Abstract
Purpose :
Data suggest the presence of a core ocular surface (OS) microbiome in healthy individuals; however, information regarding microbiome stability over time and its interaction with ocular surface immune cells is lacking. Our study aims to examine the OS microbiome and conjunctival immune cell composition longitudinally in a healthy population.
Methods :
This is a prospective study of healthy adults (n=7) without symptoms and signs of dry eye disease. To characterize the ocular microbiome, the inferior palpebral conjunctiva was swabbed for either sequencing or culturomics to identify live bacteria at the ocular surface. Live immune cells were acquired from the temporal conjunctiva via EyePrim from both eyes. Immune cell populations were analyzed and defined using flow cytometry. Samples for each set of analyses were taken at 3 timepoints: 0, 1 week, and 3 months. Synthetic long-read sequencing was used to identify bacterial RNA and DNA signatures, and culturomics was used to identify viable bacteria.
Results :
Mean age was 36±8.9 years; 43% self-identified as White, 71% as female, and 86% as non-Hispanic. Sequencing data revealed that healthy subjects clustered together and showed differences from the reagent controls, supporting the notion that sampling hits were not driven by environmental contamination. Bacillus and Lactobacillus were the two most abundant organisms in both eyes. Culturomics showed growth on cooked media broth at all time points. Flow cytometry results revealed that myeloid cells and αβ T cells dominated the immune cell signature within the human conjunctiva. Further, there were no statistical changes in immune cell frequencies across the 0, 1 week, and 3-month time points, suggesting that the immune cell niche is relatively stable over time.
Conclusions :
Preliminary data demonstrate that bacterial microbes are indeed present at the ocular surface. Overall, these bacteria appear to grow best on cooked media broth in aerobic conditions. In parallel, immune cells were consistently recovered from the OS and immune cell populations were stable over time. Given the microbiome signatures and the stability of immune cells within the ocular mucosal niche, our data suggest that interactions between the human microbiome and immune system may exist.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.