In vitro cultivation and characterization of Mycobacterium lepraemurium.

Three different strains of M. lm were regularly grown in vitro from suspensions of mouse organs if at least 10(5) organisms were inoculated on Ogawa egg yolk medium and incubated at 35 degrees C in a humidified, CO2 enriched atmosphere. Growth is slow and requires 2-3 months. Colonies are 1-2 mm in diameter, white to pale yellow. Microscopically the bacteria are acid-alcohol-fast pleomorphic rods with branchings and beaded filamentous forms. Mice inoculated with in vitro grown subcultures develop an infection indistinguishable from the one observed after injection with mouse passage strains of M. lm. The in vitro characteristics of the strains are identical and different from all other known mycobacteria.