Microbial keratitis in Hong Kong: relationship to climate, environment and contact-lens disinfection

Understanding Acanthamoeba Keratitis: An In-Depth Review of a Sight-Threatening Eye Infection

Acanthamoeba keratitis (AK) is a rare but potentially sight-threatening corneal infection caused by the Acanthamoeba parasite. This microorganism is found ubiquitously in the environment, often in freshwater, soil, and other sources of moisture. Despite its low incidence, AK presents significant challenges due to delayed diagnosis and the complex nature of therapeutic management. Early recognition is crucial to prevent severe ocular complications, including corneal ulceration and vision loss. Diagnostic modalities and treatment strategies may vary greatly depending on the clinical manifestation and the available tools. With the growing reported cases of Acanthamoeba keratitis, it is essential for the ophthalmic community to thoroughly understand this condition for its effective management and improved outcomes. This review provides a comprehensive overview of AK, encompassing its epidemiology, risk factors, pathophysiology, clinical manifestations, diagnosis, and treatment.

Acanthamoeba keratitis - A review

This is a comprehensive review after a thorough literature search in PubMed-indexed journals, incorporating current information on the pathophysiology, clinical features, diagnosis, medical and surgical therapy, as well as outcomes of Acanthamoeba keratitis (AK). AK is a significant cause of ocular morbidity, and early diagnosis with timely institution of appropriate therapy is the key to obtaining good outcomes. The varied presentations result in frequent misdiagnosis, and co-infections can increase the morbidity of the disease. The first line of therapy continues to be biguanides and diamidines, with surgery as a last resort.

The global epidemiology and clinical diagnosis of Acanthamoeba keratitis

Acanthamoeba keratitis is a rare parasitic infection of the cornea that can lead to permanent blindness if not diagnosed and treated promptly. We collected data on the incidences of Acanthamoeba keratitis from 20 countries and calculated an annual incidence of 23,561 cases, with the lowest rates in Tunisia and Belgium, and the highest in India. We analyzed 3755 Acanthamoeba sequences from the GenBank database across Asia, Europe, North America, South America, and Oceania and genotyped them into T1, T2, T3, T4, T5, T10, T11, T12, and T15. Many genotypes possess different characteristics, yet T4 is the most prevalent genotype. As efficient treatment against Acanthamoeba remains lacking, prevention from early diagnosis via staining, PCR, or in vivo confocal microscopy (IVCM) becomes significant for the condition's prognosis. IVCM is the most recommended approach for the early detection of Acanthamoeba. If IVCM is unavailable, PCR should be used as an alternative.

Fungal keratitis in Iran: Risk factors, clinical features, and mycological profile

Introduction

This study was intended to investigate the clinical features and predisposing factors of fungal keratitis (FK), as well as molecular identification and antifungal susceptibility of causative agents in Tehran, Iran.

Methods

This cross-sectional study was carried out from April 2019 to May 2021. All fungi isolates were identified using conventional methods and were confirmed by DNA-PCR-based molecular assays. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) was used to identify yeast species. Minimum inhibitory concentrations (MIC) of eight antifungal agents were assessed according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) microbroth dilution reference method.

Results

Fungal etiology was confirmed in 86 (7.23%) of 1189 corneal ulcers. A significant predisposing factor for FK was ocular trauma caused by plant materials. Therapeutic penetrating keratoplasty (PKP) was required in 60.4% of cases. The predominant fungal species isolated was Fusarium spp. (39.5%) followed by Aspergillus spp. (32.5%) and Candida spp. (16.2%).

Discussion

The MIC results indicate that amphotericin B may be appropriate for treating FK caused by Fusarium species. FK caused by Candida spp. can be treated with flucytosine, voriconazole, posaconazole, miconazole, and caspofungin. In developing countries such as Iran, corneal infection due to filamentous fungi is a common cause of corneal damage. In this region, fungal keratitis is observed primarily within the context of agricultural activity and subsequent ocular trauma. Fungal keratitis can be managed better with understanding the "local" etiologies and antifungal susceptibility patterns.

Impact of the COVID-19 Pandemic on the Incidence and Characteristics of Culture-Positive Microbial Keratitis at a Tertiary Eye Hospital in the UK

Purpose

The COVID-19 pandemic has led to drastic changes to the daily lives of those living in the United Kingdom. We hypothesized that the effect of the imposed lockdown on both behaviour and social interaction has the potential to influence the characteristics of microbial keratitis presenting locally to Manchester Royal Eye Hospital — a major tertiary eye centre in the UK.

Methods

We conducted a retrospective case-note review of all positive corneal scrape cultures identified by our local microbiology laboratory during the year since the announcement of lockdown measures in the UK (23 March 2020 to 23 March 2021). Culture results were compared with previously collated, published “baseline” data from prior to the onset of the COVID-19 pandemic (2004–2019). Statistical analysis was undertaken, predominantly looking at the incidence of microbial keratitis and the variety of cultured pathogens.

Results

A total of 6243 corneal scrape results were reviewed. Comparison of data between the COVID-19 pandemic and subsequent lockdown did not show a significant change in the incidence of culture-positive microbial keratitis: mean annual positive samples during 2004–2019 were 128 (35%) vs 91 (29%) during lockdown (P=0.096). No statistically significant shifts in the incidence of organism subtypes — fungi, acanthamoeba, Gram-positive bacteria, or Gram negative bacteria — were identified (P=0.196, 1, 0.366, and 0.087, respectively).

Conclusion

Contrary to our hypothesis, our results suggest that the COVID-19 pandemic did not alter the incidence or characteristics of microbial keratitis presenting to Manchester Royal Eye Hospital in the year following the implementation of lockdown measures in the UK.

The Risk Factors and Clinical Features of Acanthamoeba Keratitis: First Time Detection of Acanthamoeba T5 Genotype from Keratitis Patients in Turkey

PURPOSE

The primary aim of this study is to investigate Acanthamoeba in clinical samples of keratitis cases (n = 60), in contact lens (CL) and lens care solutions of asymptomatic CL users (n = 41), and to identify the genotypes in positive samples. The secondary aim is to assess the risk factors and clinical features of Acanthamoeba keratitis (AK) patients.

METHODS

All samples from patients and asymptomatic CL users were examined by microscopy and inoculated in non-nutrient agar plates. PCR was performed using the DNA isolated from corneal scrapings, CL and lens care solution samples. Positive DNA samples were sequenced to determine the genotype of Acanthamoeba.

RESULTS

In none of the samples, Acanthamoeba was identified by microscopy, while Acanthamoeba was detected in a patient with keratitis by culture method. However, Acanthamoeba was detected in 11.66% (7/60) of the keratitis patients by PCR. The genotypes of these isolates detected by sequencing were T4 (4), and T5 (3). Acanthamoeba was detected in none of the samples of asymptomatic CL users by any of the three methods.

CONCLUSION

To best of our knowledge, this is the first study to detect T5 genotype in AK patients from Turkey. In addition, the CL use was found to be an important risk factor for AK.

