Geographical and Ethnic Differences Influence Culturable Commensal Yeast Diversity on Healthy Skin - PubMed (original) (raw)

Geographical and Ethnic Differences Influence Culturable Commensal Yeast Diversity on Healthy Skin

Cheryl Leong et al. Front Microbiol. 2019.

Abstract

Commensal fungi such as Malassezia, Candida, and Rhodotorula are common on healthy skin but are also associated with opportunistic invasive and superficial infections. Skin microbial community characterization has been extensively performed worldwide, with a focus on the 16S bacterial community. These studies have focused on geographically distinct or targeted cohorts with variable reported species distributions of commensal yeast species. To determine the effects of extrinsic environmental factors such as geography, climate, and ethnicity on detected healthy skin commensal yeast diversity, we compared cohorts from Singapore and Zürich, Switzerland, representative of two geographically and climatically distinct regions comprising multi-ethnic (Chinese, Malay, Indian, Caucasian) and predominantly white Caucasian cohorts, respectively, using identical skin sampling and culture methods. We chose to use a culture-based approach as cultures isolated from patients are still required for studies of pathogenicity and antifungal susceptibility. Detection of yeast species by culture-dependent and independent sequencing-based methods suggest healthy skin diversity reflects a species distribution representative of the geography, climate and ethnic background of their local populations. Culture success and species diversity was also found to be dependent on climate, with warm tropical climates favoring high positive culture rates and greater species diversity. Multilocus sequence typing data suggests some strains are geographically distinct and may be used to segregate potential disease-causing commensals. For accurate collection and characterization of skin microbial communities, it remains recommended to employ a combination of culture-dependent and sequence-based culture-independent methods. Characterization of healthy mycobiomes in geographically distinct local populations will be useful in defining the role of commensal fungi in health and disease.

Keywords: Malassezia; commensal yeast; ethnicity; fungi; geography; skin.

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Figures

FIGURE 1

FIGURE 1

(A) Radar plot of percentage of subjects that were culture positive for each species (_y_-axis) as sampled from the respective cohorts and body sites, (B) pie charts showing percentage of each Malassezia species isolated from the skin of the nose calculated as a percentage of total Malassezia isolates from each respective cohort, and (C) Malassezia species isolated from the skin of nose of Singapore (n = 37, 10 Chinese, 7 Malay, 10 Indian, and 10 Caucasian, equal gender) and Swiss (n = 11) cohort subjects, represented as a percentage of the total Malassezia species isolated from each ethnic group.

FIGURE 2

FIGURE 2

(A) Multiple Correspondence Analysis (MCA) plot showing the clustering of 48 individuals form Singapore and Zürich, Switzerland based on geography, gender, race, and Malassezia species cultured from the skin of the nose, (B) factor maps of individual clustering by gender (M – Male, F – Female), geography (SG – Singapore, ZH – Zürich), and race (Ch – Chinese, Ma – Malay, Ind – Indian, Ca – Caucasian) as defined by a 95% confidence ellipse, and (C) clustering dendrogram showing the clustering of individuals by hierarchical clustering. Numbering of individuals correspond to the legend in (A). Circles indicate individuals that do not cluster according to their expected geography or race.

FIGURE 3

FIGURE 3

(A) Table comparison of commensal yeast species detection by culture-dependent and culture independent methods in four subjects and (B) PCR detection using species-specific primers of gDNA isolated from the parallel side of the skin of the nose from which cultures were swab-derived. gDNA isolated from reference strain cultures representative of common isolates of Malassezia (CBS 9369, CBS 7222, CBS 7966, CBS 7877, CBS 7956), Rhodotorula (ATCC 9449), and Candida (ATCC 22019) were used as positive controls. A 100 bp ladder (GeneRulerTM) was run on the leftmost column of each gel.

FIGURE 4

FIGURE 4

(A) Percentage conserved bases of five commonly isolated species of Malassezia across five loci (Internal transcribed spacer region – ITS, Intergenic spacer region (IGS), Elongation factor – 1α (EF-1α), ß-tubulin and the 26S ribosomal region) as tested across sequences derived from isolates collected and NCBI databases and (B) unrooted dendrogram derived from 13 unique ITS sequences of M. furfur identify healthy and disease clusters which are representative of strains isolated in Singapore and internationally. Sequences not represented by any known reference database ID are indicated by their subject/strain codes.

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