An in-vitro investigation of synergy and antagonism between antimicrobials against Chlamydia trachomatis.

Chequerboard titrations of antimicrobials were carried out against Chlamydia trachomatis in vitro to assess possible synergy or antagonism. None of the antimicrobial pairs produced any detectable antagonism. Penicillin and ciprofloxacin showed independent activity. Tetracycline and penicillin, tetracycline and erythromycin, tetracycline and chloramphenicol, erythromycin and penicillin, and erythromycin and chloramphenicol showed additive inhibitory activity and limited synergy. Trimethoprim and sulphamethoxazole was the only combination to produce clear synergistic activity against Chlam. trachomatis in vitro.