Description of a new yeast species, Malassezia japonica, and its detection in patients with atopic dermatitis and healthy subjects

Abstract

Lipophilic yeasts of the genus Malassezia are part of the normal cutaneous microflora and are considered one of the factors that trigger atopic dermatitis (AD). We isolated two strains of Malassezia from a healthy Japanese female. Analysis of the D1/D2 26S ribosomal DNA and internal transcribed spacer region sequences of the isolates suggested that they are new members of the genus Malassezia. We propose the name Malassezia japonica sp. nov. for the isolates. M. japonica is easily distinguished from the seven known lipophilic species by its ability to assimilate Tween 40 and Tween 60 and its inability to assimilate Tween 20 and Tween 80 and to grow at 40 degrees C. Furthermore, by applying transparent dressings to the skin lesions of 36 patients with AD and the skin of 22 healthy subjects, M. japonica DNA was detected by a non-culture-based method consisting of nested PCR with M. japonica species-specific primers. M. japonica DNA was detected from 12 of the 36 patients (33.3%) and 3 of the 22 healthy subjects (13.6%). Although it is not known whether M. japonica plays a role in AD, this species was part of the microflora in both patients with AD and healthy subjects.

FIG. 1.

Phylogenetic trees constructed by using the D1/D2 26S rRNA sequences of M. japonica sp. nov. and related species of the class Ustilaginomycetes (A) and the ITS1 region of M. japonica sp. nov. and other members of the genus Malassezia (B). The DDBJ and GenBank accession numbers are indicated in parentheses. The numerals represent the confidence levels from 100 replicate bootstrap samplings (frequencies less than 50% are not indicated). Knuc, Kimura's parameter (12).

FIG. 2.

Vegetative cells of M. japonica M 9966 grown in LNA for 7 days at 32°C. Bar, 10 μm.