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

Abstract

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.