Interaction of cephalosporins with penicillin-binding proteins of methicillin-resistant Staphylococcus aureus.

The binding affinity of cefmetazole for penicillin binding proteins (PBPs) of methicillin resistant Staphylococcus aureus (MRSA) was compared with the affinities of cefazolin, cefotetan, and cefoxitin for these same sites. Overall, cefmetazole was found to have comparable or higher affinity for PBP1, PBP2, and PBP3 than cefoxitin or cefotetan; its affinity for these PBPs is lower than that of cefazolin. Interestingly, the antibiotic showed a somewhat greater affinity for PBP2' (PBP2a) than cefazolin, cefotetan, and cefoxitin. These results suggest that the somewhat lower MICs detected with cefmetazole for MRSA may be a consequence of the interaction of the antibiotic with PBP2'.