Seasonal trends of microbial keratitis in South India

Streptococcus pneumoniae keratitis: epidemiology and outcomes over 6 years in a French eye care center

PURPOSE

We evaluated the epidemiology, clinical features, microbiology, management and visual outcome of Streptococcus pneumoniae keratitis.

METHODS

We retrospectively reviewed the medical charts of patients diagnosed with culture-proven Streptococcus pneumoniae keratitis in a French tertiary center between January 2015 and December 2020.

RESULTS

We analyzed data from 51 eyes of 51 patients with Streptococcus pneumoniae keratitis followed for 64 (19-105) days, out of a total of 1222 eyes with documented bacterial keratitis (4.17%). Most cases (55%) occurred in winter or spring (p = 0.037). A local or systemic risk factor was identified in 39 (76%) and 32 (63%) eyes respectively: previous ocular surgery (55%) followed by glaucoma (24%), and diabetes (18%). Forty-one patients (80%) with severe keratitis remained in hospital for 7 (1-60) days. Polymicrobial infection was detected in 6 eyes (12%) and multidrug resistant strain in 9 eyes (18%). Medical treatment lasted 36 (21-60) days. Adjuvant surgery was required in 13 eyes (25%) mainly for delayed ulcer healing (n = 10), with amniotic membrane transplantation (n = 12) or tectonic keratoplasty (n = 1). In multivariate analysis, endothelial plaque (OR 65.87, p = 0.028), hypopyon (OR 17.8, p = 0.040), and infiltrate > 5mm2 (OR 2.49, p = 0.012) were significantly associated with the need for adjuvant surgery. Baseline visual acuity (VA) 2.00(1.33-2.00) logMAR did not improve significantly at final visit (p = 0.121). Eyes requiring adjuvant surgery had worse final VA (p = 0.009).

CONCLUSION

Streptococcus pneumoniae keratitis are rare in France but may be sight-threatening. Overall VA is poor, most of patients require hospitalization, and some local factors at presentation predict the need for adjuvant surgery.

Multimodal Deep Learning for Differentiating Bacterial and Fungal Keratitis Using Prospective Representative Data

Objective

This study develops and evaluates multimodal machine learning models for differentiating bacterial and fungal keratitis using a prospective representative dataset from South India.

Design

Machine learning classifier training and validation study.

Participants

Five hundred ninety-nine subjects diagnosed with acute infectious keratitis at Aravind Eye Hospital in Madurai, India.

Methods

We developed and compared 3 prediction models to distinguish bacterial and fungal keratitis using a prospective, consecutively-collected, representative dataset gathered over a full calendar year (the MADURAI dataset). These models included a clinical data model, a computer vision model using the EfficientNet architecture, and a multimodal model combining both imaging and clinical data. We partitioned the MADURAI dataset into 70% train/validation and 30% test sets. Model training was performed with fivefold cross-validation. We also compared the performance of the MADURAI-trained computer vision model against a model with identical architecture but trained on a preexisting dataset collated from multiple prior bacterial and fungal keratitis randomized clinical trials (RCTs) (the RCT-trained computer vision model).

Main Outcome Measures

The primary evaluation metric was the area under the precision-recall curve (AUPRC). Secondary metrics included area under the receiver operating characteristic curve (AUROC), accuracy, and F1 score.

Results

The MADURAI-trained computer vision model outperformed the clinical data model and the RCT-trained computer vision model on the hold-out test set, with an AUPRC 0.94 (95% confidence interval: 0.92-0.96), AUROC 0.81 (0.76-0.85), accuracy 77%, and F1 score 0.85. The multimodal model did not substantially improve performance compared with the computer vision model.

Conclusions

The best-performing machine learning classifier for infectious keratitis was a computer vision model trained using the MADURAI dataset. These findings suggest that image-based deep learning could significantly enhance diagnostic capabilities for infectious keratitis and emphasize the importance of using prospective, consecutively-collected, representative data for machine learning model training and evaluation.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

The Temporal Distribution and Microbial Spectrum in Infectious Keratitis: A Comprehensive Single-Center Study

Purpose: To elucidate pathogen-specific seasonal patterns in infectious keratitis through a comprehensive long-term analysis of microbiologically proven cases in a Japanese tertiary care center. Methods: This retrospective study analyzed 500 consecutive cases of culture-proven infectious keratitis diagnosed and treated by corneal specialists at Yamaguchi University Hospital between 2009 and 2021. Seasonal distribution patterns were analyzed for each pathogen category and specific microorganisms. Results: Among the 500 cases, bacteria were identified in 249 eyes (49.8%), viruses in 173 eyes (34.6%), fungi in 51 eyes (10.2%), and Acanthamoeba in 27 eyes (5.4%). The top 10 causative microorganisms constituted 80.4% of all cases. Distinct seasonal patterns emerged: bacterial keratitis peaked during winter months (October-March), Pseudomonas aeruginosa infections clustered in late summer (August-September), Acanthamoeba keratitis showed summer predominance (June-August), and HSV keratitis was most frequent in winter to spring (January-May). Overall incidence peaked from January to March and reached its nadir in June. Conclusions: This long-term study revealed distinct seasonal patterns for specific pathogens causing infectious keratitis in Japan. The findings suggest that geographical location and climate may influence the temporal distribution of corneal infections. These pathogen-specific seasonal trends could aid in the preliminary diagnosis and empirical treatment of infectious keratitis.

Spectrum of bacterial keratitis at a tertiary eye center in Indonesia

The purpose of this study is to analyze the bacterial spectrum and antibiotic susceptibility patterns in bacterial keratitis at a tertiary eye center in Jakarta, Indonesia. The study design is a retrospective analytic study. A retrospective cross-sectional analytic review of medical records was conducted for patients with bacterial keratitis who underwent corneal cultures over an 8-year period. The study exclusively included eyes with culture-positive bacterial keratitis. The data were divided into two distinct periods: January 2012 to December 2017 and January 2018 to June 2020. A total of 129 eyes with keratitis were examined, and culture-positive bacteria were found in 74 eyes. Gram-negative bacteria were identified in 65 eyes (69.1%), and Gram-positive bacteria were identified in 29 eyes (30.9%). The most common bacteria identified was Pseudomonas aeruginosa (34 positive cultures, 36.2%). Gram-negative bacteria had the highest susceptibility toward ceftazidime (94.7%; 95% CI, 88.9-100). Gram-positive bacteria had the highest susceptibility toward vancomycin (100%; 95% CI, 98.8-100). Gentamicin demonstrated broad sensitivity across all bacterial types (85.7%; 95% CI, 78.2-93.2%), surpassing fluoroquinolones. There were no significant changes in antibiotic susceptibility patterns between the two periods studied (P > 0.05). The stability observed in both the bacterial spectrum and antibiotic susceptibility patterns throughout the study period indicates that the current empirical treatment is still effective. However, the results highlight gentamicin as a highly valuable option for the empirical treatment of bacterial keratitis, while targeted treatment with ceftazidime should be considered for Gram-negative infections and vancomycin for Gram-positive infections when culture results are available.

IMPORTANCE

Bacterial keratitis poses a significant public health concern in Indonesia due to its potential for vision loss and morbidity. Understanding the spectrum of bacterial pathogens causing keratitis is crucial for guiding appropriate treatment strategies and improving patient outcomes. This study aims to investigate the prevalence, antibiotic susceptibility patterns, and risk factors associated with bacterial keratitis cases, providing valuable insights for clinicians to optimize management protocols and enhance the overall ocular health landscape in Indonesia or in other countries that have similar geographical conditions.

Predisposing factors, clinical and microbiological insights of bacterial keratitis: analysis of 354 cases from a leading French academic centre

AIMS

To report an epidemiological update of bacterial keratitis (BK) in a tertiary ophthalmology centre over 20 months compared with a previous study on the same timeframe from 1998 to 1999.

METHODS

354 patients with BK documented by microbiological corneal scraping or resolutive under antibiotics treatment from January 2020 to September 2021 were analysed retrospectively.

