The normal fungal communities that inhabit healthy skin are much more diverse in children than adults, a new study has discovered.

That diversity dwindles, however, around puberty, when the lipophilic taxa Malassezia surges in abundance. This is probably mediated by the increase in sebaceous gland activation and sebum composition that occurs around sexual maturity, Jay-Hyun Jo, PhD, wrote ( J Invest Dermatol. 2016 Jul 28; doi: 10.1016/j.jid.2016.05.130 ).

The diversity of the childhood mycobiome may also play into the larger prevalence of fungal skin diseases in children, wrote Dr. Jo of the National Cancer Institute.

“Several fungal skin infections (dermatophytoses), such as tinea capitis and tinea corporis, are more frequently seen in children. This epidemiological dichotomy in fungal infections may relate to the physiologic characteristics of younger skin, which appears more permissive to colonization by diverse fungi.”

The researchers used the fungal internal transcribed spacer–1 (ITS1) sequence to pinpoint the taxonomic details of the mycobiome of 14 healthy children and 19 healthy adults. They looked at samples from 10 sites on each subject: the external auditory canal, forehead, occiput, retroauricular crease, back, manubrium, antecubital fossa, inguinal crease, volar forearm, and nares.

Malassezia monopolized the adult samples, constituting 80%-99% of the communities on each skin site. In children, however, Malassezia was much less common, comprising 35%-76% of the samples of each site.

However, children boasted a much more diverse mycobiome. Other constituents included members of the Ascomycota, Aspergillus, Epicoccum, and Phoma taxae. Ascomycota species were found on 40% of samples from children, compared with 9.5% of samples from adults. Children also played host to communities of Epicoccum, Cladosporium, and Cryptococcus.

There were individual variations in diversity, however, the authors noted. “For clinical samples from children, decreased diversity was correlated with increased relative abundance of Malassezia, especially on sebaceous sites. Given the predominance of Malassezia on sebaceous skin, it is possible that reduction in diversity was attributed to relative overexpansion of Malassezia.”

The team also discovered gender differences in the mycobiome of children. The sebaceous skin sites of boys were much more likely to host species of Epicoccum and Cryptococcus. Girls showed an early enrichment of Malassezia. “These results suggested that gender may affect mycobiome structures during sexual maturation.”

“Since Malassezia is an obligatory lipophilic fungus, differential Malassezia abundance might be due to the full activation of sebaceous glands during puberty,” they theorized. “Therefore, it would be intriguing to identify the sebaceous gland activity and sebum signatures during childhood in conjunction with sequence-based mycobiome analysis.”

The National Institutes of Health funded the study. Dr. Jo had no financial disclosures.

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