Abstract
Summary
A variant of the H37Rv strain of Mycobacterium tuberculosis var. hominis which appears to be avirulent for mice and guinea pigs, was developed in vitro by continual subculture over 3 years on a nitrogen-free synthetic medium. This new strain, designated H37RaN, resembled the parent H37Rv strain both macroscopically and microscopically, but differed metabolically from the parent strain in its reduced ability to utilize for growth carbon compounds related to the tricarboxylic acid cycle. This strain immunized mice as well as the frequently used immunogenic strains, H37Ra and BCG.
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