Diversity of microbial species implicated in keratitis: a review

Updates in Diagnostic Imaging for Infectious Keratitis: A Review

Infectious keratitis (IK) is among the top five leading causes of blindness globally. Early diagnosis is needed to guide appropriate therapy to avoid complications such as vision impairment and blindness. Slit lamp microscopy and culture of corneal scrapes are key to diagnosing IK. Slit lamp photography was transformed when digital cameras and smartphones were invented. The digital camera or smartphone camera sensor's resolution, the resolution of the slit lamp and the focal length of the smartphone camera system are key to a high-quality slit lamp image. Alternative diagnostic tools include imaging, such as optical coherence tomography (OCT) and in vivo confocal microscopy (IVCM). OCT's advantage is its ability to accurately determine the depth and extent of the corneal ulceration, infiltrates and haze, therefore characterizing the severity and progression of the infection. However, OCT is not a preferred choice in the diagnostic tool package for infectious keratitis. Rather, IVCM is a great aid in the diagnosis of fungal and Acanthamoeba keratitis with overall sensitivities of 66-74% and 80-100% and specificity of 78-100% and 84-100%, respectively. Recently, deep learning (DL) models have been shown to be promising aids for the diagnosis of IK via image recognition. Most of the studies that have developed DL models to diagnose the different types of IK have utilised slit lamp photographs. Some studies have used extremely efficient single convolutional neural network algorithms to train their models, and others used ensemble approaches with variable results. Limitations of DL models include the need for large image datasets to train the models, the difficulty in finding special features of the different types of IK, the imbalance of training models, the lack of image protocols and misclassification bias, which need to be overcome to apply these models into real-world settings. Newer artificial intelligence technology that generates synthetic data, such as generative adversarial networks, may assist in overcoming some of these limitations of CNN models.

Elucidating the Molecular Interactions between Lipids and Lysozyme: Evaporation Resistance and Bacterial Barriers for Dry Eye Disease

Dry eye disease (DED) is a chronic condition characterized by ocular dryness and inflammation. The tear film lipid layer (TFLL) is the outermost layer composed of lipids and proteins that protect the ocular surface. However, environmental contaminants can disrupt its structure, potentially leading to DED. Although the importance of tear proteins in the TFLL functionality has been clinically recognized, the molecular mechanisms underlying TFLL-protein interactions remain unclear. In this study, we investigated tear protein-lipid interactions and analyzed their role in the TFLL functionality. The results show that lysozyme (LYZ) increases the stability of the TFLL by reducing its surface tension and increasing its surface pressure, resulting in increased TFLL evaporation and bacterial invasion resistance, with improved wettability and lubrication performance. These findings highlight the critical role of LYZ in maintaining ocular health and provide potential avenues for investigating novel approaches to DED treatment and patient well-being.

Bacterial keratitis in a tertiary hospital in São Paulo: a 21-year review of the epidemiological, laboratory, and clinical data

Infectious keratitis is a sight-threatening condition that is usually an ocular emergency. The visual outcome depends on prompt and accurate clinical management as well as geographic and epidemiological awareness. We conducted a retrospective observational study to define the epidemiological and laboratory profile, as well as the clinical course of bacterial keratitis in a tertiary hospital in São Paulo over 21 years. Information about age, sex, predisposing factors, topical and surgical treatment, visual acuity, ulcers' classification, bacterioscopy, culture, and antibiotic sensitivity tests were collected. This study included 160 patients. The mean age was 65.1 ± 18.4 years and risk factors were identified in 83.1 % of the patients. Empirical topical fortified cephalosporin with an aminoglycoside or fourth-generation fluoroquinolone was curative for 66.2 % of the cases. The mean treatment duration was 22.5 ± 9 days. The mean variation of visual acuity was -0.25 logMAR, p < 0.001. Culture revealed 64 % of Gram-positive bacteria. All Gram-positive bacteria were sensitive to cephalothin, vancomycin, and quinolones. All Gram-negative bacteria were sensitive to gentamicin, tobramycin, amikacin, and ciprofloxacin. These findings reinforce the importance of prompt empirical treatment of severe corneal ulcers with a fortified cephalosporin and aminoglycoside or a fourth-generation fluoroquinolone as there are equally effective. Collected data was insufficient to evaluate resistance of ocular infections over time in this population.

Managing Corneal Infections: Out with the old, in with the new?

There have been multiple reports of eye infections caused by antibiotic-resistant bacteria, with increasing evidence of ineffective treatment outcomes from existing therapies. With respect to corneal infections, the most commonly used antibiotics (fluoroquinolones, aminoglycosides, and cephalosporines) are demonstrating reduced efficacy against bacterial keratitis isolates. While traditional methods are losing efficacy, several novel technologies are under investigation, including light-based anti-infective technology with or without chemical substrates, phage therapy, and probiotics. Many of these methods show non-selective antimicrobial activity with potential development as broad-spectrum antimicrobial agents. Multiple preclinical studies and a limited number of clinical case studies have confirmed the efficacy of some of these novel methods. However, given the rapid evolution of corneal infections, their treatment requires rapid institution to limit the impact on vision and prevent complications such as scarring and corneal perforation. Given their rapid effects on microbial viability, light-based technologies seem particularly promising in this regard.

The Case for Fungal Keratitis to Be Accepted as a Neglected Tropical Disease

Amongst the treatable cause of blindness among young people, fungal keratitis ranks high. There are an estimated 1,051,787 to 1,480,916 eyes affected annually, with 8–11% of patients having to have the eye removed. Diagnosis requires a corneal scraping, direct microscopy and fungal culture with a large number of airborne fungi implicated. Treatment involves the intensive application of antifungal eye drops, preferably natamycin, often combined with surgery. In low-resource settings, inappropriate corticosteroid eye drops, ineffective antibacterial therapy, diagnostic delay or no diagnosis all contribute to poor ocular outcomes with blindness (unilateral or bilateral) common. Modern detailed guidelines on fungal keratitis diagnosis and management are lacking. Here, we argue that fungal keratitis should be included as a neglected tropical disease, which would facilitate greater awareness of the condition, improved diagnostic capability, and access to affordable antifungal eye medicine.

Assessing global fungal threats to humans

Fungi are an integral part of the earth's biosphere. They are broadly distributed in all continents and ecosystems and play a diversity of roles. Here, I review our current understanding of fungal threats to humans and describe the major factors that contribute to various threats. Among the 140,000 or so known species out of the estimated six million fungal species on Earth, about 10% directly or indirectly threaten human health and welfare. Major threats include mushroom poisoning, fungal allergies, infections of crop plants, food contamination by mycotoxins, and mycoses in humans. A growing number of factors have been identified to impact various fungal threats, including human demographics, crop distributions, anthropogenic activities, pathogen dispersals, global climate change, and/or the applications of antifungal drugs and agricultural fungicides. However, while models have been developed for analyzing various processes of individual threats and threat managements, current data are primarily descriptive and incomplete, and there are significant obstacles to integration of the diverse factors into accurate quantitative assessments of fungal threats. With increasing technological advances and concerted efforts to track the spatial and temporal data on climate and environmental variables; mycotoxins in the feed and food supply chains; fungal population dynamics in crop fields, human and animal populations, and the environment; human population demographics; and the prevalence and severities of fungal allergies and diseases, our ability to accurately assess fungal threats will improve. Such improvements should help us develop holistic strategies to manage fungal threats in the future.

A methacrylated hyaluronic acid network reinforced Pluronic F-127 gel for treatment of bacterial keratitis

In this study, we developed a novel in situ thermoresponsive gel by introducing crosslinked methacrylated hyaluronic acid (HA-MA) networks into Pluronic F-127 (PF-127) gel (HP gel) to achieve levofloxacin (LFX) delivery in bacterial keratitis treatment. The interactions between PF-127 and HA-MA networks were studied by scanning electron microscopy, rheology, dynamic light scattering, differential scanning calorimetry, and small angle X-ray scattering. The results showed that the HP gel exhibited a higher critical gelling temperature and lower viscosity than the PF-127 gel (P gel), and could form a uniform thin layer on the ocular surface. Moreover, the drug release profile and gel dissolution rate revealed that the HA-MA network could retard the diffusion and dissolution of drug molecules and prolong the drug release time, which corresponded to an enhanced antibacterial ability of the HP-LFX gel. Furthermore, the HP gel exhibited low cytotoxicity to human corneal epithelial cells (HCECs). Finally, an in vivo pharmacodynamic study was conducted with rabbit keratitis models. An improved treatment efficacy was observed after application of the HP-LFX gels. This study highlights the potential of HP gels in ophthalmic drug delivery.

Nanoparticles Loaded Thermoresponsive In Situ Gel for Ocular Antibiotic Delivery against Bacterial Keratitis

Antibiotics delivered through conventional dosage against ophthalmic infections show lower therapeutic efficacy due to their low residence time. Therefore, there is a great need to design and develop novel dosage forms that would increase the ocular residence time of antibiotics at the site of infection. This study describes the development of nanoparticles laden in situ gelling solution, intended to sustain antibiotic release for improved therapeutic efficiency. Oxytetracycline-loaded gelatin-polyacrylic acid nanoparticles were prepared and incorporated in poloxamer-N407 solution. The rheological properties of the system were studied concerning time and temperature. Moreover, in vivo biocompatibility of the system was ascertained using the Draize test and histological studies. Finally, the optimized formulation was evaluated for in vitro antibacterial activity against one of the most common keratitis causing bacteria, Pseudomonas aeruginosa. Additionally, the in vivo efficacy was evaluated on the rabbit's eye conjunctivitis model. The formulation showed a sustained effect against keratitis; furthermore, the antibacterial activity was comparable with the commercial product.

Differential Antimicrobial Efficacy of Preservative-Free Contact Lens Disinfection Systems against Common Ocular Pathogens

Microbial keratitis is a devastating disease that can cause eye damage and blindness and can be the result of infections by several common ocular pathogens. Importantly, some of these pathogens, such as Acanthamoeba, are particularly unsusceptible to biocides in common contact lens care solutions. Therefore, the disinfection efficacy of preservative-free (PF) disinfection systems against bacteria, fungi, and Acanthamoeba trophozoites and cysts should be assessed as products with the most potential to be efficacious against resistant organisms. PF disinfection systems were analyzed for antimicrobial efficacy. These were the one-step (hydrogen peroxide-based) Clear Care and Clear Care Plus systems and the two-step (povidone-iodine-based) Cleadew system. Stand-alone challenges using bacteria, fungi, and Acanthamoeba were prepared according to the International Standards Organization method 14729. These same challenges were also conducted in the presence of the following contact lenses: Boston RGP, Acuvue Oasys, Biofinity, Ultra, and 2-week PremiO. All challenges were performed at the manufacturer's recommended disinfection time. All preservative-free disinfection systems demonstrated similarly high rates of antimicrobial efficacy when challenged with bacteria or fungi, with or without lenses. However, both Clear Care and Clear Care Plus demonstrated significantly greater disinfection efficacy against Acanthamoeba trophozoites and cysts, with and without lenses (P < 0.05). Cleadew efficacy was impacted by the addition of contact lenses, whereas Clear Care/Clear Care Plus maintained similar efficacies in the absence or presence of lenses. While both hydrogen peroxide and povidone-iodine are highly effective against bacteria and fungi, hydrogen peroxide maintains significantly greater disinfection capabilities than povidone-iodine against all forms of Acanthamoeba. IMPORTANCE Understanding the most efficacious products will allow clinicians to best communicate to patients and consumers the safest products on the market to reduce adverse events, including microbial keratitis, during contact lens use.

Fungi of the human eye: Culture to mycobiome

The focus of the current review is multi-fold and compares the diversity and abundance of fungi on the ocular surface by the conventional culture-based method with the more sensitive, high throughput, culture-independent NGS method. The aim is to highlight the existence of a core ocular mycobiome and explore the transition of the ocular fungal microbiota from the normal eye to the diseased eye. PubMed, Google Scholar and Medline were used to search for publications and reviews related to cultivable fungi and the mycobiome of the normal and diseased eye. The conventional cultivable approach and the NGS approach confirm that the eye has its own mycobiome and several confounding factors (age, gender, ethnicity etc.) influence the mycobiome. Further, dysbiosis in the mycobiome appears to be associated with ocular diseases and thus impacts the health of the human eye. Considering that the mycobiome of the eye is influenced by several confounding factors and also varies with respect to the disease status of the eye there is a need to extensively explore the mycobiome under different physiological conditions, different ethnicities, geographical regions etc. Such studies would unravel the diversity and abundance of the mycobiomes and contribute to our understanding of ocular health. Research focused on ocular mycobiomes may eventually help to build a targeted and individualized treatment.

Determination of probability of causative pathogen in infectious keratitis using deep learning algorithm of slit-lamp images

Corneal opacities are important causes of blindness, and their major etiology is infectious keratitis. Slit-lamp examinations are commonly used to determine the causative pathogen; however, their diagnostic accuracy is low even for experienced ophthalmologists. To characterize the “face” of an infected cornea, we have adapted a deep learning architecture used for facial recognition and applied it to determine a probability score for a specific pathogen causing keratitis. To record the diverse features and mitigate the uncertainty, batches of probability scores of 4 serial images taken from many angles or fluorescence staining were learned for score and decision level fusion using a gradient boosting decision tree. A total of 4306 slit-lamp images including 312 images obtained by internet publications on keratitis by bacteria, fungi, acanthamoeba, and herpes simplex virus (HSV) were studied. The created algorithm had a high overall accuracy of diagnosis, e.g., the accuracy/area under the curve for acanthamoeba was 97.9%/0.995, bacteria was 90.7%/0.963, fungi was 95.0%/0.975, and HSV was 92.3%/0.946, by group K-fold validation, and it was robust to even the low resolution web images. We suggest that our hybrid deep learning-based algorithm be used as a simple and accurate method for computer-assisted diagnosis of infectious keratitis.

Late onset of microbial keratitis after laser in situ keratomileusis surgery: case series

PURPOSE

To report predisposing factors, clinical features, microbiology spectrum, antibiotic resistance, antimicrobial therapy, and outcomes of patients with a previous laser in situ keratomileusis (LASIK) surgery and diagnosed with presumed microbial keratitis.

SETTING

Sydney Eye Hospital, Sydney, New South Wales, Australia.

DESIGN

Retrospective case review.

METHODS

Patients were identified from pathology and hospital coding data from 2012 to 2016. Inclusion criteria were all patients with a previous LASIK surgery, a presumed diagnosis of microbial keratitis, and a corneal scrape performed and aged older than 18 years. Demographics, clinical details, and outcomes were collated from the medical records.

