Analysis of Fungal Flora in the Dust of Bedding in Japanese Houses and Genetic Identification of Yeasts Isolated from the Dust.

This study examined the fungal flora contained in the dust of bedding used in 50 houses in Japan. The result showed that the mycoflora having the largest isolation rate was yeasts, which were isolated by 42 out of 50 houses (84%), and exceeded the isolation rate of Cladosporium spp. (80%) and Aspergillus spp. (66%). In addition, the isolation rate of Alternaria, which was an important fungus causing asthma, 66% was being considered as a high isolation rate, and this result was very interesting. The isolation rate of xerophilic fungi such as Aspergillus restrictus and Wallemia often found in house dust on the floor, was not very high. Forty-one strains of yeasts isolated from each dust sample were identified, and Naganishia diffluens species complex and Filobasidium magnum had a larger number of 13 strains, respectively. Since N. diffluens was the yeasts often isolated from human skin, it was thought to be an association between the fungal skin flora and fungal flora of bed dust. Meanwhile, there was no report of isolation of F. magnum from house dust previously. To the best of our knowledge, this is the first study showing its isolation from bedding with relatively high frequency.