Laboratory diagnosis in ulcerative keratitis

Factors Associated With Laboratory Test Negativity Following a Transition in Specimen Collection in Microbial Keratitis Cases

PURPOSE

Negative laboratory results make targeting microbial keratitis treatment difficult. We investigated factors associated with laboratory negativity in patients with microbial keratitis in the context of a transition to a new specimen collection method.

METHODS

Microbial keratitis patients with associated laboratory tests were identified in the electronic health record of a tertiary care facility from August 2012 to April 2022. Patient demographics and laboratory results were obtained. Random sampling of 50% of charts was performed to assess the impact of the ocular history and pretreatment measures. The relationship between probability of negative laboratory results with demographics, ocular history, pretreatment measures, and utilization of a new specimen collection method (i.e. ESwab) was evaluated by multivariable logistic regression.

RESULTS

Of 3395 microbial keratitis patients identified, 31% (n = 1051) had laboratory tests. Laboratory testing increased over time (slope = 2.5% per year, p < 0.001; 19.6% in 2013 to 42.2% in 2021). Laboratory negative rate increased over time (slope = 2.2% per year, p = 0.022; 48.5% in 2013 to 62.3% in 2021). Almost one-third of patients (31.2%, n = 164) were pretreated with steroids. Over two-thirds of patients were pretreated with antibiotics (69.5%, n = 367). 56.5% (n = 297) of patients were outside referrals. In multivariable regression, patients with corticosteroid pretreatment had lower odds of negative laboratory results (odds ratio [OR] = 0.49, p = 0.001). There were higher odds of negative laboratory results for every additional antibiotic prescribed to a patient prior to presentation (OR = 1.30, p = 0.006) and for specimens collected using ESwabs (OR = 1.69, p = 0.005). Age, prior eye trauma, outside referrals, and contact lens wear were not significantly associated with negative laboratory results.

CONCLUSION

More microbial keratitis associated laboratory tests are being taken over time. Over 60% of tests were negative by 2022. Factors associated with negative laboratory test results included pretreatment with antibiotics and specimens collected with the new collection method.

Diagnosis of Fungal Keratitis in Low-Income Countries: Evaluation of Smear Microscopy, Culture, and In Vivo Confocal Microscopy in Nepal

Clinically diagnosing fungal keratitis (FK) is challenging; diagnosis can be assisted by investigations including in vivo confocal microscopy (IVCM), smear microscopy, and culture. The aim of this study was to estimate the sensitivity in detecting fungal keratitis (FK) using IVCM, smear microscopy, and culture in a setting with a high prevalence of FK. In this cross-sectional study nested within a prospective cohort study, consecutive microbial keratitis (MK) patients attending a tertiary-referral eye hospital in south-eastern Nepal between June 2019 and November 2020 were recruited. IVCM and corneal scrapes for smear microscopy and culture were performed using a standardised protocol. Smear microscopy was performed using potassium hydroxide (KOH), Gram stain, and calcofluor white. The primary outcomes were sensitivities with 95% confidence intervals [95% CI] for IVCM, smear microscopy and culture, and for each different microscopy stain independently, to detect FK compared to a composite referent. We enrolled 642 patients with MK; 468/642 (72.9%) were filamentous FK, 32/642 (5.0%) were bacterial keratitis and 64/642 (10.0%) were mixed bacterial-filamentous FK, with one yeast infection (0.16%). No organism was identified in 77/642 (12.0%). Smear microscopy had the highest sensitivity (90.7% [87.9-93.1%]), followed by IVCM (89.8% [86.9-92.3%]) and culture (75.7% [71.8-79.3%]). Of the three smear microscopy stains, KOH had the highest sensitivity (85.3% [81.9-88.4%]), followed by Gram stain (83.2% [79.7-86.4%]) and calcofluor white (79.1% [75.4-82.5%]). Smear microscopy and IVCM were the most sensitive tools for identifying FK in our cohort. In low-resource settings we recommend clinicians perform corneal scrapes for microscopy using KOH and Gram staining. Culture remains an important tool to diagnose bacterial infection, identify causative fungi and enable antimicrobial susceptibility testing.

