Acanthamoeba keratitis and contact lens disinfecting solutions

OBJECTIVES: To report cases of culture-proved Acanthamoeba keratitis in Greece over a 10-year period and to evaluate the effectiveness of the commonly used commercial contact lens disinfecting systems in clinical cases of Acanthamoeba keratitis. MATERIAL AND METHODS: During the years 1994-2004, 45 contact lens wearers and 3 non-contact lens wearers presenting with symptoms and signs of keratitis underwent corneal sampling. The scrapings obtained were inoculated directly onto appropriate culture media for bacteria, fungi and Acanthamoeba. All proved positive for Acanthamoeba. The contact lenses and contact lens disinfecting solutions (16 one-step 3% hydrogen peroxide and 3 multipurpose solutions) of 19/45 patients with culture-proven Acanthamoeba keratitis were cultured for bacteria, fungi and Acanthamoeba. RESULTS: Acanthamoeba was isolated from contact lenses and contact lens disinfecting solutions in all 19 cases of Acanthamoeba keratitis studied. CONCLUSIONS: The main risk factor for corneal infection in contact lens wearers is the use of contact lens disinfecting systems ineffective at killing Acanthamoeba cysts and trophozoites, as well as bacteria and fungi. Improvement or development of new contact lens disinfecting systems by manufacturers is needed to prevent Acanthamoeba keratitis.     

Acanthamoeba as a cause of peripheral ulcerative keratitis

PURPOSE: To report a case of peripheral ulcerative keratitis caused by Acanthamoeba. METHODS: Case report and review of the literature. A 37-year-old woman with a history of pain and redness of the right eye with no apparent predisposing factors, on examination, revealed a peripheral ulcerative keratitis. RESULT: Microbiological investigations of the corneal infiltrate revealed Acanthamoeba cysts. CONCLUSION: All cases of peripheral ulcerative keratitis should be subjected to routine microbiological evaluation including those for Acanthamoeba.     

The etiology of infectious corneal ulceration in Sierra Leone

The microbial etiology of infectious corneal ulceration in Sierra Leone has been investigated. Patients either presenting to district health centers or encountered on rural surveillance expeditions with suspected infectious ulcerative keratitis were recruited into the study. Infectious corneal ulceration was defined as clinical evidence of corneal infection with epithelial defect with or without hypopyon. Cultures were obtained in a standard fashion and subsequent microbial analysis performed on all specimens. Seventy-three (73) cases of suspected infectious ulcerative keratitis were obtained between January 2005 and January 2006. The most commonly isolated organisms from microbial cultures of infected eyes were Gram-negative bacteria (45.2%), Gram-positive bacteria (37.0%), and fungal species (35.6%). Mixed bacterial and fungal organisms were isolated from ten eyes (13.7%) and no organisms were isolated from four eyes (5.5%). There is a high incidence of Gram-negative and fungal ulcerative keratitis in the population studied in Sierra Leone. Empirical therapy for corneal ulceration in this region should be aimed towards treatment of bacterial, fungal, and mixed infections.     

Infectious keratitis related to orthokeratology

PURPOSE: To report 28 cases of infectious keratitis related to orthokeratology lens overnight wear in China. METHODS: From March 2000 to August 2001, 28 cases of infectious keratitis related to overnight orthokeratology lens wear were diagnosed in Beijing Institute of Ophthalmology. These were retrospectively reviewed with regard to the pathogens isolated, duration of wear, the time since onset of symptoms, and age. Cultures of corneal scrapes for bacteria, fungus and Acanthamoeba were performed in all of the 28 cases. RESULTS: All cases were students, including 10 males and 18 females, average age was 16 years (range 10-21 years). The duration of orthokeratology overnight wearing was from 2 weeks to 2 years. Uncorrected visual acuity (UCVA) on initial examination in our institute was from 20/200 to light perception. Of 28 isolates, 24 were culture positive (including 11 bacteria, 11 Acanthamoeba and two fungi), and four were culture negative. In two of the four culture negative cases, Acanthamoeba cysts were detected in the corneal stroma with the confocal microscope. Acanthamoeba and Pseudomonas aeruginosa accounted for 75% (21 of 28) of the cases of infectious keratitis. CONCLUSION: Infectious keratitis is a severe complication associated with overnight orthokeratology lens wear. Ophthalmologists should pay more attention to this complication in practice.     

