Isolation of Cryptococcus neoformans from the pigeon excreta in the Okayama district was attempted. As the result, 8 strains of Cryptococcus neoformans were isolated from 61 specimens collected at 56 different places in the district.
1. Studies on the pathogenicity to mice of 3 isolated strains, A1, C2 and C9, revealed that pigeon strains were less pathogenic than the Kurata strain isolated from human cyptococcosis.
2. In the mice, Cryptococcus neoformans provoked 2 kinds of lesions, either cystic or granulomatous lesions.
3. By way of intranasal inoculation the fungal metastasis to the brain was difficult, whereas intravenous inoculation induced cystic lesions within the parenchyma of the brain instead of meningitis in the most instances.
4. Though the Cryptococcus neoformans was able to be cultured at 37°C, the strains which had been cultured at 25°C was difficult to produce large colonies in the first generation at 37°C.
5. The capsule of Cryptococcus neoformans was large in vivo but it was found to disappear or become thinner on transplantation to a culture medium.