Shifting Trends in Bacterial Keratitis in Taiwan: A 10-Year Review in a Tertiary-Care Hospital

Perspectives on the incidence of Acanthamoeba Keratitis: A Systematic Review and Meta-Analysis

TOPIC

To provide an overview on the incidence of Acanthamoeba Keratitis (AK).

CLINICAL RELEVANCE

Although being a major and sight-threatening cause of infectious keratitis in the population, a comprehensive assessment of the incidence of this condition is lacking.

METHODS

Incidence of AK was computed as the number of AK eyes, per healthcare center, per year (annualized-center-incidence, or ACI). Two meta-analytical ratios were also calculated: a) the ratio of AK eyes to the count of non-viral microbial keratitis (MK) eyes; b) the ratio of AK eyes to the overall population (i.e., the total number of subjects of a nation or region, as indicated by the authors in each study). Center was defined as the healthcare facility (e.g., Hospital, Private Practice, Clinic) where the study took place. Actual and projected estimates of the number of AK eyes in years were calculated multiplying the ratio of AK to the total population and the corresponding present and projected population estimates (age range: 15 to 70), sourced from the United Nations (UN) Population Prospects.

RESULTS

Overall, 105 articles were included, published between 1987 and 2022. The total number of eyes identified was 91,951, with 5,660 affected by AK and 86,291 by non-viral MK. The median ACI was 1.9 new AK eyes per healthcare center per year (95%CI of the median: 1.5 to 2.6), with no statistically significant differences observed among continents. The ratio of AK eyes to the total number of MK eyes was 1.52% (95%CI: 1.02% to 2.24%), while the ratio of AK in relation to the entire population was estimated at 0.0002% (95%CI: 0.0001 to 0.0006), or 2.34 eyes per 1,000,000 subjects (95%CI: 0.98 to 5.55 per 1.000.000 subjects). The projected increase in the numbers of AK eyes indicates a rise of +18.5% (15,356 AK eyes) in 2053 and +25.5% (16,253 AK eyes) in 2073, compared to the baseline of 2023 (12,954 AK eyes) CONCLUSION: AK emerged as a relatively low-incident disorder, and no significant differences in terms of its incidence were found among different continents.

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

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

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.

Impact of SARS-CoV-2 pandemic and lockdown measures on microbial keratitis in Taiwan

PURPOSE

This study aimed to evaluate how the SARS-CoV-2 pandemic and associated lockdown measures influenced microbial keratitis in Taiwan by comparing demographic data, predisposing factors, pathogen profiles, and treatment outcomes in 2019 and 2020.

METHODS

Data from patients diagnosed with microbial keratitis at National Chung Kung University Hospital between January 2019 and December 2020 were examined, focusing on patient demographics, predisposing factors, isolated pathogens, antibiotic usage, and clinical progress.

RESULTS

No significant differences were found in patient sex, laterality, or average age between the two years. Predisposing factors, such as contact lens use and chronic ocular/systemic disorders, remained unchanged. While fungal isolates slightly increased during the lockdown, bacterial isolates remained consistent. Medical treatment effectiveness, treatment strategies, and antibiotic susceptibility for common bacteria showed no significant alterations.

CONCLUSION

Despite the challenges posed by the SARS-CoV-2 pandemic and lockdown measures, this study revealed minimal changes in microbial keratitis trends in Taiwan. This highlights the importance of maintaining access to medical care during crises and offers insights into potential treatment strategies for patients facing difficulties in receiving timely care. Further research should investigate the pandemic's impact on healthcare access and patient outcomes in various populations and regions.

Antimicrobial resistance in ocular infection: A review

Antimicrobial resistance (AMR) is a global public health threat with significant impact on treatment outcomes. The World Health Organization's Global Action Plan on AMR recommended strengthening the evidence base through surveillance programs and research. Comprehensive, timely data on AMR for organisms isolated from ocular infections are needed to guide treatment decisions and inform researchers and microbiologists of emerging trends. This article aims to provide an update on the development of AMR in ocular organisms, AMR in bacterial ocular infections and on AMR stewardship programs globally. The most common ocular pathogens are Pseudomonas aeruginosa, Staphylococcus spp., Streptococcus pneumoniae, and Haemophilus influenzae in ocular infections. A variety of studies and a few surveillance programs worldwide have reported on AMR in these infections over time. Fluoroquinolone resistance has increased particularly in Asia and North America. For conjunctivitis, the ARMOR cumulative study in the USA reported a slight decrease in resistance to ciprofloxacin. For keratitis, resistance to methicillin has remained stable for S. aureus and CoNS, while resistance to ciprofloxacin has decreased for MRSA globally. Methicillin-resistance and multidrug resistance are also emerging, requiring ongoing monitoring. Antimicrobial stewardship (AMS) programmes have a critical role in reducing the threat of AMR and improving treatment outcomes. To be successful AMS must be informed by up-to-date AMR surveillance data. As a profession it is timely for ophthalmology to act to prevent AMR leading to greater visual loss through supporting surveillance programmes and establishing AMS.

Trends in antibiotic resistance in ocular samples in a tertiary eye centre in Saudi Arabia in 2003-2019

OBJECTIVE

The aim of this study was to analyze the antibiotic resistance in ocular samples over a 16-year period.

METHODS

This was a retrospective cohort study conducted at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia (2003-2019). The study included corneal and conjunctival swabs and aqueous and vitreous samples.

RESULTS

Coagulase-negative staphylococci exhibited a significant trend of increasing resistance over time to erythromycin (p < 0.001), oxacillin (p < 0.001), fusidic acid (p < 0.001), and moxifloxacin (p = 0.003). Staphylococcus aureus also showed a significant increase in oxacillin (p = 0.001), ofloxacin (p = 0.003), and moxifloxacin (p = 0.001) resistance patterns. Streptococcus pneumoniae demonstrated a significant increase in resistance to erythromycin (p = 0.01) and ofloxacin, which jumped from 0.80% in 2003 to 80% in 2019 (p = 0.015). No statistically significant increase in antibiotic resistance trend was observed for Pseudomonas.

