The Microbiome of the Meibum and Ocular Surface in Healthy Subjects

Abstract

Purpose: The purpose of this study was to investigate the microbiome in the meibum, conjunctival sac, and eyelid skin in young and elderly healthy subjects, and analyze the effect that age, sex, and region have on microbiome composition.

Methods: This study involved 36 healthy subjects (young-age subjects: 9 men/9 women, age range: 20-35 years; elderly age subjects: 9 men/9 women, age range: 60-70 years). In all subjects, lower-eyelid meibum, lower conjunctival sac, and lower-eyelid skin specimens were collected from one eye, and then stored at -20°C. Taxonomic composition of the microbiome was obtained via 16S rRNA gene sequencing, and then analyzed.

Results: The meibum microbiome showed a high α-diversity (within-community diversity), particularly in the young subjects. However, in approximately 30% of the elderly subjects, a low-diversity microbiome dominated by Corynebacterium sp. or Neisseriaceae was observed. In the young subjects, the microbiome of the meibum resembled that of the conjunctival-sac, yet in the elderly subjects, the microbiome of the conjunctival-sac became more similar to that of the eyelid skin. The eyelid-skin microbiome was relatively simple, and was typically dominated by Propionibacterium acnes in the young subjects, or by Corynebacterium sp. or Neisseriaceae in the elderly subjects. In both age groups, no significant difference was seen between the men and women in regard to the meibum, conjunctival-sac, and eyelid-skin microbiome.

Conclusions: Our findings confirmed that the meibum of healthy adult-age subjects harbors highly diverse microbiota, and revealed that the meibum microbiome, especially the decrease of its diversity, alters with aging and may affect the homeostasis of the ocular surface.

Figure 1.

The composition of bacterial microbiota in the samples collected at the meibum, conjunctival sac, and eyelid skin sites. The 10 most abundant taxa are shown. Shannon index (SI), a measure of species diversity in a sample, is indicated by the gray-scale color. The subjects were sorted by SI of the meibum sample in ascending order, within each group of young male, young female, elderly male, and elderly female subjects. ID, subject identification number.

Figure 2.

Analyses based on the weighted UniFrac pairwise distance between samples. (A) Distribution of the pairwise distances. All pairs of the samples from either of meibum, conjunctival sac (CS), or eyelid skin (skin) were divided into “within the same age groups” and “between the different age groups” (left) or “within the same sex groups” and “between the different sex groups” (right). The weighted UniFrac distances of each set of pairs are depicted in the box plot. Blue, pairs within the same age/sex groups; red, pairs between the different age/sex groups. The numbers above the box plots are P values of the Mann-Whitney U test. n.s., not significant (or P > 0.05). (B) A principal coordinate analysis plot based on the weighted UniFrac distance. Samples representing each of the collection sites, and subject age are shown by distinct symbols. Clusters of the samples with characteristic microbiomes are indicated. (C) Weighted UniFrac distances of the samples collected at the three different sites of the same subject. M–C, sample pairs between the meibum and the CS; M–S, sample pairs between the meibum and the skin; C–S, sample pairs between the CS and the skin. The numbers above the box plots are P values of the Wilcoxon signed-rank test. n.s., not significant (or P > 0.05).

Figure 3.

Microbiomes collected at either the meibum, conjunctival sac (CS), or eyelid skin (skin) sites were compared between the young subjects (blue) and the elderly subjects (red) in the Shannon index (A) and relative abundance of P. acnes (B), Corynebacterium sp. (C), or S. epidermidis (D). The numbers above the box plots are the P values of the Mann-Whitney U test. n.s., not significant (or P > 0.05).