Role of corneal biopsy in the management of infectious keratitis

PURPOSE OF REVIEW

The aim of this study was to review the existing literature and investigate the role of microbiologic culture and histopathologic examination of corneal biopsies in the management of infectious keratitis.

RECENT FINDINGS

Corneal biopsy continues to be a significantly useful tool in the diagnosis and tailored management of infectious keratitis. Several techniques can be employed for tissue collection, handling and processing to optimize diagnostic yield and maximize safety, including emerging femtosecond laser-assisted biopsy.

SUMMARY

Corneal opacities represent a significant cause of global blindness, and infectious keratitis is the most common cause. Organism identification in progressive infectious keratitis is essential for proper management. However, microbiological culture alone has a high rate of false-negative results. Records from the Bascom Palmer Eye Institute were retrospectively searched for patients between 1 January 2015, and 31 December 2019, who underwent corneal biopsy, therapeutic keratoplasty or endothelial graft removal for infectious keratitis and had specimens bisected and submitted for evaluation with both microbiologic culture and histopathologic examination. Detection of bacteria, fungus and mycobacteria was not statistically different between culture and histopathology. Microbiology and histopathology are complementary methods for the identification of causative microorganisms in corneal specimens with presumed infectious keratitis.

Positive Microbiological Stains of Corneal Scrapings among Patients with Keratitis in a Tertiary Care Centre: A Descriptive Cross-sectional Study

Introduction

Keratitis, an ocular emergency, requires rapid and accurate treatment to prevent vision impairment. Wet mount direct microscopy examination of corneal scraping smear using gram and 10% potassium hydroxide stain helps in early diagnosis and treatment. The main objective of this study was to find out the prevalence of positive microbiological stains of corneal scrapings among patients with keratitis in a tertiary care centre.

Methods

A descriptive cross-sectional study was conducted in the Department of Ophthalmic Pathology and Laboratory Medicine from January, 2018 to December, 2019. Data collection was done after taking ethical approval from the Institutional Review Committee of the hospital (Reference number: BEH-IRC-35/A). All corneal smear samples received in this department were included in this study. Case records with incomplete data were excluded. Whole sampling was done. The data were analyzed using Statistical Package for the Social Sciences version 22.0. Frequency and percentage was calculated for binary data.

Results

Among 4631 corneal scrapings, microbiological stains were positive in 3538 (76.40%) patients.

Conclusions

The prevalence of positive microbiological stains of corneal scrapings in our study was higher in comparison to other studies done in similar settings. This technique could be used where culture facilities are unavailable or unaffordable.

Keywords

keratitis; microscopy; Nepal.

Village-integrated eye workers for prevention of corneal ulcers in Nepal (VIEW study): a cluster-randomised controlled trial

BACKGROUND

Corneal ulcers are a common cause of blindness in low-income and middle-income countries, usually resulting from traumatic corneal abrasions during agricultural work. Antimicrobial prophylaxis of corneal abrasions can help prevent corneal ulcers, but delays in the initiation of therapy are frequent. We aimed to assess whether a community-based programme for corneal ulcer prevention would reduce the incidence of corneal ulceration.

METHODS

A cluster-randomised trial was performed in village development committees (VDCs) in Nepal. VDCs in the catchment area of Bharatpur Eye Hospital, Nepal with less than 15 000 people were eligible for inclusion. We randomly assigned (1:1) VDCs to either an intervention group or a control group. In the intervention VDCs, existing female community health volunteers (FCHVs) were trained to diagnose corneal abrasions and provide a 3-day course of ophthalmic antimicrobials to their patients. In the control VDCs, FCHVs did not provide this intervention. Participants were not masked given the nature of the intervention. Both groups were followed up for 3 years for photographic evidence of corneal ulceration. The primary outcome was the incidence of corneal ulceration, determined by masked assessment of corneal photographs. The analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, NCT01969786.

