The effect of dioxyphenylalanine (DOPA), amides and some potential sources of energy on the multiplication of Mycobacterium leprae.

The multiplication of 2 out of 3 M. leprae strains on a medium containing substances from digested non-acid-fast microorganisms or even free of them was significally promoted to D-3,4-dihydroxyphenylalanine (DOPA). The following organic substances exerted growth-promoting effects on several strains: 0.02-0.10% concentrations of succinate greater than fumarate greater than alpha-ketoglutarate and acetate greater than glycerol; 0.2% concentrations of citrate and pyruvate greater than isonicotinamide and benzamide greater than lecithin. 0.5% concentrations of oleate greater than citrate greater than pyruvate greater than acetate greater than fumarate greater than succinate; 5.0% concentrations of butanol and butandiol greater than propanol greater than sorbitol greater than ethanol. However, these effects were variable and strains of various origins acted differently. On media containing DOPA, malachite-green (MG) and at least 0.12 x 10(6) microorganisms/ml the following oxidation-reduction reaction was observed: DOPA was oxidized to a brown compound and malachite-green reduced to an almost colourless product. Consequently, the blue-colour of the cultures turned from blue to brown. This DOPA-MG reaction and the inability to grow on conventional media were used for the identification of 10 cultures (inocula directly from patients) as M. leprae, while a DOPA-MG negative patient-strain grew on media employed for cultivable mycobacteria and was not identical with M. leprae, as proved by the foot-pad test in mice.