Pathogens and Antibiotic Susceptibilities of Global Bacterial Keratitis: A Meta-Analysis

Bacterial keratitis (BK) is the most common type of infectious keratitis. The spectrum of pathogenic bacteria and their susceptibility to antibiotics varied with the different regions. A meta-analysis was conducted to review the global culture rate, distribution, current trends, and drug susceptibility of isolates from BK over the past 20 years (2000–2020). Four databases were searched, and published date was limited between 2000 and 2020. Main key words were “bacterial keratitis”, “culture results” and “drug resistance”. Forty-two studies from twenty-one countries (35 cities) were included for meta-analysis. The overall positive culture rate was 47% (95%CI, 42–52%). Gram-positive cocci were the major type of bacteria (62%), followed by Gram-negative bacilli (30%), Gram-positive bacilli (5%), and Gram-negative cocci (5%). Staphylococcus spp. (41.4%), Pseudomonas spp. (17.0%), Streptococcus spp. (13.1%), Corynebacterium spp. (6.6%) and Moraxella spp. (4.1%) were the most common bacterial organism. The antibiotic resistance pattern analysis revealed that most Gram-positive cocci were susceptive to aminoglycoside (86%), followed by fluoroquinolone (81%) and cephalosporin (79%). Gram-negative bacilli were most sensitive to cephalosporin (96%) and fluoroquinolones (96%), followed by aminoglycoside (92%). In Gram-positive cocci, the susceptibility trends of fluoroquinolones were decreasing since 2010. Clinics should pay attention to the changing trends of pathogen distribution and their drug resistance pattern and should diagnose and choose sensitive antibiotics based on local data.

Clinical and Mycological Features in Fungal Keratitis: Retrospective Single Center Study (2012-2018)

Objectives:

To present the demographic, etiological, clinical, and mycological characteristics and treatment results of fungal keratitis patients admitted to our clinic.

Materials and Methods:

The medical records of patients diagnosed with fungal keratitis between October 2012 and 2018 were reviewed. The diagnosis of fungal keratitis was confirmed mycologically and/or cytologically. Treatment response was defined as complete infiltrate resolution and re-epithelization with medical treatment and minor surgical interventions. Patients who underwent penetrating keratoplasty or evisceration due to clinical deterioration despite treatment were classified as treatment nonresponders and were compared with responders in terms of demographic, etiological, and clinical characteristics.

Results:

Seventy-two (12.8%) of 559 patients diagnosed with microbial keratitis in the 6-year period were fungal keratitis. Of these, 38 cases (38 eyes) without polymicrobial etiology were included in the study. The patients’ mean age was 44.9±19.0 years (range: 2-80) and males predominated (14 females [36.8%], 24 males [63.2%]). Trauma (63.6%) was the most common predisposing factor in patients younger than 40 years old, whereas pathologies impairing ocular surface immunity were the leading risk factor (48.1%) in patients older than 40 years. Filamentous fungi were detected in 34 (89.5%) cases, while yeasts were found in 4 (10.5%) cases. Among 26 cases with positive cultures, Aspergillus species were the most common pathogens (42.3%). Infiltrate size before treatment was larger in nonresponders (14/38, 36.8%) compared to treatment responders (19/38, 50%) (p=0.049). In addition, rates of treatment response were higher in cases in which the infiltrate was located paracentrally compared to other cases (p=0.036).

Conclusion:

Fungal keratitis is an important public health problem in our region. Ocular trauma is a leading etiology in men under the age of 40 years. In the 6-year period, we observed that the main causes of fungal keratitis were filamentous fungi, and most commonly Aspergillus species. In cases presenting with large and central lesions, aggressive treatment options should be considered and these patients should be followed up more closely.

Effect of Antimicrobial Contact Lenses on Corneal Infiltrative Events: A Randomized Clinical Trial

Purpose

To determine whether Mel4-coated antimicrobial contact lenses (MACLs) can reduce the incidence of corneal infiltrative events (CIEs) during extended wear.

Methods

A prospective, randomized, double-masked, single-center, contralateral, extended contact lens wear clinical trial was conducted with 176 subjects. Each participant was randomly assigned to wear a MACL in one eye and an uncoated control contact lens in the contralateral eye or an extended-wear biweekly disposable modality for 3 months. The main outcome measures were the incidence of CIEs per 100 eye-months, identification of the microbial types colonizing the contact lenses or eyes at the time of the CIEs, and their susceptibility to Mel4.

Results

Nine participants (5.1%) experienced unilateral CIEs; six participants had contact lens acute red eye, and three participants had infiltrative keratitis. The incidence rate for CIEs (0.4 events per 100 participant months; 1.7%) in the Mel4-coated lenses (test) was 69% less than that of the control lenses (1.3 events per 100 participant months; 3.4%; P = 0.29). All Gram-negative bacteria isolated from lenses and lids of participants with CIEs (Citrobacter diversus, Acinetobacter haemolyticus, and Acinetobacter lwoffii) were susceptible to Mel4 peptide; minimum inhibitory concentrations ranged from 15.6 to 62.5 µg/mL. Reduction of adhesion of these bacteria by Mel4-coated lenses ranged from 2.1 to 2.2 log10 colony-forming units/lens.

Conclusions

MACLs had the capacity to reduce CIEs by at least 50% compared with uncoated control lenses during extended wear over 3 months; however, due to the relatively low rates of CIEs, the reduction was not statistically different compared with control lenses.

Translational Relevance

This study provides evidence that antimicrobial contact lenses have the potential to reduce the incidence of corneal infiltrative events during extended wear.

Comparison of Clinical Features and Treatment Outcomes of Pseudomonas aeruginosa Keratitis in Contact Lens and Non-Contact Lens Wearers

PURPOSE

To compare the outcomes of Pseudomonas aeruginosa keratitis (PAK) in contact lens wearers (CLWs) and non-contact lens wearers (non-CLWs) and identify risk factors for poor visual acuity (VA) outcomes in each group.

DESIGN

Retrospective cohort study METHODS: Two hundred fourteen consecutive cases of PAK were included between January 2006 and December 2019. Clinical features, microbiologic results, and treatment course were compared between CLW and non-CLW groups. Analyses of clinical features predicting poor final VA were performed.

RESULTS

This study identified 214 infected eyes in 207 patients with PAK, including 163 eyes (76.2%) in CLWs and 51 eyes (23.8%) in non-CLWs. The average age was 39.2 years in CLWs and 71.9 years in non-CLWs (P < .0001). The average logMAR visual acuity (VA) at presentation was 1.39 in CLWs and 2.17 in non-CLWs (P < .0001); average final VA was 0.76 in CLWs and 1.82 in non-CLWs (P < .0001). Stromal necrosis required a procedural or surgical intervention in 13.5% of CLWs and 49.0% of non-CLWs (P < .0001). A machine learning-based analysis yielded a list of clinical features that most strongly predict a poor VA outcome (worse than 20/40), including worse initial VA, older age, larger size of infiltrate or epithelial defect at presentation, and greater maximal depth of stromal necrosis.

CONCLUSIONS

Non-CLWs have significantly worse VA outcomes and required a higher rate of surgical intervention, compared with CLWs. Our study elucidates risk factors for poor visual outcomes in non-CLWs with PAK.

Pediatric Microbial Keratitis With Overnight Orthokeratology in Russia

OBJECTIVES

To estimate the incidence of microbial keratitis in children wearing overnight orthokeratology lenses in Moscow, Russia.