FINDINGS

We assessed 112 VDCs, of which 24 were enrolled. The study was performed between Feb 4, 2014, and Oct 20, 2017. 12 VDCs were randomly assigned to the intervention group and 12 to the control group. 252 539 individuals were included in the study (130 579 in the intervention group and 121 960 in the control group). FCHVs diagnosed and provided antimicrobials for 4777 corneal abrasions. The census identified 289 corneal ulcers among 246 893 person-years in the intervention group (incidence 1·21 cases [95% CI 0·85-1·74] per 1000 person-years) and 262 corneal ulcers among 239 170 person-years in the control group (incidence 1·18 cases [0·82-1·70] per 1000 person-years; incidence rate ratio 1·03 [95% CI 0·63-1·67]; p=0·93). Medication allergy was self-reported in 0·2% of participants.

INTERPRETATION

We did not detect a reduction in the incidence of corneal ulceration during the first 3 years of a community-based corneal ulcer prevention programme. Further study might be warranted in more rural areas where basic eye care facilities are not available.

FUNDING

National Eye Institute.

Bacterial keratitis: identifying the areas of clinical uncertainty

Bacterial keratitis is a common corneal infection that is treated with topical antimicrobials. By the time of presentation there may already be severe visual loss from corneal ulceration and opacity, which may persist despite treatment. There are significant differences in the associated risk factors and the bacterial isolates between high income and low- or middle-income countries, so that general management guidelines may not be appropriate. Although the diagnosis of bacterial keratitis may seem intuitive there are multiple uncertainties about the criteria that are used, which impacts the interpretation of investigations and recruitment to clinical studies. Importantly, the concept that bacterial keratitis can only be confirmed by culture ignores the approximately 50% of cases clinically consistent with bacterial keratitis in which investigations are negative. The aetiology of these culture-negative cases is unknown. Currently, the estimation of bacterial susceptibility to antimicrobials is based on data from systemic administration and achievable serum or tissue concentrations, rather than relevant corneal concentrations and biological activity in the cornea. The provision to the clinician of minimum inhibitory concentrations of the antimicrobials for the isolated bacteria would be an important step forward. An increase in the prevalence of antimicrobial resistance is a concern, but the effect this has on disease outcomes is yet unclear. Virulence factors are not routinely assessed although they may affect the pathogenicity of bacteria within species and affect outcomes. New technologies have been developed to detect and kill bacteria, and their application to bacterial keratitis is discussed. In this review we present the multiple areas of clinical uncertainty that hamper research and the clinical management of bacterial keratitis, and we address some of the assumptions and dogma that have become established in the literature.

Alterations in the Ocular Surface Microbiome in Traumatic Corneal Ulcer Patients

Purpose

Corneal ulcers are a common eye inflammatory disease that can cause visual impairment or even blindness if not treated promptly. Ocular trauma is a major risk factor for corneal ulcers, and corneal trauma in agricultural work can rapidly progress to corneal ulcers. This study aims to evaluate the changes in the ocular surface (OS) microbiome of patients with traumatic corneal ulcer (TCU).

Methods

Among 20 healthy control (HC) subjects and 22 patients with TCU, 42 eyes were examined to investigate the OS microbial flora using metagenomic shotgun sequencing.

Results

At the taxonomic composition level, our findings showed that dysbiosis (alterations in richness and community structure) occurs in the OS microbiome of patients with TCU. Notably, Pseudomonas was present at a greater than 30% relative abundance in all individuals in the TCU group. At the species level, the abundance of Pseudomonas fluorescens and Pseudomonas aeruginosa was significantly elevated in the TCU group compared to the HC group. At the functional level, we identified significant differences in the HC and TCU groups. We observed that inflammation-related pathways involved in bacterial chemotaxis, flagellar assembly, and biofilm formation were significantly more abundant in the TCU group. Besides, the pathways related to biosynthesis, degradation, and metabolism were also increased significantly in the TCU group.

Conclusions

These findings indicate an altered OS microbiome in the affected eyes of patients with TCU. Further research is needed to determine whether these alterations contribute to the pathogenesis of TCU or impact disease progression.

The Spectrum of Microbial Keratitis: An Updated Review

Background:

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

Objective:

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

Methods:

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

Results:

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

Conclusion:

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

The 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.

A comparative, retrospective, observational study of the clinical and microbiological profiles of post-penetrating keratoplasty keratitis

Infectious keratitis after penetrating keratoplasty (PK) is a devastating condition that may result in graft failure and poor visual outcome. In this study, we retrospectively reviewed the medical records of patients who underwent PK between 2009 and 2014, and recorded those who developed infectious keratitis. We compared the predisposing factors and organisms isolated to those identified in our previous study, conducted between 1989 and 1994. The incidence of post-PK infectious keratitis decreased from 11.6% (41 out of 354 cases, 1989–1994) to 6.5% (9 out of 138 cases, 2009–2014). Graft epithelial defect and suture-related problems remained the leading two risk factors of infectious keratitis after PK. Gram-positive and Gram-negative bacterial infection decreased from 58.5% and 46.3% to 11.1% and 22.2%, respectively (P = 0.023 and P = 0.271). In contrast, fungus infection increased from 9.8% to 66.7% (P = 0.001); fungi have become the major pathogen for post-PK infectious keratitis. In conclusion, while the incidence of post-PK infectious keratitis has decreased over time, the number and frequency of fungal infections have significantly increased in the recent study period. Clinicians should be aware of the shifting trend in pathogens involved in post-PK infectious keratitis.

Filamentous fungal infections of the cornea: a global overview of epidemiology and drug sensitivity

Fungal keratitis is a serious suppurative, usually ulcerative corneal infection which may result in blindness or reduced vision. Epidemiological studies indicate that the occurrence of fungal keratitis is higher in warm, humid regions with agricultural economy. The most frequent filamentous fungal genera among the causal agents are Fusarium, Aspergillus and Curvularia. A more successful therapy of fungal keratitis relies on precise identification of the pathogen to the species level using molecular tools. As the sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal RNA gene cluster (rDNA) is not discriminative enough to reveal a species-level diagnosis for several filamentous fungal species highly relevant in keratitis infections, analysis of other loci is also required for an exact diagnosis. Molecular identifications may also reveal the involvement of fungal species which were not previously reported from corneal infections. The routinely applied chemotherapy of fungal keratitis is based on the topical and systemic administration of polyenes and azole compounds. Antifungal susceptibility testing of the causal agents is of special importance due to the emergence and spread of resistance. Testing the applicability of further available antifungals and screening for new, potential compounds for the therapy of fungal keratitis are of highlighted interest.

Trends in bacterial and fungal keratitis in South India, 2002-2012

OBJECTIVE

To assess the trends in microbiological organisms identified from corneal scrapings from patients with infectious keratitis at a tertiary care medical centre in South India.

METHODS

We reviewed the records of the microbiology laboratory at Aravind Eye Hospital in Madurai, India, from 2002 until 2012. We identified the microbiological causes of all corneal ulcers from the culture and smear results, and assessed for trends in bacterial and fungal keratitis over time.

RESULTS

Of 23 897 corneal patients with ulcer with a corneal smear from 2002 to 2012 a fungal organism was identified in 34.3%, a bacterial organism in 24.7% and no organism in 38.3%. During this period, the annual number of keratitis cases due to bacteria decreased from 677 to 412, and the annual number due to fungus increased from 609 to 863. In analyses accounting for the total number of outpatients seen each year, the decline in number of smears positive for bacteria was statistically significant (p<0.001) but the increase in the number positive for fungus was not (p=0.73). The relative frequency of individual bacterial or fungal organisms remained relatively stable over this time.

CONCLUSIONS

At a tertiary eye care centre in South India, there has been a reduction in the numbers of smear-positive bacterial keratitis over the past 11 years. This decline likely reflects economic development in India and increased access to antibiotics.

