Niacin production test in mycobacteria: Replacement of benzidine-cyanogen bromide reagent by o-tolidine-cyanogen bromide.
Venkataraman, P.; Prabhakar, R.
Indian Journal of Tuberculosis; 1977; 24; 153-154.
The identification of M. tuberculosis depends primarily on the niacin production test. Runyon and others (1959) described a method based on the observations of Konno (1956) using aniline as the reagent. However, the aniline reagent gives a yellow colour which can cause difficulty in the interpretation of the results, particularly in the case of the chromogenic mycobacteria. Hence several workers prefer the test employing benzidine (Medveczky, 1960) or o-tolidine (Guttierrez-Vazquez, 1960), since the pink colour produced in these tests is easier to read.
The standard method for niacin production test at this Centre has been the one using benzidine. However, satisfactory supplies of benzidine are no longer available, as the manufacture of this compound has recently been stopped. Hence it was decided to investigate the test using o-tolidine. Though other workers (Tarshis, 1960, 1961: Gangadharam and Droubi, 1971) have compared the benzidine and o-tolidine methods on small numbers of cultures, no large scale investigation of these two methods has been reported. Therefore a direct controlled comparison of these two methods was undertaken, the results of which are reported here.
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