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Louis Tong, Aihua Hou, Florentin Constancias, Liang Yang, Staffan Kjelleberg; Metagenomics approach to the human conjunctival microbiome. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3306.
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The ocular surface microbiome is not well-characterised, though ocular microbiome studies have employed sequencing of the 16S rRNA gene. For a more comprehensive characterisation, we use a metagenomics strategy to profile the human conjunctival microbiome and its potential association with clinical parameters.
A standardised examination of participants was undertaken including Oculus keratograph 5M and schirmer testing. An inferior palpebral conjunctival swab was taken after topical local anesthesia. After DNA extraction, deep sequencing was performed and non-human reads assigned to various phyla, genera and species.
There is a surprisingly low microbial diversity in the conjunctiva compared to gut and oral microbiomes, with Proteobacteria forming the predominant phylum, and Achromobacter spp being the preponderant microbe. Although there is no alteration in microbial species composition in people with dry eye compared to age-matched controls, several microorganisms, including members of the genus Streptococcus,increased in representation with age, and the abundance of Staphylococcus and Skermanellaspecies correlated with higher Schirmer readings. Following principal component analysis of the microbial composition, there emerged two clusters of participants: the younger cluster (n=17) aged 39.6±13.6 years and the older cluster (n=7) aged 53.5±13.7 years. The difference in age was statistically significant (p=0.028). The older cluster had increased Achromobacter spp and reduced proportion of a number of microbial species (eg., Acidovorax temperans, Phenylobacterium zucineum, and Noviherbaspirillum spp) compared to the younger cluster.Since A.xylosoxidans is numerically the most abundant species, we evaluated the potential influence of this microbe on cornea epithelia. When cultured corneal epithelial cells were exposed to three strains of A xylosoxidans, there was an up-regulation of human cytokines such as TNF and IL-6, in the culture media as well as in the cellular proteins.
We characterised the conjunctival microbiome using a metagenomics approach. Age of the participants is the major factor that determines the composition of several major microbes. Although dry eye does not change the microbial composition, the specific microorganisms in the ocular surface microbial community may have a protective effect on tear secretion, whereas others exert a pro-inflammatory influence at higher abundance.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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