RESULTS

One or several risk factors were found in 95.2% of patients: contact lens wear (45.2%), ocular surface disease (25.0%), systemic disease (21.8%), ocular trauma (11.9%) and ocular surgery (8.8%). The positivity rate of corneal scrapings was 82.5%, with 18.2% polybacterial. One hundred seventy-five (59.9%) bacteria were Gram-negative, and 117 (40.1%) were Gram-positive. The most common bacteria were Pseudomonas aeruginosa (32.5%), Moraxella spp (18.1%) and Staphylococcus aureus (8.2%). Final visual acuity (logarithm of the minimum angle of resolution) was associated with age (r=+0.48; p=0.0001), infiltrate size (r=+0.32; p<0.0001), ocular surface disease (r=+0.13; p=0.03), ocular trauma (r=-0.14; p=0.02) and contact lens wear (r=-0.26; p<0.0001). Gram-negative bacteria were responsible for deeper (r=+0.18; p=0.004) and more extensive infiltrates (r=+0.18; p=0.004) in younger patients (r=-0.19; p=0.003). Compared with the previous period, the positivity rate of corneal scrapings and the proportion of Gram-negative bacteria, especially Moraxella spp, increased. All P. aeruginosa and Moraxella spp were sensitive to quinolones, and all S. aureus were sensitive to both quinolones and methicillin.

CONCLUSION

Contact lens wear remained the leading risk factor. The bacteria distribution was reversed, with a predominance of Gram-negative bacteria and increased Moraxella spp.

Fungal Keratitis in Northwestern Spain: Epidemiology, Risk Factors and Outcomes

PURPOSE

To review the clinical features, risk factors, microbiological profile, and treatment regimens of fungal keratitis in Galicia, a region in Northwestern Spain with temperate humid weather.

PATIENTS AND METHODS

A retrospective case series was employed, including patients with fungal keratitis from nine hospitals within the region of Galicia, Spain, between 2010 and 2020. Data obtained from clinical records were analysed.

RESULTS

Out of 654 cases of infectious keratitis, 77 cases (9.9%) were identified as fungal keratitis. The median age of affected patients was 68.0 years, with a higher incidence in rural areas (62.3%). Candida spp. infections were the most frequent type (55.8%) and were associated with a higher median age than were the non-dermatophyte mould infections. The primary risk factors included steroid eyedrop use (29.9%), recent keratoplasty (18.2%), ocular trauma (19.5%), and contact with vegetable matter (11.7%). Most ulcers displayed stromal involvement, and 37.7% presented corneal thinning. The median duration of infection was longer in fungal than in bacterial keratitis, and surgical intervention was required in 48.1% of cases.

CONCLUSIONS

Fungal keratitis, mainly involving Candida spp., accounted for 9.9% of microbial keratitis cases in Galicia, Spain, with significant risk factors being topical steroid use, ocular trauma, and contact with vegetable matter. Delayed diagnosis often resulted in poor outcomes, highlighting the need for early detection through awareness and new technologies to improve prognosis.

A Study of Clinico-Microbiological Profile and Treatment Outcomes of Infectious Keratitis

Background  Infectious keratitis (IK) is one of the major causes of corneal blindness in developing and developed nations. Numerous infections, including bacterial, fungal, viral, and protozoa, have been linked to IK. Corneal perforations can happen as one of the complications of IK. In this study, we aim to determine the clinical and microbiological profile and to study the treatment outcomes of IK. Material and methods It is a prospective, observational, and experimental study conducted in a tertiary care hospital and research center in Western Maharashtra, India, from September 2022 to June 2024. The sample size was 107 patients with IK. All patients were above 15 years of age, and all cases of microbial keratitis were within the inclusion criteria. Patients less than 15 years of age, patients with any other associated corneal pathology, healed cases of infectious keratitis, peripheral ulcerative keratitis, patients not willing to participate in the study, or not giving consent were excluded. Patients were examined thoroughly, and corneal scraping samples were collected and sent for microbiological examination. Appropriate treatment was provided through medical or surgical management, and treatment outcomes were evaluated during frequent follow-up visits. Results In our study, the majority of patients originated from rural areas, with most being over 60 years of age. Diabetes mellitus was seen in 24.3%, and a history of ocular trauma was present in 48.5% of patients. Staphylococcus epidermidis (3.74%) was the most common organism seen on gram staining, followed by Staphylococcus aureus (2.8%). Pseudomonas aeruginosa was the only gram-negative organism seen. The number of patients who had fungal isolates positive on culture was 57%, 12.1% had bacterial, and 30% had no growth of microorganisms. Fusarium species were seen in 39.2% of culture isolates, followed by Aspergillus flavus and Niger in 7.47% each. In 96% of medically managed patients, ulcers healed within two months. All ulcers with severe and moderate depth required therapeutic penetrating keratoplasty. A graft was in place in 95.2% after therapeutic penetrating keratoplasty, while one patient had graft rejection, and in one patient, endophthalmitis was seen. Conclusion Staphylococcus epidermidis was the most common bacterial agent isolated on gram staining, and Pseudomonas aeruginosa was the only gram-negative bacillus isolated on gram staining. Fungal isolates were the most common isolates observed on culture, seen in more than half of the IK patients in our study. The majority of patients who underwent medical management had ulcers healed in two months. The majority of the patients who underwent surgical management had fungal isolates positive. We recommend further research to be conducted in a generalized population, including urban settings, to understand the risk factors, microbiological profile, and treatment outcomes for IK.

In vitro and ex vivo models of microbial keratitis: Present and future

Microbial keratitis (MK) is an infection of the cornea, caused by bacteria, fungi, parasites, or viruses. MK leads to significant morbidity, being the fifth leading cause of blindness worldwide. There is an urgent requirement to better understand pathogenesis in order to develop novel diagnostic and therapeutic approaches to improve patient outcomes. Many in vitro, ex vivo and in vivo MK models have been developed and implemented to meet this aim. Here, we present current in vitro and ex vivo MK model systems, examining their varied design, outputs, reporting standards, and strengths and limitations. Major limitations include their relative simplicity and the perceived inability to study the immune response in these MK models, an aspect widely accepted to play a significant role in MK pathogenesis. Consequently, there remains a dependence on in vivo models to study this aspect of MK. However, looking to the future, we draw from the broader field of corneal disease modelling, which utilises, for example, three-dimensional co-culture models and dynamic environments observed in bioreactors and organ-on-a-chip scenarios. These remain unexplored in MK research, but incorporation of these approaches will offer further advances in the field of MK corneal modelling, in particular with the focus of incorporation of immune components which we anticipate will better recapitulate pathogenesis and yield novel findings, therefore contributing to the enhancement of MK outcomes.

Clinical perspective and outcome of culture-negative microbial keratitis: A retrospective study

PURPOSE

To study the risk factors, clinical features, and treatment outcomes of patients with culture-negative keratitis (CNK).

METHODS

A retrospective data review of 933 patients with CNK was performed from January 2018 to December 2020. The variables such as the history of injury, visual acuity, slit-lamp findings with measurements of size and depth of ulcer, microbiological evaluation, duct patency, blood glucose levels, and treatment were considered, and clinical outcome was analyzed.

RESULTS

Of the 933 patients with CNK, 763 (81.8%) were medically managed, with a mean treatment duration of 2.08 ± 1.7 weeks. Among them, 622 (66.7%) were both smear and culture-negative, and 311 (33.3%) showed only smear positivity. Smear-positive patients showed a positive correlation with the history of injury. A higher incidence of fungal growth on repeat culture was observed. Surgical interventions were done only in 18.2% of the patients; the rest were treated with topical medications alone.

CONCLUSION

High clinical suspicion, differentiation of causative organisms based on clinical findings, and initiating empirical therapy with broad-spectrum antibiotics and antifungals improve the ultimate prognosis in patients with CNK, even though a standard protocol for empirical medical treatment may differ among institutions and surgeons based on their clinical experience and geographical variations.

Etiopathology, Epidemiology, Diagnosis, and Treatment of Fungal Keratitis

Fungal keratitis (FK) is a severe ocular condition resulting from corneal infection that is prevalent in tropical countries, particularly in developing regions of Asia and Africa. Factors like corneal lens misuse, inappropriate steroid use, and diagnostic challenges have provoked the epidemic. FK causes significant vision impairment, scarring, and ocular deformities. Accurate pathological diagnosis is crucial for effective therapeutic intervention. Topical antifungal therapy with surface healing medications proves effective in preventing fungal-borne ulcers. Managing FK requires a comprehensive understanding of fungal pathogenesis, guiding formulation strategies and preventive measures to curb global ocular blindness. This review provides in-depth insights into FK, covering etiology, epidemiology, pathogenesis, therapeutic interventions, antifungal resistance, limitations, prevention, and future perspectives on ocular surface disease management.

