Niacin production test in mycobacteria: Replacement of benzidine - cyanogen bromide reagent by o-tolidne - cyanogen bromide

摘要

The identification of M. tuberculosis dependsudprimarily on the niacin production test. Runyonudand others (1959) described a method based onudthe observations of Konno (1956) using anilineudas the reagent. However, the aniline reagentudgives a yellow colour which can cause difficultyudin the interpretation of the results, particularlyudin the case of the chromogenic mycobacteria.udHence several workers prefer the test employingudbenzidine (Medveczky, 1960) or o-tolidineud(Guttierrez-Vazquez, 1960), since the pink colourudproduced in these tests is easier to read.udThe standard method for niacin productionudtest at this Centre has been the one usingudbenzidine. However, satisfactory supplies ofudbenzidine are no longer available, as the manufactureudof this compound’ has recently beenudstopped. Hence it was decided to investigate theudtest using o-tolidine. Though other workersud(Tarshis, 1960, 1961; Gangadharam and Droubi,ud1971) have compared the benzidine and o-tolidineudmethods on small numbers of cultures, no largeudscale investigation of these two methods has beenudreported. Therefore a direct controlled comparisonudof these two methods was undertaken, theudresults of which are reported here.