棘阿米巴角膜炎的实验室检查和临床诊断

目的：为了解棘阿米巴角膜炎的临床病程特征,采用简便实用的实验室检查方法对棘阿米巴角膜炎进行病因诊断。方法：对棘阿米巴角膜炎患者13例（13只眼）各病程阶段的特征性眼表现,通过角膜刮片材料镜检,阿米巴分离培养及角膜病理确诊。结果：与戴角膜接触镜有关者4例,非角膜接触镜配戴者9例,10％KOH湿封片镜检诊断阳性率81．25％,棘阿米巴培养阳性率56．25％,角膜病检阿米巴阳性率68．75％,结论：本病并非罕见,除载接触镜外,许多因素可接触感染,10％KOH湿封片可对棘阿米巴角膜炎作初步诊断,最后诊断须经原虫培养获得,角膜病理切片可进一步证实原虫培养的结果。     

The clinical diagnosis of microbial keratitis

PURPOSE: To evaluate the ability of ophthalmologists to predict the laboratory results of presumed microbial keratitis and to explore which findings may influence diagnostic prognostication. DESIGN: Prospective, cross-sectional study. METHODS: Fifteen ophthalmologists completed study forms at the initial presentation of patients with presumed microbial keratitis. After predicting the category of microbial recovery, clinicians submitted corneal scrapings for masked laboratory processing. The relative effects of ocular inflammatory signs on correct microbial diagnosis were explored with Poisson regression. RESULTS: Clinical examiners correctly predicted the presence or absence of microbial recovery in 79 (76%) of 104 ulcerative keratitis cases and successfully distinguished among bacterial, fungal, and amebic keratitis for 54 (73%) of 74 culture-positive infections, although only 31 (42%) were subcategorized properly. The positive predictive value of clinical diagnosis was 65% (95% confidence interval [CI], 43% to 84%) for 20 eyes with Pseudomonas keratitis cases, 48% (95% CI, 32% to 63%) for 38 other bacterial keratitis, 45% (95% CI, 17% to 77%) for 13 fungal keratitis, and 89% (95% CI, 52% to 100%) for nine Acanthamoeba keratitis cases. The recognition of Pseudomonas keratitis significantly improved by the occurrence of a larger infiltrate (P = .02), and correctly predicting Acanthamoeba keratitis was enhanced by observing a ring infiltrate (P < .001). Antimicrobial use before referral significantly attenuated clinical diagnosis (P = .03) and hampered microbial recovery (P = .004). CONCLUSIONS: Established Pseudomonas keratitis and Acanthamoeba keratitis can be suspected before laboratory confirmation, but overlapping inflammatory features and recent empiric antimicrobial treatment limits etiologic recognition of most microbial corneal infections.     

Evaluation of immunoperoxidase staining technique in the diagnosis of Acanthamoeba keratitis

PURPOSE: We describe a simple procedure of Immunoperoxidase (IP) technique, using indigenously raised antibody, to screen corneal scrapings for Acanthamoeba cysts and trophozoites. This study sought to determine the utility of this test in the diagnosis of Acanthamoeba keratitis. METHODS: A high titre polyclonal antibody against a local clinical isolate (axenic) of Acanthamoeba species (trophozoite lysate antigen) was raised in rabbits and used for standardization of IP technique for corneal scrapings. Twenty two smears of corneal scrapings, collected from patients showing Acanthamoeba cysts in corneal scrapings stained with calcofluorwhite (pool-1) and patients showing no cysts in similar scrapings (pool-2), were coded and stained by IP technique by a masked technician. All 22 patients had also been tested for bacteria, fungus, and Acanthamoeba in their corneal scrapings by smears and cultures. IP stained smears were examined for organisms including cysts and trophozoites of Acanthamoeba and background staining by two observers masked to the results of other smears and cultures. The validity of the IP test in detection of Acanthamoeba cysts and trophozoites was measured by sensitivity, specificity, positive predictive value and negative predictive value in comparison (McNemar test for paired comparison) with calcofluor white staining and culture. RESULTS: Based on the readings of observer 1 and compared to calcofluor white staining, the IP test had a sensitivity of 100%, a specificity of 94%, positive predictive value of 80% and negative predictive value of 100%. When compared to culture, the values were 83%, 100%, 100% and 94% respectively. Trophozoites missed in calcofluor white stained smears, were detected in 2 out of 6 cases of culture-positive Acanthamoeba keratitis. The Kappa coefficient of interobserver agreement was determined as fair (30.4%). CONCLUSION: The immunoperoxidase technique is a simple and useful test in the diagnosis of Acanthamoeba keratitis. This can supplement the culture results.     