The effect of climatic and seasonal factors on the microbial keratitis profile

PURPOSE

To compare retrospective data on microbial keratitis (MK) from two different climatic regions in Turkey over 11 years.

STUDY DESIGN

Retrospective cohort.

METHODS

This retrospective cohort study included patients diagnosed with presumed MK at two referral centers. Center A was located in the subtropical region of Turkey, whereas Center B was located in a continental temperate climate zone. Clinical and laboratory data were also recorded. The results were evaluated for seasonal variations.

RESULTS

This study included data from 665 patients with presumed MK (351 and 314 patients from centers A and B, respectively). The most common predisposing factors were ocular trauma in Center A, prior ocular surgery, and systemic disease in Center B. Severe keratitis was related to prior ocular surgery, presence of systemic disease, and fungal infection at presentation. The culture positivity rate was higher in spring and lower in summer at both centers. Gram-positive bacteria were the most commonly isolated bacteria in both centers in all seasons. The fungal and mixed keratitis ratios were higher in Center A than in Center B. In Center A, filamentous fungi were common pathogens that were found year-round, and peaks were observed in July and October.

CONCLUSION

The results of this study show that climatic and seasonal factors may affect the microbial profile of keratitis. Fungal keratitis appears to be a climatic disease. Understanding the regional profile of MK can aid clinicians in their disease management.

Seasonal and Temporal Trends of Infectious Keratitis in Northern Vietnam

The epidemiology of corneal ulcers in Vietnam has not been well characterized. In this report, we reviewed retrospectively the microbiological data of patients with a clinical diagnosis of corneal ulcer at the microbiology laboratory of Vietnam National Eye Hospital from January 1, 2010 to March 31, 2023. We observed a seasonal pattern for fungal and microsporidial keratitis, with an annual peak in November, and an inverse relationship between fungal keratitis and inclement weather. The November peak coincided with one of the major harvesting seasons in Vietnam. We also observed increasing numbers of microsporidial and Acanthamoeba keratitis cases in recent years. Knowledge of these trends are helpful in guiding empirical treatment of corneal infections and preventing corneal blindness.

Demographic and microbiological profile of corneal ulcer patients presenting at a tertiary healthcare center of Eastern India during the COVID era: A hospital-based cross-sectional study

Purpose

To determine the demographic and microbiological profile involved in the causation of corneal ulcers in Eastern India during the COVID era.

Method

Patients presenting with corneal ulcers fulfilling the inclusion and exclusion criteria were taken as the case. The study duration was from January 2021 to December 2021. Socio-demographic details and information about risk factors were noted. A detailed corneal examination followed by corneal scraping was performed for microbiological evaluation.

Results

In 1 year, 99 infective corneal ulcer patients were evaluated. Farmers (24.2%) were found to be maximally affected by corneal ulcers. The peak in cases was recorded from October to December (38.4%). Ocular trauma was the commonest risk factor (42.4%). The majority (80.8%) of patients were already on some topical antimicrobials. 22.2% of samples showed fungal filaments on KOH mount; 54.5% of these cases turned out to be culture-positive. 17.56% of KOH-negative samples turned out to be culture-positive (fungal). Overall, the culture positivity rate was 28.28% out of which fungal isolates were 89.28% and bacterial isolates were 10.72%. Fusarium species were identified as the most common organism contributing 42.85%, followed by Aspergillus fumigatus (14.28%). 10.72% of cases were culture positive for Pseudomonas aeuroginosa.

Conclusion

Trauma with the organic matter was the predominant cause of fungal keratitis. In this study, fungal keratitis was found to be more common. Fusarium was the most common isolate.

Epidemiological and microbiological profiles of microbial keratitis in a tertiary eye center in Eastern India (Bihar)

Purpose

To determine the demography, risk factors, and causative organisms of microbial keratitis (MK) in Bihar, an eastern state of India.

Design

Retrospective study.

Methods

We reviewed the demographic, clinical, and microbiological data of 2303 patients with MK (non-viral) presenting between January 2019 and December 2022.

Results

This study revealed a predominance of males (65.0%) compared to females (34.9%), with a mean age of 48.4 ± 16.5 years. The majority of patients (63.1%) presented after 2 weeks from the onset of symptoms. The most common risk factor observed was corneal injury (58.1%), followed by ocular surface diseases (13.6%) and diabetes mellitus (13.3%). The majority of patients (73.16%) were involved in agriculture. Prior to presentation, almost all patients (92%) had received topical antibiotics. Unsupervised use of topical corticosteroids was observed in 29.2% of the patients for the median duration of 3 days (odds ratio, 0.17). At presentation, the median size of corneal ulcers was 5 mm, the best-corrected visual acuity was less than 20/400 in 51.4% of patients, and corneal perforation was in 14% of patients. The smear and culture positivity rate were 75.4% and 47.9%, respectively. The common causative organism was fungus (48.8%), followed by bacteria (17.4%). Aspergillus spp. and Staphylococcus spp. were the most commonly identified organisms; a quarter of the patients (24.5%) remained unidentified. All bacteria showed good sensitivity to vancomycin.

Conclusion

MK is a significant cause of ocular morbidity in Bihar. The knowledge of epidemiology, risk factors, and microbiological profiles of MK can provide a valuable approach to disease prevention, diagnosis, and management.

The Epidemiological Profile and Predisposing Factors of Microbial Keratitis Over a 10-Year Period at a Tertiary Hospital in Central Saudi Arabia

PURPOSE

To evaluate the demographic and predisposing factors and clinical presentation of microbial keratitis (MK) patients over 10 years at a tertiary hospital in central Saudi Arabia.

METHOD

In 2020, a retrospective review of data from clinical and pathology departments from 2010 to 2019 was conducted. Demography includes age, gender, residence, and the risk factor of microbial keratitis, clinical features, and organism profile as number and percentage.

RESULT

We reviewed 181 eyes of 179 patients with microbial keratitis. The mean age was 40.1 years. Contact lens usage (55; 30%), ocular trauma (30; 16.5%), and ocular surface diseases (42; 23.2%) were the main predisposing factors. Hypopyon was noted in 60 (33%) eyes, impaired vision at presentation was observed in 78 (43%) eyes, and endophthalmitis with microbial keratitis was noted in eight (4.4%) eyes at presentation. Ninety-eight (54,1%) cases were culture positive, while gram-positive organisms were seen in 50 (27.6%) eyes, gram-negative organisms in 35 (19.3%) patients, and fungi in 13 (7.2%) patients. Microbial keratitis was central in 67 (37%), paracentral in 94 (52%), and peripheral in 20 (11.3%) patients. All instances of fungal keratitis occurred in the eyes of men who work in the agriculture field.

CONCLUSION

Standard operating procedures to manage microbial keratitis at primary and secondary eye care levels are recommended. Health promotion to prevent trauma, appropriate use of contact lens, and early treatment could prevent the incidence of microbial keratitis.

Indications and types of keratoplasties: Trends in the past 10 years (2011-2020) in Eastern India

Purpose

To observe the trends of various types of keratoplasties in different etiologies over a period of 10 years (2011-2020) in a tertiary eye care center of eastern India.

Methods

A retrospective review of patients undergoing keratoplasties from 2011 to 2020 was performed in a tertiary eye care hospital situated in eastern part of India. Apart from demographic data, primary indication for each surgery and type of procedure carried out was recorded. For comparison, data were divided into two time periods: Group I: Jan 2011 to Dec 2015 and Group II: Jan 2016 to Dec 2020.

Results

Over a period of 10 years, a total of 2365 (Group I: 902, Group II: 1463) keratoplasties were performed. The average age of patients was 45.8 ± 19.9 and 46.9 ± 20.9 years in Group I and Group II, respectively. Among all the corneal grafts, 1747 (74%) surgeries were full-thickness. Although optical penetrating keratoplasty (OPK) was most the common indication for full-thickness keratoplasties, Descemet's stripping endothelial keratoplasty (DSEK) remained most performed lamellar keratoplasty. Keratitis, corneal scars, and bullous keratopathies remain to be most common indications in both groups. Number of lamellar keratoplasties increased significantly from Group I to Group II for corneal scars (P = 0.02), bullous keratopathies (P = 0.01), and endothelial dystrophies (P = 0.00).

