Impact of Sample Collection Order on the Diagnostic Performance of Metagenomic Deep Sequencing for Infectious Keratitis

The application of high-throughput sequencing technology in corneal diseases

High-throughput sequencing technology, also known as next-generation sequencing technology, can explore new biomarkers and specific gene mutations. It has a pivotal role in promoting the gene research, which can limit the detection area, lessen the time needed for sequencing. Also, it can quickly screen out the suspected pathogenic genes of patients, gain the necessary genetic data, and provide the basis for clinical diagnosis and genetic counseling. In the research of corneal diseases, through the DNA sequencing of patients' diseased cells, it can provide a deeper understanding of corneal diseases and improve the diagnosis, classification and treatment alternatives of various corneal diseases. This article will introduce the application progress of high-throughput sequencing technology in corneal diseases, which will help to understand the application of this technology in various corneal diseases.

Metagenomic sequencing for investigation of a national keratoconjunctivitis outbreak, Israel, 2022

BackgroundEpidemics of keratoconjunctivitis may involve various aetiological agents. Microsporidia are an uncommon difficult-to-diagnose cause of such outbreaks.AimDuring the third quarter of 2022, a keratoconjunctivitis outbreak was reported across Israel, related to common water exposure to the Sea of Galilee. We report a comprehensive diagnostic approach that identified Vittaforma corneae as the aetiology, serving as proof of concept for using real-time metagenomics for outbreak investigation.MethodsCorneal scraping samples from a clinical case were subjected to standard microbiological testing. Samples were tested by calcofluor white staining and metagenomic short-read sequencing. We analysed the metagenome for taxonomical assignment and isolation of metagenome-assembled genome (MAG). Targets for a novel PCR were identified, and the assay was applied to clinical and environmental samples and confirmed by long-read metagenomic sequencing.ResultsFluorescent microscopy was suggestive of microsporidiosis. The most abundant species (96.5%) on metagenomics analysis was V. corneae. Annotation of the MAG confirmed the species assignment. A unique PCR target in the microsporidian rRNA gene was identified and validated against the clinical sample. The assay and metagenomic sequencing confirmed V. corneae in an environmental sludge sample collected at the exposure site.ConclusionsThe real-time utilisation of metagenomics allowed species detection and development of diagnostic tools, which aided in outbreak source tracking and can be applied for future cases. Metagenomics allows a fully culture-independent investigation and is an important modality for public health microbiology.

Therapy for contact lens-related ulcers

PURPOSE OF REVIEW

The current review covers the current literature and practice patterns of antimicrobial therapy for contact lens-related microbial keratitis (CLMK). Although the majority of corneal ulcers are bacterial, fungus and acanthamoeba are substantial contributors in CLMK and are harder to treat due to the lack of commercially available topical medications and low efficacy of available topical therapy.

RECENT FINDINGS

Topical antimicrobials remain the mainstay of therapy for corneal ulcers. Fluoroquinolones may be used as monotherapy for small, peripheral bacterial ulcers. Antibiotic resistance is a persistent problem. Fungal ulcers are less responsive to topical medications and adjunct oral or intrastromal antifungal medications may be helpful. Acanthamoeba keratitis continues to remain a therapeutic challenge but newer antifungal and antiparasitic agents may be helpful adjuncts. Other novel and innovative therapies are being studied currently and show promise.

SUMMARY

Contact lens-associated microbial keratitis is a significant health issue that can cause vision loss. Treatment remains a challenge but many promising diagnostics and procedures are in the pipeline and offer hope.

Diagnostic armamentarium of infectious keratitis: A comprehensive review

Infectious keratitis (IK) represents the leading cause of corneal blindness worldwide, particularly in developing countries. A good outcome of IK is contingent upon timely and accurate diagnosis followed by appropriate interventions. Currently, IK is primarily diagnosed on clinical grounds supplemented by microbiological investigations such as microscopic examination with stains, and culture and sensitivity testing. Although this is the most widely accepted practice adopted in most regions, such an approach is challenged by several factors, including indistinguishable clinical features shared among different causative organisms, polymicrobial infection, long diagnostic turnaround time, and variably low culture positivity rate. In this review, we aim to provide a comprehensive overview of the current diagnostic armamentarium of IK, encompassing conventional microbiological investigations, molecular diagnostics (including polymerase chain reaction and mass spectrometry), and imaging modalities (including anterior segment optical coherence tomography and in vivo confocal microscopy). We also highlight the potential roles of emerging technologies such as next-generation sequencing, artificial intelligence-assisted platforms. and tele-medicine in shaping the future diagnostic landscape of IK.