In-vitro activity of gatifloxacin against Chlamydia trachomatis and Chlamydia pneumoniae.

We compared the activity of gatifloxacin, a new quinolone, ofloxacin and erythromycin against five isolates of Chlamydia trachomatis and 20 isolates of Chlamydia pneumoniae, including TW183 and clinical isolates from the USA and Japan. Testing was done in cycloheximide-treated HEp-2 cells. Gatifloxacin was slightly less active against C. trachomatis and slightly more active against C. pneumoniae than ofloxacin, with MICs at which 90% of the isolates had no inclusions and minimal chlamydicidal concentrations at which 90% of the isolates had no inclusions after passage of 0.25 mg/L. Gatifloxacin was less active than erythromycin for both species.