USE OF NORMAL C57BL 6 MICE WITH ESTABLISHED MYCOBACTERIUM-AVIUM INFECTIONS AS AN ALTERNATIVE MODEL FOR EVALUATION OF ANTIBIOTIC-ACTIVITY/

Several murine models have been used to evaluate the activities of ant imicrobial agents against Mycobacterium avium infection. The main mode l used is the beige mouse model, but beige mice are expensive and not easily available. Thus, we developed a model of infection in wild C57B L/6 mice. The drugs that exhibited some activity in a previous model o f early infection were evaluated in a new model of established infecti on, Sparfloxacin (50 mg.kg of body weight), ethambutol (50 mg/kg), min ocycline (25 mg/kg), and the inhibitor of the cortisol receptors RU-40 555 (LOG mg/kg) were compared with clarithromycin (50 mg/kg). Treatmen ts were started 5 weeks after the inoculation and were continued for 2 1 days. Sparfloxacin and RU-40555, which exhibited a moderate activity in the model of early infection, were not effective in this model of established infection. Clarithromycin and combinations with clarithrom ycin kept their activities against M. avium infection, both in the spl een and in lungs, The present model of established infection of normal C57BL/6 mice is more relevant than the model of early infection for a stringent evaluation of drugs.