RESULTS

Sixteen patients were included, with median age of 41.5 years (range 22 to 85 years) and 56.2% of women. The median time between LASIK procedure and microbial keratitis presentation was 38.3 months (interquartile range 6.7 to 77.45 months). Cultures were positive for bacteria in 12 (75%) of 16 scrapes. Of the bacterial isolates, 12 (85.7%) were gram-positive and 2 (14.3%) gram-negative. Sensitivity profiles for the isolated bacteria were similar between fortified antibiotics (cefalotin and gentamicin) and commercial products (chloramphenicol and ofloxacin). Complications included the need for tectonic grafts, nonhealing epithelial defects, thinning, and neovascularization.

CONCLUSIONS

Late onset of keratitis after LASIK can occur with no positive cultures for nontuberculous mycobacteria, no interface involvement, and no other usual features reported in case series of infectious keratitis in LASIK patients. It has a similar clinical course to non-LASIK keratitis, such that the surgery may not have been a risk factor for infection.

A Review On digital image processing techniques for in-Vivo confocal images of the cornea

This work reviews the scientific literature regarding digital image processing for in vivo confocal microscopy images of the cornea. We present and discuss a selection of prominent techniques designed for semi- and automatic analysis of four areas of the cornea (epithelium, sub-basal nerve plexus, stroma and endothelium). The main context is image enhancement, detection of structures of interest, and quantification of clinical information. We have found that the preprocessing stage lacks of quantitative studies regarding the quality of the enhanced image, or its effects in subsequent steps of the image processing. Threshold values are widely used in the reviewed methods, although generally, they are selected empirically and manually. The image processing results are evaluated in many cases through comparison with gold standards not widely accepted. It is necessary to standardize values to be quantified in terms of sensitivity and specificity of methods. Most of the reviewed studies do not show an estimation of the computational cost of the image processing. We conclude that reliable, automatic, computer-assisted image analysis of the cornea is still an open issue, constituting an interesting and worthwhile area of research.

Clinical Manifestations and Prognostic Factors of Fungal Keratitis: Analysis in Patients Over a 20-year Period

Purpose: To describe the clinical manifestations, causative organisms, treatment, and prognostic factors of fungal keratitis based on analysis of patients over the past 20 years. Methods: A total of 177 patients (177 eyes) with fungal keratitis, who were diagnosed by smears and cultures, were reviewed retrospectively. Sex, age, predisposing factors, causative organisms, clinical manifestations, treatment, and prognosis were evaluated. The patients were divided into three groups: only potassium hydroxide (KOH)-positive, only culture-positive, and KOH- and culture-positive. Logistic regression was performed to identify the factors associated with a poor clinical outcome. Results: The mean age of the patients was 67.4 ± 11.3 years; 107 (60.5%) patients were men. The most common predisposing factor was ocular trauma (57.6%), especially by plants (29.4%). The most prevalent filamentous fungi were Fusarium species (31.6%, 49 isolates), and the most prevalent yeasts were Candida species (11.0%, 17 isolates). In cases of bacterial and fungal keratitis, filamentous fungus with Gram-positive bacterial infection (70.7%, 29/41) was the most common presentation. Visual improvement after treatment was common in the KOH-positive group (79.2%, 19/24), while visual deterioration after treatment was common in the culture-positive group (40.4%, 36/89). Previous ocular disease (odds ratio [OR]: 3.744, p = 0.010), hypopyon (OR: 2.941, p = 0.030), and surgical treatment (OR: 24.482, p < 0.001) were risk factors for a poor clinical outcome in the multivariate logistic regression model. Conclusions: Clinical prognosis was good in the KOH-positive only group, but poor in the culture-positive group. If fungal keratitis is suspected, diagnostic KOH staining and culture tests should be performed initially. Early intensive antifungal medical treatments are necessary for patients with risk factors for poor clinical outcomes.

Development of a novel micro-bead force spectroscopy approach to measure the ability of a thermo-active polymer to remove bacteria from a corneal model

Microbial keratitis occurs from the infection of the cornea by fungi and or bacteria. It remains one of the most common global causes of irreversible blindness accounting for 3.5% (36 million) of blind people as of 2015. This paper looks at the use of a bacteria binding polymer designed to bind Staphylococcus aureus and remove it from the corneal surface. Mechanical unbinding measurements were used to probe the interactions of a thermo-active bacteria-binding polymer, highly-branched poly(N-isopropyl acrylamide), functionalised with modified vancomycin end groups (HB-PNIPAM-Van) to bacteria placed on rabbit corneal surfaces studied ex-vivo. This was conducted during sequential temperature phase transitions of HB-PNIPAM-Van-S. aureus below, above and below the lower critical solution temperature (LCST) in 3 stages, in-vitro, using a novel micro-bead force spectroscopy (MBFS) approach via atomic force microscopy (AFM). The effect of temperature on the functionality of HB-PNIPAM-Van-S. aureus showed that the polymer-bacteria complex reduced the work done in removing bacterial aggregates at T > LCST (p < 0.05), exhibiting reversibility at T < LCST (p < 0.05). At T < LCST, the breaking force, number of unbinding events, percentage fitted segments in the short and long range, and the percentage of unbinding events occurring in the long range (> 2.5 µm) increased (p < 0.05). Furthermore, the LCST phase transition temperature showed 100 × more unbinding events in the long-range z-length (> 2.5 µm) compared to S. aureus aggregates only. Here, we present the first study using AFM to assess the reversible mechanical impact of a thermo-active polymer-binding bacteria on a natural corneal surface.

Diagnostic approach and epidemiology of Microbial Keratitis: findings from an Italian Tertiary Care center

Rapid identification of causative microorganisms of microbial keratitis (MK) and knowledge of the most common local pathogens are prerequisites for rational antimicrobial therapy. We retrospectively reviewed the characteristics of MK diagnosed at the IRCCS Arcispedale Santa Maria Nuova of Reggio Emilia (Italy) in a 5-years period, where the Ophthalmologist Unit is a reference center for corneal infections. During the study period, 183 MK were evaluated through corneal scrapings cultures. The positivity rate was 54,1%. A total of 107 microorganisms have been isolated: Acanthamoeba species was the etiologic agent in 19 cases. Pseudomonas aeruginosa and Staphylococcus aureus were more frequently isolated in bacterial keratitis, while Fusarium spp., Candida albicans, and Alternaria alternata were predominant among the fungal isolates. Strict cooperation between ophthalmologists and clinical microbiologists is advisable to allow the best diagnostic approach for MK.

Therapeutic Ophthalmic Lenses: A Review

An increasing incidence of eye diseases has been registered in the last decades in developed countries due to the ageing of population, changes in lifestyle, environmental factors, and the presence of concomitant medical conditions. The increase of public awareness on ocular conditions leads to an early diagnosis and treatment, as well as an increased demand for more effective and minimally invasive solutions for the treatment of both the anterior and posterior segments of the eye. Despite being the most common route of ophthalmic drug administration, eye drops are associated with compliance issues, drug wastage by lacrimation, and low bioavailability due to the ocular barriers. In order to overcome these problems, the design of drug-eluting ophthalmic lenses constitutes a non-invasive and patient-friendly approach for the sustained drug delivery to the eye. Several examples of therapeutic contact lenses and intraocular lenses have been developed, by means of different strategies of drug loading, leading to promising results. This review aims to report the recent advances in the development of therapeutic ophthalmic lenses for the treatment and/or prophylaxis of eye pathologies (i.e., glaucoma, cataract, corneal diseases, or posterior segment diseases) and it gives an overview of the future perspectives and challenges in the field.

In Vivo Confocal Microscopy and Anterior Segment Optical Coherence Tomography Analysis of the Microcystic Keratitis

Purpose

To describe the findings of in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT) in a case of bilateral acute microcystic epitheliopathy after daily soft contact lens wear.

Methods

IVCM and AS-OCT were used in the course of the bilateral epitheliopathy of a 23-year-old patient at the acute stage of the disease and at recovery after four days of treatment. The images were analyzed and compared.

Results

On AS-OCT of the right eye, general hyperreflectivity and the increased thickness of the central corneal epithelium to 150 μm with numerous hyporeflective small, oval cysts were revealed and resolved completely at day 4 after diagnosis and treatment. AS-OCT scans of the left eye revealed oval shaped, hyperreflective material within the corneal epithelium. IVCM of both eyes showed numerous microcysts of different sizes filled with hyperreflective material mostly within superficial epithelial layers. Epithelial cells showed a polymorphism along with disruption of a cytoarchitecture. Basal epithelial cells and anterior stroma showed inflammatory changes. Posterior corneal stroma and endothelium presented normal morphology.

Conclusions

Microcystic keratitis appeared as localized microcystic inflammation of epithelium on AS-OCT, which was confirmed by IVCM. Both IVCM and AS-OCT are helpful diagnostic instruments in case of cystic inflammation of corneal epithelium.

Severe Keratitis and Corneal Perforation by Paenibacillus glucanolyticus

PURPOSE

To report the first case of Paenibacillus glucanolyticus, a spore-forming bacteria, to be isolated in a human ocular infection.

METHODS

We describe a severe case of noncontact lens-related microbial keratitis due to P. glucanolyticus presenting with a large corneal abscess, severe ocular inflammation, and a large epithelial defect.

RESULTS

The corneal scrapes with no growth initially cultured P. glucanolyticus on blood agar after 48 hours, with sensitivity to gentamicin and fluoroquinolones. No other organism was cultured. The patient had severe keratitis with a protracted course requiring cyanoacrylate glue patching because of keratolysis and perforation. The patient may benefit from a penetrating keratoplasty and extracapsular cataract extraction in due course to aid visual rehabilitation.

CONCLUSIONS

This is the first reported ocular case of P. glucanolyticus demonstrating its bacterial virulence and pathogenic potential when infecting the cornea. Rapid identification with newer technology enable us to accurately identify these opportunistic bacteria and may give a more favorable visual outcome as correct sensitivities lead to timely treatment administration.

The role of fungi in fungal keratitis

Fungal keratitis (FK) accounts for approximately half of the microbial keratitis encountered in low middle income countries (LMICs) and predominantly affect the working rural-poor. FK causes significant morbidity with the majority of patients left with moderate or worse visual impairment and approximately 25% requiring expensive and often unsuccessful surgical interventions. The severity of FK and the resultant corneal damage or resolution can be attributed to i) the virulence and bioburden of the fungal pathogen, ii) the host defense mechanism and immune response and iii) sub-optimal diagnostics and anti-fungal treatment strategies. This review provides a comprehensive overview of the multifaceted components that drive FK progression and resolution, highlighting where knowledge gaps exist and areas that warrant further research.

Periconia species - An unusual fungal pathogen causing mycotic keratitis

PURPOSE

The purpose of this study is to determine the epidemiology, risk factors, clinical features, and treatment outcome of molecularly diagnosed Periconia keratitis.

METHODS

Clinical records of all culture proven fungal ulcers with molecular identification suggestive of Periconia species who presented to a single tertiary referral center from January 2012 to December 2013 were retrospectively analysed.

RESULTS

Among 1356 cases of keratomycosis, 8 (0.6%) patients were affected due to Periconia species. The mean age of presentation was 59 years with males (n = 6; 75%) were more commonly affected than females (n = 2; 25%). Significant history of trauma was present only in one patient. The infiltrate size was less than 5 mm in majority of patients 75% (n = 6). 50% (n = 4) responded to antifungal, 12.5% (n = 1) responded to antibacterial, 12.5% (n = 1) required therapeutic penetrating keratoplasty, 25% (n = 2) lost to follow up after first visit. The mean duration of treatment in healed cases was 20 days.

CONCLUSION

This is the first report on Periconia sp causing human corneal ulcer. This study signifies the importance of molecular identification in the diagnosis of rare fungi which will improve our understanding on disease pathology and outcome. Visual prognosis appears good if the infection is diagnosed and topical antifungal interventions started early.

Multi-Drug Resistant Post Corneal Repair Klebsiella oxytoca's Keratitis

Background

Bacterial keratitis can threaten vision through permanent corneal scarring and even perforation, resulting in loss of the eye. Klebsiella oxytoca is resistant to several antibiotics because it produces extended-spectrum β-lactamase encapsulated with polysaccharide. Thus, this article is aimed at reporting a rare case of Klebsiella oxytoca-induced keratitis in Jimma University Medical Centre, Jimma, Ethiopia.

Case Presentation

TA 25-year-old female patient presented with photophobia, redness, and purulent discharge from the right eye. She had matted cilia of the eyelid, conjunctiva injection, corneal ulcer, and deep fibrinous anterior chamber reaction. She had light perception (LP) visual acuity for the same eye and it was firm when examined digitally. The cornea-scleral repair was performed one month earlier, due to open globe injury. The patient had taken empirical fortified antibiotics before the identification of the specific pathogen. Culture and drug sensitivity test was performed in order to identify the aetiology. The result of the test revealed that the identified pathogen was multi-drug-resistant Klebsiella oxytoca. Based on this result and drug availability, high dose topical fluoroquinolones eye drops (Ciprofloxacin eye drop 0.3% and Ofloxacin 0.3%) were given. Besides, dexamethasone 0.1% eye drop was added to the aforementioned antibiotics. After four months of treatment, the visual outcome was changed from LP to hand motion.

Conclusion

A rare case of multi-drug resistant Klebsiella oxytoca induced keratitis which was isolated in a biochemical test was successfully treated with a high dose of fluoroquinolones.

Seven-Year Analysis of Microbial Keratitis Tendency at an Ophthalmology Department in Poland: A Single-Center Study

This study aimed to analyze the frequency, drug susceptibility, and drug resistance of pathogens causing microbial keratitis (a corneal inflammation) in the Clinical Department of Ophthalmology, Medical University of Silesia, Katowice. Despite intensive treatment, severe inflammation causes irreversible blindness in ∼7% of cases and eye loss (evisceration or enucleation of the eyeball) in ∼1% of cases at our hospital. The choice of a targeted drug depends on the culture result and drug resistance of the microorganism. This was a retrospective observation study. Conjunctival swabs and corneal scrapes were collected between January 1, 2013, and December 31, 2019, in the tertiary reference center for keratitis. The collected data included the type of material received, culture result, and antimicrobial susceptibilities. Of the 2482 samples analyzed, 679 were positive and 1803 were negative. Of the total pathogens isolated, 69.9% were Gram-positive bacteria, 20.8% were Gram-negative bacteria, and 7.1% were fungi. A significant increase in the number of Gram-positive methicillin-resistant Staphylococcus aureus and a partial increase in the number of Gram-negative beta-lactams-resistant bacteria were observed. All fungal species were sensitive to amphotericin B, 82.81% were sensitive to voriconazole, and 56.25% were sensitive to fluconazole. Dual drug therapy (levofloxacin and tobramycin) was the first-line treatment. Drug susceptibility testing of the cultured microorganisms is necessary to initiate targeted treatment. Increased drug resistance was observed in this study. In the present study, most bacteria were sensitive to fluoroquinolones. Ciprofloxacin therapy remains the recommended empirical treatment in microbial keratitis. According to our study, voriconazole remains a first-line antifungal drug, when a fungal infection is suspected.

