Septicemic infection in nude mice caused by a virulent strain of Mycobacterium bovis.

Following i.v. infection with 2.3 to 2 X 10(6) viable organisms of Mycobacterium bovis strain Ravenel, congentitally athymic nude (nu/nu) mice of BALB/c background died earlier than their heterozygous (nu/+) counterparts, showing necrotic nodules in the heart and kidney with the involvement of liver and spleen. Pulmonary lesions in nu/nu mice, however, were less severe than those of dead nu/+ mice. In the reticuloendothelial organs of nu/nu mice, macrophages loaded numerous acid fast bacilli were transiently proliferated and later, necrotic-exudative lesions were produced without epithelioid granuloma formation, while necrotic lesions appeared at very early stage of infection in the other organs as well as adipose tissues. After thymocyte-reconstitution nu/nu mice were capable of developing epithelioid granulomas as seen in nu/+ mice, though having more numerous bacilli in granulomas than those of nu/+.