ENUMERATION OF VIABLE TUBERCLE BACILLI FROM THE ORGANS OF NONIMMUNIZED AND IMMUNIZED MICE

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Abstract
The fate of the pathogenic H37Rv strain of Mycobacterium tuberculosis in the lungs, livers, and spleens of "Strong A" and "C57" strain mice was determined by plate-count enumeration studies. Various doses of H37Rv were given to mice. An acute response was found with higher doses of H37Rv and was characterized by rapid multiplication of tubercle bacilli and early death of the mice. The chronic response seen with the lower doses of H37Rv followed an initial short period of multiplication and was characterized by no significant change in the number of tubercle bacilli for as long as 82 days and by prolonged survival of the mice. Immunized mice were challenged with the nonpathogenic H37Ra strain and the results indicated that the immune mice eliminated the nonpathogenic bacilli more rapidly than did normal mice.