CONCLUSIONS

An increasing antibiotic resistance pattern was demonstrated, particularly among gram-positive organisms. Such findings warrant revision of the common ocular antibiotic prescribing strategy and consideration of alternative antibiotics.

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

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

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.

Bacterial Keratitis: Clinical Features, Causative Organisms, and Outcome During a 13-year Study Period

PURPOSE

This study aimed to review clinical features, causative organisms, complications, and outcome of bacterial keratitis cases at a tertiary eye hospital.

METHODS

A retrospective study was conducted on clinically diagnosed bacterial keratitis cases from 2007 to 2019. Poor outcome was flagged if any of the following was identified: final visual acuity (VA) worse than 20/200, decrease in VA (1 line or worse compared with presenting VA), corneal perforation, endophthalmitis, failed graft, or cases requiring enucleation or evisceration.

RESULTS

The study included 263 cases of bacterial keratitis with 169 cases (64.3%) of culture-positive bacterial keratitis. Gram-positive bacteria were found to be the causative organism in 106 cases (62.8%). The most common types were coagulase-negative staphylococci (23.1%) and Pseudomonas (23.1%). Culture-positive bacterial keratitis was associated with the development of anterior chamber reaction (≥1+) on multivariate analysis [adjusted odds ratio (OR): 3.03, confidence interval (CI): 1.23-7.45, P = 0.016]. The complications that occurred in the current cohort included visually significant scar (64.7%), perforation (10.8%), cataract (8.8%), nonhealing epithelial defects (8.0%), corneal neovascularization (4.9%), endophthalmitis (4.6%), and hypotony (1.5%). On multivariate analysis, diabetes mellitus (adjusted OR: 3.51, CI: 1.59-7.76, P = 0.002), poor presenting best-corrected VA (adjusted OR: 3.95, CI 1.96-7.96, P < 0.001), and positive cultures (adjusted OR: 2.36, CI: 1.11-5.00, P = 0.025) were associated with poor outcome.

CONCLUSIONS

Culture-negative keratitis had less severe infection and better outcomes when compared to culture-positive bacterial keratitis. Factors associated with poor outcome included diabetes, poor presenting VA, and positive cultures.

Cutibacterium (Formerly Propionibacterium ) acnes Keratitis: A Review

ABSTRACT

Infectious keratitis is a devastating cause of vision loss worldwide. Cutibacterium acnes ( C. acnes ), a commensal bacterium of the skin and ocular surface, is an underrecognized but important cause of bacterial keratitis. This review presents the most comprehensive and up-to-date information for clinicians regarding the risk factors, incidence, diagnosis, management, and prognosis of C. acnes keratitis (CAK). Risk factors are similar to those of general bacterial keratitis and include contact lens use, past ocular surgery, and trauma. The incidence of CAK may be approximately 10%, ranging from 5% to 25% in growth-positive cultures. Accurate diagnosis requires anaerobic blood agar and a long incubation period (≥7 days). Typical clinical presentation includes small (<2 mm) ulcerations with deep stromal infiltrate causing an anterior chamber cell reaction. Small, peripheral lesions are usually resolved, and patients recover a high visual acuity. Severe infections causing VA of 20/200 or worse are common and often do not significantly improve even after treatment. Vancomycin is considered the most potent antibiotic against CAK, although other antibiotics such as moxifloxacin and ceftazidime are more commonly used as first-line treatment.

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.

Comparative Evaluation of Pseudomonas aeruginosa Adhesion to a Poly-(2-Methacryloyloxyethyl Phosphorylcholine)-Modified Silicone Hydrogel Contact Lens

Pseudomonas aeruginosa is the most common causative agent associated with microbial keratitis. During contact lens wear, pathogens may be introduced into the ocular environment, which might cause adverse events. Lehfilcon A is a recently developed contact lens with a water gradient surface composed of polymeric 2-methacryloyloxyethyl phosphorylcholine (MPC). MPC is re-ported to impart anti-biofouling properties onto modified substrates. Therefore, in this in vitro experimental study, we tested the capability of lehfilcon A to resist adhesion by P. aeruginosa. Quantitative bacterial adhesion assays using five strains of P. aeruginosa were conducted to compare the adherence properties of lehfilcon A to five currently marketed silicone hydrogel (SiHy) contact lenses (comfilcon A, fanfilcon A, senofilcon A, senofilcon C, and samfilcon A). Compared to lehfilcon A, we observed 26.7 ± 8.8 times (p = 0.0028) more P. aeruginosa binding to comfilcon A, 30.0 ± 10.8 times (p = 0.0038) more binding to fanfilcon A, 18.2 ± 6.2 times (p = 0.0034) more binding to senofilcon A, 13.6 ± 3.9 times (p = 0.0019) more binding to senofilcon C, and 29.5 ± 11.8 times (p = 0.0057) more binding to samfilcon A. These results demonstrate that, for various strains of P. aeruginosa, lehfilcon A reduces bacterial adhesion compared to other contact lens materials.

Citrobacter keratitis: predisposing factors and clinical characteristics

PURPOSE

To report predisposing factors, clinical presentation, antibiotic sensitivity, and management of Citrobacter-caused infectious keratitis.

METHODS

We retrospectively reviewed the medical records of culture-proven cases of Citrobacter keratitis in a tertiary referral center for 8 years (from January 2012 to September 2020). Demographic data of the patients, predisposing factors, and presenting signs were extracted.

