title: Selection of cefoxitin-resistant bacteroides thetaiotaomicron mutants and mechanisms involved in beta-lactam resistance.
abstract: The beta-lactam antibiotics are the most widely used of all the groups of antimicrobials, but beta-lactam resistance is increasingly common among members of the Bacteroides fragilis group. Three major mechanisms are involved in beta-lactam resistance, and they act together in certain instances. In the present study, 2 resistant mutants (238m and 1186m) of Bacteroides thetaiotaomicron, obtained from clinical isolates (238 and 1186) by selection with increasing concentrations of cefoxitin, showed decreased susceptibilities to cefoxitin and other beta-lactam antibiotics. Alterations in both penicillin-binding proteins (PBPs) and outer-membrane proteins (OMPs) were observed in the mutants in comparison with their parent strains. The similar alteration in OMPs was also observed in clinical isolates. In conclusion, the beta-lactam-resistant mutants of B. thetaiotaomicron with deficiency in both PBPs and OMPs can be selected for by exposure to cefoxitin, and several mechanisms are involved in the beta-lactam resistance in the strains investigated.
authors.affiliation: Department of Microbiology, Pathology, and Immunology, Karolinska Institute, Huddinge University Hospital, and Södertörns högskola (University College), Stockholm, Sweden.
authors.forename: Hong
authors.initials: H
authors.lastname: Fang
authors.forename: Charlotta
authors.initials: C
authors.lastname: Edlund
authors.forename: Carl Erik
authors.initials: CE
authors.lastname: Nord
authors.forename: Maria
authors.initials: M
authors.lastname: Hedberg
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins; D001439:Bacteroides / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D002440:Cefoxitin / Q000494:pharmacology*; D002513:Cephamycins / Q000494:pharmacology*; D006602:Hexosyltransferases; D006801:Humans; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D018440:beta-Lactam Resistance / Q000502:physiology*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002513:Cephamycins; D046915:Penicillin-Binding Proteins; D002440:Cefoxitin; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase