Predisposing factors, microbiological features and outcomes of patients with clinical presumed concomitant microbial and herpes simplex keratitis

Infectious Keratitis in Patients Over 65: A Review on Treatment and Preserving Eyesight

Infectious keratitis (IK) represents a significant global health concern, ranking as the fifth leading cause of blindness worldwide despite being largely preventable and treatable. Elderly populations are particularly susceptible due to age-related changes in immune response and corneal structure. However, research on IK in this demographic remains scarce. Age-related alterations such as increased permeability and reduced endothelial cell density further compound susceptibility to infection and hinder healing mechanisms. Additionally, inflammaging, characterized by chronic inflammation that develops with advanced age, disrupts the ocular immune balance, potentially exacerbating IK and other age-related eye diseases. Understanding these mechanisms is paramount for enhancing IK management, especially in elderly patients. This review comprehensively assesses risk factors, clinical characteristics, and management strategies for bacterial, viral, fungal, and acanthamoeba keratitis in the elderly population, offering crucial insights for effective intervention.

Herpes simplex keratitis: A brief clinical overview

The aim of our minireview is to provide a brief overview of the diagnosis, clinical aspects, treatment options, management, and current literature available regarding herpes simplex keratitis (HSK). This type of corneal viral infection is caused by the herpes simplex virus (HSV), which can affect several tissues, including the cornea. One significant aspect of HSK is its potential to cause recurrent episodes of inflammation and damage to the cornea. After the initial infection, the HSV can establish a latent infection in the trigeminal ganglion, a nerve cluster near the eye. The virus may remain dormant for extended periods. Periodic reactivation of the virus can occur, leading to recurrent episodes of HSK. Factors triggering reactivation include stress, illness, immunosuppression, or trauma. Recurrent episodes can manifest in different clinical patterns, ranging from mild epithelial involvement to more severe stromal or endothelial disease. The severity and frequency of recurrences vary among individuals. Severe cases of HSK, especially those involving the stroma and leading to scarring, can result in vision impairment or even blindness in extreme cases. The cornea's clarity is crucial for good vision, and scarring can compromise this, potentially leading to visual impairment. The management of HSK involves not only treating acute episodes but also implementing long-term strategies to prevent recurrences and attempt repairs of corneal nerve endings via neurotization. Antiviral medications, such as oral Acyclovir or topical Ganciclovir, may be prescribed for prophylaxis. The immune response to the virus can contribute to corneal damage. Inflammation, caused by the body's attempt to control the infection, may inadvertently harm the corneal tissues. Clinicians should be informed about triggers and advised on measures to minimize the risk of reactivation. In summary, the recurrent nature of HSK underscores the importance of both acute and long-term management strategies to preserve corneal health and maintain optimal visual function.

Monitoring the Progression of Clinically Suspected Microbial Keratitis Using Convolutional Neural Networks

Purpose

For this study, we aimed to determine whether a convolutional neural network (CNN)-based method (based on a feature extractor and an identifier) can be applied to monitor the progression of keratitis while managing suspected microbial keratitis (MK).

Methods

This multicenter longitudinal cohort study included patients with suspected MK undergoing serial external eye photography at the 5 branches of Chang Gung Memorial Hospital from August 20, 2000, to August 19, 2020. Data were primarily analyzed from January 1 to March 25, 2022. The CNN-based model was evaluated via F1 score and accuracy. The area under the receiver operating characteristic curve (AUROC) was used to measure the precision-recall trade-off.

Results

The model was trained using 1456 image pairs from 468 patients. In comparing models via only training the identifier, statistically significant higher accuracy (P  < 0.05) in models via training both the identifier and feature extractor (full training) was verified, with 408 image pairs from 117 patients. The full training EfficientNet b3-based model showed 90.2% (getting better) and 82.1% (becoming worse) F1 scores, 87.3% accuracy, and 94.2% AUROC for 505 getting better and 272 becoming worse test image pairs from 452 patients.

Conclusions

A CNN-based approach via deep learning applied in suspected MK can monitor the progress/regress during treatment by comparing external eye image pairs.

Translational Relevance

The study bridges the gap between the investigation of the state-of-the-art CNN-based deep learning algorithm applied in ocular image analysis and the clinical care of suspected patients with MK.

Role of tear exosomes in the spread of herpes simplex virus type 1 in recurrent herpes simplex keratitis

BACKGROUND

Herpes simplex keratitis (HSK) is the most common but serious infectious keratitis with high recurrence. It is predominantly caused by herpes simplex virus type 1 (HSV-1). The spread mechanism of HSV-1 in HSK is not entirely clear. Multiple publications indicate that exosomes participate in the intercellular communication process during viral infections. However, there is rare evidence that HSV-1 spreads in HSK by exosomal pathway. This study aims to investigate the relationship between the spread of HSV-1 and tear exosomes in recurrent HSK.

METHODS

Tear fluids collected from total 59 participants were included in this study. Tear exosomes were isolated by ultracentrifugation, then identified by silver staining and western blot. The size was determined by dynamic light scattering (DLS). The viral biomarkers were identified by western blot. The cellular uptake of exosomes was studied using labelled exosomes.

RESULTS

Tear exosomes were indeed enriched in tear fluids. Collected exosomes own normal diameters consistent with related reports. The exosomal biomarkers existed in tear exosomes. Labelled exosomes were successfully taken up by human corneal epithelial cells (HCEC) in large numbers in a short time. After cellular uptake, HSK biomarkers were detectable by western blot in infected cells.

CONCLUSIONS

Tear exosomes should be the latent sites of HSV-1 in recurrent HSK and might be involved in the spread of HSV-1. Besides, this study verifies HSV-1 genes can be indeed transferred between cells by exosomal pathway, providing new inspiration for the clinical intervention and treatment as well as the drug discovery of recurrent HSK.

