Can unknown microbiomes drive keratoconus and cross-linking outcomes?

Session Details

Session Title: Keratoconus

Session Date/Time: Monday 16/09/2019 | 14:00-16:00

Paper Time: 15:30

Venue: Free Paper Forum: Podium 2

First Author: : P.Khamar INDIA

Co Author(s): :    R. Shetty   A. Ghosh   N. Kumar                       

Abstract Details

Purpose:

Corneal inflammation has been demonstrated to be associated with secreted factors in the tear film. Raised levels of such inflammatory mediators have been shown to correlate with Keratoconus (KC) disease severity as well as outcomes of corneal collagen crosslinking. Resident tissue microbiome is known to influence immune status in other organs such as the human gut. Therefore, we evaluated if the ocular surface microbiome can influence the tear inflammatory status in KC.

Setting:

Narayana Nethralaya , India

Methods:

All subjects were subjected to topography and ocular surface examination. Swabs were obtained from the lower corneal fornix of 15 healthy controls and 34 KC subjects separated into grades 1, 2 and 3 (Amsler-Krumeich classification). Microbiome analysis was performed by V3-V4 amplicon sequencing followed by bioinformatics analysis of long read non-chimera sequences. Tear samples collected using Schirmer’s strips were utilised to measure 35 soluble factors by flow-cytometry based multiplex ELISA.

Results:

The ocular surface microbiome analysis identified 21 phyla, 53 classes, 103 orders, 213 families and 515 genus. Four phyla- Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes, were dominant across the clinical groups. Actinobacteria reduced, but Alphaproteobacteria increased across KC grades compared to controls. Propionibacterium was the predominant genus, followed by Corynebacterium and Staphylococcus. Lactobacilli, Streptococcus, Rothia and Brevibacterium were reduced, while Dienococcus, Brevundimonas, Phycicoccus, Bacillus were increased across KC grades. IL-8, CD121 and MPO levels significantly correlated with Actinobacteria. Proteobacteria positively correlated with IL-17A and IL-12. Bacteroidetes correlated with Perforin levels.

Conclusions:

The data demonstrates that KC has a unique ocular microbiome signature that correlated with disease severity. Association between phyla and genera with tear molecular factors indicate existence of interactions of immune mediators with ocular surface microbiome which may be pathologic in KC and its therapy. These findings may have implications on outcomes of collagen crosslinking.

Financial Disclosure:

None