Conjunctival Microbiota in Patients With Type 2 Diabetes Mellitus and Influences of Perioperative Use of Topical Levofloxacin in Ocular Surgery

High-throughput sequencing reveals differences in microbial community structure and diversity in the conjunctival tissue of healthy and type 2 diabetic mice

BACKGROUND

To investigate the differences in bacterial and fungal community structure and diversity in conjunctival tissue of healthy and diabetic mice.

METHODS

RNA-seq assays and high-throughput sequencing of bacterial 16 S rDNA and fungal internal transcribed spacer (ITS) gene sequences were used to identify differentially expressed host genes and fungal composition profiles in conjunctival tissues of diabetic BKS-db/db mice and BKS (control) mice. Functional enrichment analysis of differentially expressed genes and the correlation between the relative abundance of bacterial and fungal taxa in the intestinal mucosa were also performed.

RESULTS

Totally, 449 differential up-regulated genes and 1,006 down-regulated genes were identified in the conjunctival tissues of diabetic mice. The differentially expressed genes were mainly enriched in metabolism-related functions and pathways. A decrease in conjunctival bacterial species diversity and abundance in diabetic mice compared to control mice. In contrast, fungal species richness and diversity were not affected by diabetes. The microbial colonies were mainly associated with cellular process pathways regulating carbohydrate and lipid metabolism, as well as cell growth and death. Additionally, some interactions between bacteria and fungi at different taxonomic levels were also observed.

CONCLUSION

The present study revealed significant differences in the abundance and composition of bacterial and fungal communities in the conjunctival tissue of diabetic mice compared to control mice. The study also highlighted interactions between bacteria and fungi at different taxonomic levels. These findings may have implications for the diagnosis and treatment of diabetes.

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.

Leger AJ, Galor A. Living with your biome: how the bacterial microbiome impacts ocular surface health and disease

Introduction

Microbiome research has grown exponentially but the ocular surface microbiome (OSM) remains an area in need of further study. This review aims to explore its complexity, disease-related microbial changes, and immune interactions, and highlights the potential for its manipulation as a therapeutic for ocular surface diseases.

Areas Covered

We introduce the OSM by location and describe what constitutes a normal OSM. Second, we highlight aspects of the ocular immune system and discuss potential immune microbiome interactions in health and disease. Finally, we highlight how microbiome manipulation may have therapeutic potential for ocular surface diseases.

Expert Opinion

The ocular surface microbiome varies across its different regions, with a core phyla identified, but with genus variability. A few studies have linked microbiome composition to diseases like dry eye but more research is needed, including examining microbiome interactions with the host. Studies have noted that manipulating the microbiome may impact disease presentation. As such, microbiome manipulation via diet, oral and topical pre and probiotics, and hygienic measures may provide new therapeutic algorithms in ocular surface diseases.

Ocular surface microbiota dysbiosis contributes to the high prevalence of dry eye disease in diabetic patients

People with diabetes mellitus (DM) are at an increased risk for developing dry eye disease (DED). However, the mechanisms underlying this phenomenon remain unclear. Recent studies have found that the ocular surface microbiota (OSM) differs significantly between patients with DED and healthy people, suggesting that OSM dysbiosis may contribute to the pathogenesis of DED. This hypothesis provides a new possible explanation for why diabetic patients have a higher prevalence of DED than healthy people. The high-glucose environment and the subsequent pathological changes on the ocular surface can cause OSM dysbiosis. The unbalanced microbiota then promotes ocular surface inflammation and alters tear composition, which disturbs the homeostasis of the ocular surface. This "high glucose-OSM dysbiosis" pathway in the pathogenesis of DED with DM (DM-DED) is discussed in this review.

Antibiotic-Therapy-Induced Gut Dysbiosis Affecting Gut Microbiota-Brain Axis and Cognition: Restoration by Intake of Probiotics and Synbiotics

Antibiotic therapy through short-term or repeated long-term prescriptions can have several damaging effects on the normal microbiota of the gastrointestinal tract. Changes in microbiota could be multiple including decreased diversity of species in gut microbiota, changed metabolic activity, and the occurrence of antibiotic-resistant strains. Antibiotic-induced gut dysbiosis in turn can induce antibiotic-associated diarrhoea and recurrent infections caused by Clostridioides difficile. There is also evidence that the use of different chemical classes of antibiotics for the treatment of a variety of ailments can lead to several health issues including gastrointestinal, immunologic, and neurocognitive conditions. This review discusses gut dysbiosis, its symptoms and one important cause, which is antibiotic therapy for the induction of gut dysbiosis. Since the maintenance of good gut health is important for the well-being and functioning of physiological and cognitive activities through the normal gut-microbiota-brain relationship, the condition of dysbiosis is not desirable. Specific therapies are prescribed by medical practitioners for the cure of a variety of ailments, and, if the prescription of antibiotics becomes unavoidable, there is a possibility of the onset of gut dysbiosis as the side or after effects. Therefore, the restoration of imbalanced gut microbiota to its balanced condition becomes necessary. A healthy relationship between gut microbiota and the brain can be achieved with the introduction of probiotic strains into the gut in a practical and consumer-friendly way, such as consumption of food and beverages prepared with the use of characterised probiotic species, fermented foods as the potential biotics, or synbiotic supplements.

