Characterising the tear bacterial microbiome in young adults

Conjunctival swabs (CS) are the major source of sampling for ocular microbiome studies, however collecting CS from the diseased eyes is difficult and painful. In this study, as an alternative to CS, a less invasive approach of tear collection was used to establish the bacterial microbiome in healthy eyes. Tear bacterial microbiome was generated from the DNA of tears (n = 24; male = 16 and female = 8) of healthy volunteers aged from 20 to 52 years. Sequencing of V3-V4 region of 16S rRNA gene was performed on the Illumina platform. Reads were processed in QIIME to assign the taxa. Statistical analysis of the tear microbiome was done in R to assess the alphadiversity and betadiversity indices. Tear microbiome was generated in all the 24 tear samples. Eight out of the top 10 predominant bacterial genera remained same in both tear and CS microbiomes, which include genera such as Corynebacterium, Staphylococcus, Streptococcus, Mycobacterium, Escherichia-Shigella, Lactobacillus, Bacillus and Acinetobacter. The similarity network analysis indicates that 144 out of 145 genera of tear cohort matched with conjunctival swabs. However, tear and CS microbiomes differed in the abundance of the predominant bacterial genera. The bacterial microbiome of tears in adults appears to be stable and is comparable with that of CS microbiome.