Pediatric Microbial Keratitis: Experience From Tertiary Referral Centers in New South Wales, Australia

AIMS

The purpose of this study was to report the epidemiology, etiology, microbiologic profile and management of pediatric microbial keratitis in a quaternary and 3 tertiary ophthalmic referral centers across Sydney, New South Wales, Australia.

METHODS

This is a retrospective cohort study of patients ≤ 18 years of age with a clinical diagnosis of microbial keratitis presenting between 1 January 2010 and 31 December 2016 identified from hospital coding and pathology databases. Data were extracted from the medical records. Epidemiology, predisposing factors, referral patterns, microbial profile and treatment outcomes were analyzed.

RESULTS

Eighty eyes from 80 pediatric patients with microbial keratitis were included in the study (10% had bilateral disease). The mean age was 11 ± 5.3 years (range 0-18 years), and 44 were male (55%). Thirty-six percent of patients had ocular and 13.5% systemic comorbidities. The most common risk factor overall was contact lens wear in 26%, trauma (24%), and external lid and eye disease (20%). Overall, 74 organisms were identified, and of those, the most common isolates were Gram-positive organism. Antimicrobial resistance to common antibiotics was low across all isolates. Visual acuity following treatment was worse than 6/60 for 7 patients (11.3%%), 6/15-6/60 for 15 patients (24.2%) and better than 6/12 for 40 patients (64.5%). Preexisting corneal disease and delay of presentation were associated with worse visual prognosis. Serious complications were noted in 16 (21.3%) of patients.

CONCLUSIONS

Contact lens wear, trauma and existing ocular disease remain the most significant risk factors in the pediatric population. Preexisting corneal disease and delay in presentation were associated with poor visual acuity. The majority of patients have a good visual outcome although serious complications are not uncommon and may cause lifelong visual disability.

Imprinted Contact Lenses for Ocular Administration of Antiviral Drugs

A variety of ocular diseases are caused by viruses, and most treatments rely on the use of systemic formulations and eye drops. The efficient ocular barriers that oppose antiviral drug penetration have prompted the development of improved topical delivery platforms. The aim was to design hydrogel contact lenses endowed with an affinity for acyclovir (ACV) and its prodrug valacyclovir (VACV), first-choice drugs against herpes simplex virus (HSV) ocular keratitis, and that can sustain the release of therapeutic doses during daily wearing. Functional monomers suitable for interaction with these drugs were screened using computational modeling. Imprinted and non-imprinted hydrogels were prepared with various contents in the functional monomer methacrylic acid (MAA) and characterized in terms of swelling, transmittance, mechanical properties, and ocular compatibility (hen’s egg test on chorioallantoic membrane (HET-CAM) assay). The values were in the range typical of soft contact lenses. Compared to ACV, the capability to load VACV was remarkably higher due to stronger electrostatic interactions with MAA. The advantages of the imprinting technology were evidenced for VACV. Stability of VACV loading solution/hydrogels under steam heat sterilization and subsequent drug release was investigated. Permeability studies through bovine and porcine cornea and sclera of the drug released from the hydrogels revealed that VACV accumulates in the cornea and can easily cross the sclera, which may facilitate the treatment of both anterior and posterior eye segments diseases.

Clinical diagnosis and treatment of rare painless keratitis caused by three pathogens: clinical practice and experiential discussion

There have been numerous reports regarding the occurrence of keratitis in patients with soft contact lenses, but few reports in patients with rigid gas permeable contact lenses. To the best of our knowledge, the occurrence of infection associated with three species of pathogens has never been reported. Here, we describe a patient who exhibited refractory painless keratitis caused by three pathogens (Staphylococcus epidermidis, Acanthamoeba, and herpes simplex virus) and summarize similar reports published at multiple centers worldwide, with the aim of providing guidance for clinicians who might encounter mixed-type corneal infections. We describe the results of many ophthalmologic and laboratory investigations, which guided our treatment selection. We achieved good treatment efficacy, such that the patient exhibited a corrected visual acuity of 20/20 in the affected eye after a series of treatments, including curettage of ulcer lesions. Corneal infections caused by multiple pathogens are challenging in clinical practice. This summary of our experience in patient diagnosis and treatment can help clinicians to achieve a favorable prognosis in treatment of future patients.

The Spectrum of Microbial Keratitis: An Updated Review

Background:

In microbial keratitis, infection of the cornea can threaten vision through permanent corneal scarring and even perforation resulting in the loss of the eye. A literature review was conducted by Karsten, Watson and Foster (2012) to determine the spectrum of microbial keratitis. Since this publication, there have been over 2600 articles published investigating the causative pathogens of microbial keratitis.

Objective:

To determine the current spectrum of possible pathogens implicated in microbial keratitis relative to the 2012 study.

Methods:

An exhaustive literature review was conducted of all the peer-reviewed articles reporting on microbial pathogens implicated in keratitis. Databases including MEDLINE, EMBASE, Scopus and Web of Science were searched utilising their entire year limits (1950-2019).

Results:

Six-hundred and eighty-eight species representing 271 genera from 145 families were implicated in microbial keratitis. Fungal pathogens, though less frequent than bacteria, demonstrated the greatest diversity with 393 species from 169 genera that were found to cause microbial keratitis. There were 254 species of bacteria from 82 genera, 27 species of amoeba from 11 genera, and 14 species of virus from 9 genera, which were also identified as pathogens of microbial keratitis.

Conclusion:

The spectrum of pathogens implicated in microbial keratitis is extremely diverse. Bacteria were most commonly encountered and in comparison, to the review published in 2012, further 456 pathogens have been identified as causative pathogens of microbial keratitis. Therefore, the current review provides an important update on the potential spectrum of microbes, to assist clinicians in the diagnosis and treatment of microbial keratitis.

The clinical and microbiological features and outcomes of fungal keratitis over 9 years in Sydney, Australia

To describe the clinical features, management and outcomes in patients with fungal keratitis at the Sydney Eye Hospital, Australia, over a 9-year period to guide appropriate initial therapy. A retrospective case review was conducted. Patients diagnosed with fungal keratitis from 1 January 2009 to 31 December 2017 were identified from hospital coding and pathology databases. Data were extracted from the medical records. A total of 55 episodes from 51 patients were included. Mean age was 60 ± 20 years (range: 19-91 years), and 33 were male. The fungal species was not identified in two patients. Predisposing factors included ocular surface disease in 17 eyes (32%); corneal disease, 15 (28%); corneal trauma, 12 (23%); and contact lens wear, 13 (24.5%). Fusarium spp. (15, 27%) and Candida parapsilosis (10, 18%) were the most common isolates. The median visual acuity at presentation was 1.3 logMAR (range: 0 to 3) and after treatment 0.7 logMAR (range: -0.02 to 3) (P = .008). Despite medical therapy, most commonly with natamycin and topical and oral voriconazole, surgical intervention was required in 21 eyes (40%); including antifungal injections in 9 (16%); corneal transplantation, 16 (30%); evisceration, 2 (4%); and enucleation, 1 (2%). A poor visual outcome was recorded in 27 of 43 (63%) patients. Fungal keratitis remains a cause of significant ocular morbidity; the majority of patients face a poor outcome despite intense medical and at times surgical treatment. In our setting, fungal keratitis was more commonly associated with corneal or ocular surface disease.