Conclusion

With change in time, the indication and technique of keratoplasty has witnessed a changing trend from full-thickness keratoplasty to lamellar keratoplasty. There is rise in trend of lamellar keratoplasties over the period.

Ocular Bacterial Infections: A Ten-Year Survey and Review of Causative Organisms Based on the Oklahoma Experience

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

Corneal Culture and Antibiotic Susceptibility Results for Microbial Keratitis in the Mid-Atlantic Region of the United States, 2016 to 2020

OBJECTIVE

To examine the microbial distribution and antimicrobial susceptibility of culture-positive microbial keratitis at a large tertiary referral center in the mid-Atlantic region of the United States.

METHODS

Retrospective review of culture-positive microbial keratitis cases at the Wilmer Eye Institute from 2016 through 2020.

RESULTS

Of the 474 culture-positive microbial keratitis cases, most were bacterial (N=450, 94.9%), followed by fungal (N=48, 10.1%) and Acanthamoeba keratitis (N=15, 3.1%). Of the 450 bacterial isolates, 284 (69.5%) were gram-positive organisms, whereas 157 (28.4%) were gram-negative organisms. The most common bacterial species isolated was coagulase-negative Staphylococcus spp (N=154, 24.8%), and the most common gram-negative isolate was Pseudomonas aeruginosa (N=76, 12.3%). Among fungi, the most common isolates were Candida (N=25, 45.4%), whereas Fusarium (N=6, 10.9%) and Aspergillus (N=3, 5.5%) were less common. Of the 217 bacterial isolates tested for erythromycin susceptibility, 121 (55.7%; ∼60% of coagulase-negative staphylococci and corynebacteria tested) showed resistance to erythromycin.

CONCLUSIONS

Microbial keratitis in the Baltimore Mid-Atlantic region of the United States is most commonly caused by bacteria, with fungi and acanthamoeba being less common. Gram-positive bacterial infections predominate. Among fungal keratitis cases, Candida species are more commonly encountered than are filamentous species. Use of erythromycin as infection prophylaxis should be reexamined. Findings from our study may guide empiric treatment in this geographic region.

TFOS lifestyle: Impact of societal challenges on the ocular surface

Societal factors associated with ocular surface diseases were mapped using a framework to characterize the relationship between the individual, their health and environment. The impact of the COVID-19 pandemic and mitigating factors on ocular surface diseases were considered in a systematic review. Age and sex effects were generally well-characterized for inflammatory, infectious, autoimmune and trauma-related conditions. Sex and gender, through biological, socio-economic, and cultural factors impact the prevalence and severity of disease, access to, and use of, care. Genetic factors, race, smoking and co-morbidities are generally well characterized, with interdependencies with geographical, employment and socioeconomic factors. Living and working conditions include employment, education, water and sanitation, poverty and socioeconomic class. Employment type and hobbies are associated with eye trauma and burns. Regional, global socio-economic, cultural and environmental conditions, include remoteness, geography, seasonality, availability of and access to services. Violence associated with war, acid attacks and domestic violence are associated with traumatic injuries. The impacts of conflict, pandemic and climate are exacerbated by decreased food security, access to health services and workers. Digital technology can impact diseases through physical and mental health effects and access to health information and services. The COVID-19 pandemic and related mitigating strategies are mostly associated with an increased risk of developing new or worsening existing ocular surface diseases. Societal factors impact the type and severity of ocular surface diseases, although there is considerable interdependence between factors. The overlay of the digital environment, natural disasters, conflict and the pandemic have modified access to services in some regions.

The epidemiology of infectious keratitis

Infectious keratitis is a rare but potentially severe sight-threatening disease, associated with considerable societal burden, cost and morbidity. This review summarises the most recent evidence for the incidence, risk factors and impact of disease, all of which vary widely according to region, access to health care, socioeconomic and environmental factors, predisposing conditions and causative organisms. The frequency and societal impact of infectious keratitis are significantly higher in low-income countries. In non-viral infectious keratitis, bacterial causes predominate in most regions. Fungi, particularly linked with agricultural trauma, are more frequently associated with infectious keratitis in low-income regions, particularly in India and certain African countries. The disease impact is compounded by poverty and limited access to services and treatment. Early diagnosis, access to appropriate treatment, prophylaxis in ocular trauma, availability of eye protection, awareness of risk factors may be associated with reduced disease severity and vision loss. Evidence for the incidence and burden of disease is lacking in certain regions and well-designed epidemiological studies to identify independent risk factors for the disease and those associated with more severe outcomes may better identify causation and guide resource allocation and preventative strategies.

Deep Convolutional Neural Networks Detect no Morphological Differences Between Culture-Positive and Culture-Negative Infectious Keratitis Images

Purpose

To determine whether convolutional neural networks can detect morphological differences between images of microbiologically positive and negative corneal ulcers.

Methods

A cross-sectional comparison of prospectively collected data consisting of bacterial and fungal cultures and smears from eyes with acute infectious keratitis at Aravind Eye Hospital. Two convolutional neural network architectures (DenseNet and MobileNet) were trained using images obtained from handheld cameras collected from culture-positive and negative images and smear-positive and -negative images. Each architecture was trained on two image sets: (1) one with labels assigned using only culture results and (2) one using culture and smear results. The outcome measure was area under the receiver operating characteristic curve for predicting whether an ulcer would be microbiologically positive or negative.

Results

There were 1970 images from 886 patients were included. None of the models were better than random chance at predicting positive microbiologic results (area under the receiver operating characteristic curve ranged from 0.49 to 0.56; all confidence intervals included 0.5).

Conclusions

These two state-of-the-art deep convolutional neural network architectures could not reliably predict whether a corneal ulcer would be microbiologically positive or negative based on clinical photographs. This absence of detectable morphological differences informs the future development of computer vision models trained to predict the causative agent in infectious keratitis using corneal photography.

Translational Relevance

These deep learning models were not able to identify morphological differences between microbiologically positive and negative corneal ulcers. This finding suggests that similar artificial intelligence models trained to identify the causative pathogen using only microbiologically positive cases may have potential to generalize well, including to cases with falsely negative microbiologic testing.

Social Media Evaluation of Seasonal and Geographic Trends of Corneal Ulcers in the United States

OBJECTIVES

The purpose of this study is to evaluate if social media and Google search data can identify seasonal and geographic trends in the incidence of corneal ulcers in the United States.

METHODS

This is a case series of all corneal ulcer-related data collected from two major social media platforms and Google trends from US users between 2017 and 2021. Instagram and Twitter were searched for posts and hashtags related to "corneal ulcer." Web and image search volume of "corneal ulcer" were collected from Google trends ( https://trends.google.com ). Data were compared between seasons, defined by 3-month intervals, and chi-square tests were used to determine the statistical significance.

RESULTS

One hundred and sixty-five individuals (79% female) and 164 individuals (79% female) posted personal new corneal ulcer diagnoses on Twitter and Instagram, respectively. Summer resulted in the highest number of both Twitter (34%, P =0.07) and Instagram (33%, P =0.68) posts. Summer was also the most popular season for Google web and image searches of "corneal ulcer" (search volume average of 58.4 and 41.2, P =0.74 and P =0.01, respectively, with 100 being peak popularity). Across all platforms, the South was the most represented (32% Twitter, 38% Instagram, 32% Google Web, and 33% Google Images).

CONCLUSIONS

Our results indicate that social media and Google trends may reflect seasonal and geographic patterns of corneal ulcer incidence in the United States. However, further study with increased power is needed.

Trends of ocular fungal infections in North China (2001-2020)

OBJECTIVES

To analyze the epidemiologic features, culture positivity, the fungal spectrum of different sites of ocular infection in North China over 20 years from 2001 to 2020.

METHODS

11, 635 patients suspected of ocular fungal infection were reviewed. The demographic profile, fungal positive culture rate among different sites, the distribution, and trends of main pathogens among cornea and intraocular fluid were analyzed.

