Molecular analysis of malassezia microflora on the skin of the patients with atopic dermatitis

Abstract

Background: The yeasts of the genus Malassezia are members of the normal flora on human skin and they are found in 75~80% of healthy adults. Since its association with various skin disorders have been known, there have been a growing number of reports that have implicated Malassezia yeast in atopic dermatitis (AD).

Objective: The aim of the present study is to isolate the various Malassezia species from AD patients by using 26S rDNA (ribosomal Deoxyribonucleic acid) PCR-RFLP and to investigate the relationship between a positive Malassezia culture and the severity of AD.

Methods: Cultures for Malassezia yeasts were taken from the scalp, cheek, chest, arm and thigh of 60 patients with atopic dermatitis. We used a rapid and accurate molecular biological method 26S rDNA PCR-RFLP, and this method can overcome the limits of the morphological and biochemical methods.

Results: Positive Malassezia growth was noted on 51.7% of the patients with atopic dermatitis by 26S rDNA PCR-RFLP analysis. The overall dominant species was M. sympodialis (16.3%). M. restricta was the most common species on the scalp (30.0%) and cheek (16.7%). M. sympodialis (28.3%) was the most common species on the chest. The positive culture rate was the highest for the 11~20 age group (59.0%) and the scalp showed the highest rate at 66.7%. There was no significant relationship between the Malassezia species and SCORing for Atopic Dermatitis (SCORAD).

Conclusion: The fact that the cultured species was different for the atopic dermatitis lesion skin from that of the normal skin may be due to the disrupted skin barrier function and sensitization of the organism induced by scratching in the AD lesion-skin. But there was no relationship between the Malassezia type and the severity score. The severity score is thought to depend not on the type, but also on the quantity of the yeast.

Keywords: 26S rDNA PCR-RFLP; Atopic dermatitis; Malassezia.

Fig. 1

PCR-RFLP patterns of the 26S rDNA PCR digested with Hha1 (A) and BstF51 (B) of the 11 standard strains of Malassezia. Lanes: M means molecular marker, 1: M. furfur (KCTC 7743), 2: M. sympodialis (KCTC 7985), 3: M. globosa (CBS 7966), 4: M. restricta (KCTC 7848), 5: M. slooffiae (KCTC 17431), 6: M. pachydermatis (KCTC 17008), 7: M. japonica (CBS 9432), 8: M. nana (JCM 12085), 9: M. dermatis (JCM 11348), 10: M. obtusa (KCTC 7847), 11: M. yamatoensis (CBS 9725).

Fig. 2

The identified Malassezia species from atopic dermatitis patients by age.

Fig. 3

The identified Malassezia species from the atopic dermatitis groups according to body sites.