Challenges in the diagnosis of microbial keratitis: A detailed review with update and general guidelines

The incidence of microbial keratitis (MK) is variable worldwide with an estimated 1.5–2 million cases of corneal ulcers in developing countries. The complications of MK can be severe and vision threatening. Therefore, proper diagnosis of the causative organism is essential for early successful treatment. Accurate sampling of microbiological specimens in MK is an important step in identifying the infective organism. Corneal scrapping, tear samples and corneal biopsy are examples of specimens obtained for the investigative procedures in MK. Ophthalmologists especially in an emergency room setting should be aware of the proper sampling techniques based on their microbiology-related basic information for each category of MK. This review article briefly describes the clinical presentation and defines in details the best updated diagnostic methods used in different types of MK. It can be used as a guide for ophthalmology trainees and general ophthalmologists who may be handling such cases at initial presentation.

Alterations in the Ocular Surface Fungal Microbiome in Fungal Keratitis Patients

Keratitis, an inflammatory disease of the eye, when neglected could lead to sight-threatening complications and ultimately blindness. Globally, over a million people are affected by keratitis annually. Keratitis has a microbial etiology and is caused by bacteria, fungi, viruses, etc. The present study compared the ocular surface fungal microbiome of healthy individuals and individuals with fungal keratitis. Fungal microbiomes from the conjunctival swabs of healthy individuals and from conjunctival swabs and corneal scrapings of individuals with fungal keratitis were generated using ITS2 region amplicons. Microbiomes were sequenced using Illumina MiSeq 2 × 250 base pair chemistry with a paired-end protocol. Based on Alpha diversity indices, phylum and genera level diversity, abundance differences, and heat map analysis, the fungal microbiomes of conjunctival swabs and corneal scrapings of individuals with fungal keratitis exhibited dysbiosis (alterations in the diversity and abundance) compared to the ocular surface microbiome of the healthy control individuals. This is the first report indicating dysbiosis in the fungal microbiome of conjunctival swabs and corneal scrapings in individuals with fungal keratitis. A total of 11 genera present in the majority of the eyes constituted the variable core ocular microbiome.

Microbial Keratitis and Ocular Surface Disease: A 5-Year Study of the Microbiology, Risk Factors and Clinical Outcomes in Sydney, Australia

Purpose: To report the microbiological and clinical profiles, and outcomes of patients with microbial keratitis who had ocular surface disease (OSD) at the Sydney Eye Hospital, Australia over a 5-year period.Methods: A retrospective case-series study was conducted. Patients diagnosed with microbial keratitis who had a history of OSD (dry eye, blepharitis, Steven Johnson syndrome (SJS) and ocular cicatricial pemphigoid (OCP)) from 1^st January 2012 to 31^st December 2016 were identified from hospital coding and pathology data. Data were extracted from the medical records.Results: 189 eyes from 171 patients with a mean age of 60 ± 19 years (range 20-96 years) were included. OSD included blepharitis (79%), dry eye (25%), SJS (4%) and OCP (2%). Coagulase-negative Staphylococcus (CoNS) (48%) were the most common isolated microorganism, made up of mostly Staphylococcus epidermidis (n = 37, 48%), Staphylococcus capitis (n = 16, 21%), and Staphylococcus warneri (n = 10, 13%). Median visual acuity at initial presentation was 0.52 logMAR and 0.30 logMAR at final visit. Median healing time was 12 days (IQR 6-27). The most common initial antimicrobial treatment prescribed was a combination of topical fortified cephalothin and gentamicin (n = 65, 34%); or topical ofloxacin (n = 56, 30%). Complications occurred in 69 eyes (37%), mainly non or slow-healing epithelial defects (n = 53, 43%) or corneal perforations (n = 24, 20%); and were more common in the elderly (n = 48/69, 70%).Conclusion: Microbial keratitis can affect those with OSD. In our setting, CoNS were the main organisms identified. Furthermore, patients prescribed a combination therapy of fortified antibiotics had poorer outcomes compared to monotherapy fluoroquinolones.

Keratomycosis due to Purpureocillium lilacinum: A case report from Sub-Himalayan region of Uttarakhand

The fungus Purpureocillium lilacinum previously known as Paceliomyces lilacinus is an emerging pathogen that can cause severe human infections including devastating oculomycosis. Treatment with traditional antifungals often fails, and the organism shows variable susceptibility to novel triazoles. We hereby report a case of keratomycosis caused by Pur. lilacinum in an immunocompetent male patient following trauma. The patient was successfully treated with voriconazole. The drug shows good activity against Pur. lilacinum and could be a promising therapeutic alternative to treat infections caused by this fungus, which generally shows resistance to conventional antifungal agents including novel triazoles.

Paecilomyces lilacinus Keratitis in a Soft Contact Lens Wearer

We describe a case of keratitis caused by Paecilomyces lilacinus in a contact lens wearer with a history of diabetes.

Immune Response and Mechanisms of IFN-γ in Administration for Keratomycosis

Purpose: To investigate the immune response and mechanisms of interferon-γ (IFN-γ) in the fungal keratitis in mice. Methods: Mice were divided into two groups: group A, topical PBS four times daily post-infection; group B: topical IFN-γ four times daily post-infection. At1, 3, 5, and 7 days, the corneal lesions and inflammatory responses were observed by slit lamp, and immunofluorescence staining was performed to evaluate F4/80+ and CD4+ cells. Using ELISA, and RT-PCR to detect the expression levels of macrophage migration inhibitory factor (MIF), macrophage inflammatory protein-2 (MIP-2), IL-4, IL-10, IL-12, and IFN-γ. Results: The treatment with IFN-γ decreased clinical scores and expression levels of IL-4, increased expression of F4/80+ and CD4+ cells, whereas IL-12, MIF, and MIP-2 were expressed highly, and the peaks of IL-10 and IFN-γ move forward. Conclusion: This experiment showed that IFN-γ eye drops increase the accumulation of macrophages and shorten the duration of fungal keratitis.

Contact lens-related polymicrobial keratitis: Acanthamoeba spp. genotype T4 and Candida albicans

A 31-year-old female daily user of contact lenses sought medical attention, reporting blurred vision and irritation of the left eye. Slit-lamp examination revealed hyperemia and an irregular corneal epithelium surface, and empirical treatment was started. A corneal scrape was obtained and examined for the presence of fungi, bacteria, and Acanthamoeba spp. The results of the microbial culture revealed growth of Acanthamoeba spp. and Candida albicans. The Acanthamoeba isolate was characterized by cyst morphology as belonging to group II according to Pussard and Pons. Sequencing of the diagnostic fragment 3 (DF3) region located on the 18S ribosomal DNA identified the isolate as genotype T4. The patient was treated with chlorhexidine 0.02% and polyhexamethylene biguanide (PHMB) 0.02% drops for 5 months until the infection resolved. Lately, rare cases of polymicrobial keratitis associated with Acanthamoeba and Candida albicans have been reported. Cases of co-infection are more difficult to treat, since the specific treatment depends on precise identification of the agents involved.

