[Different pathogenic power of the original BCG strain of the Pasteur Institute and of an isoniazid resistant strain. Histopathological study and significance of local abscesses after inoculation of guinea pig].

The inoculation into guinea pigs of 10 mg of BCG, obtained either from the Pasteur Institute original strain, or from a mutant isoniazid resistant strain, B1 catalase positive, caused in 40.4% of cases, the onset of abscesses at the point of injection. The frequency and course of these abscesses appear quite different with the two strains, 92.8% with the classical strain, persisting in more than half of the cases after one year, and 23.5% with the INH-resistant strains which regressed within 6 months. Histologically, the structure of the recent abscesses, with a large histiocytic wall often rich in bacteria, and a very cellular necrotic content, appears different from that of old abscesses with a thin wall and a heterogeneous content, calcification with reaction to foreign bodies, and presence of granules due to the persistance of bacteria. The INH-resistant strain is thus in the guinea pig, less aggressive and more rapidly eliminated than the classical Pasteur strain. The course and morphology of abscesses in guinea pigs are very similar to certain old lesions of human tuberculosis and involve, in all strains, phenomena of cell immunity both general and local.