INTERMITTENT AZITHROMYCIN FOR TREATMENT OF MYCOBACTERIUM-AVIUM INFECTION IN BEIGE MICE

The activity of azithromycin (AZI) was evaluated in the beige mouse mo del of disseminated Mycobacterium avium infection. Mice were infected intravenously with approximately 10(7) viable M. avium ATCC 49601. AZI at 50, 100, or 200 mg/kg of body weight or clarithromycin (CLA) at 20 0 mg/kg was given by gavage 5 days per week for 4 weeks. Groups of tre ated mice were compared with untreated control animals. A dose-related reduction in cell counts in organs was observed with AZI treatment. A ZI at 200 mg/kg was more active than CLA at 200 mg/kg against organism s in spleens. The activities of these two agents at 200 mg/kg were com parable against organisms in lungs. In a second study, AZI at 200 mg/k g was given daily for 5 days; this was followed by intermittent AZI; t reatment for the next 3 weeks. The activities of AZI given on a three- times- and five-times-per-week basis in the continuation phase were co mparable. AZI given on a once-weekly basis was less active. The regime n of AZI given in combination with rifapentine on a once-weekly basis for 8 weeks showed promising activity. Clinical evaluation of AZI and rifapentine will help to define the roles of these agents in the treat ment of disseminated M, avium complex infection.