RESULTS

Among 11, 635 samples, the positive culture rate of ocular fungal infection was 23.6%. Most of samples (83.1%) were from cornea, and their culture positivity was 26.9%. Fungal keratitis occurred more often during the harvesting season (October to December; 34.0%) than in other seasons (average: 22.0%). Fusarium sp. (53.2%), Aspergillus sp. (15.9%) and Alternaria sp. (12.5%) were the most common fungal species of ocular mycotic infections in the past two decades in north China. 2562 organisms were identified from cornea, of which 1443 (56.3%) were Fusarium sp., 403 (15.7%) and 329 (12.8%) were Aspergillus sp., and Alternaria sp., respectively. Of the 120 fungi isolated from the intraocular fluid, the most common was Aspergillus sp. (33.3%), followed by Fusarium sp. (24.2%) and Candida sp. (15.0%).

CONCLUSIONS

Fusarium sp., Aspergillus sp. and Alternaria sp. were the most common organisms in cases of fungal keratitis, while Aspergillus sp., Fusarium sp. and Candida sp. were the most frequent isolates for fungal endophthalmitis.

Enterobacter cloacae Keratitis: Clinicomicrobiological Profiles, Risk Factors, and Outcomes

PURPOSE

The purpose of the study was to report the clinical features, risk factors, antibiotic susceptibility, and treatment outcomes in a series of Enterobacter cloacae keratitis.

METHODS

A retrospective analysis was performed of the electronic medical records of microbial keratitis caused by E. cloacae identified by the Vitek 2 system (BioMerieux, Craponne, France). We collected data pertaining to demographics, risk factors, ulcer characteristics, antibiogram, visual acuity at presentation and final follow-up, and management outcome. The main outcome measure was resolution of infection. The final visual acuity was the secondary outcome measure.

RESULTS

Ten episodes of E. cloacae keratitis in 9 patients were identified between January 2009 and December 2019. Nine (90%) cases had undergone penetrating keratoplasty and 8 were failed grafts. Other risk factors included topical steroid use and irregular ocular surface due to epithelial bullae. The mean ulcer size was 17.55 ± 13.99 mm 2 . More than 80% of isolates were sensitive to chloramphenicol, gentamicin, and colistin. Nine (90%) cases healed on medical management within 56.55 ± 26.74 days (range 9-120 d), although almost all required adjunctive procedures: tissue adhesive application (n = 6) and/or tarsorrhaphy (n = 4). One case with a near total infiltrate had a mixed infection with Kocuria kristinae requiring therapeutic penetrating keratoplasty. One case developed endophthalmitis and phthisis after the corneal infiltrate resolved.

CONCLUSIONS

E. cloacae keratitis is a rare clinical entity seen more often in immunocompromised host conditions such as failed corneal transplants with concomitant topical steroids. Most cases healed with medical management.

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.

Potential new fluoroquinolone treatments for suspected bacterial keratitis

Topical fluoroquinolones (FQs) are an established treatment for suspected microbial keratitis. An increased FQ resistance in some classes of bacterial pathogens is a concern. Some recently developed FQs have an extended spectrum of activity, making them a suitable alternative for topical ophthalmic use. For example, the new generation FQs, avarofloxacin, delafloxacin, finafloxacin, lascufloxacin, nadifloxacin, levonadifloxacin, nemonoxacin and zabofloxacin have good activity against the common ophthalmic pathogens such as Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae and several of the Enterobacteriaceae. However, because there are no published ophthalmic break-point concentrations, the susceptibility of an isolated micro-organism to a topical FQ is extrapolated from systemic break-point data and wild type susceptibility. The purpose of this review is to compare the pharmacokinetics and pharmacodynamics of the FQs licensed for topical ophthalmic use with the same parameters for new generation FQs. We performed a literature review of the FQs approved for topical treatment and the new generation FQs licensed to treat systemic infections. We then compared the minimum inhibitory concentrations (MIC) of bacterial isolates and the published concentrations that FQs achieved in the cornea and aqueous. We also considered the potential suitability of new generation FQs for topical use based on their medicinal properties. Notably, we found significant variation in the reported corneal and aqueous FQ concentrations so that reliance on the reported mean concentration may not be appropriate, and the first quartile concentration may be more clinically relevant. The provision of the MIC for the microorganism together with the achieved lower (first) quartile concentration of a FQ in the cornea could inform management decisions such as whether to continue with the prescribed antimicrobial, increase the frequency of application, use a combination of antimicrobials or change treatment.

Spectrum of bacterial keratitis in North India: A retrospective analysis of six years at a tertiary care eye center

Purpose

To analyze the pattern of bacterial pathogens causing infective keratitis and their resistance to the recommended antibiotics over six years.

Methods

It was a retrospective study of 9,357 cases of bacterial keratitis from January 2015 to December 2020, at a tertiary care ophthalmic center. A total of 9,547 corneal specimens were obtained from the study subjects. Demographic details of the patients, pathogenic bacteria isolated, and their antimicrobial susceptibility were noted and analyzed.

Results

Bacterial pathogens were identified in 23.52% of the specimens. The most common isolates were coagulase-negative Staphylococci (60.75%), followed by Pseudomonas aeruginosa (14.23%), Staphylococcus aureus (13.92%), gram negative bacilli of the family Enterobacterales (8.64%), Streptococcus spp. (1.72%), Acinetobacter spp. (0.13%), and other non-fermenting gram-negative bacilli (0.57%). In Staphylococci, 55-80% of isolates were resistant to erythromycin, and 40-70% to fluoroquinolones, while no resistance was observed against vancomycin. 40-60% of isolates of P. aeruginosa were resistant to cephalosporins, 40-55% to fluoroquinolones, and 30-60% to aminoglycosides. Also, 40-80% of isolates of Enterobacterales were resistant to cephalosporins, and 50-60% to fluoroquinolones. Most gram-negative isolates were susceptible to carbapenems and polymyxin B.

Conclusion

To the best of our knowledge, our study is the largest compilation of microbiological profile of bacterial keratitis from North India. It highlights the current trend of the bacterial pathogens that cause infectious keratitis. Staphylococci and Pseudomonas were found to be the most common pathogens. Increased resistance was seen against some of the commonly prescribed empirical antibiotics. Such evidence is useful for restructuring the empirical prescription practices from time to time.

Mycobiomes of the Ocular Surface in Bacterial Keratitis Patients

Inflammation of the cornea is known as keratitis, and bacteria, fungi, protozoans, and viruses are the etiological agents of this disease. Delayed treatment of keratitis could result in loss of vision and, under certain severity conditions, the removal of an eye and its associated structures. In the current study, the ocular surface (conjunctiva and cornea) mycobiomes of individuals with bacterial keratitis were compared with the ocular mycobiome (conjunctiva) of healthy individuals, free of any ocular morbidity. Mycobiomes were generated through NGS approach using conjunctival swabs and corneal scrapings as the source of DNA from which ITS2 was amplified and sequenced, as a proxy to identify fungi. The results indicated significant changes in the alpha-diversity indices and in the abundance at the phylum and genera level. Hierarchical clustering using a heatmap showed that the mycobiomes were different. Furthermore, NMDS plots also differentiated the mycobiomes in the three cohorts, implying dysbiosis in the mycobiomes of the conjunctivae and corneal scrapings of bacterial keratitis individuals compared to control individuals. A preponderance of negative interactions in the hub genera in the conjunctival swabs of bacterial keratitis individuals compared to healthy controls further re-emphasized the differences in the mycobiomes. The dysbiotic changes at the genera level in conjunctivae and corneal scrapings of bacterial keratitis individuals are discussed with respect to their possible role in causing or exacerbating ocular surface inflammation. These results demonstrate dysbiosis in the ocular mycobiome in bacterial keratitis patients compared to healthy controls for the first time.

