Genetic identification of dematiaceous Fungi isolated from washing machine in Japan, and considering of Fungal removal methods

Abstract

In 2017, 2 household washing machines which were used at a house in Saitama prefecture were tested for fungal flora sampling. The fungi were identified in detail via genetic analysis of the ITS region. The number of fungi which were isolated were 8.7×1066.1×107 cfu/100cm2 and dematiaceous fungi such as Ochroconis musae, Exophiala, Cyphellophora, Knufia epidermidis were dominant. As for Knufia epidermidis, this is the first report for identification from a Japanese household. The number of isolated Cladosporium, which is common in the environment, was fewer compared with the above 4 genera. The identified fungi were Cladosporium halatolerans, which is recently being recognized as the main species of Cladosporium. In our research, we have cleaned the 2 washing machines with different bleaches. Residual fungi was detected in washing machine A, which was cleaned with an oxygen bleach. On the other hand, no fungi was detected in washing machine B, which was cleaned with a chlorine bleach.