Acanthamoeba keratitis: clinical signs and analysis of outcome

Clinical outcomes and prognostic factors in Acanthamoeba keratitis

PURPOSE

To report clinical findings and prognostic factors for visual and morphological outcomes in patients with Acanthamoeba keratitis (AK).

METHODS

Single-center, retrospective, longitudinal study of 51 cases of AK diagnosed by real-time polymerase chain reaction (RT-PCR) between March 2010 and October 2022. The primary outcome was the final best corrected visual acuity (BCVA). Poor visual outcome was defined as a final BCVA ≥ 1 logMAR unit, while good visual outcome was defined as a final BCVA < 1 logMAR unit. Eyes from these two groups were compared, regarding demographic and initial clinical variables, anti-Acanthamoeba treatment used, and complications of the disease. Early diagnosis was defined as ≤ 14 days from symptom onset to diagnostic confirmation and initiation of Acanthamoeba medical treatment. Multivariable logistic regression was used to determine predictors of poor visual outcome.

RESULTS

A total of 51 eyes from 46 patients diagnosed with AK, all contact lens (CL) wearers, were included in this study. Average follow-up was 39.0 ± 30.2 [total range 14-120] months. Thirty-one eyes (60.8 %) presented good visual outcome, with a lower baseline age (30.5 ± 9.0 vs. 42.3 ± 15.8; p = 0.020), better initial BCVA (0.8 ± 0.7 logMAR units vs. 1.3 ± 0.9 logMAR units; p = 0.047), higher rate of early diagnosis (45.2 % vs. 5.6 %; p = 0.004), and higher rate of therapeutic epithelial debridement (64.5 % vs. 10 %; p < 0.001). 20 eyes (39.2 %) presented poor visual outcome, with 12 eyes undergoing evisceration/enucleation (23.5 %). These 20 eyes presented a higher rate of complications (90 % vs. 61.3 %; p = 0.031). In multivariable analysis, early diagnosis of AK (OR 19.78; 95 % CI 2.07-189.11; p = 0.010) and therapeutic epithelial debridement (OR 19.02; 95 % CI 3.27-110.57; p = 0.001) were associated with a good visual outcome.

CONCLUSIONS

In the present study, poor visual outcome was present in 39 % of affected eyes. Early AK diagnosis (≤14 days from symptom onset) and therapeutic epithelial debridement were associated with good final visual outcome.

Effectiveness of Polyclonal Antibody Immunoconjugate Treatment with Propamidine Isethionate for Amoebic Keratitis in Golden Hamsters

Acanthamoeba griffini is known to cause amoebic keratitis (AK); its main causes are inadequate hygiene when contact lenses are handled and/or its prolonged use at night, as well as the use of contact lenses during underwater activities. The most used treatment for AK is the combination of propamidine isethionate combined with polyhexamethylene biguanide, which disrupts the cytoplasmic membrane, and damages cellular components and respiratory enzymes. We proposed an immunoconjugate treatment obtained from Acanthamoeba immunized rabbit serum combined with propamidine isethionate; the corneas of hamsters inoculated with A. griffini (MYP2004) were treated with the combined, at 1, 2, and 3 weeks. Propamidine isethionate is frequently used for AK treatment, in vivo study we are found IL-1β and IL-10 expression and caspase 3 activity is significantly increased with respect to the group that was inoculated with the amoeba without receiving any treatment, suggesting that it may be an effect of the toxicity of this drug on the corneal tissue. Application of the immunoconjugate showed enhanced amoebicidal and anti-inflammatory activities, with comparison to propamidine isethionate only. The aim of this study is to evaluate the effect of the immunoconjugate of propamidine isethionate and polyclonal antibodies as a treatment of AK in golden hamsters (Mesocricetus auratus).

Corticosteroids in the Management of Infectious Keratitis: A Concise Review

Microbial keratitis is devastating corneal morbidity with a variable spectrum of clinical manifestations depending on the infective etiology. Irrespective of the varied presentation delayed treatment can lead to severe visual impairment resulting from corneal ulceration, possible perforation, and subsequent scarring. Corticosteroids with a potent anti-inflammatory activity reduce host inflammation, thus minimizing resultant scarring while improving ocular symptoms. These potential effects of corticosteroids have been applied widely to treat various corneal diseases ranging from vernal keratoconjunctivitis to dry eye disease. However, antimicrobial therapy remains the mainstay of treatment in microbial keratitis, whereas the use of adjunctive topical corticosteroid therapy remains a matter of debate. Understandably, the use of topical corticosteroids is a double-edged sword with pros and cons in the treatment of microbial keratitis. Herein we review the rationale for and against the use and safety of topical corticosteroids in the treatment of infective keratitis. Important considerations, including type, dose, efficacy, the timing of initiation of corticosteroids, use of concomitant antimicrobial agents, and duration of corticosteroid therapy while prescribing corticosteroids for microbial keratitis, have been discussed. This review intends to provide new insights into the therapeutic utility of steroids as adjunctive treatment of corneal ulcer.

