Analysis of Conjunctival Sac Microbiome in Dry Eye Patients With and Without Sjögren's Syndrome

Multi-cohort analysis identifying core ocular surface microbiome and bacterial alterations in eye diseases

PURPOSE

Inconsistency exists among reported studies on the composition of human ocular surface microbiome (OSM). The roles of OSM in ocular diseases remain uncertain. In this study, we aimed to determine the composition of OSM and to evaluate its potential roles and functions from multiple cohorts.

METHODS

Raw 16 s sequencing data were obtainable from publicly available repositories, sourced from 17 published studies. Employing a standardized method, we processed the data and conducted a cross-cohort analysis. Through bioinformatics pipelines QIIME2 and PICRUSt2, we processed a total of 1875 ocular surface samples. Core microbiome analyses, genera comparisons, and MetaCyc pathway analyses were performed within each cohort independently. The results were then combined to identify shared patterns across different datasets.

RESULTS

The core OSM comprised seven genera: Corynebacterium, Staphylococcus, Acinetobacter, Streptococcus, Pseudomonas, Cutibacterium and Bacillus. Corynebacterium and Staphylococcus are the most abundant genera on ocular surface. Most ocular diseases showed OSM alterations and eight genera demonstrated a non-specific, shared response among two or more ocular diseases. Moreover, changes in various metabolic pathways were predicted following OSM alteration, indicating potential roles of OSM in biological processes.

CONCLUSION

We refined the core OSM candidates combining multiple cohorts. The common pattern shared by different cohorts is worth further investigation. Changes in metabolic pathways based on bioinformatic analysis indicated a role of OSM on ocular diseases. Our results help extend the knowledge and encourage further investigations on the associations between OSM and ocular diseases.

Microbiome alterations in primary Sjögren's syndrome: Regional dysbiosis and microbiome-targeted therapeutic strategies

Primary Sjögren's syndrome (pSS) is a complex autoimmune disease characterized by diverse clinical manifestations. While xerophthalmia and xerostomia are hallmark symptoms, the disease often involves multiple organ systems, including the kidneys, lungs, nervous system, and gastrointestinal tract, leading to systemic morbidity in severe cases. Despite extensive research, the precise pathogenesis of pSS remains unclear, likely involving infectious, hormonal, and genetic factors. Emerging evidence highlights the microbiome as a key contributor to autoimmune diseases, including pSS. Dysbiosis in the oral, ocular, gut, and genital microbiomes plays a critical role in disease onset, progression, and variability. This review summarizes current findings on microbiome alterations in pSS, emphasizing their role in pathogenesis and clinical features, and explores microbiome-targeted therapies. Understanding the role of the microbiome in pSS pathophysiology could advance disease management and inspire targeted therapeutic strategies.

Systems biology of dry eye: Unraveling molecular mechanisms through multi-omics integration

Dry eye disease (DED) is a multifactorial condition with complex and incompletely understood molecular mechanisms. Advances in multi-omics technologies, including genomics, transcriptomics, proteomics, metabolomics, and microbiomics, have provided new insights into the pathophysiology of DED. Genomic analyses have identified key genetic variants linked to immune regulation and lacrimal gland function. Transcriptomic studies reveal upregulated inflammatory pathways in ocular surface tissues, implicating these as core drivers of chronic inflammation. Proteomic research highlights significant alterations in tear protein composition, especially proteins involved in inflammation and tissue repair. Metabolomics studies focus on disrupted lipid metabolism and oxidative stress, which are crucial in maintaining tear film stability. Furthermore, microbiome research has demonstrated reduced microbial diversity and increased pathogenic bacteria, exacerbating inflammatory responses. The integration of multi-omics data allows for the identification of novel biomarkers and therapeutic targets, enabling precision diagnostics and personalized treatments. Therefore, this review highlights the critical importance of multi-omics approaches in deepening our understanding of DED's complex molecular mechanisms and their potential to transform clinical management and therapeutic innovations in this challenging field.