Novel drug delivery systems for ocular therapy: With special reference to liposomal ocular delivery

Delivery of drugs to eyes is a great challenge to researchers because of a number of barriers in the eye preventing the actual dose from reaching the site. A number of ophthalmic delivery systems have been developed in the past couple of years that are not only new but also safe and reliable and help to overcome all those barriers in the eye which are responsible for the very less bioavailability of drugs. In this review, we tried to focus on current research in ocular delivery of drug substances giving special emphasis to liposomal delivery system. A brief analysis of other novel ocular delivery systems, ocular physiology, and microbial sources of disease are also highlighted herein. We analyzed the various research findings for churning a general idea for novel ocular delivery system and its future use. The novel formulations may overcome the addressed problems of ophthalmic medication and comply with the quality assurance issues. The liposomal delivery is advantageous as they have the ability to entrap both hydrophobic and hydrophilic drugs and are suitable for delivery to both the anterior and posterior segment of the eye. Therefore, the use of this alternative approach is quite a necessity.

Biofilm testing of microbiota: An essential step during corneal scrap examination in Egyptian acanthamoebic keratitis cases

PURPOSE

To detect co-infections in the culture-proven acanthamoebic keratitis (AK) cases, and to test the capability of biofilm formation in the isolated microbiota. The clinical findings, habit of wearing contact lens and in-vitro antibiotic resistance were analyzed further according to the biofilm formation capability.

METHODS

After clinical examination, corneal scraps and swabs were taken from 240 clinically suspected AK cases, for Acanthamoeba and microbiological cultures. In cases of keratoplasty, trimmed corneal tissue was collected and sent for histopathological examination. Scanning electron microscopy was done for some samples. Biofilm formation capability was investigated using a tissue culture plate method. Antibiotic resistance pattern was determined using a modified-Kirby-Bauer disc diffusion method.

RESULTS

In 102 AK culture proven cases, 11 had no co-infection, 74 had a single co-infection and 17 had double co-infections. Enterobactericae and Aspergillus were the commonest bacterial and fungal isolates, respectively. Regarding the biofilm formation, 64.7% of Enterobactericae, 50% of Pseudomonas aeuroginosa, 43.75% of Staph aureus, 76.92% of Streptococcus pneumoniae, 28.57% of Corynebacterium, 60% of α-haemolytic streptococci, 40% of Acinetobacter, 100% of Candida and 77.8% Aspergillus isolates were biofilm producers. Severe manifestations were more frequently reported in cases co-infected with biofilm producers than with non-biofilm producers. Generally, high percentages of the biofilm forming bacterial isolates were sensitive to antibiotics in-vitro.

CONCLUSIONS

Routine investigations for co-infection and biofilm formation in addition to Acanthamoeba culture are strongly recommended in suspected AK cases. Co-infection with biofilm producers may precipitate extrinsic in-vivo drug resistance despite of the in-vitro sensitivity. Designing a biofilm-dissolving topical drug is highly recommended to enhance the response to the standard therapeutic regimen especially in the resistant AK cases.

Reducing oral contamination during corneal scrapes

Aims

To identify potential contaminants of the corneal sampling procedure and examine the effect of wearing surgical face masks on the rate of contamination.

Methods

Ten surgeons recited out loud a 30 s standardised script for corneal scraping with blood agar plates positioned 30 cm away from them. Three groups were identified: in group 1 a surgical mask was worn; group 2 had no mask worn; and group 3 had no mask but used agar plates pretreated with 5% povidone-iodine as a negative control. Each surgeon repeated the process 10 times for all groups, totalling 30 plates per surgeon and 300 plates for the experiment. All plates were masked and incubated aerobically at 37°C for 24 hours, and the number of colony forming units (CFUs) was determined.

Results

At 24 hours, group 1 had a mean of 0.3 CFUs per surgeon; group 2 had 6.4 CFUs per surgeon and group 3 had 0.1 CFUs per surgeon. The difference between group 1 and group 2 was significant (p<0.001) whereas the difference between group 1 and group 3 was non-significant (p=0.4). Use of face masks decreased the number of plates with CFUs by 93% (from 29 to 2 plates) and decreased the total number of CFUs by 95% (from 63 to 3 CFUs). The most common microbiota identified was Streptococcus species.

Conclusions

Oral bacterial microbiota may contaminate the slides and media used to collect samples during corneal sampling. Use of a face mask can significantly decrease the rate of contamination of such samples.

Bacterial profile of ocular infections: a systematic review

BACKGROUND

Bacteria are the major contributor of ocular infections worldwide. Ocular infections, if left untreated, can damage the structures of the eye with possible blindness and visual impairments. This work was aimed to review the bacterial profile of ocular infections.

METHODS

Literature search was made in different electronic databases; the review was systematically made to get concrete findings.

RESULTS

As far as this review, Staphylococcus aureus, Coagulase negative Staphylococci, Streptococcus pneumoniae and Pseudomonas aeruginosa are the leading isolates in ocular infections. Frequent pathogens of the respective clinical diagnose include Staphylococci, Streptococcus pyogenes and Pseudomonas aeruginosa in blepharitis; Staphylococci, Streptococus pneumoniae, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli in Conjunctivitis; Staphylococci, P. aeruginosa and E. coli in dacryocystitis; Coagulase negative Staphylococci, Pseudomonas aeruginosa and Staphylococcus aureus in keratitis; Streptococcus viridians, Streptococcus pneumoniae and Coagulase negative Staphylococci in endophthalmitis diagnoses. Endogenous endophthalmitis is associated with Klebsiella pneumoniae whereas Coagulase negative Staphylococci and Bacillus spp. are common causes of post-operative and post-traumatic endophthalmitis. However, the predominant pathogens may not be exactly same in all areas of the world, in the United States for instance, Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae are the major causes of conjunctivitis.

CONCLUSION

Gram positive bacteria are the major contributor of bacterial ocular infections. The distribution and proportion of bacterial isolates among clinical diagnoses varied but without exclusive anatomical restriction. To mitigate the burden of bacterial ocular infections, physicians should regard on risk reduction and comply with etiologic approach of diagnosis.

Esculentin-1a derived peptides kill Pseudomonas aeruginosa biofilm on soft contact lenses and retain antibacterial activity upon immobilization to the lens surface

Contact lens (CL) wear is a risk factor for development of microbial keratitis, a vision threatening infection of the eye. Adverse events associated with colonization of lenses, especially by the multi-drug resistant and biofilm forming bacterium Pseudomonas aeruginosa remain a major safety issue. Therefore, novel strategies and compounds to reduce the onset of CL-associated ocular infections are needed. Recently, the activity of the frog skin-derived antimicrobial peptide Esc(1-21) and its diastereomer Esc(1-21)-1c was evaluated against both planktonic and sessile forms of this pathogen. Furthermore, Esc(1-21) was found to significantly reduce the severity of P. aeruginosa keratitis in a mouse model and preserve antipseudomonal activity in the presence of human basal tears. Here, we have analyzed the activity of the peptides on P. aeruginosa biofilm formed on soft CLs. Microbiological assays and scanning electron microscopy analysis indicated that the peptides were able to disrupt the bacterial biofilm, with the diastereomer having the greater efficacy (up to 85% killing vs no killing at 4 μM for some strains). Furthermore, upon covalent immobilization to the CL, the two peptides were found to cause more than four log reduction in the number of bacterial cells within 20 minutes and to reduce bacterial adhesion to the CL surface (77%-97% reduction) in 24 hours. Importantly, peptide immobilization was not toxic to mammalian cells and did not affect the lens characteristics. Overall, our data suggest that both peptides have great potential to be developed as novel pharmaceuticals for prevention and treatment of CL-associated P. aeruginosa keratitis.