RESULTS

Eighteen cases of microbial keratitis due to Citrobacter spp. were identified. The median age of the patients was 66 years (range: 10-89, interquartile range : 59-81). Thirteen patients were male and 5 were female. Multiple predisposing factors were identified in all eyes, including ocular surface disease (n = 8), previous corneal surgery (n = 6), and history of ocular trauma (n = 6). Five patients were diabetic. Corrected distance visual acuity (CDVA) of patients was light perception (LP) in 8 patients, hand motion (HM) in 7, counting fingers (CF) at 1 m in 1, and CF at 2 m in 2 patients. Thirteen eyes exhibited hypopyon. An area of corneal thinning was observed in 7 eyes (38.9%). Endophthalmitis due to infectious keratitis developed in one patient. In vitro susceptibility testing confirmed high sensitivity to ceftazidime and aminoglycosides. Medical management consisted primarily of topical amikacin (20 mg/ml) combined with topical cefazoline (50 mg/ml) (72.2%). Surgical tectonic procedures were carried out in 7 eyes (38.9%).

CONCLUSION

Citrobacter spp. is a rare cause of bacterial keratitis.Previous keratoplasty and ocular surface problems are important risk factors. The prognosis is not good and surgical tectonic intervention is required in many cases to resolve the corneal infection.

Microbial Keratitis in Patients With Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: Experience From a Tertiary Centre in Taiwan

PURPOSE

The purpose of this study was to analyze the clinical features, causative microorganisms, antibiotic susceptibility, and treatment outcomes in culture-proven microbial keratitis (MK) in patients with Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and to analyze the potential risk factors.

METHODS

We reviewed the medical records of all patients with SJS/TEN who attended our department between 2009 and 2018. Patients with a diagnosis of MK who underwent corneal cultures were enrolled. Demographics; clinical characteristics including ocular findings, treatment, time between onset of SJS/TEN and keratitis; changes in visual acuity; culture results; and antibiotic susceptibility were analyzed. Culture results from prior conjunctival swabs and keratitis were also compared.

RESULTS

Sixteen eyes from 12 patients (mean age 40.1 ± 27.7 years) with MK were identified. These patients had the most severe ocular involvement in the acute stage and had more severe ocular complications (SOCs) in the chronic stage compared with patients with SJS/TEN without MK. There were 26 infection episodes during 4.4 ± 6.9 (1.0-25.8) years of follow-up. Oral nonsteroidal anti-inflammatory drugs accounted for half of the causative drugs. Severe dry eye was the most common predisposing factor, followed by topical steroid use, trichiasis, and lid margin keratinization. Staphylococcus was the most common pathogen, and over half of the gram-positive bacteria were resistant to oxacillin/methicillin. Fungal infections (notably Candida ) accounted for nearly one-third of the causative microorganisms. Culture reports from periodic conjunctival swabs were not consistent with those from corneal scrapings. Recurrence of infection was associated with inferior visual outcome.

CONCLUSIONS

Patients with SJS/TEN with SOCs are subject to recurrent corneal infections, which are responsible for deterioration of vision. Identifying the risk factors and aggressive treatment as early as possible is pivotal for infection control.

Spectrum and resistance in bacterial infections of the ocular surface in a German tertiary referral center 2009-2019

PURPOSE

Aim of this study was to evaluate the frequencies, trends, and antibiotic resistance of bacteria collected from ocular surface or contact lens material in a German tertiary referral center from 2009 to 2019.

METHODS

Microbiological data from 2009 to 2019 was analyzed. Culture-dependent microbial identification and analysis of antibiotic sensitivity was completed by the Institute of Microbiology. Statistical analysis of age- and sex-specific differences as well as changes in the microbial spectrum and resistance over the study period was performed with GraphPad Prism 9.0 applying nonparametric tests (level of significance: p ≦ 0.05).

RESULTS

A total of 6361 specimens were analyzed. Positivity rate was 18.6%. Sixty-three percent (n = 680) of the bacterial isolates were derived from ocular surface and 37% (n = 399) from contact lens material. The ratio of gram-negative bacteria was significantly higher in contact lens material. Multiresistant bacteria showed a significant increase with patient age (p < 0.0001). An overall increase in resistance to levofloxacin (p = 0.0239) was detected. Only 2.4% and 3.1% isolates were resistant to a combination of moxifloxacin and gentamicin, respectively, levofloxacin and gentamicin.

CONCLUSIONS

The reported bacterial spectrum is similar to comparable centers. Our data show that it should not be assumed that the newest classes of antibiotics have the best efficacy or lowest resistance levels. In suspected bacterial conjunctivitis, we propose using gentamicin as first-line therapy. In therapy refractive cases and in involvement of the cornea, we recommend a combination of gentamicin and ofloxacin or moxifloxacin. Overall, the evaluated organisms showed good sensitivity to the regularly used antibiotics.

Trends in Infectious Keratitis in Taiwan: An Update on Predisposing Factors, Microbiological and Antibiotic Susceptibility Patterns

Infectious keratitis (IK) represents a major cause of corneal blindness. This study aims to investigate the demographics, risk factors, microbiological characteristics and antibiotic susceptibility patterns of IK in Taiwan over the past 15 years. A retrospective population-based study was conducted using the Chang Gung Research Database. Patients with IK were identified by diagnostic codes for corneal ulcer from 2004 to 2019. Of 7807 included subjects, 45.2% of patients had positive corneal cultures. The proportion of contact lens-related IK declined, while that of IK related to systemic diseases grew. The percentage of isolated gram-positive bacteria surpassed that of gram-negative bacteria in the 15-year period. The prevalence of Pseudomonas aeruginosa showed a decreasing trend (p = 0.004), whereas coagulase-negative Staphylococcus (CNS) and Propionibacterium species were increasingly detected (p < 0.001). Overall, the trend of antibiotic susceptibility of both gram-positive and gram-negative bacteria did not change throughout the study period. The susceptibility to the test antibiotics maintained over 90% in gram-negative isolates over 15 years. Vancomycin preserved 100% susceptibility to all gram-positive isolates. Since most tested antibiotics exhibited stable susceptibility over decades, this study reinforced that fluoroquinolones and fortified vancomycin continue to be good empiric therapies for treating bacterial keratitis in Taiwan.

