Interaction of FCE 22101 with penicillin-binding proteins of Staphylococcus aureus

FCE 22101 is a new penem characterized by a broad spectrum of activity which includes activity against methicillin-resistant strains of Staphylococcus aureus. The interaction of FCE 22101 with penicillin-binding protein 2a of a methicillin-resistant S. aureus strain has been investigated in the present study. In competition experiments, the penem showed a very low affinity for this protein, and a concentration more than 4 times the MIC was required for penicillin-binding protein 2a saturation. When the classical competitive procedure was modified by increasing the time of incubation of either membranes or growing cells with FCE 22101, the antibiotic showed a much higher affinity for penicillin-binding protein 2a and saturated the protein at a concentration close to the MIC, with slow kinetics.