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Gauri Shankar Shrestha, Ajay Kumar Vijay, Fiona Stapleton, Andrew JR White, Russell Pickford, Nicole Ann Carnt; Tear metabolite expression in bacterial keratitis: Outcomes of an untargeted approach. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1948.
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© ARVO (1962-2015); The Authors (2016-present)
To identify and characterise tear metabolites expression in participants with bacterial keratitis and compare these to expression in healthy controls.
Twelve tear samples were received from participants with bacterial keratitis (n = 6) at initial presentation and age (case: median age = 59; control: median age = 52; P = 0.44) and sex (case: male:female = 2:4; control: male:female = 3:3; P = 0.70) matched healthy controls (n = 6). Metabolites underwent methanol extraction from the tear samples, chromatographic separation using the Ultimate 3000 System, along with C18 Column, and Mass Spectrometry using QExactive HF. Compound discoverer software v3.1 was used for data analysis. Differential analysis was used to explore fold-change and ratio between cases and controls. The difference in m/z features was adjusted using the Benjamini-Hochberg (B-H) correction for false discovery rate (FDR) with q = 0.05.
Of six cases with bacterial keratitis, two were culture negative and four were culture positive for S. lugdunensis, S. pneumonia, Multidrug-resistant S. aureus or M. lacunata. Of 47 metabolites differentially expressed, 25 were upregulated, and 22 were downregulated in the cases compared to controls. Phenylalanyl-lysin (Log2 fold-change = 11, Padj. < 0.0001) and adenine (Log2 fold-change = -6.4, Padj. < 0.0001) were the most upregulated or downregulated metabolites in the study, respectively. Purine, tryptophan and amino acid metabolism pathways were primarily observed in tears of participants with bacterial keratitis.
A wide range of tear metabolites was detected in tears of participants with bacterial keratitis. Biologically plausible differences between several metabolite classes such as amino acids, indoles, carbohydrates and nucleosides were observed in tears of participants with bacterial keratitis compared to healthy controls.
This is a 2021 ARVO Annual Meeting abstract.
Figure 1. Volcano-plot showing 41 metabolites significantly detected in C18 reverse-phase positive-ion mode. seven metabolites were detected in C18 reverse-phase negative-ion mode. Of 41 metabolites, 21 were upregulated and 18 were down-regulated in the tears of participants with bacterial keratitis than in the tears of healthy controls.
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