One-tenth ml each of bacterial suspensions derived from nodules of 4 different L-type patients was inoculated into 0.1% semiliquid agar media of various semi-synthetic base compositions and incubated at 37°C. The results revealed that rather large colony-like masses of bacteria had appeared, in most cases, after about 20 weeks and persisted even after about one year of incubation at 37°C. These masses varied in size and shape. Generally, they were composed of smaller, round bacterial masses of 10 to 20μ in diameter, confluent with one another. Each mass seemed to have boundary around it. It consisted of strongly acid-fast rods, stainable with malachite green. It was suggested that the bacterial masses might be colonial growths.
Bacterial suspensions prepared from nearly one-year-old cultures by centrifugation induced essentially the same intradermal reaction in leprous patients as Dharmendra's antigen. Therefore, it was revealed clearly that the bacterial masses appearing in culture tubes were composed of M. leprae.