Ocular surface microbiome in diabetes mellitus

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.