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.

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.

Photodynamic therapy for treatment of bacterial keratitis

Microbial keratitis is the main cause of corneal opacification and the fourth leading cause of blindness worldwide, with bacteria the major infectious agent. Recently, bacterial keratitis has become a serious threat due to routine use of antibiotics leading to selection of resistant and multidrug-resistant bacteria strains. New approaches for treatment of bacterial keratitis are necessary to outcome the increasing antibiotic resistance. Antimicrobial photodynamic therapy is based on three agents: photosensitizer, oxygen, and light radiation. This therapy has been successful for treatment of infections in different tissues and organs as well as against different type of infectious agents and no resistance development. Also, new photosensitizers are being developed that has increased the spectrum of therapeutic protocols for treatment of a number of infectious diseases. Thus, antimicrobial photodynamic therapy has an extraordinary potential for treatment of those bacterial keratitis cases that actually are not solved by traditional antibiotic therapy.

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.

Hydroxypropyl methacrylamide-based copolymeric nanoparticles loaded with moxifloxacin as a mucoadhesive, cornea-penetrating nanomedicine eye drop with enhanced therapeutic benefits in bacterial keratitis

Bacterial keratitis (BK) is a leading cause of visual impairment. The fluoroquinolone antibiotic moxifloxacin (Mox), being highly water-soluble, suffers from poor corneal penetration leading to unsatisfactory therapeutic outcomes in BK. Here, we prepared Mox-loaded co-polymeric nanoparticles (NPs) by entrapping the drug in co-polymeric NPs constituted by the self-assembly of a water-soluble copolymer, poly(ethylene glycol)-b-p(hydroxypropyl) methacrylamide (mPH). The polymer (mPH) was prepared using a radical polymerization technique at different mPEG: HPMA ratios of 1:70/100/150. The polymer/nanoparticles were characterized by GPC, CAC, DLS, SEM, XRD, DSC, FTIR, % DL, % EE, and release studies. The ex vivo muco-adhesiveness and corneal permeation ability were judged using a texture analyzer and Franz Diffusion Cells. In vitro cellular uptake, cytotoxicity, and safety assessment were performed using HCE cells in monolayers, spheroids, and multilayers in transwells. The DOE-optimized colloidal solution of Mox-mPH NPs (1:150) displayed a particle size of ~116 nm, superior drug loading (8.3%), entrapment (83.2%), robust mucoadhesion ex vivo, and ocular retention in vivo (~6 h) (judged by in vivo image analysis). The non-irritant formulation, Mox-mPH NPs (1:150) (proven by HET-CAM test) exhibited intense antimicrobial activity against P. aeruginosa, S. pneumoniae, and S. aureus in vitro analyzed by live-dead cells assay, zone of inhibition studies, and by determining the minimum inhibitory and bactericidal concentrations. The polymeric nanoparticles, mPH (1:150), decreased the opacity and the bacterial load compared to the other treatment groups. The studies warrant the safe and effective topical application of the Mox-mPH NPs solution in bacterial keratitis.

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.

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.

Clinico-microbiological profile of Burkholderia cepacia keratitis: a case series

Background

Burkholderia cepacia, an opportunistic pathogen mainly affecting patients with cystic fibrosis or immunocompromised, has rarely been documented as a cause of corneal infection. The clinical and microbiological profiles of B. cepacia keratitis are reported herein.

Methods

We retrospectively reviewed the medical record of 17 patients with culture-proven B. cepacia keratitis, treated between 2000 and 2019 at Chang Gung Memorial Hospital, Taiwan. Our data included predisposing factors, clinical presentations, treatments, and visual outcomes of B. cepacia keratitis as well as the drug susceptibility of the causative agent.

Results

The most common predisposing factor for B. cepacia keratitis was preexisting ocular disease (seven, 41.2%), particularly herpetic keratitis (five). Polymicrobial infection was detected in seven (41.2%) eyes. All B. cepacia isolates were susceptible to ceftazidime. Main medical treatments included levofloxacin or ceftazidime. Surgical treatment was required in five (29.4%) patients. Only four (23.5%) patients exhibited final visual acuity better than 20/200.

Conclusions

B. cepacia keratitis primarily affects patients with preexisting ocular disease, particularly herpetic keratitis, and responds well to ceftazidime or fluoroquinolones. However, the visual outcomes are generally poor.

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.

Spectrum of Microbial Keratitis Encountered in the Tropics

PURPOSE

To report the predisposing factors, microorganisms, antibiotic sensitivity associated with bacterial keratitis, and treatment outcomes in Miri, Borneo which has a tropical climate.

METHODS

This is a retrospective study on patients presenting with microbial keratitis in Miri, Sarawak, Borneo over a 7-year period from January 1, 2010 until December 31, 2016. Demographic data, predisposing factors, culture and sensitivity results together with treatment outcomes were studied.

RESULTS

There were a total of 221 cases treated as microbial keratitis with a peak age group of 21 to 30 years. The predisposing factors were trauma (49.3%), improper contact lens usage (29.1%), ocular surface diseases (5.9%), ocular surgeries (0.9%), drugs (1.8%), and other factors (19.0%). Occupational injuries among oil palm plantation workers was the leading cause within the trauma cohort (28.8%). Corneal scraping was performed in 189 cases, 61.4% of them yielded positive cultures. The cultures demonstrated that 49.1% were of bacterial origin, 46.6% were fungal, and 4.3% showed mixed growth. The most common bacteria isolated was Pseudomonas aeruginosa, which was sensitive toward ceftazidime and gentamicin antibiotics. One hundred ninety-two cases (86.9%) were treated with purely topical medication, whereas 29 cases (13.1%) required further interventions.

