COMPARATIVE STUDY OF THE ANILINE-CYANOGEN BROMIDE AND O-TOLIDINE-CYANOGEN BROMIDE DIRECT QUALITATIVE MICRONIACIN TESTS FOR DIFFERENTIATING HUMAN TUBERCLE BACILLI FROM OTHER MYCOBACTERIA - RESULTS OBTAINED USING FRESH CULTURES
An investigation was undertaken to compare two recently described direct qualitative micro-niacin tests. When used under the conditions described, these tests can be performed, in most instances, on cultures only 7 to 10 days old, thus reducing the testing time by approximately 2 to 3 weeks. When used on cultures from 7 to 10 days old, the sensitivity of the aniline-cyanogen bromide method was slightly better than the o-tolidine-cyanogen bromide procedure. When used on older cultures, however, the sensitivity of both tests was essentially the same. The Tween -albumin niacin test medium used to culture the organisms and perform the tests was found to give not only early, eugonic, and uniform growth, but also reproducible and consistent results. The chief advantages of both tests are simplicity, efficiency, safety, economy, and the shorter time required before performing them. They have proved useful as a screening procedure for differentiating human tubercle bacilli from other mycobacteria.