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

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 Chiamydia psittaci, C. trachomatis, and C. pneumoniae with MICs that ranged from 0.031 to 0.125,g/ml. These values were higher than those of minocycline (0.0075 to 0.015 j±g/ml) but lower than those of erythromycin (0.25 to 0.5 ji.g/ml) and ofloxacin and ciprofloxacin (0.5 to 1.0 ig/ml). Mice were challenged with 105 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%o, respectively, 7 days after the challenge. The survval 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. Sparfloxacin (SPFX), OPC-17116 (OPC), and tosufloxacin (TFLX) are three newly developed quinolone antimicrobial agents characterized by potent and broad antibacterial ac-tivities. They have been reported to show potent in vitro activities not only against common gram-positive and-neg-ative bacteria but also against mycoplasmal, mycobacterial, and chlamydial species, and they may be considered drugs of first choice for the treatment of respiratory tract infections. In this study, we investigated the in vitro activities of these agents against three chlamydial species and compared them with those of other antimicrobial agents. Most previous studies have been concerned with genitourinary tract infec-tions caused by Chlamydia trachomatis. We also studied the in vivo therapeutic effects of these compounds using a mouse experimental model of C. psittaci-caused pneumonia