Efficacy of 0.5% Levofloxacin and 5.0% Povidone-Iodine Eyedrops in Reducing Conjunctival Bacterial Flora: Metagenomic Analysis

Next-Generation Sequencing of the Human Aqueous Humour Microbiome

The microbiome of the ocular surface has been characterised, but only limited information is available on a possible silent intraocular microbial colonisation in normal eyes. Therefore, we performed next-generation sequencing (NGS) of 16S rDNA genes in the aqueous humour. The aqueous humour was sampled from three patients during cataract surgery. Air swabs, conjunctival swabs from patients as well as from healthy donors served as controls. Following DNA extraction, the V3 and V4 hypervariable regions of the 16S rDNA gene were amplified and sequenced followed by denoising. The resulting Amplicon Sequence Variants were matched to a subset of the Ribosomal Database Project 16S database. The deduced bacterial community was then statistically analysed. The DNA content in all samples was low (0-1.49 ng/µL) but sufficient for analysis. The main phyla in the samples were Acinetobacteria (48%), Proteobacteria (26%), Firmicutes (14%), Acidobacteria (8%), and Bacteroidetes (2%). Patients' conjunctival control samples and anterior chamber fluid showed similar patterns of bacterial species containing many waterborne species. Non-disinfected samples showed a different bacterial spectrum than the air swab samples. The data confirm the existence of an ocular surface microbiome. Meanwhile, a distinct intraocular microbiome was not discernible from the background, suggesting the absence of an intraocular microbiome in normal eyes.

Shotgun metagenomic sequencing analysis of ocular surface microbiome in Singapore residents with mild dry eye

The ocular surface microbiome has implications for ocular surface inflammation and immunology. Previous shotgun metagenomics analyses were performed in China, showing results that differed according to environment and age. Patients with Sjogren's syndrome were reported to have altered conjunctival microbiome, but such studies have not been done in milder dry eye. The aim of this study is to describe the conjunctival microbiome in people with mild dry eye in Singapore. Samples were collected from 14 participants with mild dry eye and 10 age-matched comparison participants recruited from Singapore National Eye Centre (SNEC) clinics. Shotgun metagenomic sequencing analysis was employed to evaluate the conjunctival microbiome composition. Proteobacteria formed the predominant phylum in the conjunctiva. As in a study from a coastal city in China, Achromobacter spp. was numerically most abundant. Compared to age-matched controls, the conjunctival microbial composition in mild dry eye was similar. Several microorganisms, including Streptococcus spp. increased in representation with age, and the abundance of Staphylococcus correlated with Schirmer readings. In addition, when cultured corneal epithelial cells were exposed to three strains of Achromobacter xylosoxidans, cytokines such as TNF-α and IL-6 were upregulated in the cell lysates and supernatants. Ourresults suggest that age is an important factor that affects composition of the conjunctival microbiome, and relative abundance of specific microorganism may vary according to the environment of the human host.

Bacterial Keratitis Following Small Incision Lenticule Extraction

Purpose

To describe the development of bacterial keratitis after small incision lenticule extraction in 5 patients and to explore its appropriate therapies.

Methods

We retrospectively summarized the clinical treatments of five patients with postoperative bacterial infection after small incision lenticule extraction, who were referred to our hospital from 2019 to 2021.

Results

Five male patients had undergone bilateral SMILE in the local hospital due to myopia aged from 18 to 26 years. The onset of keratitis during 1–3 days postoperatively and four of them were severe infection (2 bilateral, 2 unilateral). In five cases, 1 patient (1 eye) who was infected mild keratitis after SMILE was treated with only topical antibiotics; the others who respond poorly to topical antibiotics require surgical treatment, which 1 patient (1 eye) infected necrotic mass of the corneal cap was scraped and irrigated with antibiotic, and 3 patients (5 eyes) were treated by converting the cap to flap, curetting the necrotic tissue and irrigating with the antibiotic solution. In all patients, the duration from onset to resolution was 1–5 weeks. The final uncorrected visual acuity was above 20/32.

Conclusion

Owing to the upward popularity of refractive surgery, the incidence of keratitis after SMILE should not be ignored. Early diagnosis and timely treatment of post-SMILE keratitis are essential. For severe keratitis that fails to respond to topical antibiotics, the corneal cap should be opened as a flap.

