Differential susceptibilities of Mycobacterium avium and Mycobacterium intracellulare to sodium nitrite

Sixty-seven of 72 strains of Mycobacterium avium (93.1%) were resistant to sodium nitrite at a concentration of 3 mg/ml in 7H11 agar medium, while 57 of 59 strains of Mycobacterium intracellulare (96.6%) were susceptible to the agent. The difference in the susceptibilities of M. avium and M. intracellulare to sodium nitrite is therefore useful for the differentiation of the two species.