THE GROWTH OF TUBERCLE BACILLI ON NUTRIENT AGAR AND THE BIOLOGICAL PROPERTIES OF THE STRAINS SUBCULTURED ON THE MEDIUM

Abstract

Three hundred and eight strains of Mycobacterium tuberculosis isolated from patients with pulmonary tuberculosis were inoculated on nutrient agar. The tests were performed four times. The proportion of positive cultures ranged from 13.6 to 30.1%. The development of colonies on the medium was not consistent even in materials successively obtained from the same patient; sometimes it was observed and sometimes not.
The thirteen strains grown on the nutrient aga r were subcultured on the same medium every thirty days, and four of them were subcultured up to the 30th generation. The biological properties of these four strains were compared with those of the original ones.
No significant differences were observed on niacin production, nitrate re d uction, peroxidase activity, neutral-red reaction, methyleneblue reduction, acid-fastness in boiling water, catalase activity and acid-formation from carbohydrates and organic acids. The degree of growth on nutrient agar was not promoted during subcultures. It is notable that the ability of cord formation of agar-subcultured strains was lost.
The pathogenicity of three of the four strains to mouse showed marked decrease after agar-subcultures.