In vitro and in vivo antichlamydial activities of HSR-903, a new fluoroquinolone antibiotic.

The in vitro and in vivo antichlamydial activities of HSR-903 were investigated. The MICs of HSR-903 for different species of chlamydia were 0.016 to 0.063 microg/ml, which were superior to those of conventional fluoroquinolones. The therapeutic effect of HSR-903 in experimental mouse Chlamydia psittaci pneumonia was also excellent and almost equal to that of minocycline and superior to that of ofloxacin. These results indicate that HSR-903 may be useful in the treatment of respiratory infections caused by chlamydiae.