Enriched and Decreased Intestinal Microbes in Active VKH Patients

Microbiome-based therapeutics for ocular diseases

The relationship between the gut microbiome and ocular health has garnered increasing attention within the scientific community. Recent research has focused on the gut-eye axis, examining whether imbalances within the gut microbiome can influence the development, progression and severity of ocular diseases, including dry eye disease, uveitis, and glaucoma. Dysbiosis within the gut microbiome is linked to immune dysregulation, chronic inflammation, and epithelial barrier dysfunction, all of which contribute to ocular pathology. This review synthesises current evidence on these associations, exploring how gut microbiome alterations drive disease mechanisms. Furthermore, it examines the therapeutic potential of microbiome-targeted interventions, including antibiotics, prebiotics, probiotics, and faecal microbiota transplantation, all of which aim to restore microbial balance and modulate immune responses. As the prevalence of these conditions continues to rise, a deeper understanding of the gut-eye axis may facilitate the development of novel, targeted therapies to address unmet needs in the management of ocular diseases.

Bacteremia due to Lachnoanaerobaculum umeaense in a patient with acute myeloid leukemia during chemotherapy: A case report, and a review of the literature

The present case reports a bacteremia due to Lachnoanaerobaculum umeaense (a Gram-positive, filamentous, rod-shaped, anaerobic, spore-forming bacillus present in the human oral microbiota) in a patient treated for acute myeloid leukemia. After failed identification by MALDI-TOF, identification was done by sequencing of 16s rRNA. The patient was successfully treated with Amoxicillin-clavulanic acid and ciprofloxacin for seven days. Comparison of V1-V3 regions of the bacterial 16S rRNA gene gene with published sequences failed to classify the strain as pathogenic or non-pathogenic based on this phylogenetic classification alone. Although Lachnoanaerobaculum gingivalis are known to be associated with bacteremia in patients with acute myeloid leukemia, this clinical case of infection by L. umeaense argues for further studies that will lead to more efficient classification of the infection by these microorganisms.

Decreased Abundance of Genus Slackia in Individuals With Obesity and Colorectal Adenoma

Background and Aims

The increasing prevalence of obesity has significantly contributed to the global burden of colorectal cancer and the precancerous colorectal adenoma (CRA). Gut microbiota vary at each stage of colorectal carcinogenesis and participate in energy homeostasis. Elucidating gut microbiotal characteristics in obesity-related CRA may help prevent and treat colorectal tumors; however, this remains unclarified. Therefore, this study investigated the gut microbiota profile of patients with obesity-related CRA.

Methods

This hospital setting-based cross-sectional study included 113 participants (66 [without CRA control group] and 37 [with CRA group]; each group was divided into obese and nonobese groups) who underwent screening colonoscopy between June 2019 and January 2020. Gut microbiota were analyzed using 16S rRNA and polymerase chain reaction techniques and the data compared between the aforementioned groups.

Results

No between-group difference was observed in the diversity index; however, α diversity was the lowest in the obese CRA group. The CRA group had significantly higher and lower numbers of 26 and 17 genera, respectively. Genus Slackia was significantly lower in the obese CRA group than in the nonobese CRA group. Multivariate analysis of the quartiles according to genus Slackia relative abundance rates revealed that the first quartile was an independent risk factor for CRA (odds ratio, 3.57; 95% confidence interval 1.19-10.7). The proportion of equol reductase-positive participants was lowest in the obese CRA group (P = .04). Multivariate odds ratio for CRA was 5.46 (95% confidence interval 1.35-22.0) for genus Slackia and equol reductase-negative participants.

Conclusion

Decreased abundance of genus Slackia and absence of equol reductase potentially influence obesity-related CRA development.

Mechanisms of blood-retinal barrier disruption related to intraocular inflammation and malignancy

Blood-retinal barrier (BRB) disruption is a common accompaniment of intermediate, posterior and panuveitis causing leakage into the retina and macular oedema resulting in vision loss. It is much less common in anterior uveitis or in patients with intraocular lymphoma who may have marked signs of intraocular inflammation. New drugs used for chemotherapy (cytarabine, immune checkpoint inhibitors, BRAF inhibitors, EGFR inhibitors, bispecific anti-EGFR inhibitors, MET receptor inhibitors and Bruton tyrosine kinase inhibitors) can also cause different types of uveitis and BRB disruption. As malignant disease itself can cause uveitis, particularly from breast, lung and gastrointestinal tract cancers, it can be clinically difficult to sort out the cause of BRB disruption. Immunosuppression due to malignant disease and/or chemotherapy can lead to infection which can also cause BRB disruption and intraocular infection. In this paper we address the pathophysiology of BRB disruption related to intraocular inflammation and malignancy, methods for estimating the extent and effect of the disruption and examine why some types of intraocular inflammation and malignancy cause BRB disruption and others do not. Understanding this may help sort and manage these patients, as well as devise future therapeutic approaches.

