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Antimicrobial Agents and Chemotherapy, 03 1996, 546-551, Vol 40, No. 3
LE Bermudez, CB Inderlied, P Kolonoski, M Wu, L Barbara-Burnham and LS Young
Levofloxacin, ofloxacin, and Bay Y 3118 are new fluoroquinolones with
variable in vitro bacteriostatic and bactericidal activities against the
Mycobacterium avium complex (MAC). The potential therapeutic activities of
these agents both alone and combined with ethambutol were evaluated in a
human macrophage test system and in the beige mouse animal test system with
MAC strain 101. Bay Y 3118 at a human- equivalent dose of 30 mg/kg/day for
4 weeks caused a significant reduction in mortality compared with that in
untreated controls (P = 0.02). Bay Y 3118 also caused significant
reductions in the number of MAC organisms in the blood, liver tissue, and
spleen tissue compared with those in untreated controls. Levofloxacin at a
human-equivalent dose of 200 mg/kg/day was associated with a significant
reduction in mortality (10 versus 39%); however, treatment with either
levofloxacin or ofloxacin (200 mg/kg/day) did not result in significant
reductions in the numbers of MAC organisms in blood, liver, and spleen
compared with those in untreated controls. When Bay Y 3118 was combined
with ethambutol, there was no enhancement in therapeutic activity except in
the spleen in terms of CFU per gram (reductions of 89% compared with the
untreated control, 63% compared with Bay Y 3118 alone, and 72.5% compared
with ethambutol alone). Levofloxacin in combination with ethambutol was
more active than either drug alone in the reduction of organisms in blood,
liver, and spleen. Bay Y 3118 was the most active fluoroquinolone for
monotherapy of MAC infection in beige mice, and the combination of
ethambutol plus either levofloxacin or ofloxacin was at least additive. In
summary, this study demonstrates that quinolones, although active, are
inhibitory against MAC in vivo and that there is little correlation between
the activity of quinolones in vitro and the activity in mice.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Activities of bay Y 3118, levofloxacin, and ofloxacin alone or in combination with ethambutol against Mycobacterium avium complex in vitro, in human macrophages, and in beige mice
California Pacific Medical Center Research Institute, San Francisco 94115, US
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