Temperature-Sensitive Strain of Cryptococcus neoformans Producing Hyphal Elements in a Feline Nasal Granuloma

We report the isolation of a temperature-sensitive, serotype A, mating type α strain of Cryptococcus neoformans from a case of nasal cryptococcosis in a cat. The strain grew extremely slowly at 35°C and failed to grow at 37°C in vitro. Histopathological sections of the infected tissue revealed yeast cells producing hyphae up to several hundred micrometers in length, in addition to numerous encapsulated yeast cells typical of C. neoformans. The cultures grown on yeast extract-peptone-glucose agar at 35°C also produced some yeast cells with germ tube-like hyphal elements up to 100 μm in length.