Clinical utility of caspofungin eye drops in fungal keratitis

Treatment of fungal keratitis remains challenging. To date, only the polyenes and azoles are commonly used topically in the management of fungal keratitis. Natamycin, a polyene, is the only antifungal eye drop that is commercially available; the remainder are prepared in-house and are used in an 'off-label' manner. Failure of medical treatment for fungal keratitis is common, hence there is a need for more effective topical antifungal therapy. To increase the antifungal eye drop armamentarium, it is important to investigate the utility of other classes of antifungal agents for topical use. Caspofungin, an echinocandin antifungal agent, could potentially be used to address the existing shortcomings. However, little is known about the usefulness of topically administered caspofungin. This review will briefly explore the incidence, epidemiology and antifungal treatment of fungal keratitis. It will focus primarily on evidence related to the efficacy, safety and practicality of using caspofungin eye drops in fungal keratitis.

A 3½-Year Study of Bacterial Keratitis From Odisha, India

PURPOSE

To report the clinical and microbiological characteristics and treatment outcome of bacterial keratitis at a tertiary eye care center in eastern India.

DESIGN

Retrospective analysis of medical and microbiology records.

METHODS

All patients had undergone complete clinical and microbiological evaluation for microbial keratitis. Patients with laboratory-proven bacterial keratitis were included in the study.

RESULTS

Between July 2006 and December 2010, 1417 microbial keratitis was clinically diagnosed in the patients. Whereas no organisms were found in 27.8% (394/1417) of cases, 21.4% (303/1417) were bacterial. From 303 patients, 347 bacterial isolates were cultured, 260 (74.9%) of which were gram-positive, 67 were gram-negative, and 20 were acid-fast. Streptococcus pneumoniae was the predominant isolate (86/347 [24.7%]), followed by Staphylococcus species [64/347 (18.4%)]. Pseudomonas aeruginosa (29/347 [8.3%]) was the most common gram-negative bacterial isolate. High level of susceptibility to cefazolin (96.2%) and vancomycin (96.5%) was found in gram-positive cocci, whereas susceptibility of Pseudomonas species to gatifloxacin was 95.1%. Fifty-three patients (17.5%) required tissue adhesive, and 47 (15.5%) needed penetrating keratoplasty. Healed corneal scar was achieved in 188 patients (62%), whereas 34 (11.2%) were lost to follow-up. Large stromal infiltrate size, older age group, and poor presenting visual acuity were significant factors that adversely affected final outcome (P < 0.05).

CONCLUSIONS

Proportion of bacterial keratitis was low compared with other studies from India. Gram-positive bacteria were a common cause of bacterial keratitis with high susceptibility to cefazolin and vancomycin. Gram-negative bacteria were sensitive to gatifloxacin with overall good treatment outcome.

Keratomycosis after incidental spillage of vegetative material into the eye: Report of two cases

Fungal corneal ulcers mostly occur after incidental corneal trauma by plant leaves in farm lands or the use of topical corticosteroids or antibiotics. The infection is more prevalent among farmers and harvesters and in some parts of the world is considered as an occupational disease; however, there have been a few reports on the occurrence of such ulcers in healthy individuals after incidental spillage of vegetative material into the eye. The importance of these ulcers is their long-term and refractory course, which makes the visual prognosis unfavorable in most patients, even after appropriate antifungal therapy or ocular interventions. Herein, we present two rare cases of fungal ulcers caused by incidental spillage of vegetative material into the eye while eating nuts and corn. We also discuss the diagnostic and therapeutic approaches, as well as visual outcome reviewing the relevant literature.

Photo-activated riboflavin therapy of refractory corneal ulcers

PURPOSE

To evaluate the therapeutic effect of photo-activated riboflavin (PAR) for treating refractory corneal ulcers.

