Abstract
PurposeTo analyze the conjunctival sac microbial communities in patients with Sjögren's syndrome-associated dry eyes (SSDE) and non-Sjögren's syndrome-associated dry eyes (NSSDE), compared with normal controls (NC).MethodsConjunctival sac swab samples from 23 eyes of SSDE, 36 eyes of NSSDE, and 39 eyes of NC were collected. The V3–V4 region of the 16S ribosomal RNA (rRNA) gene high-throughput sequencing was performed on an Illumina MiSeq platform and analyzed using Quantitative Insights Into Microbial Ecology (QIIME). Alpha diversity was employed to analyze microbiome diversity through Chao1 and Shannon indexes. Beta diversity was demonstrated by the principal coordinates analysis (PCoA) and Partial Least Squares Discrimination Analysis (PLS-DA). The relative abundance was bioinformatically analyzed at the phylum and genus levels.ResultsThe alpha diversity was lower in patients with dry eye disease (Shannon index: NC vs. SSDE: P = 0.020, NC vs. NSSDE: P = 0.029). The beta diversity showed divergent microbiome composition in different groups (NC vs. SSDE: P = 0.001, NC vs. NSSDE: P = 0.001, NSSDE vs. SSDE: P = 0.005). The top 5 abundant phyla were Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota, and Cyanobacteria in all three groups. The top five abundant genera included Acinetobacter, Staphylococcus, Bacillus, Corynebacterium, and Clostridium_sensu_stricto_1. The relative microbiome abundance was different between groups. The Firmicutes/Bacteroidetes (F/B) ratio was 6.42, 7.31, and 9.71 in the NC, NSSDE, and SSDE groups, respectively (NC vs. SSDE: P = 0.038, NC vs. NSSDE: P = 0.991, SSDE vs. NSSDE: P = 0.048).ConclusionThe diversity of conjunctival sac microbiome in patients with NSSDE and SSDE was diminished compared with NC. The main microbiome at the phylum and genus level were similar between groups, but the relative abundance had variations. The Firmicutes/Bacteroidetes ratio was higher in the SSDE group.
Highlights
Dry eye disease (DED) is a multifactorial inflammatory ocular disease featured by tear film instability and hyperosmolarity, inflammation, and neurosensory abnormalities [1, 2]
The lacrimal gland becomes infiltrated with activated CD4+ T cells and B cells, and ocular surface diseases develop from reduced lubrication, as well as from cytokines produced by activated epithelial cells and infiltrating inflammatory cells [7, 8]
Dry eye was diagnosed based on the Chinese Expert Consensus on dry eyes [13] as follows: patients presenting with dry eye symptoms, such as burning, foreign body sensation, blurred vision, and photophobia; Ocular surface disease index (OSDI) ≥13; Fluorescein breakup time (FBUT) ≤5 s or Schirmer’s test ≤5 mm/5 min
Summary
Dry eye disease (DED) is a multifactorial inflammatory ocular disease featured by tear film instability and hyperosmolarity, inflammation, and neurosensory abnormalities [1, 2]. Autoimmune disease-associated dry eye is one of the most important types of DED [4]. Sjögren’s syndrome (SS) is a chronic autoimmune disease featured by dry mucosal surfaces and other systemic muscular pain, and dry eye is one of the most discomforting symptoms that patients with SS complain about [5, 6]. It is hypothesized that similar mechanisms are active on the ocular surface and are involved in the pathophysiology of DED including SS. The production of lipases and toxins by different proportions of colonizing bacteria may destabilize the lipid layer of the tear film, interact with the conjunctival mucins [11, 12] and cause ocular surface cellular damage. Dysbiosis might be associated with tear film instability, inflammation, and ocular irritation
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