METHODS

To estimate the number of children wearing overnight orthokeratology lenses in 2018, 1,368 patient records from 13 Doctors Lens clinics were selected at random and extrapolated to the entire patient base. To identify cases of microbial keratitis, all episodes of infiltrative keratitis from Morozovskaya City Children's Clinical Hospital in 2018 were recorded and adjudicated by three experienced ophthalmologists. Incidence was calculated as the number of cases divided by the estimated number of wearers.

RESULTS

There were 23,049 overnight orthokeratology fits between 2010 and 2018. Among the 1,368 records surveyed, 1,078 (79%) were younger than 18 years at initial fitting. Based on a 7% or 10% annual discontinuation rate, the estimated number of children wearing lenses in 2018 was 10,307 or 9,422, respectively. During 2018, there were 139 cases of corneal infiltrative keratitis in children and 45 were adjudicated as microbial keratitis (32%). Of these, 20 cases were associated with contact lens wear (44%): 15 soft lens wearers (33%) and 5 overnight orthokeratology wearers (11%). Based on the 5 cases and assuming a 7% or 10% discontinuation rate, the annual incidence is 4.9 (95% confidence interval[CI]: 2.1-11.4) or 5.3 (95% CI: 2.3-12.4) per 10,000 patient years.

CONCLUSION

The incidence of microbial keratitis in children wearing overnight orthokeratology is lower than a previous United States study and similar to rates associated with use of daily wear soft contact lenses.

Mycotic Keratitis-A Global Threat from the Filamentous Fungi

Mycotic or fungal keratitis (FK) is a sight-threatening disease, caused by infection of the cornea by filamentous fungi or yeasts. In tropical, low and middle-income countries, it accounts for the majority of cases of microbial keratitis (MK). Filamentous fungi, in particular Fusarium spp., the aspergilli and dematiaceous fungi, are responsible for the greatest burden of disease. The predominant risk factor for filamentous fungal keratitis is trauma, typically with organic, plant-based material. In developed countries, contact lens wear and related products are frequently implicated as risk factors, and have been linked to global outbreaks of Fusarium keratitis in the recent past. In 2020, the incidence of FK was estimated to be over 1 million cases per year, and there is significant geographical variation; accounting for less than 1% of cases of MK in some European countries to over 80% in parts of south and south-east Asia. The proportion of MK cases is inversely correlated to distance from the equator and there is emerging evidence that the incidence of FK may be increasing. Diagnosing FK is challenging; accurate diagnosis relies on reliable microscopy and culture, aided by adjunctive tools such as in vivo confocal microscopy or PCR. Unfortunately, these facilities are infrequently available in areas most in need. Current topical antifungals are not very effective; infections can progress despite prompt treatment. Antifungal drops are often unavailable. When available, natamycin is usually first-line treatment. However, infections may progress to perforation in ~25% of cases. Future work needs to be directed at addressing these challenges and unmet needs. This review discusses the epidemiology, clinical features, diagnosis, management and aetiology of FK.

Understanding clinical and immunological features associated with Pseudomonas and Staphylococcus keratitis

Pseudomonas aeruginosa and Staphylococcus aureus are the two dominant Gram-negative and -positive species, respectively, isolated from patients with contact lens-related bacterial keratitis. The clinical features of bacterial keratitis vary, such that timely differential diagnosis can be challenging, which may cause a delay in diagnosis resulting in poorer outcome. This review aims to explore the current understanding of clinical and immunological features associated with contact lens-related P. aeruginosa and S. aureus keratitis based on currently available evidence. Firstly, the review characterises contact lens-related P. aeruginosa and S. aureus keratitis, based on clinical features and prognostic factors. Secondly, the review describes the primary immune response associated with a bacterial infection in in-vivo non-scratch contact lens-wearing animal models, colonised by bacteria on contact lens and topical administration of bacteria on the cornea. Finally, the review discusses the role of macrophage inflammatory protein-2 (MIP-2) and intercellular adhesion molecule (ICAM-1) in neutrophil recruitment based on both in-vivo scratch models of bacterial keratitis and bacterial challenged in cell culture models.

Development of a contact Lens risk survey

PURPOSE

To describe the development and report psychometric properties of the Contact Lens Risk Survey (CLRS) to identify patients at risk for soft contact lens-related complications.

METHODS

Psychometric properties of the CLRS, a web-based survey with branching logic, were determined using data from 5 multi-site fieldings (n = 1059), including re-fielding to sub groups. Responses from participants with and without an active red eye were used to identify risk factors of a red eye event and calculate an overall risk score. A 6th fielding of the CLRS (n = 171) was used to assess discriminate validity.

RESULTS

Participants needed 11-12 min to complete the survey with a negligible difference by age. Internal consistency was excellent (Cronbach's α ≥ 0.70) for 3 of the 5 constructs identified by factor analysis. Twelve of the 17 survey items exhibited excellent within-subject repeatability (Kappa ≥ 0.61). Between-subject agreement, assessed in 18-25 year olds, was high for the majority of items, suggesting good generalizability across different populations of SCL wearers. The ability of the model using individual items of the CLRS to discriminate Controls and participants with a red eye was good with an area under the curve of 0.779.

CONCLUSION

The CLRS tool is a repeatable and valid instrument to standardize documentation of demographic, behavior, and exposure factors which appear to drive the greatest risk of a contact lens related red eye event.

Corneal Infection Models: Tools to Investigate the Role of Biofilms in Bacterial Keratitis

Bacterial keratitis is a corneal infection which may cause visual impairment or even loss of the infected eye. It remains a major cause of blindness in the developing world. Staphylococcus aureus and Pseudomonas aeruginosa are common causative agents and these bacterial species are known to colonise the corneal surface as biofilm populations. Biofilms are complex bacterial communities encased in an extracellular polymeric matrix and are notoriously difficult to eradicate once established. Biofilm bacteria exhibit different phenotypic characteristics from their planktonic counterparts, including an increased resistance to antibiotics and the host immune response. Therefore, understanding the role of biofilms will be essential in the development of new ophthalmic antimicrobials. A brief overview of biofilm-specific resistance mechanisms is provided, but this is a highly multifactorial and rapidly expanding field that warrants further research. Progression in this field is dependent on the development of suitable biofilm models that acknowledge the complexity of the ocular environment. Abiotic models of biofilm formation (where biofilms are studied on non-living surfaces) currently dominate the literature, but co-culture infection models are beginning to emerge. In vitro, ex vivo and in vivo corneal infection models have now been reported which use a variety of different experimental techniques and animal models. In this review, we will discuss existing corneal infection models and their application in the study of biofilms and host-pathogen interactions at the corneal surface.

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.

Comparison of fungal and bacterial keratitis between tropical and subtropical Taiwan: a prospective cohort study

Background

Fungal keratitis (FK) has been shown to be a climate-sensitive disease. The differentiation between FK from bacterial keratitis (BK) was difficult. The purpose of this study was to compare the bacteriology and mycology between tropical and subtropical Taiwan and to investigate the independent risk factors for identification of fungi from bacteria.

