Salicylate Degradation Test for Differentiation of Mycobacterium Fortuitum from Other Mycobacteria

Abstract

SUMMARY: Most isolates of Mycobacterium fortuitum decomposed salicylate and stained black the Sauton agar medium containing salicylate (0.5 or 1 mg./ml.); and all isolates capable of decomposing salicylate were identified as M. fortuitum. Other species, including rapidly growing mycobacteria, did not decompose salicylate. Most but not all of the salicylate-decomposing isolates showed also PAS degradation and a positive 3-day arylsulphatase test. The salicylate-decomposing isolates utilized nitrite as sole nitrogen source and about one-half of them grew on a nitrite medium within 7 days. These reactions, salicylate degradation, PAS degradation, utilization of nitrite, and 3-day arylsulphatase activity, are shown to be useful for identifying M. fortuitum. The 3-day arylsulphatase test showed some exceptional cases; therefore, a positive reaction in this test was not sufficient to identify M. fortuitum. Positive reactions in the above four tests seemed to mean that an isolate is certainly M. fortuitum.