Candida species causing fungal keratitis: molecular identification, antifungal susceptibility, biofilm formation, and clinical aspects

The study aimed to evaluate the clinical aspects, molecular identification, biofilm formation, and antifungal susceptibility profile of Candida species isolated from fungal keratitis. Thirteen Candida isolates from 13 patients diagnosed with Candida keratitis were retrieved and grown in pure culture. Species identification was performed by micromorphology analysis and ITS-rDNA sequencing. The broth microdilution method tested the minimum inhibitory concentration (MIC) of four antifungal drugs (fluconazole, amphotericin B, voriconazole, and anidulafungin). The biofilms were cultured and incubated with antifungal drugs for 24 h. The XTT reduction assay measured the biofilm activity. Biofilm MICs were calculated based on a 50% reduction in metabolic activity compared with the activity of the drug-free control. Among isolates, two were C. albicans, 10 were C. parapsilosis (sensu stricto), and one was C. orthopsilosis. All isolates were classified as susceptible or intermediate to all four antifungal drugs. Four isolates were very low biofilm producers (30%). Nine isolates were biofilm producers, and all biofilm samples were unsusceptible to all drugs tested. Previous ocular surgery was the most common underlying condition for fungal keratitis (84.6%), and C. parapsilosis was the most frequent Candida species (76.9%). Four patients (30.7%) needed keratoplasty, whereas two (15.3%) required evisceration. The biofilm formation ability of Candida isolates decreased antifungal susceptibility compared with planktonic cells. Despite in vitro antifungal susceptibility, almost half of the patients were unresponsive to clinical treatment and needed surgery.

Eye fungal infections: a mini review

Ocular fungal infections annually affect more than one million individuals worldwide. The management of these infections is problematic, mainly due to the limited availability of effective antifungal agents. Thus, ocular infections are increasingly recognized as important causes of morbidity and blindness, especially keratitis and endophthalmitis. Thus, this review aims to demonstrate the importance of fungal eye infections through the description of the main related aspects, with emphasis on the treatment of these infections. For this purpose, a search for scientific articles was conducted in databases, such as Medline, published from 2000 onwards, addressing important aspects involving fungal eye infections. In addition, this work highlighted the limited therapeutic arsenal available and the severity associated with these infections. Thus, highlighting the importance of constantly updating knowledge about these pathologies, as it contributes to agility in choosing the available and most appropriate therapeutic alternatives, aiming at positive and minimally harmful results for that particular patient.

Diagnostic performance of deep learning in infectious keratitis: a systematic review and meta-analysis protocol

INTRODUCTION

Infectious keratitis (IK) represents the fifth-leading cause of blindness worldwide. A delay in diagnosis is often a major factor in progression to irreversible visual impairment and/or blindness from IK. The diagnostic challenge is further compounded by low microbiological culture yield, long turnaround time, poorly differentiated clinical features and polymicrobial infections. In recent years, deep learning (DL), a subfield of artificial intelligence, has rapidly emerged as a promising tool in assisting automated medical diagnosis, clinical triage and decision-making, and improving workflow efficiency in healthcare services. Recent studies have demonstrated the potential of using DL in assisting the diagnosis of IK, though the accuracy remains to be elucidated. This systematic review and meta-analysis aims to critically examine and compare the performance of various DL models with clinical experts and/or microbiological results (the current 'gold standard') in diagnosing IK, with an aim to inform practice on the clinical applicability and deployment of DL-assisted diagnostic models.

METHODS AND ANALYSIS

This review will consider studies that included application of any DL models to diagnose patients with suspected IK, encompassing bacterial, fungal, protozoal and/or viral origins. We will search various electronic databases, including EMBASE and MEDLINE, and trial registries. There will be no restriction to the language and publication date. Two independent reviewers will assess the titles, abstracts and full-text articles. Extracted data will include details of each primary studies, including title, year of publication, authors, types of DL models used, populations, sample size, decision threshold and diagnostic performance. We will perform meta-analyses for the included primary studies when there are sufficient similarities in outcome reporting.

ETHICS AND DISSEMINATION

No ethical approval is required for this systematic review. We plan to disseminate our findings via presentation/publication in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42022348596.

Immunity to pathogenic fungi in the eye

Fusarium, Aspergillus and Candida are important fungal pathogens that cause visual impairment and blindness in the USA and worldwide. This review will summarize the epidemiology and clinical features of corneal infections and discuss the immune and inflammatory responses that play an important role in clinical disease. In addition, we describe fungal virulence factors that are required for survival in infected corneas, and the activities of neutrophils in fungal killing, tissue damage and cytokine production.

Outcomes of therapeutic penetrating keratoplasty in Pythium insidiosum keratitis managed with a combination of antibiotics

Purpose

To describe the clinical outcomes of therapeutic penetrating keratoplasty (TPK) in patients with Pythium insidiosum keratitis following treatment with anti-pythium therapy (APT) consisting of linezolid and azithromycin.

Methods

A retrospective review of medical records from May 2016 to December 2019 of patients with P. insidiosum keratitis was carried out. Patients who were treated with APT for a minimum of 2 weeks and then subsequently underwent TPK were included in the study. Data on demographic characteristics, clinical features, microbiology characteristics, and intraoperative details, postoperative outcomes were documented.

Results

A total of 238 cases of Pythium keratitis were seen during the study period and 50 cases that satisfied the inclusion criteria were included. The median of the geometric mean of the infiltrate was 5.6 mm (IQR 4.0-7.2 mm). The patients received topical APT for a median of 35 days (IQR 25-56) prior to surgery. The most common indication of TPK was worsening keratitis (41/50, 82%). No recurrence of infection was observed. An anatomically stable globe was noted in 49/50 eyes (98%). The median graft survival rate was 2.4 months. A clear graft was present in 10 eyes (20%) with a final median visual acuity of 20/125 after a median follow-up period of 18.4 months (IQR 11-26 months). Graft size of less than 10 mm [OR: 5.824 (CI:1.292-41.6), P = 0.02] was found to be significantly associated with a clear graft.

Conclusion

Performing TPK following the administration of APT has good anatomical outcomes. A smaller graft of <10 mm was associated with a higher chance of graft survival.

Rapid detection and diagnosis of herpetic keratitis using quantitative microfluidic polymerase chain reaction system for herpes simplex and varicella-zoster virus DNA: a case series

BACKGROUND

A microfluidic real-time polymerase chain reaction (PCR) system can rapidly detect the viral DNA in specimens. Detection of herpes simplex virus (HSV) and varicella-zoster virus (VZV) DNA in tears is a useful diagnostic tool for herpes simplex virus keratitis (HSK) and herpes zoster ophthalmicus (HZO).

METHODS

In total, 20 patients were included in this cross-sectional study. Among them, 8 patients with infectious epithelial HSK and 12 patients with HZO were included in HSK and HZO groups, respectively. In addition, 8 patients with non-herpetic keratitis and 4 healthy individuals without keratitis were included in the control group. Numbers of HSV and VZV DNA copies in tears of all patients and individuals were evaluated using a microfluidic real-time PCR system. Regarding HSV/VZV DNA test, tear specimens were collected by filter paper method using Schirmer's test paper, and subsequently, DNA was extracted from the filter paper using an automated nucleic acid extractor. Afterward, quantitative PCR was performed using a microfluidic real-time PCR system.

RESULTS

From tear collection to real-time PCR result determination, the HSV/VZV DNA test took approximately 40 min. In the HSK group, the sensitivity and specificity of the HSV DNA tests were 100% each. The median value (range) of number of HSV DNA copies for affected eyes was 3.4 × 10⁵ copies/μL (under a lower detection limit of 7.6). In the HZO group, the sensitivity and specificity of the VZV DNA tests were 100% each. The median value (range) of number of VZV DNA copies for affected eyes was 5.3 × 10⁵ copies/μL (under a lower detection limit of 5.6 × 10^-2).

CONCLUSION

In conclusion, quantitative PCR for HSV and VZV DNA in tears using a microfluidic real-time PCR system is useful for diagnosing and monitoring HSK and HZO.

Predatory bacteria can reduce Pseudomonas aeruginosa induced corneal perforation and proliferation in a rabbit keratitis model

PURPOSE

Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included.

METHODS

Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic ΔlasR mutant and co-injected with PBS or B. bacteriovorus. After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines.

RESULTS

We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n = 24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n = 25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The ΔlasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus.

CONCLUSION

These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Atypical microbial keratitis

Atypical microbial keratitis refers to corneal infections caused by micro-organisms not commonly encountered in clinical practice. Unlike infections caused by common bacteria, cases of atypical microbial keratitis are often associated with worse clinical outcomes and visual prognosis. This is due to the challenges in the identification of causative organisms with standard diagnostic techniques, resulting in delays in the initiation of appropriate therapies. Furthermore, due to the comparatively lower incidence of atypical microbial keratitis, there is limited literature on effective management strategies for some of these difficult to manage corneal infections. This review highlights the current management and available evidence of atypical microbial keratitis, focusing on atypical mycobacteria keratitis, nocardia keratitis, achromobacter keratitis, and pythium keratitis. It will also describe the management of two uncommonly encountered conditions, infectious crystalline keratopathy and post-refractive infectious keratitis. This review can be used as a guide for clinicians managing patients with such challenging corneal infections.

Ocular Mycobacterium haemophilum infection originating in the cornea: a case report

BACKGROUND

Mycobacterium haemophilum is a slow-growing non-chromogenic nontuberculous Mycobacterium species that can cause skin infection or arthritis in an immunocompromised population or in children. Primary infection of the healthy adult cornea is rare. The special requirements for culture make this pathogen difficult to diagnose. The study aims to report the clinical manifestation and treatment process of corneal infection and notify the awareness of M. Haemophilus keratitis among clinicians. This is the first case report of primary M. haemophilum infection in the cornea of healthy adults reported in the literature.

CASE PRESENTATION

A 53-year-old healthy goldminer presented with left eye redness and a history of vision loss for four months. The patient was misdiagnosed with herpes simplex keratitis until M. haemophilum was detected using high-throughput sequencing. Penetrating keratoplasty was performed, and a large number of mycobacteria were detected by Ziehl-Neelsen staining of the infected tissue. Three months later, the patient developed conjunctival and eyelid skin infections that manifested as caseous necrosis of the conjunctiva and skin nodules. After excision and debridement of the conjunctival lesions and systemic antituberculosis drug treatment for 10 months, the patient was cured.

CONCLUSION

M. haemophilum could cause primary corneal infection in healthy adults, which is an infrequent or rare infection. Owing to the need for special bacterial culture conditions, conventional culture methods do not provide positive results. High-throughput sequencing can rapidly identify the presence of bacteria, which aids in early diagnosis and timely treatment. Prompt surgical intervention is an effective treatment option for severe keratitis. Long-term systemic antimicrobial therapy is crucial.

Eosinophilic Keratoconjunctivitis in Cats

Eosinophilic keratitis is a disease of the feline ocular surface. It is characterized by conjunctivitis, white to pink raised plaques on the corneal and conjunctival surfaces, corneal vascularization, and variable ocular pain. Cytology is the diagnostic test of choice. Identification of eosinophils in a corneal cytology sample usually confirms the diagnosis, although lymphocytes, mast cells, and neutrophils are often present concurrently. Immunosuppressives are the mainstay of therapy, topically or systemically. The role of feline herpesvirus-1 in the pathogenesis of eosinophilic keratoconjunctivitis (EK) remains unclear. Eosinophilic conjunctivitis is a less common manifestation of EK and presents as severe conjunctivitis without corneal involvement.

Impact of implementation of polymerase chain reaction on diagnosis, treatment, and clinical course of Acanthamoeba keratitis

PURPOSE

Acanthamoeba keratitis (AK) is a painful and possibly sight-threatening ocular infection. While the correct diagnosis and specific treatment in the early stages significantly improve the prognosis, the disease is often misdiagnosed and in clinical examination confused with other forms of keratitis. Polymerase chain reaction (PCR) for the detection of AK was first introduced in our institution in December 2013 to improve the timely diagnosis of AK. The aim of this study was to assess the impact of implementation of Acanthamoeba PCR on the diagnosis and treatment of the disease in a German tertiary referral center.

PATIENTS AND METHODS

Patients treated for Acanthamoeba keratitis between 1st of January 1993 and 31st of December 2021 in the Department of Ophthalmology of the University Hospital Duesseldorf were identified retrospectively via in-house registries. Evaluated parameters include age, sex, initial diagnosis, method of correct diagnosis, duration of symptoms until correct diagnosis, contact lens use, visual acuity, and clinical findings as well as medical and surgical therapy by keratoplasty (pKP). In order to assess the impact of implementation of Acanthamoeba PCR, the cases were divided into two groups (before (pre-PCR group) and after PCR implementation (PCR group).

RESULTS

Seventy-five patients with Acanthamoeba keratitis were included (69.3% female, median age 37 years). Eighty-four percent (63/75) of all patients were contact lens wearers. Until PCR was available, 58 patients with Acanthamoeba keratitis were diagnosed either clinically (n = 28), by histology (n = 21), culture (n = 6), or confocal microscopy (n = 2) with a median duration until diagnosis of 68 (18; 109) days. After PCR implementation, in 17 patients, the diagnosis was established with PCR in 94% (n = 16) and median duration until diagnosis was significantly shorter with 15 (10; 30.5) days. A longer duration until correct diagnosis correlated with a worse initial visual acuity (p = 0.0019, r = 0.363). The number of pKP performed was significantly lower in the PCR group (5/17; 29.4%) than in the pre-PCR group (35/58; 60.3%) (p = 0.025).

CONCLUSIONS

The choice of diagnostic method and especially the application of PCR have a significant impact on the time to diagnosis and on the clinical findings at the time of confirmation of diagnosis and the need for penetrating keratoplasty. In contact lens-associated keratitis, the first crucial step is to take AK into consideration and perform a PCR test as timely confirmation of diagnosis of AK is imperative to prevent long-term ocular morbidity.

Characteristics and Management of Ocular Involvement in Individuals with Mpox Disease

Ocular complications of mpox infection have a prevalence of 1% in the current outbreak. Although conjunctivitis is the most common presentation, corneal involvement may occur. Tecovirimat is recommended for severe ocular mpox involvement.

A Review of Monkeypox Ocular Manifestations and Complications: Insights for the 2022 Outbreak

Monkeypox (MPVX) infection has been associated with multiorgan presentations. Thus, monkeypox infection's early and late complications are of particular concern, prompting health systems to decipher threatening sequels and their possible countermeasures. The current article will review the clinical signs and symptoms of the present and former outbreaks, differential diagnoses, workup and treatment of the ocular manifestations of MPXV infection in detail. One of the uncommon yet considerable MPXV complications is ocular involvement. These injuries are classified as (1) more frequent and benign lesions and (2) less common and vision-threatening sequels. Conjunctivitis, blepharitis and photophobia are the most uncomplicated reported presentations. Moreover, MPXV can manifest as eye redness, frontal headache, orbital and peri-ocular rashes, lacrimation and ocular discharge, subconjunctival nodules and, less frequently, as keratitis, corneal ulceration, opacification, perforation and blindness. The ocular manifestations have been less frequent and arguably less severe within the current outbreak. Despite the possibility of underestimation, the emerging evidence from observational investigations documented rates of around 1% for ocular involvement in the current outbreak compared to a 9-23% incidence in previous outbreaks in the endemic countries. The history of smallpox immunization is a protective factor against these complications. Despite a lack of definite and established treatment, simple therapies like regular lubrication and prophylactic use of topical antibiotics may be considered for MPXV ocular complications. Timely administration of specific antivirals may also be effective in severe cases. Monkeypox usually has mild to moderate severity and a self-limited course. However, timely recognition and proper management of the disease could reduce the risk of permanent ocular sequelae and disease morbidity.

Therapeutic effect of Atractylenolide I on Aspergillus fumigatus keratitis by affecting MyD88/ NF-κB pathway and IL-1β, IL-10 expression

PURPOSE

Atractylenolide I (AT-I) is a natural sesquiterpene with anti-inflammatory effects. The purpose of this study was to research the anti-inflammatory effect of AT-I on Aspergillus fumigatus(A. fumigatus) keratitis in mice.

METHODS

Cytotoxicity test and cell scratch test were used to determine the therapeutic concentrations of corneal infections. In vivo and in vitro studies, mouse cornea and human corneal epithelial cells (HCECs) infected with A. fumigatus were treated with AT-I or dimethyl sulfoxide (DMSO). Then, to analyze the effect of AT-I on inflammatory response, namely neutrophil or macrophage recruitment and the expression of cytokines involving MyD88, NF-κB, interleukin 1β (IL-1β) and interleukin 10 (IL-10). To study the effects of the drug, the techniques used include slit-lamp photography, immunofluorescence, myeloperoxidase (MPO) detection, quantitative real-time polymerase chain reaction (QRT-PCR), and western blot. At the same time, in order to explore the combined effect of the drug and natamycin, slit-lamp photographs and clinical scores were used to visually display the disease process.

RESULTS

No cytotoxicity was observed under the action of AT-I at a concentration of 800 μM. In mouse models, AT-I significantly suppressed inflammatory responses, reduced neutrophil and macrophage recruitment, and decreased myeloperoxidase levels early in infection. Studies have shown that AT-I may reduce the levels of IL-1β and IL-10 by inhibiting the MyD88/ NF-κB pathway. The drug combined with natamycin can increase corneal transparency in infected mice.

CONCLUSION

AT-I may inhibit MyD88 / NF-κB pathway and the secretion of inflammatory factors IL-1 β and IL-10 to achieve the therapeutic effect of fungal keratitis.

Keratitis following leech therapy for periocular eczematous dermatitis: a case report

BACKGROUND

The medicinal leech therapy (MLT) is a kind of complementary treatment method used for various diseases. The leeches (Hirudo medicinalis) have been used for more than 2500 years by surgeons. The substances presenting in the saliva of leeches have anti-inflammatory, anticoagulant, platelet inhibitory, thrombin regulatory, analgesic, extracellular matrix degradative and antimicrobial effects. The method is cheap, easy to apply, effective and its mechanisms of action have been clarified for specific diseases. Infection particularly Aeromonas infection is the most common complication of MLT.

CASE PRESENTATION

In this case report, a keratitis case developing after leech therapy applied for the periocular and facial eczematous dermatitis lesions will be presented. The patient referred to our hospital with decreased vision, ocular pain, stinging, redness and lacrimation complaints. A large corneal epithelial defect with irregular margins, dying by fluorescein, involving more than inferior half of cornea and conjunctival hyperemia were seen in the right eye. No agent was determined in microbiological investigation, as the patient had used topical moxifloxacin eye drop which was commenced in another clinic before applying to us. The patient was treated with fortified vancomycin and ceftazidime, before using besifloxacin with the diagnosis of bacterial keratitis. Three weeks later epithelial defect improved completely leaving an opacity and neovascularization.

CONCLUSIONS

MLT should be performed by certified physicians with sterile medicinal leeches and precautious antibiotics should be used before MLT for prevention against potential infections.

A Case of Nocardia africana-Related Keratitis

Nocardia spp. are gram positive, aerobic, weakly acid-fast bacteria. Nocardia spp. keratitis is a rare ocular infection classically described following corneal injury or vegetative and soil exposure. However, keratitis caused by Nocardia africana had never been reported in the literature. We first reported a 70-year-old male who had a traumatic ocular injury to his left eye a month ago. With his complaint of left eye pain, reduced vision, and light sensitivity, the slit-lamp biomicroscopy showed the superficial multi-lobulated epithelial infiltration located at the inferior cornea with a positive fluorescein stain. Microscopic workup from corneal specimens demonstrated dry and chalky white colonies on blood agar and Lowenstein-Jensen media resembling Nocardia spp. The MALDI-TOF MS analyses using VITEK® MS exhibited N. africana. The corneal lesion was treated with 2% amikacin topical eye drops and responded well. The careful history-taking, precise clinical examinations, and meticulous microscopic assessment were the cornerstones of diagnosis. Definite diagnosis and timely treatment were essential to prevention of ocular morbidity in N. africana.

Fulminant Marginal Keratitis Induced by Atezolizumab, a Programmed Death Ligand 1 Inhibitor for Lung Cancer

Introduction

With the increasing use of immune checkpoint inhibitors, ocular adverse events have gained attention. We describe a case of atypical keratitis presumably induced by atezolizumab, a programmed cell death ligand 1 inhibitor.

Case Presentation

A 73-year-old Japanese woman developed ring-shaped marginal infiltrations with epithelial breakdown of the corneas in both eyes. The patient had advanced small cell lung cancer and had received intravenous carboplatin, etoposide, and atezolizumab. She was treated with topical administration of 0.1% sodium phosphate betamethasone and 0.5% moxifloxacin six times daily. On day 14 following initial presentation, marked reduction of bilateral corneal infiltration was observed. During the succeeding cycles of chemotherapy, marginal keratitis did not recur, and then, the topical steroid was gradually tapered.

Conclusions

Cancer immunotherapy, including atezolizumab, may lead to active T-cell recruitment into the cornea, which result in autoimmune corneal keratitis. We believe that this report is informative to both ophthalmologists and oncologists involved in the treatment of patients receiving cancer immunotherapy.

Vitamin A Deficiency, COVID-19, and Rhino-Orbital Mucormycosis (Black Fungus): An Analytical Perspective

Mucormycosis is a rare but serious opportunistic fungal disease characterized by rhino-orbito-cerebral and pulmonary involvement. It is mainly seen in people with secondary immunosuppression, isolated vitamin A deficiency, measles, and AIDS patients. It showed a rise during the second wave of the COVID-19 epidemic in the spring of 2021 in India, especially in diabetic COVID-19 patients. Vitamin A deficiency is known to cause nutritional immunodeficiency and hence leading the way to increased opportunistic fungal, bacterial, and viral infections. In the eye, it causes keratitis, night blindness, xerophthalmia, conjunctivitis, Bitot spots, keratomalacia, and retinopathy. It also causes decreased tear secretion and deterioration of the anatomical/physiological defense barrier of the eye. The negative impact of vitamin A deficiency has been previously demonstrated in measles, AIDS, and COVID-19. We think that mucormycosis in COVID-19 might be rendered by vitamin A deficiency and that vitamin A supplementation may have preventive and therapeutic values against mucormycosis and other ocular symptoms associated with COVID-19. However, any vitamin A treatment regimen needs to be based on laboratory and clinical data and supervised by medical professionals.

Blepharokeratoconjunctivitis Presumably Caused by Paederus fuscipes, a Beetle: A Case Report

Toxicity of Paederus species to eyes has scarcely been reported. This report presents a case of chemical blepharokeratoconjunctivitis with delayed re-epithelialization caused by Paederus fuscipes in a patient with dry eye after laser-assisted in situ keratomileusis (LASIK). A 47-year-old woman who had undergone LASIK for myopia 10 years prior experienced visual disturbance and pain in her left eye after being hit by a P. fuscipes insect in her eye 1 day prior to evaluation. At the initial presentation, dermatitis around the patient's left eye, eyelid oedema, conjunctival chemosis, corneal epithelial defects, and a best corrected visual acuity (BCVA) of 20/200 were noted. No gram-positive/negative bacteria or indication of cellulitis/elevated inflammation was detected. Administration of topical steroids (betamethasone) and antibiotics (topical: cefmenoxime and levofloxacin; intravenous: ceftriaxone) improved the non-infectious chemical blepharokeratoconjunctivitis; however, the large corneal epithelial defect remained for 10 days. Switching from betamethasone to a preservative-free form facilitated re-epithelialization, and the patient's BCVA improved to 20/16 after 2 months. Ophthalmologists should consider the toxicity of the Paederus species on the ocular surface and eyelid.

Implementing polymeric pseudorotaxanes for boosting corneal permeability and antiaspergillus activity of tolnaftate: formulation development, statistical optimization, ex vivo permeation and in vivo assessment

Fungal keratitis (FK) is a devastating ocular disease that can cause corneal opacity and blindness if not treated effectively. Tolnaftate (TOL) is a selective fungicidal drug against Aspergillus spp. which are among the most common causes of mycotic keratitis. TOL is lipophilic drug with low water solubility and permeation which act as obstacles for its clinical ocular efficacy. Hence, this study aimed to statistically optimize a novel polymeric pseudorotaxanes (PSRs) containing TOL for enhancing its ocular permeability and antifungal effect. For achieving this goal, a full 3¹.2² factorial design was fashioned for preparing and optimizing TOL-PSRs using film hydration technique. Three formulation variables were studied: drug amount (X₁), weight ratio of Pluronics to HPβCD (X₂) and Pluronic system (X₃). Entrapment efficiency percent (EE%) (Y₁), particle size (PS) (Y₂) and zeta potential (ZP) (Y₃) were set as dependent variables. The selected optimal TOL-PSRs (PSR1) showed EE% of 71.55 ± 2.90%, PS of 237.05 ± 12.80 nm and ZP of −32.65 ± 0.92 mV. In addition, PSR1 was compared to conventional polymeric mixed micelles (PMMs) and both carriers significantly increased the drug flux and resulted in higher amount permeated per unit area in 8 h compared to drug suspension. The histopathological studies assured the safety of PSR1 for ocular use. The in vivo susceptibility testing using Aspergillus niger confirmed that PSR1 displayed sustained antifungal activity up to 24 h. The obtained results revealed the admirable potential of PSR1 to be used as novel nanocarriers for promoting TOL ocular delivery.

Toxic Keratopathy Induced by Self-Application of Seawater

To report a case of toxic keratopathy secondary to the self-application of seawater eye drops. A 60-year-old male who presented with unexplained unilateral decrease in vision and corneal thinning. Best-corrected visual acuity was 20/400 OD, slit-lamp examination indicated diffuse corneal edema with central thinning, intact sensation, and no vascularization. Laboratory analysis of the eye drops in conjunction with clinical symptoms and findings was consistent with toxic keratopathy. Toxic keratopathy can masquerade as the other forms of keratopathy, and a thorough history taking and laboratory analysis may help elucidate the diagnosis and avoid significant visual morbidity.

Pythium insidiosum Keratitis: Past, Present, and Future

Pythium insidiosum (PI) is an oomycete, a protist belonging to the clade Stramenopila. PI causes vision-threatening keratitis closely mimicking fungal keratitis (FK), hence it is also labeled as "parafungus". PI keratitis was initially confined to Thailand, USA, China, and Australia, but with growing clinical awareness and improvement in diagnostic modalities, the last decade saw a massive upsurge in numbers with the majority of reports coming from India. In the early 1990s, pythiosis was classified as vascular, cutaneous, gastrointestinal, systemic, and ocular. Clinically, morphologically, and microbiologically, PI keratitis closely resembles severe FK and requires a high index of clinical suspicion for diagnosis. The clinical features such as reticular dot infiltrate, tentacular projections, peripheral thinning with guttering, and rapid limbal spread distinguish it from other microorganisms. Routine smearing with Gram and KOH stain reveals perpendicular septate/aseptate hyphae, which closely mimic fungi and make the diagnosis cumbersome. The definitive diagnosis is the presence of dull grey/brown refractile colonies along with zoospore formation upon culture by leaf induction method. However, culture is time-consuming, and currently polymerase chain reaction (PCR) method is the gold standard. The value of other diagnostic modalities such as confocal microscopy and immunohistopathological assays is limited due to cost, non-availability, and limited diagnostic accuracy. PI keratitis is a relatively rare disease without established treatment protocols. Because of its resemblance to fungus, it was earlier treated with antifungals but with an improved understanding of its cell wall structure and absence of ergosterol, this is no longer recommended. Currently, antibacterials have shown promising results. Therapeutic keratoplasty with good margin (1 mm) is mandated for non-resolving cases and corneal perforation. In this review, we have deliberated on the evolution of PI keratitis, covered all the recently available literature, described our current understanding of the diagnosis and treatment, and the potential future diagnostic and management options for PI keratitis.

Assessment of genotypes, endosymbionts and clinical characteristics of Acanthamoeba recovered from ocular infection

Introduction

Acanthamoeba is an emerging pathogen, infamous for its resilience against antiprotozoal compounds, disinfectants and harsh environments. It is known to cause keratitis, a sight-threatening, painful and difficult to treat corneal infection which is often reported among contact lens wearers and patients with ocular trauma. Acanthamoeba comprises over 24 species and currently 23 genotypes (T1-T23) have been identified.

Aims

This retrospective study was designed to examine the Acanthamoeba species and genotypes recovered from patients with Acanthamoeba keratitis (AK), determine the presence of endosymbionts in ocular isolates of Acanthamoeba and review the clinical presentations.

Methodology

Thirteen culture-confirmed AK patients treated in a tertiary eye care facility in Hyderabad, India from February to October 2020 were included in this study. The clinical manifestations, medications and visual outcomes of all patients were obtained from medical records. The Acanthamoeba isolates were identified by sequencing the ribosomal nuclear subunit (rns) gene. Acanthamoeba isolates were assessed for the presence of bacterial or fungal endosymbionts using molecular assays, PCR and fluorescence in situ hybridization (FISH).

Results

The mean age of the patients was 33 years (SD ± 17.4; 95% CI 22.5 to 43.5 years). Six (46.2%) cases had AK associated risk factors; four patients had ocular trauma and two were contact lens wearers. A. culbertsoni (6/13, 46.2%) was the most common species, followed by A. polyphaga and A. triangularis. Most of the isolates (12/13) belonged to genotype T4 and one was a T12; three sub-clusters T4A, T4B, and T4F were identified within the T4 genotype. There was no significant association between Acanthamoeba types and clinical outcomes. Eight (61.5%) isolates harboured intracellular bacteria and one contained Malassezia restricta. The presence of intracellular microbes was associated with a higher proportion of stromal infiltrates (88.9%, 8/9), epithelial defect (55.6%, 5/9) and hypopyon (55.6%, 5/9) compared to 50% (2/4), 25% (1/4) and 25% (1/4) AK cases without intracellular microbes, respectively.

Conclusions

Genotype T4 was the predominant isolate in southern India. This is the second report of T12 genotype identified from AK patient in India, which is rarely reported worldwide. The majority of the Acanthamoeba clinical isolates in this study harboured intracellular microbes, which may impact clinical characteristics of AK.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07741-4.