Biochemical Tests for MTB

Biochemical Tests for MTB

An experienced laboratory technologist may make the presumptive diagnosis of tuberculosis on the basis of the morphological characteristics of tubercle bacilli, but it is best to do confirmatory tests.

Unfortunately, there is no completely reliable single test that will differentiate M. tuberculosis from other mycobacteria. Nevertheless, the following tests, when used in combination with the characteristics, will enable the precise identification of > 95% of M.tuberculosis strains:

 1) Susceptibility to p-nitrobenzoic acid (PNB)

 2) Niacin test

 3) Catalase activity at 68°C & pH 7. 

Of these, the PNB test can be included along with the drug susceptibility test.

Resource

Revised National TB Control Programme Training Manual for Mycobacterium tuberculosis Culture & Drug susceptibility testing.

Assessment