Appraisal of techniques for identification and characterization of non-tuberculous mycobacteria.
Paramasivan, C.N.; Kamala, T.; Daniel Herbert.
Indian Journal of Tuberculosis; 1996; 43; 67-74.
In mycobacteria, problems in taxonomic analysis relate to those of growth rate and limited accumulation of intermediate metabolic products. The International Working Group on Mycobacterial Taxonomy (IWGMT) from its inception had a deliberately permissive philosophy according to which participating investigators were free to choose whatever tests they considered would be useful. According to this philosophy, it was assumed that it was not known a prior which tests would prove to be productive and thus worthy of detailed scrutiny. The objective of numerical taxonomy is to arrange strains into a sequence such that each strain is next to those that share the greatest number of features with it and farthest from those that share the fewest. A satisfactory taxonomy is one which provides consistency, stability, utility and intellectual satisfaction. One of the purposes of an expanded numerical analysis of data is the ultimate selection of a few key tests that are easy to perform, of a high degree of reliability and of use in the diagnostic laboratory for the differential identification of clinically significant mycobacteria. Otherwise, numerical taxonomic methods are laborious, time consuming and beyond the scope of most diagnostic laboratories. Using this strategy, the tests that have been found to be most valuable in differential identification of mycobacteria in the diagnostic laboratory include the niacin test, nitrate reductase test, semi-quantitative test, test for stability of catalase at 68°C for 20 minutes, test for pigment production, tween hydrolysis test, tellurite reduction test, growth on medium containing 5% NaCl, aryl sulphatase test, test for urease and ß-galactosidase, resistance to Isoniazid (INH, 10 µg/ml), thiophen-2-carboxylic acid hydrazide (TCH, 1 µg/ml), hydroxylamine (HA, 250 m g/ml) and (PNB, 500 µg/ml) and growth on MacConkey agar.
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