Ten-Year Analysis of Pathogenic Factors and Etiological Characteristics of Endophthalmitis from a Tertiary Eye Center in North China

Purpose

To describe the etiology and spectrum of isolated pathogens in endophthalmitis over 10 years from an ophthalmic hospital in North China and report their antimicrobial susceptibilities.

Patients and Methods

The data covered the patients with endophthalmitis treated at Qingdao Eye Hospital from January 2011 to December 2020. Patients’ medical history, pathogenic factors, bacterial and fungal culture results of intraocular specimens, and in vitro drug sensitivity test results were assessed.

Results

A total of 524 cases were counted in this study. Exogenous endophthalmitis was the main component, accounting for 94.66%, of which 49.62% of eyes had a history of ophthalmic trauma, intraocular surgery in 26.72% and suppurative keratitis in 17.37%. By comparison, endogenous endophthalmitis was found in only 5.34% of eyes. Among the 292 strains of pathogenic organisms obtained by co-culture, gram-positive bacteria accounted for 64.04%, with Staphylococcus epidermidis as the predominant pathogen (29.45%). Gram-positive cocci were identified in 76.77% of eyes with traumatic endophthalmitis, while 53.70% of keratitis-associated endophthalmitis was caused by fungi. The high susceptibility of bacteria to vancomycin (77.78%~98.33%) supported its continued use as empirical treatment. Among the fluoroquinolones, gram-positive cocci showed a higher susceptibility to gatifloxacin (94.83%), while there was a significant decrease to levofloxacin (51.67%). Gram-negative bacteria were less sensitive to cephalosporins (45.95%~66.67%) than fluoroquinolones (68.42%~78.05%) and aminoglycosides (75.00%~78.05%). Fungal susceptibilities to voriconazole and amphotericin B were 90.16% and 70.31% respectively. More than half of the 11 antibiotics were observed to exhibit a trend of reduced susceptibility.

Conclusion

Ophthalmic trauma was the primary pathogenic factor of endophthalmitis. Gram-positive cocci were the most common pathogens of traumatic and postoperative endophthalmitis, while suppurative keratitis-associated endophthalmitis often resulted from fungal pathogens. Levofloxacin as the preferred antibiotic in the perioperative period and cephalosporin as the first-line drug for the treatment of empiric endophthalmitis need to be vigilant.

Profiling of the Conjunctival Bacterial Microbiota Reveals the Feasibility of Utilizing a Microbiome-Based Machine Learning Model to Differentially Diagnose Microbial Keratitis and the Core Components of the Conjunctival Bacterial Interaction Network

Both healthy and diseased human ocular surfaces possess their own microbiota. If allowed, opportunistic pathogens within the ocular microbiota may cause microbial keratitis (MK). However, the nonpathogenic component of the ocular microbiota has been proven to undermine the performance of culture, the gold standard of the etiological diagnosis for MK. As the conjunctival bacterial microbiota generates unique alterations with various oculopathies, this study aimed to evaluate the feasibility of distinguishing MK using machine learning based on the characteristics of the conjunctival bacterial microbiome associated with various types of MK. This study also aimed to reveal which bacterial genera constitute the core of the interaction network of the conjunctival bacterial microbiome. Conjunctival swabs collected from the diseased eyes of MK patients and the randomly chosen normal eyes of healthy volunteers were subjected for high-throughput 16S rDNA sequencing. The relative content of each bacterial genus and the composition of bacterial gene functions in every sample were used to establish identification models with the random forest algorithm. Tenfold cross validation was adopted. Accuracy was 96.25% using the bacterial microbiota structure and 93.75% using the bacterial gene functional composition. Therefore, machine learning with the conjunctival bacterial microbiome characteristics might be used for differentiation of MKs as a noninvasive supplementary approach. In addition, this study found that Actinobacteria, Lactobacillus, Clostridium, Helicobacter, and Sphingomonas constitute the core of the interaction network of the conjunctival bacterial microbiome.

Effects of Sodium Hyaluronate Eye Drops With or Without Preservatives on Ocular Surface Bacterial Microbiota

Purpose

This study aimed to determine the composition and diversity of bacterial communities on the ocular surface before and after the intervention with sodium hyaluronate eye drops (with or without preservatives) using 16S rRNA gene amplicon sequencing.