CONCLUSION

The commonest predisposing factor for microbial keratitis was trauma. With the nearby oil palm industries, we report a corresponding increase of incidence in fungal keratitis at our center. Culture and sensitivity reports from corneal scrapings are essential in treatment guidance; however, more than a third of the microbial keratitis cases studied were culture-negative. The organisms cultured reflect the profile expected in tropical climates. Fortunately, there was no increase in resistance rates observed for the commonly used antibiotics.

Ocular bacterial infections: Pathogenesis and diagnosis

The human eye is a rigid asymmetric structure with unique defence system. Despite considerable resident microbiota, eye is exposed to external environment where a range of microorganisms also inhabits. Opportunistically, some of these microorganisms could associate with eye pathogen that could contact incidentally, leading to destructive visual consequences. Among such microbiota, bacteria form the major proportion concerning ocular complications worldwide. The succession of genome based approach through 16S rRNA gene based identification tremendously augmented the knowledge on diversity of ocular surface bacteria. Such evidence suggests that while few bacteria contribute towards normal ocular functions, considerable number of bacteria play active role in pathophysiology of ocular diseases. Thus, understanding the complexity of ocular microflora not only throw light on their critical role towards normal function of the eye, but also enlighten on certain visual exigencies. Under these circumstances, development of a rapid, reliable and cost effective method is essential that eventually evolve as a routine diagnostic protocol. Such precise prognostic modalities facilitate ophthalmologists to formulate pioneering therapeutics towards challenging ocular diseases.

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.

Bacterial Profile and Antibiotic Susceptibility Pattern of Bacterial Keratitis at a Tertiary Hospital in Riyadh

Background

The most common cause of ocular infections worldwide is bacteria; therefore, bacterial keratitis requires rapid and proper intervention because it is a major cause of loss of vision and ocular morbidity. Resistance studies have found increases in the resistance to ciprofloxacin, cefazolin, and gentamicin in bacterial keratitis cases that are caused by gram-positive organisms.

Aim

To identify the common predisposing factors, causative organisms, and antibiotic profile of bacterial keratitis (BK) in a tertiary care hospital in Riyadh, Saudi Arabia.

Method

This is a retrospective study of the microbiological record of all patients diagnosed with BK at KAUH. From the first of May 2015 until the first of January 2018. Demographic data, diabetes mellitus, contact lens use, history of eye trauma, ocular surface disorders, recent ocular surgeries, current and recent medications, initial and final visual acuity, and location and size of the infiltrate were all used in the study. VA was converted to the logarithm of the minimum angle of resolution (LogMAR) for statistical analysis.

Results

177 cases positive for BK were included. 100 (56.5%) were males, and 77 (43.5%) were females. The mean age was 43.15. Trauma was the most common predisposing factor, which was observed in 68 (38.4%) cases, followed by Ocular surface disease [52 (29.4%)]. Staphylococcus epidermidis was the most commonly isolated organism [61 (34.5%)], followed by Streptococcus pneumoniae [23 (13%)], and Staphylococcus aureus [18 (10.2%)]. All gram-positive cases were Vancomycin sensitive. Staphylococcus epidermidis showed only 4 resistant cases to chloramphenicol (7.27%), and resistance to penicillin and ampicillin was found in 55 (90%) and 53 (89.83%) cases, respectively. All Streptococcus pneumoniae cases were resistant to gentamicin (100%). Staphylococcus aureus showed high sensitivity for erythromycin [18 (100%)].

Conclusion

The most common cause of bacterial keratitis was Staphylococcus epidermidis (N=61), followed by Streptococcus pneumoniae (N=23). Trauma was the most common predisposing factor (38.4%), while contact lens use was only identified in 14 cases (7.9%). All organisms tested were sensitive to vancomycin, and there was high resistance toward penicillin (90%).

The Spectrum of Microbial Keratitis: An Updated Review

Background:

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

Objective:

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

Methods:

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

Results:

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

Conclusion:

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

Therapeutic penetrating keratoplasty for microbial keratitis in Taiwan from 2001 to 2014

PURPOSE

To study the surgical outcome of therapeutic penetrating keratoplasty (TPK) for medically uncontrolled microbial keratitis at a tertiary hospital in Taiwan over a 14-year period.

METHODS

This is a retrospective case series study. Patients who underwent TPK at National Taiwan University Hospital in 2001-2014 were included. Patients were divided into 3 diagnostic groups: bacterial keratitis, fungal keratitis, and acanthamoeba keratitis. Each of the following criteria was evaluated: graft clarity at 1 month and 1 year postoperatively, cure of the disease, and anatomical success rate.

RESULTS

A total of 107 TPKs were included. TPK eradicated the infection in 57/62 (91.9%) of bacterial keratitis, 33/41 (80.5%) of fungal keratitis, and 9/10 (90.0%) of acanthamoeba keratitis. 22/57 grafts (38.6%) of bacterial keratitis, 22/38 grafts (57.9%) of fungal keratitis, and 5/10 grafts (50.0%) of acanthamoeba keratitis remained clear at 1 year postoperatively. The 1-year graft survival rate did not significantly differ among these 3 groups. The leading causes of graft failure were late endothelial decompensation and graft reinfection. A higher percentage of graft clarity was achieved in grafts <8.5 mm in diameter than in larger grafts (55.4% vs. 31.4%, P = 0.027). Of the 14 patients with endophthalmitis at the time of TPK, the infection was successfully treated in 13 patients except 1 patient required evisceration.

CONCLUSION

TPK is valuable in the management of medically uncontrolled microbial keratitis, although the 1-year graft survival rate is unsatisfactory. TPK combined with intravitreal antibiotics and vitrectomy is also a beneficial treatment strategy for patients with endophthalmitis secondary to microbial keratitis.