Methods

Two hundred ninety-seven patients with clinical suspected microbial keratitis were prospectively enrolled. A fungal to bacteria rate (FBR), the number of fungi divided by bacteria identified, was determined to estimate the prevalence of fungi and bacteria. Clinical presentation, profiles of microorganisms, and predisposing risk factors were determined. Univariate and multivariate logistic regression analysis were used to investigate the independent risk factors.

Results

A total of 82 fungi and 143 bacteria were laboratory confirmed. The identification rate of fungus was higher in tropical Taiwan (p = 0.010). Among the fungi and bacteria confirmed, the FBR was 0.29 (22.4% vs. 77.6%) in subtropical Taiwan, and 0.70 (41.3% vs. 58.7%) in tropical Taiwan. Samples obtained in tropical area (p = 0.019), ocular trauma (p = 0.019), and plant exposure (p = 0.003) were independent risk factors for identification of fungus from bacteria. The predominant fungus isolated from corneal scraping were Fusarium solani (25%) and Trichosporon faecale (25%) in subtropical Taiwan; in tropical Taiwan was Fusarium spp. (50%).

Conclusions

The identification rate of fungus was higher in tropical Taiwan than subtropical Taiwan. Awareness of the local epidemiology is crucial for early diagnosis of fungal keratitis in tropical area.

The relationship between environmental sources and the susceptibility of Acanthamoeba keratitis in the United Kingdom

PURPOSE

To determine whether Acanthamoeba keratitis (AK) patients have higher rates of Acanthamoeba and free-living amoeba (FLA) colonising domestic sinks than control contact lens (CL) wearers, and whether these isolates are genetically similar to the corneal isolates from their CL associated AK.

METHODS

129 AK patients from Moorefield Eye Hospital, London and 64 control CL wearers from the Institute of Optometry were included in this study. The participants self-collected home kitchen and bathroom samples from tap-spouts, overflows and drains using an instructional kit. The samples were cultured by inoculating onto a non-nutrient agar plate seeded with Escherichia coli, incubated at 32°C and examined for amoebae by microscopy for up to 2 weeks. Partial sequences of mitochondrial cytochrome oxidase genes (coxA) of Acanthamoeba isolates from four AK patients were compared to Acanthamoeba isolated from the patient's home. The association between sampling sites was analysed with the chi-square test.

RESULTS

A total of 513 samples from AK patients and 189 from CL controls were collected. The yield of FLA was significantly greater in patients' bathrooms (72.1%) than CL controls' bathrooms (53.4%) (p<0.05). Spouts (kitchen 6.7%, bathroom 11%) had the lowest rate of Acanthamoeba isolation compared to drains (kitchen 18.2%, bathroom 27.9%) and overflow (kitchen 39.1%, bathroom 25.9%) either in kitchens or bathrooms (p<0.05). There was no statistically significant difference between the average prevalence of Acanthamoeba in all three sample sites in kitchens (16.9%) compared to all three sample sites in bathrooms (21.5%) and no association for Acanthamoeba prevalence between AK patients and CL controls. All four corneal isolates had the same coxA sequence as at least one domestic water isolate from the patients' sink of the kitchen and the bathroom.

CONCLUSION

The prevalence of Acanthamoeba and FLA was high in UK homes. FLA colonisation was higher in AK patients compared to controls but the prevalence of Acanthamoeba between AK patients and CL controls domestic sinks was similar. This study confirms that domestic water isolates are probably the source of AK infection. Advice about avoiding water contact when using CL's should be mandatory.

Risk Factors of Microbial Keratitis in Uganda: A Case Control Study

Purpose: Microbial keratitis (MK), is a frequent cause of sight loss worldwide, particularly in low and middle-income countries. This study aimed to investigate the risk factors of MK in Uganda.Methods: Using a nested case control, we recruited healthy community controls for patients presenting with MK at the two main eye units in Southern Uganda between December 2016 and March 2018. Controls were individually matched for age, gender and village of the cases on a 1:1 ratio. We collected information on demographics, occupation, HIV and Diabetes Mellitus status. In STATA version 14.1, multivariable conditional logistic regression was used to generate odds ratios for risk factors of MK and a likelihood ratio test used to assess statistical significance of associations.Results: Two hundred and fifteen case-control pairs were enrolled. The HIV positive patients among the cases was 9% versus 1% among the controls, p = .0003. Diabetes 7% among the cases versus 1.4% among the controls, p = .012. Eye trauma was 29% versus 0% among the cases and controls. In the multivariable model adjusted for age, sex and village, HIV (OR 83.5, 95%CI 2.01-3456, p = .020), Diabetes (OR 9.38, 95% CI 1.48-59.3, p = .017) and a farming occupation (OR 2.60, 95%CI 1.21-5.57, p = .014) were associated with MK. Compared to a low socio-economic status, a middle status was less likely to be associated with MK (OR 0.29, 95%CI 0.09-0.89, p < .0001).Conclusion: MK was associated with HIV, Diabetes, being poor and farming as the main occupation. More studies are needed to explore how these factors predispose to MK.

The Development of an Antimicrobial Contact Lens - From the Laboratory to the Clinic

Contact lens wear is generally safe and provides excellent vision. However, contact lens wear is often associated with the risk of developing ocular surface infection and inflammation, and in severe cases, the infection can result in loss of vision. Antimicrobial peptide-coated contact lenses have been made to help reduce the incidence of infection and inflammation. This paper reviews the research progress from conception, through the laboratory and preclinical tests to the latest information on clinical testing of an antimicrobial contact lens. We provide insights into the pathways followed and pitfalls that have been encountered. The journey has not always been linear or smooth, but has resulted in some of the first published clinical testing of antimicrobial peptide-coated contact lenses in humans. We hope this may help lead to the development and commercialisation of antimicrobial contact lenses in the future.

A review of cosmetic contact lens infections

This paper provides a comprehensive review of the existing literature surrounding cosmetic contact lens infections. In this paper, lens-related, dispensing-related and patient-related factors are examined in detail.

Clinical Significance of Biofilm on Silicone Tubes Removed From Patients With Nasolacrimal Duct Stenosis

PURPOSE

To determine the relationship between the optical density of biofilms on silicone tubes and surgical outcomes.

METHODS

A total of 43 silicone tubes from 33 patients with nasolacrimal duct stenosis were enrolled at 6 months after bicanalicular silicone tube intubation. The removed silicone tubes were divided into 2 segments. One segment of silicone tube was cultured while the other segment was used to measure optical density of biofilm. Each segment was divided into 3 pieces according to average normal human nasolacrimal anatomy. The first piece was located from puncta to lacrimal sac. The second piece was inside the nasolacrimal duct. The third piece was in the nasal cavity. Surgical outcome was evaluated at postoperative 12 months based on Munk score and fluorescein dye disappearance test.

RESULTS

A total of 31 (72.1%) patients were surgically successful while 12 (27.9%) patients had surgical failure with persistent epiphora. In the second piece of silicone tube, the mean optical density of biofilm was 0.2654 nm in the surgical success group and 0.4472 nm in the surgical failure group. These results showed statistically significant (P < 0.01) difference. The most frequently isolated organism was Staphylococcus aureus in the surgical success group (7 of 31 patients, 22.6%). It was Pseudomonas aeruginosa in the surgical failure group (6 of 12 patients, 50%).