METHODS

Seven eyes with infectious keratitis, presented with a gradually deteriorating, vision-threatening, corneal ulcer, despite intense antimicrobial therapy, were treated with PAR. The surgical procedure was deepithelialization of the affected corneas followed by UV-A riboflavin (B2) cross-linking. Local antimicrobial therapy was continued after the procedure.

RESULTS

In all cases, the progression of corneal melting was halted after PAR treatment. Emergency keratoplasty was not necessary in any of the 7 eyes presented. More importantly, all the ulcers were healed without significant vascularization.

CONCLUSION

PAR is a promising option for treating patients with therapy-refractory infectious keratitis to avoid emergency keratoplasty and should be considered as a potential adjuvant therapeutic tool in such eyes.

Changing referral patterns of infectious corneal ulcers to a tertiary care facility in south India - 7-year analysis

PURPOSE

To report changing trends in referral patterns of microbial keratitis evidenced by laboratory results of culture-positive cases from a tertiary eye-care hospital in south India.

METHODS

All patients presenting with microbial (nonviral) keratitis to the cornea services of Aravind Eye Hospital from 2003 to 2009 were identified from a computerized database. Microbiologic characteristics were recorded and annual distributions of causative organisms over the 7-year study period were compared.

RESULTS

Out of a total of 3059 cases of presumed microbial keratitis, 1756 had positive cultures (57.4%). Among the culture-positive cases, fungal pathogens were isolated from 1224 cases (70%), 488 (27.7%) showed bacterial growth, 18 (1.03%) grew acanthamoeba species and 26 (1.5%) demonstrated mixed bacterial and fungal growth. The percentage of fungal isolates in culture-positive cases increased gradually over the study period from 59% in 2004 to 78% in 2009. This increase in frequency of fungal keratitis was statistically significant (P = 0.023). A proportionally decreasing trend was seen in the number of bacterial isolates ranging from 31% in 2003-2005 to 22% in 2009 (P = 0.04).

CONCLUSIONS

An incremental increase was seen in the number of fungal keratitis cases referred to our institute during the study period. Bacterial keratitis showed a decline. This disconcerting trend may lead to an increase in the incidence of corneal blindness in the developing world and thus warrants further research.

Geographic variations in microbial keratitis: an analysis of the peer-reviewed literature

The epidemiology of microbial keratitis has been investigated in several studies by analysis of organisms cultured from corneal scrapes. However, a comparison of the frequency of different organisms causing keratitis in different parts of the world is lacking. The authors present a review incorporating an analysis of data from studies worldwide. The data provide a comparison of the frequency of culture-positive organisms found in different parts of the world. Associations between a country's gross national income and types of causative organism are explored. The highest proportion of bacterial corneal ulcers was reported in studies from North America, Australia, The Netherlands and Singapore. The highest proportion of staphylococcal ulcers was found in a study from Paraguay, while the highest proportion of pseudomonas ulcers was reported in a study from Bangkok. The highest proportions of fungal infections were found in studies from India and Nepal. The Spearman correlation coefficient demonstrated statistically significant correlations between gross national income and percentages of bacterial (0.85 (95% CI 0.68 to 0.91, p<0.0001)), fungal (-0.81 (95% CI -0.90 to -0.66, p<0.0001)) and streptococcal (-0.43 (95% CI -0.66 to -0.12, p=0.009)) isolates.

A management dilemma: infectious keratitis associated with soft contact lens use and dubious treatment compliance

Purpose. To present a case of infectious keratitis caused by the microorganism Serratia marcescens in a contact lens user and further to confer on the most advantageous management of comparable situations. Case. After altering the routine that she used for contact lens disinfection, a 24-year-old patient presented with pain and conjunctival redness in both eyes. Slit-lamp examination revealed two infiltrates in the inferior part of the cornea in the right eye and five smaller infiltrates in the superior half of the left cornea. Appropriate treatment, after hospitalization, improved the symptoms while culture of the contact lens material revealed Serratia marcescens as the responsible infectious factor. Conclusion. Enhancing the availability of information with respect to contact lens users and customized analysis regarding treatment for a particular complication could be beneficial in order to reduce the frequency of admission to the eye clinic due to infectious keratitis. In addition, rapid laboratory testing of the infected materials should be a priority for selection of the optimal treatment regimen.