Microbiological Characteristics of Ocular Surface Associated With Dry Eye in Children and Adolescents With Diabetes Mellitus

Purpose

To analyze the characteristics of ocular surface microbial composition in children and adolescents with diabetes mellitus and dry eye (DE) by tear analysis.

Methods

We selected 65 children and adolescents aged 8 to 16 years with DE and non-DE diabetes mellitus and 33 healthy children in the same age group from the Shanghai Children and Adolescent Diabetes Eye Study. Tears were collected for high-throughput sequencing of the V3 and V4 region of 16S rRNA. The ocular surface microbiota in diabetic DE (DM-DE; n = 31), diabetic with non-DE (DM-NDE; n = 34), and healthy (NDM; n = 33) groups were studied. QIIME2 software was used to analyze the microbiota of each group.

Results

The DM-DE group had the highest amplicon sequence variants, and the differences in α-diversity and β-diversity of micro-organisms in the ocular surfaces of DM-DE, diabetic with non-DE, and healthy eyes were statistically significant (P < 0.05). Bacteroidetes (15.6%), Tenericutes (9.3%), Firmicutes (21.8%), and Lactococcus (7.9%), Bacteroides (7.8%), Acinetobacter (3.9%), Clostridium (0.8%), Lactobacillus (0.8%) and Streptococcus (0.2%) were the specific phyla and genera, respectively, in the DM-DE group.

Conclusions

Compared with the patients with non-DE and healthy children, the microbial diversity of the ocular surface in children and adolescents with diabetes mellitus and DE was higher with unique bacterial phyla and genera composition.

Ocular surface microbiome in diabetes mellitus

This cross-sectional, age- and gender-matched study included 20 eyes of non-diabetic subjects (non-DM group) and 60 eyes of type 2 diabetes mellitus (DM group). Subgroups of DM were classified by diabetic retinopathy (DR) staging into no DR (DM-no DR), non-proliferative DR (DM-NPDR), proliferative DR (DM-PDR), and by glycemic control (well-controlled DM; HbA1c < 7%, poorly controlled DM; HbA1c ≥ 7%). Conjunctival swabs were performed for ocular surface microbiome analysis using conventional culture and next-generation sequencing analysis (NGS). A higher culture-positive rate was found in DM (15%) than in non-DM group (5%) (p value = 0.437). Pathogenic organisms and antibiotic-resistant strains were detected in the DR groups (DM-NPDR and DM-PDR). The NGS analysis showed that potentially pathogenic bacteria such as Enterobacteriaceae, Neisseriaceae, Escherichia-Shigella, and Pseudomonas predominated in DM, especially in DR. There was dissimilarity in the ocular surface microbiome between DM and non-DM groups. The subgroup analysis showed that the DR group had significantly different microbial community from DM-no DR and non-DM groups (p value < 0.05). The microbial community in the poorly controlled DM was also significantly different from well-controlled DM and non-DM groups (p < 0.001). Using the NGS method, our study is the first to signify the importance of DR and glycemic control status, which affect the changes in the ocular surface microbiome.

Temporal impacts of topical ceftazidime and tobramycin-vancomycin mixtures on the ocular surface microbiota in rabbits

Antibiotics are one of the important factors that can alter the diversity and composition of ocular surface microbiota. At present, there are a few studies about the antibiotic effect on ocular surface microbiota, including its time-dependent changes. However, these limited studies have revealed various results, and more experiments are required. In this study, we used 16 S rRNA sequencing method to investigate the effects of topical ceftazidime and tobramycin-vancomycin mixtures on the ocular surface microbiota and the temporal changes of the microbiota after discontinuing antibiotic treatment in rabbits. Seventeen healthy rabbits were treated with 5% ceftazidime and a mixture of 0.3% tobramycin-5% vancomycin (CTV) eye drops on one eye four times a day for 7 days. Swab samples of conjunctiva sacs were collected before antibiotic treatment (D0), 12 h after the last antibiotic treatment (D8) and two further time points on Day 15 (D15) and Day 30 (D30). We found that the species diversity of the ocular surface microbiota increased significantly at D8 and was restored at D15, namely, one week after antibiotic cessation. The community structure of the ocular surface microbiota changed after treatment with CTV but recovered at D30. At D8, the relative abundances of 13 bacterial phyla of the initial top 20 phyla and 11 bacterial genera of the initial top 20 genera were significantly different from the relative abundances of the phyla and genera at D0. Furthermore, the relative abundance of the dominant phylum Epsilonbacteraeota obviously decreased, while Proteobacteria and Bacteroidetes markedly increased. For dominant genera, the relative abundance of Helicobacter notably decreased, while Acinetobacter and Pasteurella greatly increased. Thirteen altered bacterial phyla and 7 of 11 altered bacterial genera recovered to preantibiotic levels at D30. In addition, there was a group of nondominant and rare bacteria enriched at D8, and most of them were restored at D30. In conclusion, the species diversity, community structure and composition of the ocular surface microbiota changed greatly after exposure to CTV, but they tended to be restored within weeks after discontinuing antibiotic treatment.