Effects of dietary imbalances of micro- and macronutrients on the ocular microbiome and its implications in dry eye disease

Dry eye disease (DED) is a complex and multifactorial ocular surface disease affecting a large proportion of the population. There is emerging evidence of the impact of the microbiomes of the ocular surface and gut on the symptoms of DED, with many parallels being drawn to inflammatory diseases of other organ systems. A key factor involved in the promotion of healthy microbiomes, and which has been associated with ocular surface disease, is micro- and macronutrient deficiency. A comprehensive review of how these deficiencies can contribute to DED is absent from the literature. This review reports the composition of healthy ocular and gut microbiomes, and how nutrient deficiencies may impact these floral populations, with linkage to the subsequent impact on ocular health. The review highlights that vitamin B1 and iron are linked to reduced levels of butyrate, a fatty acid implicated in inflammatory conditions such as ulcerative colitis which itself is a condition known to be associated with ocular surface diseases. Vitamin B12 has been shown to have a role in maintaining gut microbial eubiosis and has been linked to the severity of dry eye symptoms. Similar beneficial effects of gut microbial eubiosis were noted with vitamin A and omega-3 polyunsaturated fatty acids. Selenium and calcium have complex interactions with the gut microbiome and have both been implicated in the development of thyroid orbitopathy. Further, diabetes mellitus is associated with ocular surface diseases and changes in the ocular microbiome. A better understanding of how changes in both the gut and eye microbiome impact DED could allow for an improved understanding of DED pathophysiology and the development of new, effective treatment strategies.

The Microbiome and Uveitis: A Narrative Review

The human intestinal microbiome is composed of hundreds of species and has recently been recognized as an important source of immune homeostasis. While dysbiosis, an altered microbiome from the normal core microbiome, has been associated with both intestinal and extraintestinal autoimmune disorders, including uveitis, causality has been difficult to establish. There are four proposed mechanisms of how the gut microbiome may influence the development of uveitis: molecular mimicry, imbalance of regulatory and effector T cells, increased intestinal permeability, and loss of intestinal metabolites. This review summarizes current literature on both animal and human studies that establish the link between dysbiosis and the development of uveitis, as well as provides evidence for the above mechanisms. Current studies provide valuable mechanistic insights as well as identify potential therapeutic targets. However, study limitations and the wide variability in the intestinal microbiome among populations and diseases make a specific targeted therapy difficult to establish. Further longitudinal clinical studies are required to identify any potential therapeutic that targets the intestinal microbiome.

Comparison of intestinal microbes and metabolites in active VKH versus acute anterior uveitis associated with ankylosing spondylitis

BACKGROUND

It has been reported that the gut microbiome is involved in the pathogenesis of uveitis, but the specific pathogenic microbes and metabolites in different types of uveitis are still unclear.

METHODS

Microbiome and metabolites were detected using 16S ribosomal DNA and LC‒MS/MS (liquid chromatography tandem mass spectrometry) in 45 individuals, including 16 patients with Vogt Koyanagi Harada (VKH), 11 patients with acute anterior uveitis (AAU) and 18 healthy controls.

RESULT

The diversity of intestinal microbes among the VKH, AAU and control groups was not significantly different. Thirteen specific microbes and 38 metabolites were detected in the VKH group, and 7 metabolites (vanillin, erythro-isoleucine, pyrimidine, 1-aminocyclopropanecarboxylic acid, beta-tocopherol, (-)-gallocatechin and N1-methyl-4-pyridone-3-carboxamide) significantly changed only in patients with VKH, which mainly acted on nicotinamide and nicotinamide metabolism and biotin metabolism (p<0.05). Compared with the VKH group, the AAU group had milder intestinal changes. Only 11 specific microbes and 29 metabolites changed in the AAU group, while these metabolites were not specific (p<0.05). These metabolites mainly acted on arachidonic acid metabolism. In addition, three microbes and two metabolites had the same changes in the VKH and AAU groups (p<0.05). Multiple correlations were found between gut microbes and metabolites in the VKH and AAU groups. Six microbes (Pediococcus, Pseudomonas, Rhodococcus, Photobacterium, Gardnerella and Lawsonia) and two metabolites (pyrimidine and gallocatechin) as biomarkers could effectively distinguish patients with VKH from patients with AAU and healthy individuals, with AUC (area under the curve) values greater than 82%. Four microbes (Lentilactobacillus, Lachnospiraceae_UCG-010, Cetobacterium, Liquorilactobacillus) could distinguish patients with AAU from patients with VKH and healthy controls with AUC>76%.

