A Mycological and Molecular Biological Study of Malassezia dermatis Isolated from Korean

Lim, Sang Hee; Kim, Sang Min; Jung, Bo Ra; Lee, Yang Won; Choe, Yong Beom; Ahn, Kyu Joong

Abstract

BACKGROUND: Malassezia (M.) yeasts are lipophilic fungi which are regarded as normal flora of the skin, and are recovered in 75~98% of healthy adults. Gueho et al reclassified the Malassezia yeasts into 7 species (M. furfur, M. obtusa, M. globosa, M. slooffiae, M. sympodialis, M. pachydermatis, M. restricta) on the basis of molecular biology and by employing an interdisciplinary approach of morphology, microstructurology and physiology. Recently novel species of the genus Malassezia have been discovered as a result of molecular analysis. But there are no additional reports in Korea regarding newly reported Malassezia species because most identification and classification of Malassezia in Korea depend on classical methods and research on molecular biologic application is insufficient.
OBJECTIVE
Five clinical isolates of M. dermatis were isolated from the skin of healthy subjects without skin disease or seborrheic dermatitis patients using molecular biology techniques for the first time in Korea. Hence the present study describes mycological and molecular biological characteristics of these five isolates as a novel species of M. dermatis.
METHODS
Morphological and biochemical analyses, such as colony morphologies, microscopic morphologies and physiological characteristic were done targeting 5 clinical isolates of M. dermatis. Molecular techniques, namely, 26S rDNA PCR-RFLP, 26S rDNA and internal transcribed spacer region 1 (ITS1) sequencing, were done for identification and phylogenetic systematic analysis.
RESULTS
Five clinical isolates of M. dermatis showed positive in the catalase test. No growth is obtained on Sabouraud's dextrose agar (SDA) without lipid supplementation but all grew in 0.5% Tween 60 and 0.1% Tween 80 added 2% glucose/1% peptone culture medium. Round and ellipsoidal yeast cells and budding of the yeast cells were observed under microscope, resembling M. sympodialis, M. furfur, and M. nana. The 26S rDNA PCR-RFLP pattern showed the same pattern as M. dermatis (JCM 11348), the standard strain. 26S rDNA and ITS1 sequencing were performed for exact identification, showing 99% accordance with M. dermatis (AB070361), and M. dermatis (AB070356), confirming the species to be new, the first to be reported in Korea. Phylogenetic trees based on the D1/D2 domains of the 26S rDNA sequences and nucleotide sequences of the ITS 1 region showed that the isolates were conspecific and belonged to the genus Malassezia and crusted with M. sympodialis.
CONCLUSION
Taking a molecular biological classification approach, we have successfully isolated 5 cases of M. dermatis-the first in Korea. Although it is not known whether M. dermatis plays a role in Malassezia-related skin disease, this species was part of the microflora in both patients with seborrheic dermatitis and healthy subjects.