In vitro and in vivo antichlamydial activities of newly developed quinolone antimicrobial agents.

The in vitro and in vivo activities of three newly developed quinolone antimicrobial agents (sparfloxacin, tosufloxacin, and OPC-17116) were investigated. All three agents showed potent in vitro activities against Chlamydia psittaci, C. trachomatis, and C. pneumoniae with MICs that ranged from 0.031 to 0.125 micrograms/ml. These values were higher than those of minocycline (0.0075 to 0.015 micrograms/ml) but lower than those of erythromycin (0.25 to 0.5 micrograms/ml) and ofloxacin and ciprofloxacin (0.5 to 1.0 micrograms/ml). Mice were challenged with 10(5) inclusion-forming units of C. psittaci each by nasal instillation. All untreated control animals died within 7 days. The survival rates of mice treated with 40 mg of sparfloxacin, OPC-17116, or tosufloxacin per kg of body weight every 12 h for 7 days were 73, 73, and 60%, respectively, 7 days after the challenge. The survival rate of mice treated with ofloxacin at the same dosage was 53%. On the basis of the above results, we concluded that these three new quinolones might be useful in the treatment of chlamydial respiratory infections.