Affinities of β-Lactams for Penicillin Binding Proteins of Chlamydia trachomatis and Their Antichlamydial Activities

Binding affinities of β-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 μg/ml) similar to the MIC (0.1 μg/ml) and minimum bactericidal concentration (0.25 μg/ml). Although the other β-lactams inhibited a wider range of PBPs than mecillinam, their antichlamydial activities were inferior to that of mecillinam.