Streptococcus pneumoniae exerts oxidative stress, subverts antioxidant signaling and autophagy in human corneal epithelial cells that is alleviated by tert-Butylhydroquinone

Streptococcus pneumoniae is one of the leading causes of bacterial keratitis in the developing world and globally. In the current study, we have determined oxidative stress as pathogenesis of S. pneumoniae infection in corneal tissues and human corneal epithelial cells (HCEC) and explored host immune response of HCEC towards S. pneumoniae. We also determined whether treatment with tert-Butylhydroquinone (tBHQ), a Nrf2 inducer, could alleviate oxidative stress and reduce bacterial cytotoxicity in these cells. Oxidative stress was determined in corneal tissues of patients and HCEC by immunohistochemistry and immunofluorescence analysis, respectively. The expression of antioxidant genes, cytokines and antimicrobial peptides was determined by quantitative PCR. Infection of HCEC by S. pneumoniae was determined by colony-forming units. The autophagy and cell death were determined by fluorescence microscopy. The phosphorylation of signaling proteins was evaluated by immunoblot analysis. S. pneumoniae induced oxidative stress during corneal infections and inhibited antioxidant signaling pathways and immune responses like autophagy. tBHQ aided in restoring Nrf2 activation, reduced reactive oxygen species generation and prevented cytotoxicity and cell death in S. pneumoniae-infected HCEC. tBHQ also induced autophagy in a Nrf2-dependent manner and reduced bacterial survival in HCEC. Increased expression of antimicrobial peptides by tBHQ might have contributed to a reduction of bacterial load and cytotoxicity, as exemplified in LL-37 depleted corneal epithelial cells exposed to S. pneumoniae compared to control siRNA-transfected cells. tBHQ mediates alleviation of oxidative stress induced by S. pneumoniae by activating Nrf2-mediated antioxidant signaling in corneal epithelial cells. tBHQ also enhances expression of antimicrobial peptides in corneal cells and aids in inhibition of bacterial survival and cytotoxicity of HCEC.

Update on fungal keratitis in France: a case-control study

PURPOSE

To report an epidemiological update of documented fungal keratitis (FK) in a French tertiary ophthalmological centre from 2014 to 2018 in comparison with a previous period from 1993 to 2008.

METHODS

Sixty-two consecutive FK documented by microbiological corneal scrapings were compared with the 64 FK of the previous study. Amphotericin B and voriconazole eye drops were administered hourly. Population characteristics, clinical findings, aetiological organisms and treatments were analysed.

RESULTS

The most frequently identified fungi were Fusarium (61%), Aspergillus (6.5%) and Candida (5%). Thirty out of 44 cases examined with in vivo confocal microscopy (IVCM) presented filaments. Ten required conventional cross-linking, 9 therapeutic penetrating keratoplasty, and 2 enucleation. Risk factors significantly associated with the absence of response to medical treatment were patient age (p = 0.01), presence of a deep stromal infiltrate at presentation (p = 0.04) and high numbers of filaments in IVCM images (p = 0.01). The two populations were comparable in age, but not in sex ratio males/females (18/44 versus 37/26 in the previous study; p = 0.001). The frequency of contact lens-associated infection increased from 35.5% to 71% (p = 0.0001) between the two periods. Since then, filamentous FK increased from 69% (44/64) to 95% (59/62) (p = 0.0001). A history of keratoplasty was less frequently reported during the last period (3.2% (2/62) versus 17% (11/64) of cases (p = 0.01)). A clear decrease in the frequency of therapeutic keratoplasty was noted from 39% (25/64) to 14% (9/62) (p = 0.02).

CONCLUSION

The frequency of filamentous keratomycosis is currently increasing. Elderly patients and the presence of numerous filaments in IVCM are associated with poor clinical outcomes.

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.

Differentiation of Active Corneal Infections from Healed Scars Using Deep Learning

PURPOSE

To develop and evaluate an automated, portable algorithm to differentiate active corneal ulcers from healed scars using only external photographs.

DESIGN

A convolutional neural network was trained and tested using photographs of corneal ulcers and scars.

PARTICIPANTS

De-identified photographs of corneal ulcers were obtained from the Steroids for Corneal Ulcers Trial (SCUT), Mycotic Ulcer Treatment Trial (MUTT), and Byers Eye Institute at Stanford University.

METHODS

Photographs of corneal ulcers (n = 1313) and scars (n = 1132) from the SCUT and MUTT were used to train a convolutional neural network (CNN). The CNN was tested on 2 different patient populations from eye clinics in India (n = 200) and the Byers Eye Institute at Stanford University (n = 101). Accuracy was evaluated against gold standard clinical classifications. Feature importances for the trained model were visualized using gradient-weighted class activation mapping.

MAIN OUTCOME MEASURES

Accuracy of the CNN was assessed via F1 score. The area under the receiver operating characteristic (ROC) curve (AUC) was used to measure the precision-recall trade-off.

RESULTS

The CNN correctly classified 115 of 123 active ulcers and 65 of 77 scars in patients with corneal ulcer from India (F1 score, 92.0% [95% confidence interval (CI), 88.2%-95.8%]; sensitivity, 93.5% [95% CI, 89.1%-97.9%]; specificity, 84.42% [95% CI, 79.42%-89.42%]; ROC: AUC, 0.9731). The CNN correctly classified 43 of 55 active ulcers and 42 of 46 scars in patients with corneal ulcers from Northern California (F1 score, 84.3% [95% CI, 77.2%-91.4%]; sensitivity, 78.2% [95% CI, 67.3%-89.1%]; specificity, 91.3% [95% CI, 85.8%-96.8%]; ROC: AUC, 0.9474). The CNN visualizations correlated with clinically relevant features such as corneal infiltrate, hypopyon, and conjunctival injection.

CONCLUSIONS

The CNN classified corneal ulcers and scars with high accuracy and generalized to patient populations outside of its training data. The CNN focused on clinically relevant features when it made a diagnosis. The CNN demonstrated potential as an inexpensive diagnostic approach that may aid triage in communities with limited access to eye care.

Expression of immune response genes in human corneal epithelial cells interacting with Aspergillus flavus conidia

Background

Aspergillus flavus, one of the causative agents of human fungal keratitis, can be phagocytosed by human corneal epithelial (HCE) cells and the conidia containing phagosomes mature into phagolysosomes. But the immunological responses of human corneal epithelial cells interacting with A. flavus are not clear. In this study, we report the expression of immune response related genes of HCE cells exposed to A. flavus spores using targeted transcriptomics.

Methods

Human corneal epithelial cell line and primary cultures were grown in a six-well plate and used for coculture experiments. Internalization of the conidia was confirmed by immunofluorescence microscopy of the colocalized endosomal markers CD71 and LAMP1. Total RNA was isolated, and the quantity and quality of the isolated RNA were assessed using Qubit and Bioanalyzer. NanoString nCounter platform was used for the analysis of mRNA abundance using the Human Immunology panel. R-package and nSolver software were used for data analysis. KEGG and FunRich 3.1.3 tools were used to analyze the differentially expressed genes.

Results

Different morphotypes of conidia were observed after 6 h of coculture with human corneal epithelial cells and found to be internalized by epithelial cells. NanoString profiling showed more than 20 differentially expressed genes in immortalized human corneal epithelial cell line and more than ten differentially expressed genes in primary corneal epithelial cells. Distinct set of genes were altered in their expression in cell line and primary corneal epithelial cells. KEGG pathway analysis revealed that genes associated with TNF signaling, NF-KB signaling, and Th17 signaling were up-regulated, and genes associated with chemokine signaling and B cell receptor signaling were down regulated. FunRich pathway analysis showed that pathways such as CDC42 signaling, PI3K signaling, and Arf6 trafficking events were activated by the clinical isolates CI1123 and CI1698 in both type of cells.

Conclusions

Combining the transcript analysis data from cell lines and primary cultures, we showed the up regulation of immune defense genes in A. flavus infected cells. At the same time, chemokine signaling and B cell signaling pathways are downregulated. The variability in the expression levels in the immortalized cell line and the primary cultures is likely due to the variable epigenetic reprogramming in the immortalized cells and primary cultures in the absence of any changes in the genome. It highlights the importance of using both cell types in host-pathogen interaction studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08218-5.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

Clinical Characteristics and Outcomes of Fungal Keratitis in the United Kingdom 2011-2020: A 10-Year Study

Fungal keratitis (FK) is a serious ocular infection that often poses significant diagnostic and therapeutic dilemmas. This study aimed to examine the causes, clinical characteristics, outcomes, and prognostic factors of FK in the UK. All culture-positive and culture-negative presumed FK (with complete data) that presented to Queen’s Medical Centre, Nottingham, and the Queen Victoria Hospital, East Grinstead, between 2011 and 2020 were included. We included 117 patients (n = 117 eyes) with FK in this study. The mean age was 59.0 ± 19.6 years (range, 4–92 years) and 51.3% of patients were female. Fifty-three fungal isolates were identified from 52 (44.4%) culture-positive cases, with Candida spp. (33, 62.3%), Fusarium spp. (9, 17.0%), and Aspergillus spp. (5, 9.4%) being the most common organisms. Ocular surface disease (60, 51.3%), prior corneal surgery (44, 37.6%), and systemic immunosuppression (42, 35.9%) were the three most common risk factors. Hospitalisation for intensive treatment was required for 95 (81.2%) patients, with a duration of 18.9 ± 16.3 days. Sixty-six (56.4%) patients required additional surgical interventions for eradicating the infection. Emergency therapeutic/tectonic keratoplasty was performed in 29 (24.8%) cases, though 13 (44.8%) of them failed at final follow-up. The final corrected-distance-visual-acuity (CDVA) was 1.67 ± 1.08 logMAR. Multivariable logistic regression analyses demonstrated increased age, large infiltrate size (>3 mm), and poor presenting CDVA (<1.0 logMAR) as significant negative predictive factors for poor visual outcome (CDVA of <1.0 logMAR) and poor corneal healing (>60 days of healing time or occurrence of corneal perforation requiring emergency keratoplasty; all p < 0.05). In conclusion, FK represents a difficult-to-treat ocular infection that often results in poor visual outcomes, with a high need for surgical interventions. Innovative treatment strategies are urgently required to tackle this unmet need.

