Relatively large viable units of mouse virulent strain 31F093T of M.avium complex were challenged to conventional ddY mice by intravenous, intraperitoneal and airborne routes, and the differences of the pathological findings among these three infection models were evaluated by using several indices for the period of 15 weeks.
As the indices for comparison, the weight of total bodies and organs (lung, spleen, liver and kidney), extent of gross lesions and histopathological changes were used. In addition, the consecutively recovered viable units of bacilli from the lungs, spleens, and kidneys were also enumerated.
With intravenous and intraperitoneal infections, the main histopathological findings of the organs of mice were granulomatous lesions in the early stage and diffuse proliferative changes in lungs, and mononuclear cell aggregates and multiple glanulomas in the liver and spleen in the later stage.
In the mice infected by airborne route, no significant lesions were noticed in liver, spleen and kidney except in lungs, which demonstrated essentially the same histopathological findings seen in mice with intravenous and intraperitoneal infections, during the entire experimental periods. Although histopathological findings of the lungs showed essentially the same disease processes in the three kinds of models, the disease has been confined solely to the lungs in airborne infection model. It was suggested that the compartmentalization of the disease process in the lungs and possibly in its vicinity by airborne infection might offer a valuable tool for the evaluations of an active inflammatory cell interactions in lung per se provoked by the mycobacterium.
