Growth of cell-wall-deficient variants of Enterobacter cloacae facilitates beta-lactamase derepressed mutants.
The degree to which cell-wall-deficient bacteria (CWDB) are involved in the generation of beta-lactamase derepressed mutants (DM) was measured using Enterobacter cloacae 3624. The frequency of DM in non-permissive isotonic ticarcillin medium was compared with their frequency in hypertonic ticarcillin medium that supports CWDB growth. DM were resistant to extended spectrum penicillins and cephalosporins and had a basal beta-lactamase activity of >300 units/mg protein. Anaerobic growth of CWDB increased the relative risk of DM 2 x 10(6)-fold. Aerobic incubation produced fewer CWDB colonies but the risk of DM was still increased 400-fold over non-permissive controls. These results define a new role for CWDB as intermediaries in the emergence of resistance.
Huber
Thomas W
TW
Department of Pathology and Laboratory Medicine (113), Department of Medical Microbiology and Immunology, Central Texas Veterans Health Care System, Texas A&M College of Medicine, 1901 South First Street, Temple, TX 76504, USA.
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002455:Cell Division; D002473:Cell Wall / Q000235:genetics*; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry; D024881:Drug Resistance, Bacterial; D004355:Drug Stability; D016972:Enterobacter cloacae / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006982:Hypertonic Solutions; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics*; D012307:Risk Factors; D013982:Ticarcillin / Q000494:pharmacology; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D003470:Culture Media; D006982:Hypertonic Solutions; D001618:beta-Lactamases; D013982:Ticarcillin