INTERACTION OF BETA-LACTAM ANTIBIOTICS WITH THE PENICILLIN-BINDING PROTEINS OF PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE

The binding of five structurally diverse beta-lactam antibiotics to pe nicillin-binding proteins (PBPs) of two clinical isolates of Streptoco ccus pneumoniae resistant to penicillin G was compared with that of a susceptible strain. A common feature of the PBP patterns of the resist ant strains was the absence of PBP 1a detected in the susceptible stra in. For each beta-lactam antibiotic tested, there appeared to be signi ficant decreases in the affinity for BPB 1b, 2a and 2b of the resistan t strains. We attempted to evaluate a quantitative correlation between the antibacterial activity of the drugs for three strains and their a ffinity for the various PBPs. A close correlation was found between th e minimum inhibitory concentrations and the affinity for PBP 2a, but n ot for any of the other PBPs.