The microbiome and the eye: a new era in ophthalmology

The human microbiome has progressively been recognised for its role in various disease processes. In ophthalmology, complex interactions between the gut and distinct ocular microbiota within each structure and microenvironment of the eye has advanced our knowledge on the multi-directional relationships of these ecosystems. Increasingly, studies have shown that modulation of the microbiome can be achieved through faecal microbiota transplantation and synbiotics producing favourable outcomes for ophthalmic diseases. As ophthalmologists, we are obliged to educate our patients on measures to cultivate a healthy gut microbiome through a range of holistic measures. Further integrative studies combining microbial metagenomics, metatranscriptomics and metabolomics are necessary to fully characterise the human microbiome and enable targeted therapeutic interventions.

The Conjunctival Microbiome and Dry Eye: What We Know and Controversies

ABSTRACT

Dry eye disease is a common multifactorial condition that may be idiopathic or associated with autoimmune conditions, such as Sjogren syndrome. Commensal microorganisms modify immune responses, so it is relevant to understand how they modify such immune-mediated diseases. Microbiota in the gut regulate inflammation in the eye, and conversely, severe inflammation of the ocular surface results in alteration of gut microbiome. The conjunctiva microbiome can be analyzed using 16S or shotgun metagenomics. The amount of microbial DNA in ocular surface mucosa relative to human DNA is limited compared with the case of the intestinal microbiome. There are challenges in defining, harvesting, processing, and analyzing the microbiome in the ocular surface mucosa. Recent studies have shown that the conjunctiva microbiome depends on age, presence of local and systemic inflammation, and environmental factors. Microbiome-based therapy, such as the use of oral probiotics to manage dry eye disease, has initial promising results. Further longitudinal studies are required to investigate the alteration of the conjunctival microbiome after local therapy and surgery.

Analysis of the mucosal chemokines CCL28, CXCL14, and CXCL17 in dry eye disease: An in vitro and clinical investigation

Mucosal chemokines have antimicrobial properties and play an important role in mucosal immunity. However, little is known about their expression on the ocular surface. This study aimed to analyze the expression of the mucosal chemokines CCL28, CXCL14 and CXCL17 in corneal and conjunctival epithelial cells under in vitro dry eye (DE) conditions, and in conjunctival samples from healthy subjects and DE patients. Human corneal epithelial cells (HCE) and immortalized human conjunctival epithelial cells (IM-HConEpiC) were incubated under hyperosmolar (400-500 mOsM) or inflammatory (TNF-α 25 ng/mL) conditions for 6 h and 24 h to measure CCL28, CXCL14, and CXCL17 gene expression by RT-PCR and their secretion by immunobead-based analysis (CCL28, CXCL14) and ELISA (CXCL17). Additionally, twenty-seven DE patients and 13 healthy subjects were included in this study. DE-related questionnaires (OSDI, mSIDEQ and NRS) evaluated symptomatology. Ocular surface integrity was assessed using vital staining. Tactile sensitivity was measured with Cochet-Bonnet esthesiometer, and mechanic and thermal (heat and cold) sensitivity using Belmonte's non-contact esthesiometer. Subbasal nerve plexus and dendritic cell density were analyzed by in vivo confocal microscopy. Conjunctival cells from participants were collected by impression cytology to measure mucosal chemokines gene expression by RT-PCR. Our results showed that HCE and IM-HConEpiC cells increased CCL28, CXCL14, and CXCL17 secretion under hyperosmolar conditions. The gene expression of CCL28 was significantly upregulated in conjunctival samples from DE patients. CCL28 expression correlated positively with symptomatology, corneal staining, heat sensitivity threshold, and dendritic cell density. CXCL14 expression correlated positively with age, ocular pain, conjunctival staining, tactile sensitivity, and image reflectivity. CXCL17 expression correlated positively with corneal staining. These results suggest that corneal and conjunctival epithelial cells could be a source of CCL28, CXCL14, and CXCL17 on the ocular surface and that CCL28 might be involved in DE pathogenesis.

Does corneal tattooing affect the conjunctival microbiota?

PURPOSE

This study aimed to investigate the effects of commercial tattoo inks used in corneal tattooing on conjunctival microbiota.