CONCLUSION

This is the first study that determines the relationship between biofilm on silicone tube and surgical outcome. Biofilm formed on silicone tubes in nasolacrimal duct might cause surgical failure.

Fungal keratitis: An overview of clinical and laboratory aspects

Mycotic keratitis or keratomycosis is a fungal infection with global distribution. The dominant aetiology of this disease varies based on geographical origin, socioeconomic status, and climatic condition. Generally, Aspergillus spp. and Fusarium spp. are common in tropical and subtropical regions and Candida spp. are dominant in temperate areas. Demonstration of fungal elements in microscopic examination besides the isolation of fungi in culture is the gold standard of laboratory diagnosis. As the culture is a time-consuming procedure, other approaches such as in vivo confocal microscopy which produces real-time imaging of corneal tissue and molecular techniques have been developed to facilitate rapid diagnosis of fungal keratitis. The first choice of treatment is topical natamycin, although topical amphotericin B is the best choice for Aspergillus and Candida keratitis. Regarding the diversity of fungal aetiology and the emergence of drug resistance in some genera and species, proper identification using molecular methods and antifungal susceptibility testing could provide useful data. Furthermore, as the better efficacy of combination therapy in comparison to monotherapy is reported, in vitro determination of interactions between various drugs seem informative. This review aims to provide a general and updated view on the aetiology, risk factors, epidemiology, clinical and laboratory diagnosis, and management of fungal keratitis.

Multicenter Testing of a Risk Assessment Survey for Soft Contact Lens Wearers With Adverse Events: A Contact Lens Assessment in Youth Study

PURPOSE

To test the ability of responses to the Contact Lens Assessment in Youth (CLAY) Contact Lens Risk Survey (CLRS) to differentiate behaviors among participants with serious and significant (S&S) contact lens-related corneal inflammatory events, those with other events (non-S&S), and healthy controls matched for age, gender, and soft contact lens (SCL) wear frequency.

METHODS

The CLRS was self-administered electronically to SCL wearers presenting for acute clinical care at 11 clinical sites. Each participant completed the CLRS before their examination. The clinician, masked to CLRS responses, submitted a diagnosis for each participant that was used to classify the event as S&S or non-S&S. Multivariate logistic regression analyses were used to compare responses.

RESULTS

Comparison of responses from 96 participants with S&S, 68 with non-S&S, and 207 controls showed that patients with S&S were more likely (always or fairly often) to report overnight wear versus patients with non-S&S (adjusted odds ratio [aOR], 5.2; 95% confidence interval [CI], 1.4-18.7) and versus controls (aOR, 5.8; CI, 2.2-15.2). Patients with S&S were more likely to purchase SCLs on the internet versus non-S&S (aOR, 4.9; CI, 1.6-15.1) and versus controls (aOR, 2.8; CI, 1.4-5.9). The use of two-week replacement lenses compared with daily disposables was significantly higher among patients with S&S than those with non-S&S (aOR, 4.3; CI, 1.5-12.0). Patients with S&S were less likely to regularly discard leftover solution compared with controls (aOR, 2.5; CI, 1.1-5.6).

CONCLUSIONS

The CLRS is a clinical survey tool that can be used to identify risky behaviors and exposures directly associated with an increased risk of S&S events.

Non-contact lens related Acanthamoeba keratitis

The purpose of the study is to describe epidemiology, clinical features, diagnosis, and treatment of Acanthamoeba keratitis (AK) with special focus on the disease in nonusers of contact lenses (CLs). This study was a perspective based on authors' experience and review of published literature. AK accounts for 2% of microbiology-proven cases of keratitis. Trauma and exposure to contaminated water are the main predisposing factors for the disease. Association with CLs is seen only in small fraction of cases. Contrary to classical description experience in India suggests that out of proportion pain, ring infiltrate, and radial keratoneuritis are seen in less than a third of cases. Majority of cases present with diffuse infiltrate, mimicking herpes simplex or fungal keratitis. The diagnosis can be confirmed by microscopic examination of corneal scraping material and culture on nonnutrient agar with an overlay of Escherichia coli. Confocal microscopy can help diagnosis in patients with deep infiltrate; however, experience with technique and interpretation of images influences its true value. Primary treatment of the infection is biguanides with or without diamidines. Most patients respond to medical treatment. Corticosteroids play an important role in the management and can be used when indicated after due consideration to established protocols. Surgery is rarely needed in patients where definitive management is initiated within 3 weeks of onset of symptoms. Lamellar keratoplasty has been shown to have good outcome in cases needing surgery. Since the clinical features of AK in nonusers of CL are different, it will be important for ophthalmologists to be aware of the scenario wherein to suspect this infection. Medical treatment is successful if the disease is diagnosed early and management is initiated soon.

Epidemiology of contact lens-induced infiltrates: an updated review

Corneal infiltrative events (CIEs) are well established as a risk associated with soft contact lens wear. The incidence of symptomatic CIEs during extended soft lens wear ranges from 2.5 to six per cent; when asymptomatic CIEs are included, the incidence can be as high as 20-25 per cent. In daily soft lens wear, the annual incidence of symptomatic CIEs is about three per cent. There are various accepted methods of categorising CIEs, and a scoring system based on clinical signs and symptoms is a good approach to grade severity. Lens-related risk factors include extended wear, silicone hydrogel material, the use of multipurpose solutions, bacterial bioburden and reusable lenses. Recent studies report that daily disposable lenses reduce the risk of CIEs.

Fungal Keratitis Associated With Airborne Organic Debris and Soft Contacts Lenses: Case Reports and Review of the Literature

OBJECTIVES

To report two cases of fungal keratitis in soft contact lens wearers who were exposed to environmental mold.

METHODS

Case reports, with review of the relevant literature.

RESULTS

Two otherwise healthy middle-aged women who were soft contact lens wearers developed fungal keratitis about 1 week after heavy exposure to environmental mold. Culture results showed Aspergillus from one patient and the unusual combination of Trichoderma and Penicillium from the other. Both were treated with topical natamycin, topical fluoroquinolone antibiotic prophylaxis, and periodic ulcer debridement. After many weeks of treatment, both ulcers healed with subsequent scarring. Because the ulcers were located in the peripheral cornea in both cases, excellent final visual acuities were achieved. Fungal keratitis cases like these are rarely seen at our referral clinic, which is located in the temperate climate of northeastern Indiana.

CONCLUSIONS

In addition to the usual recommended contact lens care guidelines, it may be prudent for eye care providers to warn patients against wearing their contact lenses in situations likely to result in heavy exposure to organic matter or, at the very least, to wear tight-fitting goggles for eye protection.

