Penicillin-binding proteins in Bacteroides fragilis and their affinities for several new cephalosporins

The penicillin-binding protein (PBP) composition in two strains of Bacteroides fragilis has been investigated using 14C-cefotaxime. This microorganism is unique among the bacteria so far investigated, which show a number of PBPs ranging from 5 to 8 in possessing only three PBPs. It lacks the PBP with molecular weight (MW) lower than 50,000 daltons, which, at least in Escherichia coli, has been demonstrated not to be essential for cell growth and division. The affinities of several cephalosporins including cefoxitin, latamoxef (moxa-lactam), cefoperazone and cefotaxime for the Bact. fragilis. PBPs have been determined by in-vitrocompetition experiments. The results obtained suggest that further studies with competition experiments performed using intact, growing cells may be useful to ascertain the killing targets ofβ-lactam antibiotics in bacteria.