The in vitro susceptibilities to
garenoxacin (BMS-284756), an investigational des-
fluoroquinolone, and eight other agents were determined for 63 Mycoplasma pneumoniae, 45 Mycoplasma hominis, 15 Mycoplasma fermentans, and 68 Ureaplasma sp. isolates.
Garenoxacin was the most active
quinolone, inhibiting all isolates at <or=1 microg/ml. The
garenoxacin MIC at which 90% of isolates are inhibited (MIC(90)s; <or=0.008 microg/ml) was at least 4-fold less than those of
moxifloxacin and
clindamycin, 8-fold less than that of
sparfloxacin, and 64-fold less than those of
levofloxacin and
ciprofloxacin for M. pneumoniae. For M. hominis, the
garenoxacin MIC(90) (<or=0.008 microg/ml) was 4-fold less than those of
clindamycin and
moxifloxacin, 8-fold less than that of
sparfloxacin, and 64-fold less than those of
levofloxacin and
ciprofloxacin. All 15 M. fermentans isolates were inhibited by
garenoxacin at concentrations <or=0.008 microg/ml, making it the most active
drug tested against this organism. For Ureaplasma spp., the
garenoxacin MIC(90) (0.25 microg/ml) was equivalent to those of
moxifloxacin and
doxycycline, 4-fold less than those of
levofloxacin and
sparfloxacin, 8-fold less than that of
azithromycin, and 32-fold less than that of
ciprofloxacin.
Garenoxacin and the other
fluoroquinolones tested were demonstrated to have bactericidal activities against M. pneumoniae and M. hominis by measurement of minimal bactericidal activities and by time-kill studies. Further study of
garenoxacin is required, as it has great potential for use in the treatment of
infections due to mycoplasmas and ureaplasmas.