Twelve-year analysis of microbial keratitis trends at a UK tertiary hospital

PurposeTo investigate the frequencies, trends, and in vitro drug susceptibilities of the causative pathogens in microbial keratitis in Manchester Royal Eye Hospital.Patients and methodsCorneal scrape results recorded by the microbiology service between 2004 and 2015 were extracted from an established database. A total of 4229 corneal scrape specimens were identified from an established database. First-line antibiotic treatment in our centre during the study period was ofloxacin and second line was cefuroxime and gentamicin.ResultsMean age was 45.9±21.0. A total of 1379 samples (32.6%) were culture positive. One hundred forty-eight (10.7%) specimens cultured multiple organisms. Of the 1539 organisms identified, 63.3% were Gram-positive bacteria, 27.3% Gram-negative bacteria, 7.1% fungi, and 2.3% Acanthamoebae. A decreasing trend in Gram-positive isolates was found together with a stable trend in Gram negatives and an increasing trend in Acanthamoeba and fungi. There appeared to be a significant increasing trend of Moraxella infection (P=0.001). In all, 83.1 and 90.8% of Gram-positive and -negative isolates tested were susceptible to ofloxacin, respectively. Cefuroxime covered 86.6% of Gram-positive and 61.4% of Gram-negative isolates, whereas gentamicin covered 88.8 and 96.5% of Gram-positive and -negative isolates, respectively.ConclusionWe found a change in the type of Gram-negative organisms isolated over time, with the Moraxella species on the rise. Reassuringly, no significant increase in resistance was observed in vitro for any of the commonly used antibiotics. Ofloxacin remains a good first-line antibiotic treatment but duo-therapy does have broader coverage and should be considered in non-responsive cases.

Prevention of Bacterial Biofilm Formation on Soft Contact Lenses Using Natural Compounds

Purpose

In eye care field, contact lenses (CL) have a great impact on improving vision, but their use can be limited by ocular infection. CL- associated infections can be reduced by good attention to CL storage case practice. CL-care solutions should be able to control microbial growth on CL.

The aim of the study was to evaluate and compare the efficacy of CL-care solutions (found in Egyptian market) with some natural compounds in removal and inhibition of bacterial biofilm formed on soft CL.

Clinical isolates were recovered from patients having conjunctivitis from Benha University Hospital and identified microbiologically. Quantification of biofilm was done using microtiter plate assay. Three multipurpose CL-care solutions were examined for their ability to remove and inhibit biofilm. Also four natural extracts having antibacterial activity and are safe on eye were tested for their anti-biofilm activity.

Results

The major bacterial isolates from eye infections were Pseudomonas aeruginosa (36%) and Staphylococcus spp. (37.8%). Only 33.3% of isolates showed ability to produce weak to moderate biofilm. The tested multi-purpose CL-care solutions showed moderate ability to remove preformed biofilm. Among the tested natural compounds, Calendula officinalis and Buddleja salviifolia extracts showed an excellent efficacy in inhibition of biofilm and also removal of preformed biofilm.

Conclusion

This study demonstrated that isolates from infected eye and CL-cases showed weak to moderate biofilm formation. Calendula officinalis and Buddleja salviifolia extracts showed excellent effect on inhibition and removal of biofilm, these extracts could be added into CL-care solutions which could markedly reduce eye-infections during CL-wear.

Efficacy of Korean Multipurpose Contact Lens Disinfecting Solutions against Acanthamoeba castellanii

Acanthamoeba keratitis has been increasing in recent years. Main risk factors are contact lens wear and their cleaning solutions. Most contact lens wearers use multipurpose disinfecting solutions (MPDS) for cleansing and disinfecting microorganisms because of its convenience. We determined amoebicidal effects of MPDS made in Korea and their cytotoxicity on human corneal epithelium cells. Fifteen commercial MPDS (A to O) were tested for their amoebicidal effects on Acanthamoeba castellanii trophozoites and cysts by using a most probable number (MPN) technique. Among them, 7 kinds of MPDS showed little or no amoebicidal effects for 24 hr exposure. Solutions A, B, G, H, L, and O showed positive amoebicidal effects, and solutions M and N killed almost all trophozoites and cysts after 24 hr exposure. However, 50%-N solution showed 56% cytotoxicity on human corneal epithelial cells within 4 hr exposure, and 50%-O solution also showed 62% cytotoxicity on human cells within 4 hr exposure. Solution A did not show any cytotoxicity on human cells. These results revealed that most MPDS made in Korea were ineffective to kill Acanthamoeba. The solutions having amoebicidal activity also showed high levels of cytotoxicity on human corneal epithelial cells. New formulations for improved MPDS that are amoebicidal but safe for host cells are needed to prevent Acanthamoeba keratitis.

[The German Acanthamoeba keratitis register: Initial results of a multicenter study]

BACKGROUND AND PURPOSE

In September 2011 the cornea section of the German Ophthalmological Society (DOG) established the first German Acanthamoeba keratitis registry. The data of this multicenter survey are being collected, compiled and evaluated at the Department of Ophthalmology at the Saarland University. The aim of this article is to present an intermediate report.

PATIENTS AND METHODS

Data from 172 eyes with Acanthamoeba keratitis were collected during the last 10 years. For this interim report we actually evaluated 121 eyes (60.2 % female patients, average age 41.3 years) and collected the following data: date of onset of symptoms, date and method of diagnosis, initial diagnosis, anamnestic data, clinical symptoms and signs at diagnosis and during follow-up, conservative and surgical therapy. Criteria for inclusion in the Acanthamoeba registry was the established diagnosis of an Acanthamoeba keratitis with at least one of the methods described in this article.

RESULTS

Acanthamoeba keratitis could be histologically proven in 55.3 % of the cases, via PCR in 25.6 %, with confocal microscopy in 20.4 % and using in vitro cultivation in 15.5 %. Clinical symptoms and signs in Acanthamoeba keratitis were pain in 67.0 %, ring infiltrates in 53.4 %, pseudodendritiform epitheliopathy in 11.7 % and keratoneuritis in 5.8 %. In 47.6 % of the cases the initial diagnosis was herpes simplex virus keratitis followed by bacterial keratitis in 25.2 % and fungal keratitis in 3.9 %. Acanthamoeba keratitis was the correct initial diagnosis in only 23.2 % of cases. The average time period between first symptoms and diagnosis was 2.8 ± 4.0 months (range 0-23 months). A triple therapy with Brolene® Lavasept® and antibiotic eye drops at least 5 ×/day was used in 54.5 % of eyes (n = 66). Penetrating keratoplasty was performed in 40.4 %, in 18 cases in combination with cryotherapy of the cornea. The mean graft diameter was 7.9 ± 1.1 mm (range 3.5-11.0 mm). The final visual acuity (Snellen visual acuity chart at 5 m) was comparable in the two groups of eyes with (5/40 ± 5/25) and without (5/32 ± 5/25) keratoplasty.

CONCLUSION

Acanthamoeba keratitis is a rare and often very late diagnosed disease and two thirds of the cases were initially misdiagnosed. The early recognition of the typical symptoms is crucial for the prognosis of the disease. All ophthalmological departments in Germany are invited to submit further data of all confirmed cases (berthold.seitz@uks.eu), whether retrospectively or prospectively in order to generate an adequate standardized diagnostic and therapeutic approach for this potentially devastating disease.

Public's knowledge of the differences between ophthalmologists and optometrists: a critical issue in eye care service utilisation

AIM

To assess the public's knowledge of the differences between ophthalmologists and optometrists and identify the factors associated with knowledge.

METHODS

The study was a population-based random survey of adults aged 18 years or older conducted in Enugu, south eastern Nigeria, between March and June, 2011. Data on respondents' socio-demographics, clinical profile, and knowledge of the differences between ophthalmologists and optometrists were collected using a 28-item questionnaire. Data were analysed using descriptive and analytical statistics. Values of P<0.05 were considered statistically significant.