METHOD

This prospective case control study consisted of 125 participants divided in the following three groups: 35 patients with corneal tattoos, 40 patients with corneal leukoma, and 50 healthy subjects. Corneal tattooing was performed in all the cases in this study using a tattoo pen machine and commercial tattoo ink. A total of 500 cultures were taken from 250 eyes of 125 individuals on chocolate and sheep blood agar. Bacteriological samples were taken from the inferior eyelid conjunctiva using a sterile cotton swab. Without any contact elsewhere, the swabs were smeared on bedside chocolate agars and 5% sheep blood agar.

RESULTS

In tattooed eyes, bacterial growth was detected in 42.9% of the chocolate and sheep blood agar samples. In other healthy eyes of patients with corneal tattoos, 54.5% bacterial growth on chocolate agar and 57.1% on sheep blood agar were detected. No statistical difference was detected in the conjunctival microbiota of chocolate and sheep blood agar (p = 0.254, p = 0.134, respectively) in the tattooed eyes compared to the other eye of the individual. No statistically significant difference was found in terms of bacterial growth in tattooed, leukoma, or healthy eyes on chocolate and sheep blood agar (p = 0.408, p = 0.349). The growth rate of Staphylococcus epidermidis decreased by 33.3% (from 12 to 8) on chocolate agar in 35 tattooed eyes, and it decreased by 28.5% (from 14 to 10) on sheep blood agar, while gram-negative bacteria Brevundimonas diminuta, Acinetobacter lwoffii, and Psychrobacter faecalis were detected in three patients.

CONCLUSION

Corneal tattooing using commercial dye does not affect conjunctival microbiota. In the past 3 years, 120 patients have been tattooed with commercial tattoo ink in Istanbul Medeniyet University Göztepe Training and Research Hospital. No complications related to infection were found in the 3-year follow-up. The gram-negative bacteria detected in the healthy control group and tattooed eyes were bacteria found on normal skin or in the respiratory tract. Although some gram-negative bacteria do not cause infection, careful eye examination, follow-up, and culture are required in suspicious cases.

Ocular surface microbiota in patients with varying degrees of dry eye severity

AIM

To elucidate the profiles of commensal bacteria on the ocular surfaces of patients with varying severity of dry eye (DE).

METHODS

The single-center, prospective, case-control, observational study categorized all participants into three distinct groups: 1) control group (n=61), 2) mild DE group (n=56), and 3) moderate-to-severe DE group (n=82). Schirmer's tear secretion strips were used, and the bacterial microbiota was analyzed using 16S ribosomal ribonucleic acid gene sequencing.

RESULTS

The three groups had significant differences in alpha diversity: the control group had the highest richness (Chao1, Faith's phylogenetic diversity), the mild DE group showed the highest diversity (Shannon, Simpson), and the moderate-to-severe DE group had the lowest of the above-mentioned indices. DE severity was positively correlated with a reduction in beta diversity of the microbial community, with the moderate-to-severe DE group exhibiting the lowest beta diversity. Linear discriminant analysis effect size presented distinct dominant taxa that significantly differed between each. Furthermore, the exacerbation of DE corresponded with the enrichment of certain pathogenic bacteria, as determined by random forest analysis.

CONCLUSION

As DE severity worsens, microbial community diversity tends to decrease. DE development corresponds with changes in microbial constituents, primarily characterized by reduced microbial diversity and a more homogenous species composition.

Role of the ocular surface microbiome in allergic eye diseases

PURPOSE OF REVIEW

The purpose of this review is to provide an update on emerging literature on the role of the ocular surface microbiome (OSM) in allergic eye diseases.

RECENT FINDINGS

Findings in the literature suggest that the ocular surface microbiome plays a role in the pathophysiology and course of allergic disease of the ocular surface.

SUMMARY

Knowledge regarding the role of the ocular surface microbiome in allergic disease is important to guide development of targets for future therapeutic interventions.

The Link Between Gastrointestinal Microbiome and Ocular Disorders

The gut-eye axis has been hypothesized to be a factor in many eye pathologies. This review examines papers from PubMed about this topic. Bacterial commensals could either be protective by regulating the immune system or prove to be damaging to the gut mucosal wall and incite an inflammatory process. The balance between the two appears to be crucial in maintaining eye health. Imbalances have been implicated in ophthalmologic conditions. The use of probiotics, dietary modifications, antibiotics, and faecal microbiota transplant in mice with pathologies such as those encountered in our practice appears to reverse disease course or at least prevent its progression. Clinical trials are currently underway to investigate their clinical significance in diseased patients.

