Ocular surface microbiome in diabetes mellitus

Abstract

This cross-sectional, age- and gender-matched study included 20 eyes of non-diabetic subjects (non-DM group) and 60 eyes of type 2 diabetes mellitus (DM group). Subgroups of DM were classified by diabetic retinopathy (DR) staging into no DR (DM-no DR), non-proliferative DR (DM-NPDR), proliferative DR (DM-PDR), and by glycemic control (well-controlled DM; HbA1c < 7%, poorly controlled DM; HbA1c ≥ 7%). Conjunctival swabs were performed for ocular surface microbiome analysis using conventional culture and next-generation sequencing analysis (NGS). A higher culture-positive rate was found in DM (15%) than in non-DM group (5%) (p value = 0.437). Pathogenic organisms and antibiotic-resistant strains were detected in the DR groups (DM-NPDR and DM-PDR). The NGS analysis showed that potentially pathogenic bacteria such as Enterobacteriaceae, Neisseriaceae, Escherichia-Shigella, and Pseudomonas predominated in DM, especially in DR. There was dissimilarity in the ocular surface microbiome between DM and non-DM groups. The subgroup analysis showed that the DR group had significantly different microbial community from DM-no DR and non-DM groups (p value < 0.05). The microbial community in the poorly controlled DM was also significantly different from well-controlled DM and non-DM groups (p < 0.001). Using the NGS method, our study is the first to signify the importance of DR and glycemic control status, which affect the changes in the ocular surface microbiome.

Figure 1

Taxonomic composition (a) Top 15 bacteria in phylum and genus levels of the ocular surface microbiome in the non-DM and DM groups. (b) Comparison of top 5 phyla between the non-DM and DM groups. (c) Comparison of top 10 genera between the non-DM and DM groups, (d) between the non-DM and DM subgroups classified by DR staging, and (e) between the non-DM and DM subgroups classified by glycemic control. *p value < 0.05; **p value < 0.001. (Abbreviations: DM diabetes mellitus, Non-DM non-diabetes mellitus, No DR  no diabetic retinopathy, NPDR non-proliferative diabetic retinopathy, PDR  proliferative diabetic retinopathy, HbA1c hemoglobin A1c).

Figure 2

Linear discriminant analysis effect size (LEfSe) represents the significant difference in bacterial distribution between groups. Bacterial taxa with LDA scores greater than 2 were considered significant. (a) Comparison of taxa lists between the non-DM and DM groups. (b) Comparison of taxa lists between the non-DM and DM subgroups classified by DR staging. (c) Comparison of taxa lists between the non-DM and DM subgroups classified by glycemic control. (Abbreviations: p phylum, c class, o order, f family, and g genus, DM diabetes mellitus, Non-DM non-diabetes mellitus, No DR no diabetic retinopathy, NPDR non-proliferative diabetic retinopathy, PDR proliferative diabetic retinopathy, HbA1c hemoglobin A1c).

Figure 3

This figure represents beta-diversity between groups by principal coordinate analysis (PCoA) plot based on unweighted UniFrac distance and comparison of ocular surface microbiome between groups (box plot): (a) between the non-DM (green-dotted circle) and DM groups (red-dotted circle); (b) between the non-DM (green-dotted circle) and DM subgroups classified by the DR staging (no DR: red-dotted circle, NPDR: blue-dotted circle, and PDR: purple-dotted circle); and (c) between the non-DM (green-dotted circle) and DM subgroups classified by the glycemic control (HbA1c < 7%: red-dotted circle, HbA1c ≥ 7%: blue-dotted circle) (*p value < 0.05; **p value < 0.001). (Abbreviations: DM diabetes mellitus, Non-DM non-diabetes mellitus, No DR no diabetic retinopathy, NPDR non-proliferative diabetic retinopathy, PDR proliferative diabetic retinopathy, HbA1c hemoglobin A1c).