa, we studied the ability of imipenem to antagonize the activity of nine other antipseudomonal beta-lactam antimicrobial agents. Imipenem caused truncation of the zones of inhibition in a disk diffusion test for 91 to 100% of the strains, depending on the beta-lactam tested. Addition of subinhibitory concentrations of imipenem caused a fourfold or greater increase in MICs for 72 of 74 isolates and in 20 to 87% of the tests, again depending on the antibiotic tested. beta-Lactamase assays with both whole-cell suspensions and cell sonicates showed that exposure to subinhibitory concentrations of imipenem resulted in a beta-lactamase production supported the hypothesis that induction of beta-lactamase was responsible for antagonism. In hydrolysis studies with a beta-lactamase extract, most of the antagonized drugs were either not hydrolyzed or only poorly hydrolyzed. We conclude that imipenem induces significantly elevated levels of beta-lactamase in P. aeruginosa. This increase in beta-lactamase is associated with increased resistance of the organism to many other beta-lactam agents.