Fungal keratitis at a tertiary eye care in Northern Thailand: Etiology and prognostic factors for treatment outcomes

PURPOSE

To evaluate etiology and prognostic factors for treatment outcomes of fungal keratitis (FK).

METHODS

Culture-positive FK patients between 2012 and 2017 were reviewed. Treatment outcomes were categorized into success (resolved within two weeks), slow response and medication failure (no improvement or required surgery). Etiology and risk factors for poor treatment outcomes were analyzed.

RESULTS

A total of 113 eyes of 113 patients (77% males) were recruited. Ocular trauma (69.0%) was the most common predisposing factor. Of this, 80% were exposed to organic foreign bodies. The most common pathogen was Fusarium spp. (45.2%), while dematiaceous fungi were discovered in 29.6%. Medical treatment was successful in 24.8% of eyes, while 29.2% had a slow response and 42.5% failed medication. Therapeutic keratoplasty was performed in 22.1% of eyes and 11.5% eventually required eye removal. Significant risk factors for medication failure were advanced age (P = 0.005), delayed antifungal treatment (P = 0.038) and large-size lesion (P = 0.003).

CONCLUSIONS

Ocular trauma was the major predisposing factor of FK in the Northern Thailand. Fusarium was the most common identified pathogen. Many cases were refractory to medications and required surgical intervention. Aging, delayed treatment and a large lesion were predictors for poor outcomes.

Human Corneal Epithelial Cells Internalize Aspergillus flavus Spores by Actin-Mediated Endocytosis

Human corneal epithelial (HCE) cells play a significant role in the innate immune response by secreting cytokines and antimicrobial peptides when they encounter fungal pathogens. But the detailed mechanism of attachment and engulfment of the fungal conidia by HCE cells is not well understood. Here, we show the phagocytosis of Aspergillus flavus conidia by RCB2280 cells and primary HCE cultures using confocal microscopy and proteomic analysis of conidium-containing phagosomes. Phalloidin staining showed actin polymerization, leading to an actin ring around engulfed conidia. Cytochalasin D inhibited the actin-mediated endocytosis of the conidia. Immunolabeling of the early endosomal markers CD71 and early endosomal antigen (EEA1) and the late endosomal markers lysosome-associated membrane protein 1 (LAMP1), Rab7, and cathepsin G showed that endosomal proteins were recruited to the site of conidia and showed maturation of the conidium-containing phagosomes. Lysotracker red DND 99 labeling showed the acidification of the phagosomes containing conidia. Phagosome-specific proteome analysis confirmed the recruitment of various phagosomal and endosomal proteins to the conidium-containing phagosomes. These results show that the ocular surface epithelium contributes actively to antifungal defense by the phagocytosis of invading fungal conidia.

Fungal Keratitis in the Egyptian Delta: Epidemiology, Risk Factors, and Microbiological Diagnosis

Purpose: The current study evaluates the epidemiological characteristics, risk factors, and microbiological diagnosis of fungal keratitis among patients living in the Egyptian Delta.Methods: This is a prospective hospital-based study that included patients who were clinically diagnosed and confirmed by culture test to have fungal keratitis. Patients were examined at baseline and risk factors were identified and collected. Patients were followed over 6 months and the outcomes were documented.Results: A total of 171 (67%) of 252 microbial keratitis patients was proved fungal by microbial culture test. Rural residence and agricultural activity were reported in 139 (81.3%) and 85 (49.7%) patients, respectively. Patients presented within 1 week from the start of symptoms were 120 (70.2%). A total of 54 (31.6%) patients reported ocular trauma. Forty patients (23.4%) had prior ocular surgery and 43 (25.1%) patients had a history of previous ocular disorders. Aspergillus species was the most common organism found in 120 (70.17%) patients, followed by Dematiceous fungi that were found in 25 (14.6%) patients. The main outcome was corneal opacity in 132 (77.2%) patients following medical treatment.Conclusion: Filamentary fungal predominance in Mansoura is influenced by the rural residence of its population. Therefore, more efforts in spreading awareness about microbial keratitis among villagers are important to reduce blindness caused by corneal opacity in rural areas.

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.

Infectious keratitis: an update on epidemiology, causative microorganisms, risk factors, and antimicrobial resistance

Corneal opacity is the 5th leading cause of blindness and visual impairment globally, affecting ~6 million of the world population. In addition, it is responsible for 1.5-2.0 million new cases of monocular blindness per year, highlighting an ongoing uncurbed burden on human health. Among all aetiologies such as infection, trauma, inflammation, degeneration and nutritional deficiency, infectious keratitis (IK) represents the leading cause of corneal blindness in both developed and developing countries, with an estimated incidence ranging from 2.5 to 799 per 100,000 population-year. IK can be caused by a wide range of microorganisms, including bacteria, fungi, virus, parasites and polymicrobial infection. Subject to the geographical and temporal variations, bacteria and fungi have been shown to be the most common causative microorganisms for corneal infection. Although viral and Acanthamoeba keratitis are less common, they represent important causes for corneal blindness in the developed countries. Contact lens wear, trauma, ocular surface diseases, lid diseases, and post-ocular surgery have been shown to be the major risk factors for IK. Broad-spectrum topical antimicrobial treatment is the current mainstay of treatment for IK, though its effectiveness is being challenged by the emergence of antimicrobial resistance, including multidrug resistance, in some parts of the world. In this review, we aim to provide an updated review on IK, encompassing the epidemiology, causative microorganisms, major risk factors and the impact of antimicrobial resistance.

Topical Corticosteroids and Fungal Keratitis: A Review of the Literature and Case Series

The management of fungal keratitis is complex since signs and symptoms are subtle and ocular inflammation is minimal in the preliminary stages of infection. Initial misdiagnosis of the condition and consequent management of inflammation with corticosteroids is a frequent occurrence. Topical steroid use is considered to be a principal factor for development of fungal keratitis. In this review, we assess the studies that have reported outcomes of fungal keratitis in patients receiving steroids prior to diagnosis. We also assess the possible rebound effect present when steroids are abruptly discontinued and the clinical characteristics of three patients in this particular clinical scenario. Previous reports and the three clinical descriptions presented suggest that in fungal keratitis, discontinuing topical steroids can induce worsening of clinical signs. In these cases, we recommend to slowly taper steroids and continue or commence appropriate antifungal therapy.

Microbial Keratitis After Corneal Collagen Cross-Linking for Corneal Ectasia

PURPOSE

The aim of this study was to report the clinical profile and microbiological of patients with microbial keratitis post accelerated corneal collagen cross-linking (CXL).

METHODS

A retrospective case series of all patients diagnosed with microbial keratitis post-CXL who attended the Sydney Eye Hospital, Australia from January 1, 2012 to December 31, 2019 were included. Patients were identified from hospital coding and pathology data. Data were extracted from patients' medical records.