In vitro activity of thimerosal against ocular pathogenic fungi

The in vitro activity of thimerosal versus those of amphotericin B and natamycin was assessed against 244 ocular fungal isolates. The activity of thimerosal against Fusarium spp., Aspergillus spp., and Alternaria alternata was 256 times, 512 times, and 128 times, respectively, greater than that of natamycin and 64 times, 32 times, and 32 times, respectively, greater than that of amphotericin B. Thimerosal's antifungal activity was significantly superior to those of amphotericin B and natamycin against ocular pathogenic fungi in vitro.

[Bacterial keratitis. Current diagnostic aspects]

Keratitis remains the third most common etiology for blindness worldwide. Whereas bacteria still predominate as causative organisms in temperate climates, fungal and mixed infections are more common in tropical and semitropical areas. In recent years, a shift in the causative organisms, as well as predisposing factors, has been reported. Risk factors that may have gained in importance, such as wearing contact lenses and corneal surgery, have been identified. Microorganisms, especially Pseudomonas spp. and mycobacteria have been frequently isolated in these patients. A changing pattern in microorganism infection has been observed that might be caused by inappropriate use of potent antimicrobial agents. Because of the sight threatening nature of bacterial keratitis, proper diagnosis and antibiotic selection are required. Management should be guided by the appropriate diagnosis, severity of clinical symptoms and underlying risk factors. Molecular techniques, such as polymerase chain reaction, have increased our diagnostic options, even when they cannot replace established procedures. This article reviews the current data and procedures available for the diagnosis of bacterial keratitis.

Demographic pattern, predisposing factors and management of ulcerative keratitis: evaluation of one thousand unilateral cases at a tertiary care centre

PURPOSE

To determine the predisposing factors, special clinical manifestations and the management of presumed microbial ulcerative keratitis.

METHODS

A retrospective study was performed in 1000 eyes of 1000 patients with presumed microbial keratitis. Information was recorded on patients' age and gender, risk factors, seasonal presentation, number of days since initiation of ulcer, prior therapy, clinical presentation, microbiological work-up and case management.

RESULTS

Fifty per cent of the patients with corneal ulcers were aged between 36 and 65 years and 13.3% were in the paediatric age group (1 month to <16 years). The male : female ratio was almost 1.6:1. Only 11.4% of patients reported to the authors during the first week of initiation of ulcer. Trauma was the cause in 47.6% of eyes, and ocular surface diseases accounted for 16.6%. Forty-two per cent of eyes received topical antibiotics alone (either one or more) prior to hospital visit and 42.2% of eyes were on topical antibiotics and antifungals. Another 8.2% were on topical corticosteroids along with antibiotics and 4.6% were receiving some unidentified drop. Only 3% of the eyes did not receive any therapy prior to visit. Contact lens use as a risk factor could be identified only in 8.2% of eyes. Ulcers were central in location in 48%. Ulcer size 6-9 mm was observed in 51.7% of eyes. Medical therapy alone was effective in 61.0% of eyes and another 9.7% eyes responded to paramedian tarsorrhaphy along with topical antimicroboial drugs.

CONCLUSION

Corneal ulcers are a frequent problem in this part of the world. The ulcers seen at this tertiary referral hospital present late in the natural history of the disease and are clinically severe. Despite the severity a majority of the eyes could be saved anatomically, but almost 65% of eyes were left with a visual acuity of <6/120. Considering the high magnitude of visual loss, public education about the potential for loss of sight and the importance of timely and appropriate treatment is recommended.

Ocular fungal isolates and antifungal susceptibility in northern China

PURPOSE

To analyze the distribution characteristics of ocular fungal isolates and antifungal susceptibility in vitro.

DESIGN

A retrospective case-series descriptive study.

