The Quantitative Study on the Distribution of Malassezia Yeasts on the Normal Skin of the Young Adults

Choe, Yong Beom; Jang, Soo Jung; Yim, Seon Mi; Ahn, Kyu Joong

Abstract

BACKGROUND
The yeasts of genus Malassezia are dimorphic and lipophilic and are numbers of the normal flora in humans. Malassezia yeasts are implicated in various diseases, including pityriasis versicolor, Malassezia folliculitis, seborrheic dermatitis and the systemic fungal infections. OBJECTIVE: The study was done to perform a comprehensive survey of the distribution of Malassezia yeasts on the normal human skin to provide a baseline for a companion study of Malassezia yeasts in patients with various dermatoses. METHODS: Malassezia yeasts were cultured from the clinically normal skin using the scrub-wash technique at four sites in sixty subjects, age range, 11~40 years. Malassezia yeasts were also cultured from the scalp of the same groups using the swabbing technique. The obtained strains were placed into the one of the seven species by their colony morphologies, microscopic morphologies and physiological characteristics. We also examined the relationship between the Malassezia species, age groups and the body sites. RESULTS: An overall positive culture rate was 75% (225/300). A positive culture rate was highest (88%) in the age groups 21~25 and 26~30 and lowest (50%) in the age group 11~15. M. restricta was recovered more frequently from the age groups 21~25 (62%), 26~30 (66%), and 31~35 (54%) and interestingly lowest in the age group 11~15 (40%). In the age group 16~20, M. globosa was the predominant species (42%). For the various age groups, body sites were more related with the kind of Malassezia yeasts and the recovery rate. A positive culture rate was highest from the chest (91%) and lowest from the thigh (60%). From the chest, M. globosa (44%) and M. restricta (35%) was recovered more frequently; from the forehead, M. restricta (75%). CONCLUSION: This study shows that Malassezia yeasts are a major component of the microbial flora of the clinically normal skin of the young adults. The kind of Malassezia species that can be recovered from the human skin varies with the age and the body site. The results of our study replicate and expand on the finding of some of the earliest studies and would be of value to investigate the role of Malassezia yeast in the related diseases.