CONCLUSION

Significant differences in intestinal microbes and metabolites suggest their different roles in the pathogenesis of uveitis entities. Changes in the metabolism of certain B vitamins may be involved in the pathogenesis of VKH.

Intestine microbiota and SCFAs response in naturally Cryptosporidium-infected plateau yaks

Diarrhea is a severe bovine disease, globally prevalent in farm animals with a decrease in milk production and a low fertility rate. Cryptosporidium spp. are important zoonotic agents of bovine diarrhea. However, little is known about microbiota and short-chain fatty acids (SCFAs) changes in yaks infected with Cryptosporidium spp. Therefore, we performed 16S rRNA sequencing and detected the concentrations of SCFAs in Cryptosporidium-infected yaks. Results showed that over 80,000 raw and 70,000 filtered sequences were prevalent in yak samples. Shannon (p<0.01) and Simpson (p<0.01) were both significantly higher in Cryptosporidium-infected yaks. A total of 1072 amplicon sequence variants were shared in healthy and infected yaks. There were 11 phyla and 58 genera that differ significantly between the two yak groups. A total of 235 enzymes with a significant difference in abundance (p<0.001) were found between healthy and infected yaks. KEGG L3 analysis discovered that the abundance of 43 pathways was significantly higher, while 49 pathways were significantly lower in Cryptosporidium-infected yaks. The concentration of acetic acid (p<0.05), propionic acid (p<0.05), isobutyric acid (p<0.05), butyric acid (p<0.05), and isovaleric acid was noticeably lower in infected yaks, respectively. The findings of the study revealed that Cryptosporidium infection causes gut dysbiosis and results in a significant drop in the SCFAs concentrations in yaks with severe diarrhea, which may give new insights regarding the prevention and treatment of diarrhea in livestock.

Comparison of Intestinal Microbes in Noninfectious Anterior Scleritis Patients With and Without Rheumatoid Arthritis

We compared intestinal microbes in anterior noninfectious scleritis patients with and without rheumatoid arthritis. Active noninfectious anterior scleritis patients without other immune diseases (G group, 16 patients) or with active rheumatoid arthritis (GY group, seven patients) were included in this study. Eight age- and sex-matched healthy subjects served as controls (N group). DNA was extracted from fecal samples. The V3-V4 16S rDNA region was amplified and sequenced by high-throughput 16S rDNA analysis, and microbial contents were determined. A significant decrease in species richness in the GY group was revealed by α- and β-diversity analyses (p = 0.02 and p = 0.004, respectively). At the genus level, 14 enriched and 10 decreased microbes in the G group and 13 enriched and 18 decreased microbes in the GY group were identified. Among them, four microbes were enriched in both the G and GY groups, including Turicibacter, Romboutsia, Atopobium, and Coprobacillus. Although two microbes (Lachnospiraceae_ND3007_group and Eggerthella) exhibited similar tendencies in the G and GY groups, changes in these microbes were more significant in the GY group (p < 0.05). Interaction analysis showed that Intestinibacter, Romboutsia, and Turicibacter, which were enriched in both the G and GY groups, correlated positively with each other. In addition, nine microbes were decreased in the GY group, which demonstrates a potential protective role for these microbes in the pathogenesis of scleritis via interactions with each other.

Microbiome in Immune-Mediated Uveitis

In the last decades, personalized medicine has been increasing its presence in different fields of medicine, including ophthalmology. A new factor that can help us direct medicine towards the challenge of personalized treatments is the microbiome. The gut microbiome plays an important role in controlling immune response, and dysbiosis has been associated with immune-mediated diseases such as non-infectious uveitis (NIU). In this review, we gather the published evidence, both in the pre-clinical and clinical studies, that support the possible role of intestinal dysbiosis in the pathogenesis of NIU, as well as the modulation of the gut microbiota as a new possible therapeutic target. We describe the different mechanisms that have been proposed to involve dysbiosis in the causality of NIU, as well as the potential pharmacological tools that could be used to modify the microbiome (dietary supplementation, antibiotics, fecal microbiota transplantation, immunomodulators, or biologic drugs) and, consequently, in the control of the NIU. Furthermore, there is increasing scientific evidence suggesting that the treatment with anti-TNF not only restores the composition of the gut microbiota but also that the study of the composition of the gut microbiome will help predict the response of each patient to anti-TNF treatment.