Progressive ulcerative keratitis related to the use of topical chlorhexidine gluconate (0.02%)

PURPOSE: To report a case of progressive ulcerative keratitis related to the use of topical chlorhexidine gluconate 0.02%. METHODS: A 45-year-old woman was treated for presumed Acanthamoeba keratitis with chlorhexidine gluconate 0.02% and propamidine 0.1% eyedrops. RESULTS: After using the chlorhexidine and propamidine eyedrops for 8 weeks, the patient developed a near total loss of the corneal epithelium and a progressive ulcerative keratitis, which eventually required penetrating keratoplasty. Histopathologic examination of the corneal button showed ulceration and loss of Bowman's membrane, massive loss of keratocytes with apparent apoptosis, and loss of the endothelial cells with inflammatory cells adherent to the remaining cells. These histopathologic findings are similar to those seen in Hibiclens keratopathy. Hibiclens contains chlorhexidine 4% with a detergent. No organisms were seen in sections stained with modified Ziehl-Neelsen, gram, Grocott, or periodic acid-Schiff, and immunohistochemistry showed no significant findings. CONCLUSION: We think that the topical use of chlorhexidine gluconate 0.02% may have resulted in a progressive ulcerative keratitis in our patient.     

Diagnosis and management of Acanthamoeba keratitis

Diagnosis and management of Acanthamoeba chronic ulcerative keratitis is difficult. Two cases of Acanthamoeba keratitis at Wills Eye Hospital were diagnosed within several months of each other during 1983. Corneal transplantation was necessary for diagnosis and therapy in these cases. Another two cases were diagnosed when histopathologic specimens from penetrating keratoplasties done between 1974 and 1983 were reviewed retrospectively. There has been no evidence of recurrent disease in any of our cases during follow-up periods averaging two years (range, 12 to 40 months). The diagnosis of Acanthamoeba keratitis must be considered in cases of chronic progressive corneal ulceration unresponsive to medical therapy.     

Inflammation of the eye in systemic inflammatory disorders: keratitis

Systemic inflammatory diseases are associated with keratitis. In addition to the much less frequently occurring non-ulcerative keratitis, ulcerative inflammation of the corneal periphery is common in systemic inflammatory diseases. Significant systemic inflammatory diseases in this context are autoimmune connective tissue diseases (including rheumatoid arthritis, systemic lupus erythematosus or primary vasculitides such as polyarteritis nodosa or Wegener's granulomatosis), systemic autoimmune dermatological disorders (such as the cicatrising pemphigoid or Stevens-Johnson syndrome) and autoimmune diseases of the lacrimal system (such as the lacrimal gland involvement in primary Sjogren's syndrome or in graft-versus-host disease). In severe cases of peripheral ulcerative keratitis intensive topical therapy is initially combined with a systemic high-dose steroid therapy. In further progressing ulceration, surgery may help to preserve or restore the integrity of the eye and may suppress the autoimmune response by shielding the corneal antigens from blood and the lymphatic system. Systemic immune modulating therapy has to be done in close consultation with the rheumatologist.     