RESULTS

The respondents (n=394) comprised 198 males and 196 females (sex ratio=1.01:1), aged 18-70 (30.9±10.8) years. The majority of respondents were single (57.4%), possessed secondary education (96.9%), employed (65.2%) and had no health insurance (77.4%). Their clinical profile showed previous eye exam 54.1%, spectacle wear 41.6% and contact lens wear 5.6%. In the multivariate analysis, participants' good knowledge of the differences between ophthalmologists and optometrists was significantly associated with educational status (OR: 0.32, 95% CI: 0.23-0.44, P<0.0001, β=-0.988), employment status (OR: 1.8, 95% CI: 1.45-2.25, P<0.0001, β=0.124) and previous eye examination (OR: 1.63, 95% CI: 1.29-2.07, P<0.0001, β=0.549).

CONCLUSION

Participants' socio-demographic and clinical characteristics are important predictors of good knowledge. The findings may have implications for all stakeholders in eye care delivery. There is need for knowledge enhancement, by the government and eye care providers, through population-based eye health literacy campaigns.

Fungal keratitis in patients with corneal ulcer attending Minilik II Memorial Hospital, Addis Ababa, Ethiopia

BACKGROUND

Fungal keratitis is an important cause of corneal blindness all over the world. Although there are several reports on fungal keratitis from developing and developed countries, fungal keratitis in Ethiopia is poorly known. The aim of this study was to determine the prevalence of fungal keratitis and spectrum of fungi implicated in causing the infection.

METHODS

The present study was a single institutional cross-sectional study carried out in Minilik II Memorial Hospital eye clinic, Addis Ababa, Ethiopia from September 2014 to August 2015. Corneal scraping was obtained under aseptic condition with sterile 21 gauge needle by an ophthalmologist from patients suspected of microbial keratitis. Each scraping was inoculated onto Sabouraud Dextrose Agar in C-shaped streaks and incubated at 25 °C aerobically for four weeks. Cultures of mycelia fungi were identified by examining macroscopic and microscopic characteristics of their colonies. Yeasts were identified by employing biochemical and assimilation test procedures and using CHROMagar Candida culture. All data were coded, double entered and analyzed using SPSS version 20.

RESULT

Out of 153 cases of microbial keratitis, fungi were recovered from 69 patients giving fungal keratitis prevalence of 45.1. Patients from rural areas were significantly affected than patients in urban regions (P = 0.005). Age groups of 25-34 (P = 0.017) and 15-24 years (P = 0.008) were significantly affected. Fungal keratitis was significantly associated with farmers (P = 0.0001), daily laborers (P = 0.0001), unemployed (P = 0001) and students (P = 0.004). Fungal keratitis was statistically associated with trauma (P = 0.006), and diabetes (P = 0.024). Seventy six fungal isolates were recovered, of which molds accounted 63 (82.9 %) of the total isolates. Fusarium and Aspergillus species were the two predominant molds accounting 27.6 and 25 % of the total isolates respectively. Yeast isolates accounted only 17.1 %.

CONCLUSION

High prevalence of fungal keratitis recorded in the present study, highlights the need for nationwide study on fungal keratitis and precise identification of the causative fungi and institution of appropriate treatment strategy.

Penicillium keratitis in a HIV-infected patient

A 36-year-old HIV-positive man presented with symptoms of redness, blurred vision and foreign body sensation in his right eye for 3 months. The slit lamp examination revealed deep stromal infiltration with a feathery margin in an otherwise minimal anterior chamber reaction. A corneal scraping was negative. Confocal microscopy demonstrated an abnormal large hyper-reflective oval shape in the corneal stroma. Corneal infiltration did not show improvement after topical, intrastromal and intracameral antifungal treatment. Therapeutic penetrating keratoplasty was performed to eradicate the infection. Corneal button culture and histopathological results confirmed the diagnosis of Penicillium marneffei keratitis. No recurrent infection occurred after corneal transplantation. This appears to be the first report of P. marneffei keratitis in an HIV-infected patient. Although it is an uncommon condition, it should be one of the differential diagnoses in an HIV-infected patient presenting with keratitis.

Bacterial spectrum and resistance patterns in corneal infections at a Tertiary Eye Care Center in South China

AIM

To investigate the spectrum and antibiotic susceptibility of bacteria isolated from patients with suspected corneal infections in Zhongshan Ophthalmic Center in South China over the past four years retrospectively.

METHODS

Totally 1943 corneal scrapes from patients with corneal infections from 2010 to 2013 were cultured and processed using standard microbiological procedures to identify bacterial isolates. Simultaneously, the bacterial isolates were tested for antibiotic susceptibility to 8 antibiotics (ceftazidime, cefuroxim, cefazolin, levofloxacin, ofloxacin, neomycin, tobramycin, chloramphenicol) using the Kirby-Bauer disc diffusion technique.

RESULTS

Of the total 1943 scrapes, 397 (20.43%) were culture-positive, of which 294 (74.06%) were gram-positive (GP) and 103 (25.94%) were gram-negative (GN) bacteria. Of the GP organisms, the most prevalent genera were Staphylococcus spp. (56.17%, n=223), Kocuria spp. (5.29%, n=21) and Micrococcus spp. (1.26%, n=5). On the other hand, the most prevalent genera were Pseudomonas spp. (12.85%, n=51), Burkholderia spp. (2.02%, n=8) and Acinetobacter spp. (1.51%, n=6) for the GN organisms. Among five antibiotics that have eye drop products, the resistant to neomycin of GP (7.82%, 95% CI: 4.72%-10.92%) and GN isolates (9.71%, 95% CI: 4.01%-15.41%) was lowest, while the resistant to chloramphenicol was highest (GP: 34.35%, 95% CI: 28.92%-39.78%; GN: 60.19%, 95% CI: 50.74%-69.64%).

CONCLUSION

Staphylococcus spp. was the most common bacterial pathogens isolated from patients with corneal infections in this setting. High percentages of GP and GN bacteria were mostly susceptible to neomycin and highly resistant to chloramphenicol.

Antimicrobial activity of four cationic peptides immobilised to poly-hydroxyethylmethacrylate

The objective of this study was to immobilise and characterise a variety of antimicrobial peptides (AMPs) onto poly-hydroxyethylmethacrylate (pHEMA) surfaces to achieve an antibacterial effect. Four AMPs, viz. LL-37, melimine, lactoferricin and Mel-4 were immobilised on pHEMA by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) which assisted covalent attachment. Increasing concentrations of AMPs were immobilised to determine the effect on the adhesion of Pseudomonas aeruginosa and Staphylococcus aureus. The AMP immobilised pHEMAs were characterised by X-ray photoelectron spectroscopy (XPS) to determine the surface elemental composition and by amino acid analysis to determine the total amount of AMP attached. In vitro cytotoxicity of the immobilised pHEMA samples to mouse L929 cells was investigated. Melimine and Mel-4 when immobilised at the highest concentrations showed 3.1 ± 0.6 log and 1.3 ± 0.2 log inhibition against P. aeruginosa, and 3.9 ± 0.6 log and 2.4 ± 0.5 log inhibition against S. aureus, respectively. Immobilisation of LL-37 resulted in up to 2.6 ± 1.0 log inhibition against only P. aeruginosa, but no activity against S. aureus. LFc attachment showed no antibacterial activity. Upon XPS analysis, immobilised melimine, LL-37, LFc and Mel-4 had 1.57 ± 0.38%, 1.13 ± 1.36%, 0.66 ± 0.47% and 0.73 ± 0.32% amide nitrogen attached to pHEMA compared to 0.12 ± 0.14% in the untreated controls. Amino acid analysis determined that the total amount of AMP attachment to pHEMA was 44.3 ± 7.4 nmol, 3.8 ± 0.2 nmol, 6.5 ± 0.6 nmol and 48.9 ± 2.3 nmol for the same peptides respectively. None of the AMP immobilised pHEMA surfaces showed any toxicity towards mouse L929 cells. The immobilisation of certain AMPs at nanomolar concentration to pHEMA is an effective option to develop a stable antimicrobial surface.