Conjunctival sac flora and drug susceptibility analysis in normal children in East China

PURPOSE

To investigate the distribution characteristics of conjunctival sac flora and assess the susceptibility of commonly used topical antimicrobial agents in normal children under the age of 18 in East China.

METHODS

In 2019, a study was conducted at Qingdao Eye Hospital of Shandong First Medical University to analyze the microorganism cultures of conjunctival sac in 1258 normal children (2516 eyes; average age, 6.21 ± 3.78 years) in East China. Exclusion criteria included children with ocular surface diseases and those who had used any topical antimicrobial agents recently. The microorganism species in the conjunctival sac were analyzed using the M-38A protocol (microdilution method; investigators read the minimum inhibitory concentration [MIC] values) by the Clinical and Laboratory Standards Institute to determine drug susceptibility.

RESULTS

The incidence of conjunctival sac microorganism in children was 32.87% (827/2516), a total of 541 cases (male 293, female 248). Children with conjunctival sac flora in a single eye were 255 and in both eyes were 286 (no statistical difference, P > 0.05). The concordance rate of children with binocular conjunctival sac flora was 32.16% (174/541; male 84, female 90). A total of 42 species of bacteria were detected. Children with Gram-positive cocci accounted for the highest proportion, 91.54% (757/827). The top three bacteria with the highest detection rates were Staphylococcus epidermidis (S. epidermidis; 52.12%), Streptococcus (12.09%), and Staphylococcus aureus (S. aureus; 10.76%). Streptococcus mitis (5.20%) accounted for the highest proportion of Streptococcus.S. epidermidis had the highest proportion in all age groups and was positively correlated with age (r = 0.89, P = 0.03). Before six years of age, the streptococcal proportion(mainly S. mitis) was greater than that of Staphylococcus aureus. The drug susceptibility analysis showed that S. epidermidis was most sensitive to gatifloxacin (98.61%), while it had the highest resistance rate to erythrocin (87.94%). S. aureus had the highest susceptibility to moxifloxacin (100%). Streptococcus was most sensitive to moxifloxacin (96.97%) and had the highest resistance rate to tobramycin (92.93%).

CONCLUSIONS

Conjunctival sac flora in children was dominated by Gram-positive cocci, mainly S. epidermidis, S. aureus, and Streptococcus. S. epidermidis increased with age; the proportion of Streptococcus was higher than S. aureus among children aged 0-6 years. The typical conjunctiva sac flora was generally sensitive to quinolones, such as moxifloxacin and gatifloxacin; Streptococcus displayed high resistance to tobramycin antibiotics; and the female children had higher resistance to tobramycin than the male children.

Comparison of Conjunctival Sac Microbiome between Low and High Myopic Eyes

Microbial communities played a vital role in maintaining homeostasis of ocular surface. However, no studies explored the myopia-associated conjunctiva microbiota changes until now. In this study, conjunctival sac swab specimens were collected from 12 eyes of low myopia (LM), and 14 eyes of high myopia (HM) patients. The V3-V4 region of the 16S rRNA gene was amplified and then sequenced. Statistical analysis was performed to investigate differences in the taxonomy and diversity between two groups. Compared to LM, higher Ocular Surface Disease Index (OSDI) scores were observed in HM group. The Shannon index of the HM was lower than that of the LM group (P = 0.017). Principle coordinate analysis and Partial Least Squares Discrimination Analysis showed distinct microbiome composition between two groups. At the phylum level, there were higher relative abundances of Proteobacteria (68.27% vs 38.51%) and lower abundances of Actinobacteria (3.71% vs 9.19%) in HM, compared to LM group (P = 0.031, 0.010, respectively). At the genus level, the abundances of Acinetobacter in HM (18.16%) were significantly higher than the LM (6.52%) group (P = 0.011). Actinobacteria levels were negatively correlated with the myopic spherical equivalent and OSDI scores. Moreover, positive correlations were found between Proteobacteria levels and OSDI scores, Acinetobacter levels were positively correlated with myopic spherical equivalent and OSDI scores. In conclusion, HM Patients have bacterial microbiota imbalance in the conjunctival sac, compared with LM patients. Proteobacteria, Actinobacteria, Acinetobacter may play roles in the HM associated ocular surface irritation.

