Objectives:
As cryptococcosis is a fatal disease in koalas (Phascolarctos cinereus), Cryptococcus spp. and related basidiomycetous yeasts are major targets for yeast microbiota analysis in koalas. In the course of a study of the yeast microbiota of koalas, we isolated a number of basidiomycetous yeasts from koalas and the breeding environments in Japanese zoological parks. We published plural new yeast species (ex. Spolobolomyces koalae1) and Cryptococcus yokohamensis2)) isolated from koalas. In this study, further new species and the basidiomycetous yeast biota of the koala from previous presentation (ISHAM 2012, Berlin) to 2017 will be reported

Methods:
Most of the morphological, biochemical, and physiological characteristics were investigated using the methods described by Kurtzman et al. (2011). Nasal smears of several healthy koalas and the breeding environments were collected with swabs and inoculated onto CHROMagar Candida (CHROMagar) spread with micafungin (30 mg per plate). The isolated strains were identified by comparison with DNA sequences registered in GenBank/EMBL/DDBJ as described previously1). Since 2016, we have checked all colonies using MALDI Biotyper.

Results:
Over 500 strains of yeast were isolated from nasal smears of koala and the breeding environments. The dominant genus was Cryptococcus (mainly C. neoformans). Rhodotorula was the next most dominant genus by culture methods. Furthermore, new species of Cryptococcus lacticolor sp. nov. and Rhodotorula oligophaga sp. nov. were discovered3).

Conclusion:
Genus Cryptococcus was predominance, but a variety of basidiomycetous yeast habitually resided to the nasal cavity of the koala.

1). Satoh K, Makimura K 2008: Int. J. Syst. Evol. Microbiol., 58, 2983-2986.
2). Alshahni MM et al. 2011: Int. J. Syst. Evol. Microbiol., 61, 3068-3071.
3). Satoh K et al. 2013: Antonie van Leeuwenhoek, 104, 83-93.

Basidiomycetous yeast biota and dynamics of koala nasal cavity