The activities of the
fluoroquinolone WIN-57273, 14-OH
clarithromycin (a human metabolite of
clarithromycin), and
minocycline against two virulent strains of Mycobacterium avium complex were evaluated in a model of intracellular
infection and compared with that of
clarithromycin. Human monocyte-derived macrophages were infected at day 6 of culture. Intracellular CFU at 60 min and intracellular and supernatant CFU on days 4 and 7 were counted after inoculation. The concentrations used, which were equal to peak levels in serum, were 3 micrograms of
WIN-57273 per ml (MICs for the two strains, 1 microgram/ml), 4 microgram of 14-OH
clarithromycin per ml (MICs, 8 and 2 micrograms/ml, respectively, at pH 7.4), 4 micrograms of
minocycline per ml (MICs, 64 and 32 micrograms/ml, respectively), and 4 micrograms of
clarithromycin per ml (MICs, 2 and 0.5 micrograms/ml, respectively, at pH 7.4). On day 7, compared with controls,
WIN-57273,
minocycline (P less than 0.02),
clarithromycin, or different combinations of
clarithromycin and the other drugs (P less than 0.001) slowed the intracellular replication of strain MO-1. 14-OH
clarithromycin (P less than 0.02),
clarithromycin (P less than 0.02), 14-OH
clarithromycin plus
clarithromycin (P less than 0.01),
clarithromycin plus
minocycline, or
clarithromycin plus
minocycline plus 14-OH
clarithromycin (P less than 0.001) slowed the intracellular replication of strain LV-2.
WIN-57273 was less effective than
clarithromycin against strain MO-1 (P less than 0.05).
Clarithromycin plus 14-OH
clarithromycin plus
minocycline (P less than 0.02) was more effective than
clarithromycin alone against strain LV-2. Thus,
clarithromycin plus
minocycline, which corresponds in humans to three active molecules, may exhibit a better efficacy than
clarithromycin in this model.