A system for the examination of tubercle bacilli and other mycobacteria.

Methods are described for the examination of mycobacteria cultured from clinical specimens. In the "screening" procedure used for new isolates tubercle bacilli are non-pigmented, do not grow at 25 degrees C and are sensitive to p-nitrobenzoic acid as well as normally to anti-tuberculosis drugs. Classification is extended when necessary by the use of four tests--temperature requirements, pigmentation, oxygen preference and Tween hydrolysis. These define 15 species or groups meeting the needs of clinical bacteriology. Drug-sensitivity tests are described which relate the end-points of titrations to the modal response of normal wild strains of M. tuberculosis. They are used not only as a guide to chemotherapy but also to support and amplify classification.