Methods

Sixteen healthy adults were randomly divided into two groups and treated with sodium hyaluronate eye drops with or without preservatives for 2 weeks. The individuals used the same artificial tears in both eyes. The microbial samples from the conjunctival sac of each participant were collected at baseline and 2 weeks after intervention. The diversity and taxonomic differences among different groups before and after intervention were compared by sequencing the V3–V4 region of the 16S rRNA gene.

Results

The similarity in the binocular microbial community was high in 1 of the 16 volunteers (Bray-Curtis dissimilarity score < 0.3). At the genus level, 11 bacteria were detected in all samples with an average relative abundance of more than 1%. The bacterial community changed significantly after the use of sodium hyaluronate eye drops (with or without preservatives), whether within individuals or between individuals in different groups (P < 0.05, PERMANOVA). Different dosage forms of sodium hyaluronate eye drops significantly decreased the relative abundance of Flavobacterium caeni and Deinococcus antarcticus, respectively (P < 0.05).

Conclusions

Healthy people had a rich diversity of the bacterial microbiota on the ocular surface, but the bacterial communities between the eyes were not completely similar. Irrespective of containing benzalkonium chloride (BAC), sodium hyaluronate eye drops can change the bacterial community on the ocular surface.

Effect of topical povidone-iodine 10% plus levofloxacin 0.5% 1 hour before cataract surgery in eliminating perioperative conjunctival flora: randomized clinical trial

PURPOSE

To evaluate the effect of a single administration of topical povidone-iodine (PVI) 10% plus levofloxacin 0.5% at 1 hour before cataract surgery on perioperative elimination rate of conjunctival flora.

SETTING

Poostchi Ophthalmology Research Center, Shiraz, Iran.

DESIGN

Randomized controlled trial.

METHOD

Patients who required cataract surgery were randomly assigned to 1 of 2 groups: intervention (administration of PVI 10% plus levofloxacin 0.5% at 1 hour preoperatively) or control. The patients in both groups received PVI just before the operation. Conjunctival cultures were obtained using thioglycollate broth at 4 timepoints: T1, before intervention; T2, before the second application of PVI; T3, 3 minutes after the second administration of PVI; and T4, just postoperatively.

RESULTS

The study comprised 142 patients. The comparative rates of positive cultures in the intervention vs control groups were as follows: T1 (70.4% vs 73.2%, P = .709); T2 (15.5% vs 71.8%, P < .001); T3 (7.0% vs 19.7%, P = .027); and T4 (5.6% vs 4.2%, P = .698). Coagulase-negative Staphylococci was the most common isolated microorganism.

CONCLUSIONS

Results showed that a single adjuvant application of PVI 10% plus levofloxacin 0.5% eyedrops at 1 hour before operation leads to a further increase in the rate of sterile conjunctiva just preoperatively.

Acute Infectious Endophthalmitis After Cataract Surgery: Epidemiological Characteristics, Risk Factors and Incidence Trends, 2008-2019

Objective

Intended to investigate the epidemiological characteristics, risk factors and incidence trend of endophthalmitis after cataract surgery in recent 12 years.

Methods

A retrospective study was conducted on the patients who underwent cataract surgery in Qingdao Eye Hospital from January 1, 2008, to December 31, 2019, including age, sex, history of diabetes, intraoperative operation and complications. In addition, the related risk factors and incidence trend of acute infective endophthalmitis were analyzed. The incidence of endophthalmitis and its related factors were analyzed by univariate and multivariate logistic regression analysis.

Results

A total of 55,612 cases of cataract surgery were performed in our hospital in 12 years, and 42 cases of acute infective endophthalmitis occurred (the incidence rate was 0.076%). The average occurrence time was 10.57 days ± 11.17, with eye pain as the main complaint and anterior chamber fibrin exudation as the main clinical manifestation. In addition, there were eight cases of anterior chamber hypopyon and 18 cases of vitreous reaction, the results of anterior aqueous humor or vitreous fluid culture in 10 patients were positive. Univariate analysis showed that intraoperative rupture of posterior capsule, non-use of antibiotics and non-use of behind-the-lens washout were the risk factors of infectious endophthalmitis after cataract surgery (P=0.032, P=0.000, P=0.000). Besides, multivariate logistic regression analysis showed that intraoperative rupture of posterior capsule was the main risk factor.

Conclusion

The occurrence of endophthalmitis after cataract surgery is mainly related to intraoperative rupture of posterior capsule, absence of antibiotics and behind-the-lens washout. In addition, the incidence of endophthalmitis after cataract surgery decreased during the past 12 years.