Epidemiology and Economic Cost Analysis of Microbial Keratitis from a Tertiary Referral Hospital in Australia

Microbial keratitis is the most common cause of infective vision loss. The causative organism varies by region, and most cases require intensive antimicrobial therapy. The purpose of this study was to analyse the causative organisms of microbial keratitis, its presentation and economic burden from a tertiary referral hospital in Australia. A retrospective review of 160 cases of microbial keratitis was performed, over a 5-year period from 2015–2020. A wide variety of costs were considered to determine the economic burden, using standardized data from the Independent Hospital Pricing Authority and the cost of personal income loss. Our study showed the most commonly occurring pathogens were Herpes Simplex (16%), Staphylococcus aureus (15.1%) and Pseudomonas aeruginosa (14.3%). A total of 59.3% of patients were admitted, with a median length of admission of 7 days. Median cost for all presentations of microbial keratitis was AUD 8013 (USD 5447), with costs significantly increasing with admission. The total annual cost of microbial keratitis within Australia is estimated to be AUD 13.58 million (USD 9.23 million). Our findings demonstrate that microbial keratitis represents a significant economic burden for eye-related diseases and the key driving factor for the cost is the length of admission. Minimizing the duration of admission, or opting for outpatient management where appropriate, would significantly reduce the cost of treatment for microbial keratitis.

Effectiveness of Commonly Used Contact Lens Disinfectants Against SARS-CoV-2

OBJECTIVE

To assess the effect of commonly used contact lens disinfectants against severe acute respiratory syndrome corona virus 2 (SARS-CoV-2).

METHODS

The efficacy of five disinfectant solutions against SARS-CoV-2 was tested in the presence and absence of contact lenses (CLs). Three types of unused CLs (hard gas permeable, soft hydrogel, and soft silicone hydrogel) and worn silicone hydrogel CLs were tested. Contact lenses were infected with SARS-CoV-2 and disinfected at various times, with and without rubbing and rinsing, as per manufacturer's instructions. Reverse-transcriptase polymerase chain reaction (RT-PCR) and viability polymerase chain reaction (PCR) were applied to detect SARS-CoV-2 RNA and viral infectivity of SARS-CoV-2, respectively.

RESULTS

In the presence of SARS-CoV-2-infected CLs, no SARS-CoV-2 RNA could be detected when disinfectant solutions were used according to the manufacturer's instructions. When SARS-Co-V2-infected CLs were disinfected without the rub-and-rinse step, SARS-CoV-2 RNA was detected at almost each time interval with each disinfecting solution tested for both new and worn CLs. In the absence of CLs, viable SARS-CoV-2 was detected with all disinfectant solutions except Menicon Progent at all time points.

CONCLUSIONS

Disinfectant solutions effectively disinfect CLs from SARS-CoV-2 if manufacturer's instructions are followed. The rub-and-rinse regimen is mainly responsible for disinfection. The viability PCR may be useful to indicate potential infectiousness.

First reported case of corneal infection caused by Atopobium vaginae

A man in his 20s, with irritation, pain and photophobia in the left eye, was clinically diagnosed with herpes simplex virus nummular keratitis at our institute and advised topical antivirals and corticosteroids, causing resolution of active infiltrates. The infection recurred after 7 months and the patient did not respond to the previous regimen, so corneal scraping was sent for microbiological evaluation. Gram-positive bacilli grew on culture, which were identified as Atopobium vaginae using VITEK 2 Compact system (bioMérieux, Marcy l'Etoile, France). Gatifloxacin eye drops were added based on antibiotic sensitivity patterns. Infiltrates resolved completely, leaving behind residual scars without any recurrences. This is the first reported case of corneal infection caused by A. vaginae, a bacterium known to reside in the urogenital tract. It caused secondary corneal infection in a case of recurrent herpes simplex keratitis. Species identification systems like VITEK 2 Compact can help identify such rare bacteria with great accuracy.

Clinical and microbiological analysis of fungal keratitis in Toronto, Canada: A 20-year study

Fungal keratitis is a devastating and difficult-to-treat ocular infection with high morbidity. Understanding geographic microbiological and clinical trends helps to guide rapid and effective treatment. We therefore report the characteristics and outcomes of fungal keratitis in Toronto, Canada over a twenty-year period. An electronic search of microbiology records at University Health Network, Toronto, ON, Canada identified all patients with positive corneal fungal culture over a 20-year period seen at our tertiary referral cornea practice. Review of corresponding patient charts identified demographic and microbiological details, clinical course, treatment regimen, and final outcomes associated with each episode of culture-positive fungal keratitis. Forty-six patients with fifty-one discrete fungal keratitis episodes were included. Five patients experienced recurrent fungal keratitis. Candida species accounted for 60.8% of positive fungal cultures, followed by Filamentous species at 35.3%. Preferred initial anti-fungal treatment was topical amphotericin at 36.7% followed by topical voriconazole at 32.6%. Surgical intervention was required in 48.9% with therapeutic penetrating keratoplasty being the most common procedure (22.4%). Final visual acuity (VA) of < 20/200 was attributed to 58% of patients in this study. Risk factors for poor outcomes included poor VA, topical steroid use at presentation, Candida involvement, history of ocular surface disease, organic ocular trauma, or prior corneal transplantation. Candida is the most frequent keratomycotic pathogen in Toronto. Risk factors for poor visual outcome include prior corneal transplantation, ocular surface disease/trauma, or pre-existing topical steroid use. Early suspicion, diagnosis and treatment are paramount for best clinical outcomes.