Difference in the Degree of Acid-fastness in Various Types of Mycobacteria A Simple Method to Distinguish Saprophytic Strains from other Types of Mycobacteria

Abstract

Various types of Mycobacteria were tested on their acid-fastness employing victoriablue simultaneous staining (a modification of Hallberg's procedure) and nitric acid alcohol of various compositions as the decolorizing agent. The results revealed that the nitric acid alcohol composed of a rather low concentration of nitric acid (0.1-0.5%) in 70% ethylalcohol was obviously stronger than 3% hydrochloric acid alcohol or 4-8% nitric acid alcohol (100%) in the decolorizing effect and resulted in the complete decolorization of the acid-fast stain of Saprophytic Mycobacteria and M. fortuitum within 20 minutes of rinsing. Noteworthy is that the decolorized cells by the acid-alcohol of the abovementioned composition are completely restainable by the ordinary acid-fast staining procedures employing 3% hydrochlonic acid alcohol or 4 % nitric acid alcohol (100%) as the decolorizer.
Seventy six strains of Saprophytic Mycobacteria were tested employing abovementiond procedure and 74 strains among them were completely decolorized. Remaining 2 strains which resisted to this procedure were confirmed as the non-photochromogens (Unclassified M.) by other biological properties.
This method seems to be practically available as a very simple test method in distinguishing saprophytic strains from other types of Mycobacteria.