title: In vitro response of Enterobacter to ampicillin.
abstract: Three strains of Enterobacter were studied for their response to ampicillin. They exhibited a basic level of resistance that depended on the medium used and high-level mutational resistance at a frequency of 10(-5) to 10(-7). Two classes of mutants were selected, one of which showed markedly enhanced antibiotic inactivation as indicated by a biological assay and the other of which resembled the wild type in this regard. Both mutants showed cross-resistance to other beta-lactam antibiotics. The results explained discrepancies between traditional broth dilution minimum inhibitory concentration tests and early read automated procedures.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000378:metabolism; D003470:Culture Media; D004754:Enterobacter / Q000187:drug effects* / Q000378:metabolism; D004755:Enterobacteriaceae / Q000187:drug effects*; D007769:Lactams / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010403:Penicillin Resistance; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D007769:Lactams; D000667:Ampicillin
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