Microbial Keratitis in Taiwan: A 20-Year Update

PURPOSE

To investigate the demographics, risk factors, microbiology, and resistance pattern at a tertiary hospital and to detect the shifting trend over 2 decades.

DESIGN

A retrospective observational case series.

METHODS

We reviewed all records of patients with microbial keratitis (MK) that were hospitalized in National Taiwan University Hospital between 2007 and 2016. Demographics, predisposing factors, pathogens, and clinical courses were compared to our previous study conducted from 1992 to 2001. Antibiotic susceptibility was compared with those conducted from 1994 to 2005.

RESULTS

The percentage of patients 60 years and older in the MK population was increasing (P = 2.1E-21). The proportion of trauma-related MK declined while MK related to chronic ocular or systemic disorders rose. The prevalence of nontuberculous mycobacteria (NTM) showed a decreasing trend (P = .0032), whereas Microsporidia has been increasingly detected. The 2 most common bacterial isolates were Pseudomonas aeruginosa (35.2%) and Staphylococcus species (13.2%). Management of these infection did not differ in common pathogens between the 2 decades. The susceptibility of Staphylococcus species to oxacillin reduced significantly (P = .002) and there was an increase in methicillin-resistant Staphylococcus aureus keratitis.

CONCLUSIONS

Contact lens wear remained the most common predisposing factor, with Pseudomonas species as the major pathogen. However, chronic disorder-related MK was on the rise along with an increasing trend of oxacillin resistance in Staphylococcus species. We found a decreasing trend in NTM keratitis while Microsporidia keratitis was considered as an emerging ocular disease. Though gram-negative isolates remained susceptible to all antibiotics tested, antibiotic resistance was more common in gram-positive isolates.

An 11-year analysis of microbial keratitis in the South West of England using brain-heart infusion broth

BACKGROUND

The aims of this study were to identify the organisms responsible for microbial keratitis, as identified by corneal scrape using brain-heart infusion broth, trends over time and antimicrobial sensitivities, over an 11-year period at two eye units in the South West of England; Bristol Eye Hospital and Royal United Hospital, Bath.

METHODS

All corneal scrapes performed and sent for microbiological analysis between 4th April 2006 and 31st October 2017 at the two eye units were retrospectively reviewed. First-line treatment was monotherapy with levofloxacin 0.5% and second-line treatment was a combination of cefuroxime 5% and gentamicin 1.5%. Both direct and enrichment cultures were used.

RESULTS

In total, 2614 corneal scrapes from 2116 patients (1082 female, mean age 47.7 ± 21.2 years) were identified. 38.1% (n = 996) were culture positive and 1195 organisms were cultured. In all, 91.6% were bacteria (69.4% were gram-positive, 30.6% gram-negative). Coagulase-negative Staphylococci (CoNS) were the most commonly cultured organism (n = 430). Pseudomonas aeruginosa was the most commonly identified gram-negative organism (n = 189). In total, 6.9% (n = 83) of organisms cultured were fungi. In all, 1.4% (n = 17) were acanthamoeba. There was no statistically significant trend in the organisms observed over the study period. Sensitivity testing confirmed reasonable sensitivity to the empiric antibiotics used in clinical practice.

CONCLUSIONS

This is the first report on microbial keratitis trends in the South West of England. Virulent organisms were likely to be detected on direct culture, whereas low virulent organisms such as CoNS were more likely to be detected on enrichment alone. Antibiotic sensitivity testing confirmed fluoroquinolone monotherapy as appropriate first-line treatment.

The persistent dilemma of microbial keratitis: Global burden, diagnosis, and antimicrobial resistance

Microbial keratitis is a potentially blinding condition that must be treated emergently to preserve vision. Although long recognized as a significant cause of corneal blindness, our understanding of its true global scale, associated burden of disease, and etiological patterns remains somewhat limited. Current epidemiological data suggest that microbial keratitis may be epidemic in parts of the world-particularly within South, South-East, and East Asia-and may exceed 2 million cases per year worldwide. Etiological patterns vary between economically developed and developing countries, with bacterial predominance in the former and fungal predominance in the latter. The key to effective management lies in timely diagnosis; however, the current gold standard of stain and culture remains time consuming and often yields no clinically useful results. For this reason, there are attempts to develop highly sensitive and accurate molecular diagnostic tools to provide rapid diagnosis, inform treatment decision making, and minimize the threat of antimicrobial resistance. We provide an overview of these key areas and of avenues for further research toward the goal of more effectively addressing the problem of microbial keratitis on both an individual and public health level.

Ten-year analysis of microbiological profile and antibiotic sensitivity for bacterial keratitis in Korea

Purpose

To investigate the risk factors, microbiological profiles, antibiotic susceptibility patterns, and treatment outcome in patients with bacterial keratitis at a Korean tertiary hospital.

Methods

A retrospective chart review was performed of patients who were diagnosed with infectious keratitis and underwent corneal scrapings for cultures at Seoul National University Hospital between 2007 and 2016. Demographics, clinical characteristics, microbiological data, antibiotic resistance and sensitivity, and treatment outcome were collected.

Results

Out of 129 scrapings, bacteria were isolated in 101 samples (78.3%). The most frequent isolates were coagulase-negative Staphylococci (CNS) (15.9%), Staphylococcus aureus (12.1%) and Pseudomonas aeruginosa (10.3%). All gram-positive isolates were sensitive to vancomycin, but methicillin resistance was found in 29.4% of CNS and 15.4% of Staphylococcus aureus. All gram-negative isolates were susceptible to ceftazidime and carbapenem while 11.5%, 3.3% and 2.8% of gram-negative isolates were resistant to gentamicin, tobramycin and amikacin, respectively. Ciprofloxacin resistance was observed in 10.3% of gram-positive isolates and 8.8% of gram-negative isolates. No significant changes were observed in profiles of microbial isolates and antibiotic sensitivity over time. Eight eyes of 101 eyes (7.9%) eventually underwent evisceration for infection control. The use of topical glaucoma medication (p = 0.006) and history of ocular surgery (p = 0.019) were significant risk factors related to evisceration.

