Chemoprophylaxis against Mycobacterium avium complex infection induced in mice

M. avium complex (MAC) is one of the important causative agents of opportunistic infections among AIDS patients. Recent evidence showed that the entry of infection is through the gastrointestinal tract. In the present study, we compared the prophylactic effect of some antimicrobials against MAC infection induced in mice. Different groups of beige mice were fed with pellets containing 0.0067% (10 mg/kg) of KRM-1648, rifabutin (RFB) and clarithromycin (CAM). Seven days after the administration of drugs, the mice were infected with M. intracellular N-241 (5 x 10(8) CFU) orally, five times, every other day and killed one and 126 days after the last infection. The effect of drug was evaluated using the frequency and severity of gross lung lesions in the mice and by the total CFU recovered from the lungs and spleen. MAC infection was not likely to be established since there was no macroscopic evidence of lesion in organs and the recovery of cultures from lungs and spleen tested was negative, in 3 of 10 mice in the control group, 2 of 9 in the CAM group, 4 of 9 in the RFB group and 4 of 10 in the KRM group. These mice were excluded from the analysis of the study results. Thus, we examined 7 mice in the control group, 7 in the CAM group, 5 in the RFB group, and 6 in the KRM group. Tubercle-like lesions were observed in the lungs of all 7 mice in the control group (severity: 3+ in 5 mice; 4+ in 2 mice), in 5 of 7 mice (71%) in the CAM group (severity: 2+ in 1 mouse; 3+ in 4 mice), and in 4 of 5 mice (80%) in the RFB group (severity: 1+ in 1 mouse; 2+ in 1 mouse; 4+ in 2 mice), while only slight lesions (severity: 1+) were observed in 4 of 6 mice (67%) in the KRM group. There was no macroscopic evidence of lesion in spleen, liver and kidneys. The log CFU was determined at the next day of the completion of the last infection. The log CFU of the lungs was 2.49 and 2.28 in the control group and the CAM group, respectively. The bacteria were not recovered either from the lungs in the RFB and KRM groups, nor from the spleen in all the groups. The order of efficacy of the drugs on the basis of the CFUs recovered from the lungs and spleen in each group determined 126 days after the completion of the last infection was as follows; KRM > CAM > RFB in the lungs and KRM > CAM [symbol: see text] RFB in the spleen, although there was no significant difference among the three drugs (P < 0.05). However, the significantly preferable effect was obtained in the three drug groups as c