METHODS

Two thousand one hundred and seventy-nine specimens collected from Tongren Hospital during 2001 to 2004 were identified at the Beijing Institute of Ophthalmology. Fungal culture-positive rate, antifungal susceptibility in vitro, and genus distribution of positive cultures were analyzed retrospectively. For the fungal culture-positive samples, the gender and age of the patients, the location of ocular involvement, and the season of the onset of mycotic ocular diseases were studied. The fungal positive isolates were subjected to antifungal susceptibility testing.

RESULTS

Out of 2,179 specimens, 681 specimens were positive cultures. The culture-positive rate was 31.25%. Out of 681 specimens of positive cultures, 591 specimens were from the cornea, 29 from the aqueous humor, 22 from the conjunctiva, 22 from the vitreous body, one from the lacrimal sac, and 16 from the other sites. Fusarium species was the most common pathogen identified in 394 (57.86% of positive cultures), followed by Aspergillus species in 116 (17.03% of positive cultures). Out of 681 positive cultures, the sensitivity in vitro to natamycin, terbinafine, itraconazole, and fluconazole were 608/681 (89.28%), 467/681 (68.58%), 260/681 (38.18%), and 101/681 (14.83%), respectively. Three hundred and sixty-eight (93.4%) of Fusarium species were sensitive to natamycin, 107 (92.2%) of Aspergillus species were sensitive to itraconazole.

CONCLUSIONS

Fusarium species was the predominant pathogen, which resulted in mycotic ocular diseases in northern China, followed by Aspergillus species. Most of the Fusarium species were sensitive to natamycin, and most of the Aspergillus species were sensitive to itraconazole.

Aureobasidium pullulans keratitis

BACKGROUND

Corneal ulcer caused by Aureobasidium pullulans is considered to be a rare entity. So far very few reports have appeared in the world literature and the authors' hospital is the first to report from Nepal. Although A. pullulans is regarded as a contaminant, it should be considered as a pathogen if isolated from corneal ulcer specimen with clinical signs of infection and with growth of the organism on two or more culture media or growth in one medium with consistent direct microscopy findings or growth of the same organism on repeated corneal scrapings. In the present study, a series of proven cases of A. pullulans corneal ulcers at a tertiary eye care centre of Eastern Nepal is reported.

METHODS

A retrospective analysis of stored data of microbiological and clinical cases of corneal ulcer was carried out. All consecutive patients (447 patients) with presumed microbial keratitis from 1 August 1998 to 31 July 2001 were evaluated with regards to clinical details, microbiological examination and management.

RESULTS

Of 200 fungal organisms isolated from the cultures, 25 were identified as A. pullulans. These ulcers showed negligible improvement to topical natamycin and required either topical fluconazole or topical itraconazole in all along with systemic intravenous fluconazole in eight patients. Of 25 eyes, 22 responded well to antifungal therapy and 2 required therapeutic penetrating keratoplasty. One patient was lost to follow up for 3 months and revealed phthisis bulbi on subsequent examination.

CONCLUSIONS

Aureobasidium pullulans corneal infection should be considered as a cause of keratomycosis.

Prevalence and spectrum of bacterial co-infection during fungal keratitis

AIMS

To estimate the propensity of keratomycosis for parallel or secondary bacterial infection and to explore affinities among fungal and bacterial co-isolates.

METHODS

A retrospective review of laboratory records over 24 years yielded 152 episodes of culture positive fungal keratitis. After collating 65 corneal specimens having bacterial co-isolates, polymicrobial co-infection was defined as detection of concordant bacteria on smear and culture or on two or more different media.

RESULTS

30 (20%) keratomycoses met laboratory criteria for polymicrobial infection. The risk of bacterial co-infection was 3.2 (95% confidence interval, 1.7 to 5.8) times greater with yeast keratitis than with filamentous fungal keratitis.

CONCLUSIONS

Bacterial co-infection occasionally complicates fungal keratitis, particularly candidiasis.