Affinities of beta-lactams for penicillin binding proteins of Chlamydia trachomatis and their antichlamydial activities

Binding affinities of beta -lactam antibiotics for the three penicillin bin ding proteins (PBPs) from Chlamydia trachomatis were determined in vitro an d compared with their antichlamydial activities. Mecillinam selectively inh ibited PBP1, with a 50% inhibitory concentration for PBP1 binding (0.2 mug/ ml) similar to the MIC (0.1 mug/ml) and minimum bactericidal concentration (0.25 mug/ml). Although the other beta -lactams inhibited a wider range of PBPs than mecillinam, their antichlamydial activities were inferior to that of mecillinam.