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 binding proteins (PBPs) from Chlamydia trachomatis were determined in vitro and compared with their antichlamydial activities. Mecillinam selectively inhibited PBP1, with a 50% inhibitory concentration for PBP1 binding (0.2 microg/ml) similar to the MIC (0.1 microg/ml) and minimum bactericidal concentration (0.25 microg/ml). Although the other beta-lactams inhibited a wider range of PBPs than mecillinam, their antichlamydial activities were inferior to that of mecillinam.