Activities of rifamycin derivatives against wild-type and rpoB mutants of Chlamydia trachomatis.

Rifalazil, a semisynthetic rifamycin, was shown previously to have exceptional potency against Chlamydia trachomatis (MIC of 0.00025 microg/ml). We therefore tested 250 additional rifamycin derivatives and identified 12 with activities that are eightfold more potent than that of rifalazil. These compounds also showed exceptional activities against rifampin-resistant strains that carry missense mutations in the rpoB gene. The antimicrobial potency and intracellular penetration of these agents suggest their potential in treatment of chlamydial infections.