Corneal biopsy in the management of progressive microbial keratitis

PURPOSE: To study the indications and role of diagnostic corneal biopsy in the management of patients with progressive microbial keratitis. METHODS: The records of 33 consecutive patients who underwent a diagnostic corneal biopsy from January 1, 1986, to December 31, 1998, were reviewed. The indication for corneal biopsy was progressive infectious keratitis despite intensive broad-spectrum topical antimicrobial therapy, or progressive stromal infiltration inaccessible to corneal scrapings. Microbiologic evaluation of all corneal biopsies was performed, and 11 of the 33 biopsies were also examined histopathologically. RESULTS: A microorganism was isolated from 27 (82%) of the 33 corneal biopsies. Of the six patients with a negative biopsy, a penetrating keratoplasty was performed in five patients and the pathogen was identified by examination of the corneal button. In one patient no microorganism was identified; however, the infection resolved with topical antimicrobial therapy. The most common risk factor for keratitis was foreign body exposure or corneal abrasion (14 patients). A solid stromal infiltrate was the most common pattern of corneal involvement. Corneal biopsy revealed previously unidentified microorganisms that led to a change in antimicrobial therapy in 24 (89%) of the 27 patients and confirmed prior culture results in the remaining 3 patients. Microbiologic evaluation of the corneal biopsy was more sensitive than histopathologic examination. Acanthamoeba was the most commonly isolated pathogen (five cases), followed by Propionibacterium acnes and Fusarium (four cases each). Gram-positive organisms were isolated in 16 patients. Only five of the 27 patients with a positive corneal biopsy required a penetrating keratoplasty, in contrast to five of the six patients with a negative corneal biopsy (P =.005). During the 13-year period of the study, only three corneal biopsies were performed in the last 6 years. CONCLUSIONS: Microbiologic evaluation of a diagnostic corneal biopsy contributed significantly to the diagnosis, treatment, and outcome of patients with progressive infectious keratitis.     

The value of calcofluor white in the diagnosis of mycotic and Acanthamoeba infections of the eye and ocular adnexa

In search of an easy and quick method for the diagnosis of fungal and Acanthamoeba infections of the eye, the authors have used calcofluor white (CFW), a fluorescent brightener with marked affinity for chitin and cellulose which are present in the cell walls of fungi and cysts of Acanthamoeba. Paraffin-embedded tissues containing mycotic organisms were stained with CFW and examined under a fluorescent microscope. Several fungi such as Candida sp, Aspergillus sp, Phycomycetes, Fusarium solani, Histoplasma capsulatum, Cryptococcus neoformans, Rhinosporidium seeberi, and others were studied. Trephine corneal biopsy specimens (2 mm) and methanol-fixed corneal scrapings containing Acanthamoeba sp were also examined. The walls of fungi and Acanthamoeba cysts stained bright greenish white in contrast to the reddish-orange background of the supporting tissues. The results demonstrate that the CFW method is a highly reliable and rapid technique for identification of mycotic organisms as well as cysts of Acanthamoeba. This method may also be applied in surgical pathology when performing frozen sections, as well as cytologic examination of corneal smears, vitrectomy specimens, and others.     

Predisposing factors and etiologic diagnosis of ulcerative keratitis

PURPOSE: To determine the predisposing factors, demographic characteristics, and etiology of ulcerative keratitis in a referral center in Bangkok, Thailand. METHODS: The medical records of admitted patients with positive-culture ulcerative keratitis were retrospectively reviewed for demographic data, predisposing factors, and microbial culture results. Predisposing factors were compared between bacterial and fungal keratitis. RESULTS: From January 2001 to December 2004, there were 127 positive-culture ulcerative keratitis cases. The most frequent microbiological diagnosis was bacterial keratitis (76 eyes, 60%), followed by fungal (48 eyes, 38%) and Acanthamoeba keratitis (3 eyes, 2%). The most common organisms isolated were Pseudomonas spp. for bacteria and Fusarium spp. for fungus. Compared with bacterial keratitis, fungal keratitis was more likely to be associated with ocular trauma (odds ratio = 11.20; 95% confidence interval, 3.62-34.66) but less likely to be associated with contact lens wear (odds ratio = 0.02; 95% confidence interval, 0.01-0.08). CONCLUSIONS: In our study, Pseudomonas and Fusarium species are the most common causes of bacterial and fungal keratitis, respectively. Fungal keratitis was more likely than bacterial keratitis to be associated with ocular trauma, whereas fungal keratitis was less likely to be associated with contact lens wear.     

