title: Induction of beta-lactamase by cefoxitin in anaerobic intestinal microflora.
abstract: Beta-lactamases produced by two anaerobic bacterial strains, Bacteroides ovatus Ax34:1 and Clostridium butyricum NBL3, were shown to be significantly inducible under anaerobic conditions in subinhibitory concentrations of cefoxitin. The induction ratio of beta-lactamase production for Bacteroides ovatus was 2.6 and for Clostridium butyricum 1.6. Incubation of faecal samples with different concentrations of cefoxitin did not result in any induction of beta-lactamase production. When adding a highly inducible aerobic strain (Citrobacter freundii F72:6, induction ratio of 26.5 in broth culture) to faecal samples, an induction ratio of 4.5 was reached. Faeces seem to inhibit beta-lactamase induction in aerobic and anaerobic bacteria. The inducible enzymes produced by the anaerobic strains did not have the same properties as beta-lactamases from aerobic inducible strains, according to substrate profiles and inhibition studies. The results of the present study indicate that increased levels of beta-lactamases in the normal intestinal microflora, which often are observed after administration of beta-lactam agents, are probably due to selection of stably derepressed mutants rather than to induction of beta-lactamase production.
authors.affiliation: Department of Immunology, Microbiology, Pathology and Infectious Diseases, Huddinge University Hospital, Karolinska Institute, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Stark
authors.forename: C
authors.initials: C
authors.lastname: Edlund
authors.forename: M
authors.initials: M
authors.lastname: Hedberg
authors.forename: C E
authors.initials: CE
authors.lastname: Nord
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001421:Bacteria, Anaerobic / Q000187:drug effects* / Q000201:enzymology*; D002440:Cefoxitin / Q000494:pharmacology*; D016971:Citrobacter freundii / Q000201:enzymology; D003470:Culture Media; D004790:Enzyme Induction / Q000187:drug effects; D005243:Feces / Q000382:microbiology; D006801:Humans; D007422:Intestines / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D013379:Substrate Specificity; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D002440:Cefoxitin; D001618:beta-Lactamases