RESULTS

Eleven eyes from 10 patients with a mean age of 29 ± 11 years (range 16-48) were included. The median time of infection after CXL surgery was 4 days [interquartile range (IQR) 3-83]. Median initial and final Visual acuity at presentation were 1.3 logMAR (IQR 1-2.0) and 0.8 logMAR (IQR 0.6-1.2), respectively. The culture positivity rate was 92%, identifying 13 isolates, predominately made up of coagulase-negative Staphylococcus (n = 6, 50%) and Staphylococcus aureus (n = 3, 25%). The median epithelial healing time was 30 days (IQR 15-53).

CONCLUSIONS

Post-CXL microbial keratitis was predominately associated with gram-positive bacteria and in some cases delayed epithelialization. Microbial keratitis post-CXL may lead to moderate to poor patient outcomes.

Infectious keratitis: trends in microbiological and antibiotic sensitivity patterns

OBJECTIVES

To report the spectrum and trends of isolated microorganisms and their antibiotic susceptibility profile in patients with infectious keratitis in a 6-year period at a referral centre in Tehran.

METHODS

The microbiology records of all corneal scrapings with a diagnosis of infectious keratitis were reviewed.

RESULTS

A total of 6282 corneal scrapings were performed during the study period, of which 2479 (39.5%) samples were culture positive. Pseudomonas aeruginosa was found to be the most common causative agent in patients with keratitis, although Streptococcus pneumonia was the most prevalently isolated microorganism in patients older than 50 years. Fusarium sp. was the most common responsible pathogen in patients with fungal keratitis. The prevalence of bacterial keratitis due to gram positive microorganisms increased over time, however the number of Pseudomonas keratitis decreased in the second half of the study. Gram negative organisms showed a good sensitivity to levofloxacin, however, 34.1% of S. aureus isolates and 29.7% of coagulase negative staphylococci were resistant to this antibiotic. The odds of ciprofloxacin and levofloxacin resistance increased 1.25 and 1.15 for each 1-year increase in culture date, respectively (P < 0.001, P = 0.004).

CONCLUSIONS

We documented an increasing trend in the percentage of gram positive bacteria. Levofloxacin monotherapy might still be a good option in patients with gram negative bacterial keratitis, however owing to increasing resistance of staphylococci to fluoroquinolones, a regimen consisting of a combination of fortified antibiotics may be more effective in staphylococcal keratitis.

Seasonal variation in acute post-cataract surgery endophthalmitis incidences in South Korea

PURPOSE

Previous studies have reported conflicting results on the influence of seasons on post-cataract surgery endophthalmitis incidences. This study aimed to investigate the seasonality associated with the incidence of postoperative endophthalmitis, and to evaluate its association with climate variables in South Korea.

SETTING

South Korea.

DESIGN

Retrospective cohort study.

METHODS

The postoperative endophthalmitis incidences were identified using the Health Insurance Review and Assessment Service claim data from July 2014 to June 2017. The monthly climate data were obtained from the Korea Meteorological Administration. The incidences of endophthalmitis were analyzed by the month of the year, and by the season. The association between postoperative endophthalmitis and the climatic variables, including mean temperature, relative humidity, precipitation, and hours of sunshine, was investigated.

RESULTS

The incidences were the highest in July, and they were the most prevalent during the summer months, although fewer cataract surgeries were performed in the summer months than during the rest of the year. The postoperative endophthalmitis incidences tended to increase with increasing relative humidity and increasing precipitation.

CONCLUSIONS

The incidences of post-cataract surgery endophthalmitis peaked during the hot and humid months. Understanding the seasonal and climatic influences on postoperative infection might help in risk stratification and outcome improvisation after the cataract surgery is performed.

Alterations in the conjunctival surface bacterial microbiome in bacterial keratitis patients

Microbial keratitis is an infectious disease of the eye, in which the cornea is inflamed. Under severe conditions, keratitis can lead to significant loss of vision and enucleation of the eye. Ocular trauma is the major risk factor causing keratitis and microorganisms viz., bacteria, fungi, viruses are the causative agents. The current study characterized the conjunctival bacterial microbiomes of healthy individuals and individuals with bacterial keratitis (BK) and assessed whether ocular microbiome dysbiosis is prevalent in BK patients. Ocular bacterial microbiomes were generated from the conjunctival swabs of healthy controls (HC-SW) and conjunctival swabs (BK-SW) and corneal scrapings (BK-CR) of BK patients using V3-V4 amplicon sequencing and data analysed using QIIME and R software. The Alpha diversity indices, diversity and abundance of different phyla and genera, heat map analysis, NMDS plots and inferred functional pathway analysis clearly discriminated the bacterial microbiomes of conjunctival swabs of healthy controls from that of BK patients. Preponderance of negative interactions in the hub genera were observed in BK-CR and BK-SW compared to HC-SW. In addition, a consistent increase in the abundance of pathogenic bacteria, as inferred from published literature, was observed in the conjunctiva of BK patients compared to HC and this may be related to causing or exacerbating ocular surface inflammation. This is the first study demonstrating dysbiosis in the ocular bacterial microbiome of conjunctiva of bacterial keratitis patients compared to the eye of healthy controls. The bacterial microbiome associated with the corneal scrapings of keratitis individuals is also described for the first time.

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.

Seasonal patterns of incidence, demographic factors and microbiological profiles of infectious keratitis: the Nottingham Infectious Keratitis Study

PURPOSE

The purpose of this study is to examine the seasonal patterns of incidence, demographic factors and microbiological profiles of infectious keratitis (IK) in Nottingham, UK.

METHODS

A retrospective study of all patients who were diagnosed with IK and underwent corneal scraping during 2008-2019 at a UK tertiary referral centre. Seasonal patterns of incidence (in per 100,000 population-year), demographic factors, culture positivity rate and microbiological profiles of IK were analysed.

RESULTS

A total of 1272 IK cases were included. The overall incidence of IK was highest during summer (37.7, 95% confidence interval (CI): 31.3-44.1), followed by autumn (36.7, 95% CI: 31.0-42.4), winter (36.4, 95% CI: 32.1-40.8) and spring (30.6, 95% CI: 26.8-34.3), though not statistically significant (p = 0.14). The incidence of IK during summer increased significantly over the 12 years of study (r = 0.58, p = 0.049), but the incidence of IK in other seasons remained relatively stable throughout the study period. Significant seasonal variations were observed in patients' age (younger age in summer) and causative organisms, including Pseudomonas aeruginosa (32.9% in summer vs. 14.8% in winter; p < 0.001) and gram-positive bacilli (16.1% in summer vs. 4.7% in winter; p = 0.014).

CONCLUSION

The incidence of IK in Nottingham was similar among four seasons. No temporal trend in the annual incidence of IK was observed, as reported previously, but there was a significant yearly increase in the incidence of IK during summer in Nottingham over the past decade. The association of younger age, P. aeruginosa and gram-positive bacilli infection with summer was likely attributed to contact lens wear, increased outdoor/water activity and warmer temperature conducive for microbial growth.

Microbial Keratitis in Corneal Transplants: A 12-Year Analysis

Purpose

To investigate the frequencies, trends, and in vitro drug susceptibilities of the causative pathogens in corneal transplant microbial infections in Manchester Royal Eye Hospital.

Methods

Corneal scrape results recorded by the microbiology service between 2004 and 2015 were extracted from an established database. This microbiological data was matched with a separate database of all corneal transplant procedures performed in our centre over this time period. Patient records were examined to collect specific patient data and to confirm the diagnosis of microbial keratitis.

Results

A total of 1508 grafts had been performed at our centre in this period. 72 episodes of graft microbial keratitis were identified from 66 eyes that had undergone keratoplasty procedures. Mean age was 56, and 51% of subjects were male. Ninety-three percent of microbial keratitis episodes occurred in penetrating keratoplasty procedures and 6% in deep anterior lamellar keratoplasty procedures. No endothelial grafts presented with infections throughout this time period. Of the 79 organisms identified, 73% were gram positive, 23% gram negative and 4% fungi. With regard to gram-positive organisms, vancomycin and gentamicin showed 100% and 91% susceptibility, respectively. Ofloxacin had a resistance rate of 13.7%. In terms of gram-negative organisms, gentamicin and chloramphenicol showed 100% sensitivity, with cefuroxime showing 69%. Resistance rates were less than 15% in all tested gram-negative antimicrobials.

Conclusion

This paper describes the largest collection of corneal transplant infections identified within the UK. This finding may aid clinicians in predicting possible causative organisms for microbial keratitis and aid antibiotic choice.