Lysis of Tubercle Bacilli in Vitro

Abstract

The results of studies on the dissociation of the H₃₇ strain of human tubercle bacilli have been reported. 1 The variants found were designated “R” indicating resistant to environment and “S” indicating sensitive to environment. This communication records an interesting lytic phenomenon observed during the study of the effect of ageing H₃₇ “R” and “S” variants on gentian violet glycerol egg and plain glycerol egg media of different pH. For clarity it seems advisable to discontinue this usage of the symbols “R” and “S” and to employ them in the usual sense as indicative of a rough or smooth colony structure. To indicate virulence or avirulence the letters (v) or (a) are appended thus “Rv” and “Ra”. Since a smooth variant of H₃₇ which manifests a typical morphology and virulence has not been obtained this terminology has been adopted to cover the virulent and avirulent strains of variants having an “R” morphology.

From a dissociated H₃₇ culture 1 extreme variants “Ra” and “Rv” were obtained. Each of these variants was seeded in flasks of gentian violet egg and plain glycerol egg media of the following pH 5.0, 5.5, 6.0, 6.2, 6.5, 6.8, 7.0, 7.3, 7.5, and incubated at 37.5°C. in order to follow single colonies. Structural and growth differences of the variants were observed at the end of 6 weeks' incubation. At this time there were no visible colonies on flasks below pH 5.5. The flasks were then returned to the incubator and were examined every 2 weeks over a period of 5 months to observe further changes.