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Clin Infect Dis. 2002 Sep 1;35(Suppl 1):S47-53.

Selection of cefoxitin-resistant bacteroides thetaiotaomicron mutants and mechanisms involved in beta-lactam resistance.

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Department of Microbiology, Pathology, and Immunology, Karolinska Institute, Huddinge University Hospital, and Södertörns högskola (University College), Stockholm, Sweden.


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.

[Indexed for MEDLINE]

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