Growth of a Form 2 Mycobacterium and Various Bacillus Species on Löwenstein-Jensen Medium

SUMMARY: Vegetative organisms of a Form 2 strain of Mycobacterium tuberculosis were inoculated on to Löwenstein-Jensen medium containing malachite green. The multiplication of the organisms was slightly delayed by the presence of the dye, but after a few days growth occurred, even when only a few organisms were used as inoculum. Stimulation of growth of Form 2 mycobacteria by the presence of Form 1 mycobacteria was not observed. Spores of Bacillus subtilis and B. licheniformis grew on Löwenstein-Jensen medium. Organisms other than Bacillus were usually obtained from Löwenstein-Jensen medium slopes deliberately exposed to airborne contamination, but have never been found in experiments in which M. tuberculosis Form 2 organisms were isolated. These results establish the validity of the uninoculated control slopes of Löwenstein-Jensen medium used in all previous experiments in which Form 2 mycobacteria were obtained from Form 1 mycobacteria.