Identification of tubercle bacilli.

Initial screening of tubercle bacilli with 2-thiophene carboxylic acid hydrazide (TCH) or 2-furoic acid hydrazide (FAH) separates them into two groups. Resistant strains are Mycobacterium tuberculosis. Sensitive strains include M. tuberculosis, M. bovis and BCG which are separated by nitratase and oxygen requirement tests. Pyrazinamide sensitivity tests allow M. bovis and M. africanum to be identified. The niacin test is not used. Most strains of M. tuberculosis from Europeans are resistant to TCH and FAH and are in phage groups A and B, while most strains from Asians are sensitive and are in phage group I.