Efficacy of topical and systemic itraconazole as a broad-spectrum antifungal agent in mycotic corneal ulcer. A preliminary study

PURPOSE: To evaluate the efficacy of topical (1%) and systemic itraconazole against common fungi such as Aspergillus and other filamentous fungi that cause mycotic corneal ulcer. METHODS: A prospective randomised, controlled study was done in 54 clinically suspected cases of fungal keratitis of which 44 were culture proven. Half the cases (n=27) with superficial involvement were treated with only topical itraconazole (1%) and the other half were treated with both topical and systemic itraconazole. RESULTS: Aspergillus, Penicillium and Fusarium were the most common fungi isolated. The ulcer resolved in 42 eyes (77%) and 12 eyes (23%) did not respond well to treatment. Four of 12 non-responding eyes were caused by Fusarium species. CONCLUSION: Itraconazole, given either topically or systemically, is effective in treating mycotic corneal ulcers.     

Acanthamoeba keratitis: persistent organisms without inflammation after 1 year of topical chlorhexidine

PURPOSE: To report a non-contact lens wearer with persistent Acanthamoeba organisms in the cornea after being treated with medical therapy that included topical chlorhexidine as 1 agent for 1 year. METHODS: A 53-year-old man with Acanthamoeba keratitis was treated with medical therapy for >1 year, followed by a penetrating keratoplasty. RESULTS: Histopathologic examination of the keratoplasty specimen revealed viable-appearing Acanthamoeba cysts and trophozoites within the deep corneal stroma in a focus of corneal scarring. CONCLUSIONS: The use of chlorhexidine as 1 agent in the medical management of Acanthamoeba keratitis may not eradicate the organisms.     

Effect of steroids on Acanthamoeba cysts and trophozoites.

PURPOSE: Topical steroids are frequently used to control corneal inflammation and uveitis or is administered after surgery, to prevent corneal graft rejection. This study was undertaken to determine whether steroids could affect the pathogenicity of Acanthamoeba castellanii. METHODS: The effect of dexamethasone phosphate on excystment, proliferation, and encystment of trophozoites and cysts of A. castellanii was examined in vitro. Cytolysis capacity of steroid-treated Acanthamoeba was quantified by a spectrophotometric assay, and plasminogen activators were measured by a fibrinolysis assay. The influence of steroid treatment on corneal infection in a Chinese hamster model of Acanthamoeba keratitis was examined in vivo. RESULTS: Treatment of Acanthamoeba cysts with dexamethasone induced 4- to 10-fold increases in the number of trophozoites compared with untreated control cultures. Acceleration of trophozoite proliferation was observed when trophozoites were treated with dexamethasone. However, dexamethasone treatment did not affect encystment of Acanthamoeba trophozoites. Dexamethasone-treated trophozoites or cysts induced a significant cytopathic effect on corneal epithelial cells compared with untreated organisms. Supernatants collected from either dexamethasone-treated or untreated organisms failed to lyse corneal epithelial cells. Treatment of organisms with dexamethasone had no effect on production of plasminogen activators by Acanthamoeba trophozoites. Intramuscular injection of dexamethasone had a profound effect on the incidence, severity, and chronicity of keratitis. Keratitis in dexamethasone-treated hamsters was significantly more severe at all time points than in untreated animals (P < 0.05). CONCLUSIONS: These findings indicate that exposure of Acanthamoeba trophozoites and cysts to dexamethasone increases the pathogenicity of the organisms. The results emphasize the importance of maintaining adequate amebicidal therapy if a topical steroid is used in the management of Acanthamoeba keratitis.     

Clinical management and prognosis in Acanthamoeba keratitis: a retrospective study of 25 cases

PURPOSE: To assess risk factors, clinical characteristics, diagnosis and outcome in patients with Acanthamoeba keratitis. METHODS: We reviewed 23 patients (25 eyes) treated for Acanthamoeba keratitis in the XV-XX Hospital between November 1994 and October 2000. Acanthamoeba were found either in corneal scrapings and/or contact lenses and/or storage solutions. RESULTS: A predisposing factor was found in 22/23 patients: most of them (20/22) were contact lens (CL) wearers, two patients had a recent history of corneal trauma, and 15/23 patients had been treated for presumed herpetic keratitis before examination in our hospital. The average delay between first symptoms and diagnosis was 2 months. All patients were treated with two or three topical antiparasitic eye drops for 2 to 6 months. Five patients received systemic treatment (ketoconazole or itraconazole). Nine eyes received surgical treatment: penetrating keratoplasty in eight cases, conjunctival flap in one case, enucleation in one case. Visual outcome was poor in ten eyes (less than 20/60) because of delayed diagnosis. CONCLUSION: Acanthamoeba keratitis is a serious vision-threatening disease. Early diagnosis and treatment are essential for improving visual outcome. Methods such as confocal microscopy and Acanthamoeba-PCR, allowing earlier diagnosis and treatment, will improve the management of Acanthamoeba keratitis.     