Study on Prevalence, Antibiotic Susceptibility, and tuf Gene Sequence-Based Genotyping of Species-Level of Coagulase-Negative Staphylococcus Isolated From Keratitis Caused by Using Soft Contact Lenses

OBJECTIVE

To study on antibiotic susceptibility and identify coagulase-negative Staphylococcus (CoNS) species based on tuf gene sequencing from keratitis followed by using soft contact lenses in Isfahan, Iran, 2013.

METHODS

This study examined 77 keratitis cases. The samples were cultured and the isolation of CoNS was done by phenotypic tests, and in vitro sensitivity testing was done by Kirby-Bauer disk diffusion susceptibility method.

RESULTS

Thirty-eight of isolates were conveniently identified as CoNS. In this study, 27 (71.1%), 21 (55.3%), and 16 (42.1%) were resistant to penicillin, erythromycin, and tetracycline, respectively. One hundred percent of isolates were sensitive to gentamicin, and 36 (94.7%) and 33 (86.8%) of isolates were sensitive to chloramphenicol and ciprofloxacin, respectively. Also, resistances to cefoxitin were 7 (18.4%). Analysis of tuf gene proved to be discriminative and sensitive in which all the isolates were identified with 99.0% similarity to reference strains, and Staphylococcus epidermidis had the highest prevalence among other species.

CONCLUSIONS

Results of this study showed that CoNS are the most common agents causing contact lens-associated microbial keratitis, and the tuf gene sequencing analysis is a reliable method for distinguishing CoNS species. Also gentamycin, chloramphenicol, and ciprofloxacin are more effective than the other antibacterial agents against these types of bacteria.

Corneal Biofilms: From Planktonic to Microcolony Formation in an Experimental Keratitis Infection with Pseudomonas Aeruginosa

PURPOSE

Microbial biofilms commonly comprise part of the infectious scenario, complicating the therapeutic approach. The purpose of this study was to determine in a mouse model of corneal infection if mature biofilms formed and to visualize the stages of biofilm formation.

METHODS

A bacterial keratitis model was established using Pseudomonas aeruginosa ATCC 9027 (1 × 10(8) CFU/ml) to infect the cornea of C57BL/6 black mouse. Eyes were examined post-infection (PI) on days 1, 2, 3, 5, and 7, and imaged by slit lamp microscopy, and light, confocal, and electron microscopy to identify the stages of biofilm formation and the time of appearance.

RESULTS

On PI day 1, Gram staining showed rod-shaped bacteria adherent on the corneal surface. On PI days 2 and 3, bacteria were seen within webs of extracellular polymeric substance (EPS) and glycocalyx secretion, imaged by confocal microscopy. Scanning electron microscopy demonstrated microcolonies of active infectious cells bound with thick fibrous material. Transmission electron microscopy substantiated the formation of classical biofilm architecture with P. aeruginosa densely packed within the extracellular polymeric substances on PI days 5 and 7.

CONCLUSION

Direct visual evidence showed that biofilms routinely developed on the biotic surface of the mouse cornea. The mouse model can be used to develop new approaches to deal therapeutically with biofilms in corneal infections.

Incidence and clinical characteristics of fungal keratitis in a Danish population from 2000 to 2013

PURPOSE

Fungal keratitis is a severe sight-threatening condition. The aim of this study was to investigate the incidence and clinical characteristics of fungal keratitis patients living in a temperate climate.

METHODS

By reviewing medical records from 2000 to July 2013, patients with fungal keratitis were identified. Risk factors, clinical signs and outcome were registered.

RESULTS

Twenty-five patients were identified: 52% with Candida, 20% with Fusarium, 16% with Aspergillus and 12% with mixed filamentous fungi. A minimum incidence of fungal keratitis of 0.6 cases per million per year was estimated. Prior topical steroid treatment was commonly found in our cases (44%). Trauma including contact lens wear was associated with infection with filamentous fungi, whereas in patients with Candida infection, ocular surface disease was a prominent feature. Median time from onset of symptoms to diagnosis was 24 days. Only a few patients exhibited classical clinical features such as endothelial plaques (28%), satellite lesions (24%) and feathery edges (16%). The final visual outcome was poor with an average best-corrected logMAR of (mean, 95% CI) 0.70 (0.4-1.0). A total of 52% were treated with corneal transplantation. Patients with Candida infections had a significantly worse visual outcome.

CONCLUSION

We found that patients with fungal keratitis had a poor visual outcome. However, knowledge of risk factors and clinical signs leading to early treatment can improve the prognosis.

In vitro susceptibility of filamentous fungi from mycotic keratitis to azole drugs

OBJECTIVE

The in vitro antifungal activities of azole drugs viz., itraconazole, voriconazole, ketoconazole, econazole and clotrimazole were investigated in order to evaluate their efficacy against filamentous fungi isolated from mycotic keratitis.

METHODS

The specimen collection was carried out from fungal keratitis patients attending Aravind eye hospital and Post-graduate institute of ophthalmology, Coimbatore, India and was subsequently processed for the isolation of fungi. The dilutions of antifungal drugs were prepared in RPMI 1640 medium. Minimum inhibitory concentrations (MICs) were determined and MIC50 and MIC90 were calculated for each drug tested.

RESULTS

A total of 60 fungal isolates were identified as Fusarium spp. (n=30), non-sporulating moulds (n=9), Aspergillus flavus (n=6), Bipolaris spp. (n=6), Exserohilum spp. (n=4), Curvularia spp. (n=3), Alternaria spp. (n=1) and Exophiala spp. (n=1). The MICs of ketoconazole, clotrimazole, voriconazole, econazole and itraconazole for all the fungal isolates ranged between 16 μg/mL and 0.03 μg/mL, 4 μg/mL and 0.015 μg/mL, 8 μg/mL and 0.015 μg/mL, 8 μg/mL and 0.015 μg/mL and 32 μg/mL and 0.06 μg/mL respectively. From the MIC50 and MIC90 values, it could be deciphered that in the present study, clotrimazole was more active against the test isolates at lower concentrations (0.12-5 μg/mL) when compared to other drugs tested.

CONCLUSION

The results suggest that amongst the tested azole drugs, clotrimazole followed by voriconazole and econazole had lower MICs against moulds isolated from mycotic keratitis.