Alterations to the penicillin-binding proteins in the Bacteroides fragilis group: a mechanism for non-beta-lactamase mediated cefoxitin resistance.

The penicillin-binding proteins (PBPs) of ATTC Type Strains of nine species of the Bacteroides fragilis group were visualized by gel electrophoresis and subsequent fluorography. Each species had a distinctive PBP pattern, although variation within species was seen. Generally, five PBPs could be visualized, ranging in molecular weight from approximately 40,000 to approximately 90,000. A laboratory-derived cefoxitin-resistant mutant of B. distasonis was compared with its wild type parent and cefoxitin-sensitive revertant. The fluorograph of the resistant mutant indicated a marked reduction of labelling to the PBP-1 complex as compared with the wild type and revertant. Cefoxitin-resistant clinical isolates of B. thetaiotaomicron and B. uniformis also showed changes to the PBP-1 complex, in comparison with sensitive strains.