Conclusions

CNS, Staphylococcus aureus and Pseudomonas aeruginosa were the most common microorganisms responsible for bacterial keratitis. The duo-therapy using vancomycin and ceftazidime should be considered for empirical treatment until the culture and sensitivity results become available.

Disease patterns of microbial keratitis in Singapore: A retrospective case series

PURPOSE

To investigate the disease patterns of Microbial Keratitis(MK) in patients seen in a tertiary referral hospital, to evaluate the clinical outcomes of MK and the risk factors for poorer visual outcomes.

METHODS

This is a retrospective case series of all culture-positive corneal scrapings between April 2012 and October 2016. A total of 230 patients(n = 230) were included into this study. Patient demographics, clinical information and microbiological characteristics of organisms are collected.

RESULTS

64.3% of patients with MK are contact lens(CL) users. Among CL users, there is a preponderance of females(68.9%) and they tend to be younger (27.1 ± 10.6 years). The most frequently isolated organism in this study is Pseudomonas aeruginosa(51.7%) with 69.6% of cases belonging to CL users. MK in non-CL users tend to involve other organisms, such as coagulase-negative Staphylococci, Staphylococcus aureus and Streptococcus pneumoniae. Pseudomonas aeruginosa exhibits good sensitivity rates to ciprofloxacin, levofloxacin and gentamicin. Non-Pseudomonas organisms display similar sensitivities to ciprofloxacin, levofloxacin and gentamicin. MK in non-CL users is related to predisposing factors of prior ocular trauma and concomitant ocular pathology. They tend to have worse visual acuity(VA) on presentation and after treatment compared to CL users. Poorer VA outcome is associated with larger ulcers, increasing age, trauma and non-CL wearers. Successful clinical outcome is achieved in 97.8% of patients, with only 2.2% requiring further surgical intervention.

CONCLUSION

CL use alters the disease patterns of MK as well as the underlying microbiological etiology. Fluoroquinolones and aminoglycosides are good empirical antibiotics for MK treatment. Early referral to a tertiary centre will likely allow for earlier treatment, which can result in better VA outcome, especially so in patients who are older, non-CL wearers and have larger ulcers with associated trauma.

Queensland Microbial Keratitis Database: 2005–2015

Aims

To estimate the incidence of culture-positive microbial keratitis in Queensland and analyse trends in the organisms and their sensitivities cultured from corneal scrapes, especially low-incidence organisms.

Methods

Retrospective multicentre case series of all positive corneal scrapes in Queensland, Australia between 2005 and 2015. Pathology organisations in Queensland were identified by online and local directory search and agreed to participate. Digital records of scrapes provided patient demographics and culture and susceptibility results. Trends in the incidence, organisms and sensitivities were monitored with linear regression. The yearly incidence of microbial keratitis was estimated from the Queensland population.

Results

The included corneal scrapes totalled 3182, while 1006 were excluded. The included scrapes yielded 4111 organisms. Pseudomonas aeruginosa was the most common single isolate (729, 17.7%), although Gram-positive organisms were more common overall (2737, 66.6%). Fungal organisms were cultured in 6% of cases, while Acanthamoeba comprised only 1% of records. Bacterial organisms were sensitive to all recorded antibiotics in 89% of all isolates and none of the reported antibiotics showed a decreasing trend in susceptibility. The incidence of protozoal isolation decreased over time (p=0.055). Cultures positive for yeasts showed a linear increase in incidence (p=0.045) while moulds showed a spike in incidence in 2010–2012 (p=0.0008).

Conclusion

The estimated incidence of microbial keratitis was 0.66 cases per 10 000 people, the rate of antibiotic susceptibility is high and stable, the incidence of keratitis secondary to protozoa is likely to be decreasing while the incidence of keratitis culturing yeast is increasing.

Infectious Keratitis: Microbiological Review of 297 Cases

Infectious keratitis is a serious ocular infection that can lead to loss of vision. The aim of this study was to investigate the microbiological characteristics of this infection at the University Hospital of Guadalajara (Spain). We retrospectively reviewed all cases diagnosed between January 2010 and December 2016. During the 7-year study period, 297 corneal scrapes corresponding to 298 patients were performed. Antibiotic treatment prior to the culture was administered in 59 cases (19.9%). Contact lens wear was the most common risk factor (33.2%). Bacterial keratitis accounted for 64.6% of cases, viral keratitis for 3.4%, and fungal keratitis for 1%. A total of 241 bacterial strains were identified. Gram-positive isolates represented 87.1%, and gram-negative 12.7%. Coagulase-negative Staphylococcus strains were the most common microorganisms isolated (30.3%). When gram-positive microorganisms were analyzed, the sensitivity prevalence rates for vancomycin (VCM), levofloxacin, gentamicin (GM), and tobramycin (TO) were 99.4%, 84.6%, 87.9%, and 88.3%, respectively. For the gram-negative organisms, the sensitivity prevalence rates for ceftazidime, ciprofloxacin, GM, and TO were 83.3%, 93.5%, 96.3%, and 100%, respectively. Our study revealed strong predominance of gram-positive microorganisms. We suggest empirically treating bacterial keratitis originating in our area with VCM and TO, especially severe bacterial keratitis and pretreated cases in the community without a clinical response.

Bacterial Keratitis in Toronto: A 16-Year Review of the Microorganisms Isolated and the Resistance Patterns Observed

PURPOSE

To review the incidence, distribution, current trends, and resistance patterns of bacterial keratitis isolates in Toronto over the past 16 years.