Persistence of acanthamoeba antigen following acanthamoeba keratitis

AIM: To investigate the hypothesis that persistent corneal and scleral inflammation following acanthamoeba keratitis is not always caused by active amoebic infection but can be due to persisting acanthamoebic antigens METHODS: 24 lamellar corneal biopsy and penetrating keratoplasty specimens were obtained from 14 consecutive patients at various stages of their disease and divided for microscopy and culture. Histological sections were immunostained and screened for the presence of Acanthamoeba cysts by light microscopy. Cultures were carried out using partly homogenised tissues on non-nutrient agar seeded with E coli. Clinical data were obtained retrospectively from the case notes of these patients. RESULTS: Of the 24 specimens, 20 were obtained from eyes that were clinically inflamed at the time of surgery. Acanthamoeba cysts were present in 16 (80%) of these 20 specimens, while only five (25%) were culture positive. Acanthamoeba cysts were found to persist for up to 31 months after antiamoebic treatment. CONCLUSION: These findings support the hypothesis that Acanthamoeba cysts can remain in corneal tissue for an extended period of time following acanthamoeba keratitis and may cause persistent corneal and scleral inflammation in the absence of active amoebic infection. In view of these findings, prolonged intensive antiamoebic therapy may be inappropriate when the inflammation is due to retained antigen rather than to viable organisms     

Corneal ulceration in the elderly in Hyderabad, south India

AIMS: To report demographic, microbiological, therapeutic, anatomical, and visual results of corneal ulceration in the elderly patients seen at a tertiary eye care centre in south India. METHODS: 102 consecutive cases of microbial keratitis in patients 65 years and older were studied. Inclusion criteria were: (i) presence of corneal stromal infiltrate upon slit lamp examination; and (ii) microbiological evaluation of corneal scrapings for suspected microbial keratitis. RESULTS: The principal predisposing factors identified in this study were ocular disease (38.2%), previous ocular surgery in the same eye (29.4%), trauma (17.6%), and severe systemic disease (16.7%). Contact lens wear was associated with only two cases (2.0%). 99 organisms were isolated in cultures of corneal scrapings from 74 (72.5%) of the 102 cases. Staphylococcus epidermidis (31.1%), filamentous fungi (25.7%), and Streptococcus pneumoniae (13.5%) were the most common isolates. 12 eyes (11.8%) required surgery, 15 (14.7%) eventually required evisceration, and nine (9.6%) of the 94 followed patients achieved an unaided vision of 20/60 or better at last follow up. CONCLUSIONS: This work represents the largest recent single centre study on (non-viral) microbial keratitis in the elderly, its management, and outcomes of therapy. While the predisposing factors differ from those of general population, the spectrum of microbes responsible for keratitis in the elderly appears to reflect the local microbial flora rather than a predilection for elderly patients. Delay in diagnosis and systemic conditions associated with advancing age probably contribute to poorer outcome from therapeutic measures.     

Microbial investigations in keratitis at the Sydney Eye Hospital

Abstract
We investigated 107 cases of presumed microbial keratitis amongst patients presenting to the Sydney Eye Hospital between October 1986 and August 1988 to determine the frequency of infection, the common causative organisms and those factors that predispose to corneal infection.
We found that 95% of culture-proven cases were caused by bacteria and that Staphylococcus epidermidis and Corynebacterium sp, accounted for 42.5% of these cases. All bacteria (except Staphylococcus epidermidis and Mycobacrerium chelonae ) were sensitive to gentamicin.
In 62.6% of cases, cultures for bacteria and fungi were negative. Retrospective review of the clinical records of these patients showed that herpes simplex virus, contact lens wear, staphylococcal marginal keratitis and recurrent erosion were important causes of keratitis in this group.