21 strains isolated from human leprosy lesions, healthy mouths, and soils were studied on their biological characteristics and the following results were obtained.
1. All of these strains were propagated in peptone water media and some of them produced turbidity in the media.(No strain produced indole and 8 strains produced HZS)
2. Only small numbers of them coagulate the lackmus milk with red color, produced catalase and fermented dextrose, lactose and sucrose but no strains produced crease, indole and HZS. The results were variable according to the strains.
3. The fastness to boiling water was also variable, and strains from leprosy nodules and soils showed stronger fastness than those from other sources. The fastness to 1% HCl was stronger tahn 5% HZSO4i and weaker against 70% alcohol. The strains from human leprosy lesions were more strongly fast than those from other sources.
5. The temperature limit of growth of most strains was from 20 to 50C and some of them grow within limit of 2 to 55C, 15 to 55C, 20 to 55C or 25 to 40C. The most strains grow luxuriantly at 37C.
The effects of some physico-chemical agents were also variable, but it was found that the strains from human leprosy lesions were more weakly resistant to ultraviolet ray, heat and some disinfectants than those from mouth cavities and soils.
7. The number of strains sensitive to INAH and streptomycin were predominant followed by those sensitive to Pas and Ciba 1906 were followed. Three strains from human leprosy lesions and one strain from soil (No. 16) showed almost the same antibiotic spectrum as tubercle bacilli. 3 strains from blood of leper were sensitive to INAH but not to PAS. DDS, penicillin and sulfathiazole showed no bactericidal effects against these strains tested.
8. The biologcial characters of strains from human leprosy lesions and one strain from soil sample were almost the same as those of tubercle bacilli tested.
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