Reduced Local Growth and Spread but Preserved Pathogenicity of a Δ purC Mycobacterium tuberculosis Auxotrophic Mutant in Gamma Interferon Receptor-Deficient Mice after Aerosol Infection

Abstract

ABSTRACT We compared the growth levels and pathogenicities of the Mycobacterium tuberculosis MT103 clinical strain with those of the Δ purC mutant strain MYC1551, which is auxotrophic for purine in wild-type and gamma interferon receptor (IFN-γR)-deficient mice. The Δ purC strain MYC1551 grew initially in both wild-type and IFN-γR-deficient mice upon aerosol infection, but it grew much less than strain MT103 did. Despite the comparable bacterial burdens of the mice, IFN-γR-deficient mice succumbed to infection with Δ purC strain MYC1551 from necrotic pneumonia within 6 weeks of those infected with MT103. In conclusion, the Δ purC mutant MYC1551 displays reduced growth but retains pathogenicity. Therefore, the use of mutant strains of M. tuberculosis as live vaccines may not be recommended.