METHODS

Microbiology records of suspected bacterial keratitis that underwent a diagnostic corneal scraping and cultures from January 1, 2000, through December 31, 2015, were retrospectively reviewed. The distribution of the main isolated pathogens and in vitro laboratory minimum inhibitory concentration testing results were used to identify resistance patterns.

RESULTS

A total of 2330 corneal scrapings were taken over 16 years. A pathogen was recovered in 1335 samples (57.3%), with bacterial keratitis accounting for 1189 of the positive cultures (86.0% of all isolates). The total number of gram-positive and gram-negative isolates was 963 and 324, respectively. Coagulase-negative Staphylococcus and Pseudomonas aeruginosa were the most common gram-positive and gram-negative bacteria isolates, respectively. A decreasing trend in the number of isolates in gram-positive bacteria (P = 0.01), specifically among Staphylococcus aureus (P < 0.0001) and Streptococcus species (P = 0.005), was identified. When analyzing the susceptibilities of gram-positive and gram-negative isolates, an increasing trend in antibiotic resistance was observed in erythromycin (P = 0.018), ceftazidime (P = 0.046), and piperacillin/tazobactam (P = 0.005). The susceptibility of tested gram-positive microorganisms to vancomycin was 99.6%.

CONCLUSIONS

There has been a decreasing trend in the number of isolates in gram-positive microorganisms over the past 16 years. An increasing trend in resistance for various antibiotics against gram-negative and gram-positive isolates was identified. High susceptibility to vancomycin reinforced the empirical use of fortified tobramycin and vancomycin in the initial management of severe bacterial keratitis.

Clinical and microbiological profile of infectious keratitis in an area of Madrid, Spain

INTRODUCTION

To study antibiotic susceptibility in bacterial keratitis (BK), its profile over 10 years and its influence on ophthalmological practice.

METHODS

Retrospective review of BK with positive corneal scraping over a 10-year period. Risk factors for keratitis, visual acuity (VA), empirical topical treatment, corneal infection characteristics and outcomes were analyzed for BK due to Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Pseudomonas aeruginosa and Propionibacterium acnes.

RESULTS

389 positive corneal scrapings were collected. All Gram-positive bacteria were susceptible to vancomycin. P. aeruginosa demonstrated >90% sensitivity to the most-commonly-used topical antibiotics. Susceptibility to methicillin was 90.2% for S. aureus and 66.3% for S. epidermidis. The results of 215 patients were available. 1.9% required enucleation and 2.8% required surgical treatments. Final VA improved after treatment in keratitis due to S. aureus (p=0.026) and S. epidermidis (p=0.005). There was a correlation between S. aureus resistance to methicillin (p=0.002) and levofloxacin (p=0.043) and enucleation (20% and 10%, respectively) compared with a 0% rate of enucleation in S. aureus-susceptible keratitis.

CONCLUSIONS

BK due to S. pneumoniae is very aggressive irrespective of antibiotic sensitivity. S. aureus was frequently isolated in patients with systemic diseases. It causes severe keratitis and remains moderately resistant to methicillin and levofloxacin. For this reason, keeping vancomycin in empirical regimens is believed to be necessary.

Flagellar Hooks and Hook Protein FlgE Participate in Host Microbe Interactions at Immunological Level

Host-microbe interactions determine the outcome of host responses to commensal and pathogenic microbes. Previously, two epithelial cell-binding peptides were found to be homologues of two sites (B, aa168–174; F, aa303–309) in the flagellar hook protein FlgE of Pseudomonas aeruginosa. Tertiary modeling predicted these sites at the interface of neighboring FlgE monomers in the fully formed hook. Recombinant FlgE protein stimulated proinflammatory cytokine production in a human cell line and in murine lung organoid culture as detected with real-time RT-PCR and ELISA assays. When administered to mice, FlgE induced lung inflammation and enhanced the Th2-biased humoral response to ovalbumin. A pull-down assay performed with FlgE-saturated resin identified caveolin-1 as an FlgE-binding protein, and caveolin-1 deficiency impaired FlgE-induced inflammation and downstream Erk1/2 pathway activation in lung organoids. Intact flagellar hooks from bacteria were also proinflammatory. Mutations to sites B and F impaired bacteria motility and proinflammatory potency of FlgE without altering adjuvanticity of FlgE. These findings suggest that the flagellar hook and FlgE are novel players in host-bacterial interactions at immunological level. Further studies along this direction would provide new opportunities for understanding and management of diseases related with bacterial infection.

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.

Bilateral simultaneous infective keratitis

AIM

To analyze the demographics, risk factors, clinical and microbiological characteristics of cases of bilateral simultaneous infective keratitis.

METHODS

In this retrospective case series, patients with clinical evidence of bilateral simultaneous infective keratitis were identified from January 1, 2011 to August 31, 2016. Demographics, risk factors, clinical and microbiological characteristics, and treatment outcomes were analyzed.

RESULTS

Five patients (ten eyes) with bilateral simultaneous infective keratitis were identified. The mean age was 32.8 years (SD,±8.8; range, 24-44). All the patients were disposable soft contact lens wearers before presentation. The average size of the infiltrate was 4.76mm² (SD±9.0; range, 0.2-31.34). A total of 4 types of bacteria were isolated, with Pseudomonas aeruginosa being the most frequently isolated bacteria involving 5 eyes of four patients. Infection resolved with medical treatment in 9 eyes, 1 patient required therapeutic corneal transplantation for impending corneal perforation. The average time taken for infection to resolve was 6.7days (SD±4.5; range, 2-16).

CONCLUSIONS

In this case series, the most common risk factor of bilateral simultaneous microbial keratitis was use of soft disposable contact lens and the most commonly isolated bacteria was Pseudomonas aeruginosa. Bilateral simultaneous infective keratitis is uncommon and is a serious complication of contact lens use in immunocompetent adult patients.