Altered Lung Microbiome and Metabolome Profile in Children With Pulmonary Arterial Hypertension Associated With Congenital Heart Disease

Backgrounds

Pulmonary arterial hypertension (PAH) is characterized by progressive pulmonary vascular functional and structural changes, resulting in increased pulmonary vascular resistance and eventually right heart failure and death. Congenital Left-to-Right shunts (LTRS) is one type of congenital heart disease (CHD) and PAH associated with the congenital Left-to-Right shunt (PAH-LTRS) is a severe disease in children. However, changes in the lung microbiome and their potential impact on PAH-LTRS have not been not fully studied. We hypothesized that lung microbiota and their derived metabolites have been disturbed in children with PAH-LTRS, which might contribute to the progression and outcomes of PAH-LTRS.

Methods

In this study, 68 age- and sex-matched children of three different groups (patients with PAH-LTRS cohort, patients with LTRS but have no pathologic features of PAH cohort, and healthy reference cohort) were enrolled in the current study. Bronchoalveolar lavage fluid samples from these participants were conducted for multi-omics analysis, including 16S rRNA sequencing and metabolomic profiling. Data progressing and integration analysis were performed to identify pulmonary microbial and metabolic characteristics of PAH-LTRS in children.

Results

We found that microbial community density was not significantly altered in PAH-LTRS based on α-diversity analysis. Microbial composition analysis indicated phylum of Bacteroidetes was that less abundant while Lactobacillus, Alicycliphilus, and Parapusillimonas were significantly altered and might contribute to PAH in children with LTRS. Moreover, metabolome profiling data showed that metabolites involved in Purine metabolism, Glycerophospholipid metabolism, Galactose metabolism, and Pyrimidine metabolism were also significantly disturbed in the PAH-LTRS cohort. Correlation analysis between microbes and metabolites indicated that alterations in the microbial composition from the lung microbiota could eventually result in the disturbance in certain metabolites, and might finally contribute to the pathology of PAH-LTRS.

Conclusion

Lung microbial density was not significantly altered in patients with PAH-LTRS. Composition analysis results showed that the relative microbiome abundance was different between groups. Metabolome profiling and correlation analysis with microbiota showed that metabolome also altered in children with PAH-LTRS. This study indicated that pulmonary microbes and metabolites disturbed in PAH-LTRS could be potentially effective biomarkers and provides valuable perspectives on clinical diagnosis, treatment, and prognosis of pediatric PAH-LTRS.

A Glimpse Into the Microbiome of Sjögren’s Syndrome

Sjögren’s syndrome (SS) is a common chronic systemic autoimmune disease and its main characteristic is lymphoid infiltration of the exocrine glands, particularly the salivary and lacrimal glands, leading to sicca symptoms of the mouth and eyes. Growing evidence has shown that SS is also characterized by microbial perturbations like other autoimmune diseases. Significant alterations in diversity, composition, and function of the microbiota were observed in SS. The dysbiosis of the microbiome correlates with worse symptoms and higher disease severity, suggesting that dysbiosis may be of great importance in the pathogenesis of SS. In this review, we provide a general view of recent studies describing the microbiota alterations of SS, the possible pathways that may cause microbiota dysbiosis to trigger SS, and the existence of the gut-ocular/gut-oral axis in SS.

Microbiome and immune-mediated dry eye: a review

In this review, we aim to summarise key articles that explore relationships between the gut and ocular surface microbiomes (OSMs) and immune-mediated dry eye. The gut microbiome has been linked to the immune system by way of stimulating or mitigating a proinflammatory or anti-inflammatory lymphocyte response, which may play a role in the severity of autoimmune diseases. Although the 'normal' gut microbiome varies among individuals and demographics, certain autoimmune diseases have been associated with characteristic gut microbiome changes. Less information is available on relationships between the OSM and dry eye. However, microbiome manipulation in multiple compartments has emerged as a therapeutic strategy, via diet, prebiotics and probiotics and faecal microbial transplant, in individuals with various autoimmune diseases, including immune-mediated dry eye.