Adjunctive Therapies for Bacterial Keratitis

Bacterial keratitis is the most common type among all types of infectious keratitis. Currently, antibiotics are the main-stay of treatment. The objective of this systematic review is to review published clinical studies which discuss the adjunctive treatment of bacterial keratitis to guide clinical decision-making. We reviewed the role of a variety of medications and surgeries which can help in managing bacterial keratitis complications, which include as thinning, perforation, and impaired wound healing. We have included appropriate animal and laboratory studies, case reports and case series, and randomized clinical trials regarding each therapy.

Epidemiology and Outcomes of Kocuria Keratitis

OBJECTIVE

To determine the characteristics of infectious keratitis caused by Kocuria spp.

METHODS

Retrospective case series. Information included demographic data, medical history, risk factors associated with infectious keratitis, clinical characteristics, microbiological results and drug sensitivity, clinical course, management, and visual outcomes.

RESULTS

Eight patients were included (7 females and 1 male; mean age, 66.2 years; age range, 42-84 years). All patients presented risk factors for infectious complications, such as filamentous keratitis, dry eye, blepharitis, and persistent corneal edema. In all cases, ulcers were classified as severe. The infection resolved with medical treatment in one eye only. One case was treated with amniotic membrane graft. Two patients required keratoplasty (lamellar and penetrating), and one case needed sclerokeratoplasty. In three cases, the keratitis was severe enough to require evisceration. The final visual acuity ranged from 20/25 to no light perception.

CONCLUSIONS

Bacterial keratitis by Kocuria spp. is a rare infection that may have an unexpected clinical course and possible serious outcomes. This pathogen should be considered in patients with unusual clinical course. Local or systemic immune compromise in the genesis of the disease must also be taken into account, and ophthalmologists should be more suspicious in this vulnerable group of patients.

Ocular Emergencies: Red Eye

"Red eye" is used as a general term to describe irritated or bloodshot eyes. It is a recognizable sign of an acute/chronic, localized/systemic underlying inflammatory condition. Conjunctival injection is most commonly caused by dryness, allergy, visual fatigue, contact lens overwear, and local infections. In some instances, red eye can represent a true ocular emergency that should be treated by an ophthalmologist. A comprehensive assessment of red eye conditions is required to preserve the patients visual function. Severe ocular pain, significant photophobia, decreased vision, and history of ocular trauma are warning signs demanding immediate ophthalmological consultation.

Ocular bacterial infections at Quiha Ophthalmic Hospital, Northern Ethiopia: an evaluation according to the risk factors and the antimicrobial susceptibility of bacterial isolates

BACKGROUND

External and intraocular infections can lead to visual impairments, which is a major public health problem. Bacteria are the most frequent pathogens affecting ocular structures; the increasing rate of antimicrobial drug resistance is a worldwide concern. The aim of this study was to determine the occurrence of bacteria in ocular infections, their antimicrobial susceptibility patterns, and risk factors in bacterial ocular infection.

METHODS

A hospital based cross-sectional study was conducted from September 2015 to December 2015 at Quiha Ophthalmic Hospital, Tigray, northern Ethiopia. Ocular specimens from blepharitis, blepharoconjunctivitis, conjunctivitis, keratitis, endophthalmitis, periorbital cellulitis and dacrocystitis were collected from 270 individuals with suspected ocular infection. Data on sociodemographic and risk factors were also collected using a structured questionnaire. Data analysis was performed using SPSS version 21 and 0.05 with a corresponding 95% confidence interval (CI) was considered statistically significant.

RESULTS

Among 270 study subjects, 180 (66.7%) were culture positive for different bacterial isolates. The predominant bacterial isolates were Staphylococcus aureus (40, 22.2%), coagulase negative staphylococci (31, 17.2%) and Pseudomonas aeruginosa (21, 11.7%). Ocular surface disease, ocular trauma, hospitalization and cosmetic application practices were significantly associated with the occurrence of bacterial infection. Concerning antimicrobial susceptibility, most isolates were susceptible to amikacin (137, 93.2%), gentamicin (131, 89.1%) and ciprofloxacin (141, 89.2%). Overall, 40 (22.5%), 34 (19.1%) and 62 (34.8%) isolates were resistant to one, two, and three or more antimicrobials, respectively.

CONCLUSION

Bacteria were isolated from the majority of the study subjects. More than half of the bacterial isolates were resistant at least to one drug and a significant rate of multidrug resistance was detected. Therefore, identification of the etiologic agent and antimicrobial susceptibility testing should be practiced to select the appropriate antimicrobial agent to treat eye infections and prevent the emergence of drug resistant bacteria.

Multidrug-resistant Fusarium keratitis: diagnosis and treatment considerations

Mycotic keratitis is an ocular infective process derived from any fungal species capable of corneal invasion. Despite its rarity in developed countries, its challenging and elusive diagnosis may result in keratoplasty or enucleation following failed medical management. Filamentous fungi such as Fusarium are often implicated in mycotic keratitis. Bearing greater morbidity than its bacterial counterpart, mycotic keratitis requires early clinical suspicion and initiation of antifungal therapy to prevent devastating consequences. We describe a case of multidrug-resistant mycotic keratitis in a 46-year-old man who continued to decline despite maximal therapy and therapeutic keratoplasty. Finally, enucleation was performed as a means of source control preventing dissemination of a likely untreatable fungal infection into the orbit. Multidrug-resistant Fusarium is rare, and may progress to endophthalmitis. We discuss potential management options which may enhance diagnosis and outcome in this condition.

Spectrum and Sensitivity of Bacterial Keratitis Isolates in Auckland

Background. The bacteria isolated from severe cases of keratitis and their antibiotic sensitivity are recognised to vary geographically and over time. Objectives. To identify the most commonly isolated bacteria in keratitis cases admitted over a 24-month period to a public hospital in Auckland, New Zealand, and to investigate in vitro sensitivity to antibiotics. Methods. Hospital admissions for culture-proven bacterial keratitis between January 2013 and December 2014 were identified. Laboratory records of 89 culture positive cases were retrospectively reviewed and antibiotic sensitivity patterns compared with previous studies from other NZ centres. Results. From 126 positive cultures, 35 species were identified. Staphylococcus was identified to be the most common isolate (38.2%), followed by Pseudomonas (21.3%). Over the last decade, infection due to Pseudomonas species, in the same setting, has increased (p ≤ 0.05). Aminoglycosides, cefazolin, ceftazidime, erythromycin, tetracycline, and doxycycline were 100% effective against tested isolates in vitro. Amoxicillin (41.6%), cefuroxime (33.3%), and chloramphenicol (94.7%) showed reduced efficacy against Gram-negative bacteria, whereas penicillin (51%) and ciprofloxacin (98.8%) showed reduced efficacy against Gram-positive bacteria. Conclusions. Despite a shift in the spectrum of bacterial keratitis isolates, antibiotic sensitivity patterns have generally remained stable and show comparability to results within the last decade from NZ centres.