Comparison of the E test and microdilution for detection of beta-lactam-resistant mutants that are stably derepressed for type I beta-lactamase.
The activities of cefotaxime, ceftazidime, piperacillin, and aztreonam were compared in the E test and broth microdilution test against 30 gram-negative bacterial mutants derepressed for type I beta-lactamases. The results demonstrated complete agreement between 24-h MICs of 80 to 83% and essential agreement between 24-h MICs of 90 to 97%. When sufficient growth was present for the E test to be read at 6 h, the essential agreement between 6- and 24-h E-test MICs was 100% for ceftazidime, piperacillin, and aztreonam and 85% for cefotaxime.
Knapp
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CC
Department of Microbiology, Cleveland Clinic Foundation, Ohio 44195-5140.
Washington
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JA
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004794:Enzyme Repression; D004795:Enzyme Stability; D006090:Gram-Negative Bacteria / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010405:Penicillinase / Q000235:genetics*; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D010405:Penicillinase