The Impact of Topical Corticosteroids Used in Conjunction with Antiamoebic Therapy on the Outcome of Acanthamoeba Keratitis

PURPOSE

To examine the impact of topical corticosteroid use after the start of antiamoebic therapy (AAT) on the outcomes of Acanthamoeba keratitis (AK) therapy.

DESIGN

Cohort study.

PARTICIPANTS

A total of 196 patients diagnosed with AK at Moorfields Eye Hospital, London, between January 1991 and April 2012. In 13 patients with bilateral AK, 1 eye was randomly excluded from analysis.

METHODS

Patient demographics and clinical examination findings were collected both at the start of AAT and subsequently at the time that topical corticosteroid therapy was initiated. Preliminary a priori investigations were used to identify effect modifiers/confounders and extreme associations requiring consideration in multivariate regression modeling. A multivariable logistic model, optimized for assessment of corticosteroid use after the start of AAT, was used to estimate the odds ratios (ORs) of a suboptimal outcome.

MAIN OUTCOME MEASURES

Suboptimal outcome was defined as final visual acuity ≤20/80, corneal perforation, or the need for keratoplasty.

RESULTS

In multivariable analysis, restricted to 129 eyes (1 eye per patient) free of scleritis and hypopyon at the start of AAT, topical corticosteroids were not associated with worse outcomes (OR, 1.08; 95% confidence interval [CI], 0.39-3.03), even when corticosteroids had been used before the start of AAT. Risk factors significantly associated with worse outcomes were topical corticosteroid use before the start of AAT (OR, 3.85; 95% CI, 1.35-11.03), a corneal ring infiltrate (together with at least 1 other feature of AK) present at the start of AAT (OR, 5.89; 95% CI, 1.17-29.67), and age ≥33 years at the start of AAT (OR, 4.02; 95% CI, 1.46-11.06).

CONCLUSIONS

Many corneal specialists currently are uncertain about the risk benefit associated with the use of topical corticosteroids for the management of inflammatory complications of AK. The evidence from this study gives clinicians and patients reassurance that the potential benefits of topical corticosteroid therapy, for treating pain and discomfort, are not associated with worse outcomes when initiated after starting modern AAT. Other potential benefits, in terms of resolution of inflammatory complications, will not be demonstrated without a carefully designed randomized clinical trial.

[Diagnosis of Acanthamoeba keratitis]

The Acanthamoeba keratitis is a relatively rare, but dangerous disease of the cornea. Its development is thought to be associated with contact lens wearing as well as corneal microwounds contaminated with soil or water. The disease has no evident distinctive clinical features and is, therefore, difficult to be distinguished from herpetic or fungal keratitis. Nevertheless, Acanthamoeba infection can be suspected judging from anamnestic data (i.e. contact lens use and corneal injury with subsequent contamination of the wound), inadequately strong pain syndrome, ring-shaped infiltration of the cornea and ineffectiveness of conventional therapy. Also helpful may be such measures as isolating the bacteria using the method of biocultures, morphological examination of corneal biopsy material (using light and luminescent microscopy), genetic testing, and in vivo confocal microscopy of the cornea. Other promising methods are also listed in this article. A widely accepted diagnostic technique is yet, however, missing.

Acanthamoeba migration in an electric field

PURPOSE

We investigated the in vitro response of Acanthamoeba trophozoites to electric fields (EFs).

METHODS

Acanthamoeba castellanii were exposed to varying strengths of an EF. During EF exposure, cell migration was monitored using an inverted microscope equipped with a CCD camera and the SimplePCI 5.3 imaging system to capture time-lapse images. The migration of A. castellanii trophozoites was analyzed and quantified with ImageJ software. For analysis of cell migration in a three-dimensional culture system, Acanthamoeba trophozoites were cultured in agar, exposed to an EF, digitally video recorded, and analyzed at various Z focal planes.

RESULTS

Acanthamoeba trophozoites move at random in the absence of an EF, but move directionally in response to an EF. Directedness in the absence of an EF is 0.08 ± 0.01, while in 1200 mV/mm EF, directedness is significantly higher at -0.65 ± 0.01 (P < 0.001). We find that the trophozoite migration response is voltage-dependent, with higher directionality with higher voltage application. Acanthamoeba move directionally in a three-dimensional (3D) agar system as well when exposed to an EF.

CONCLUSIONS

Acanthamoeba trophozoites move directionally in response to an EF in a two-dimensional and 3D culture system. Acanthamoeba trophozoite migration is also voltage-dependent, with increased directionality with increasing voltage. This may provide new treatment modalities for Acanthamoeba keratitis.

Practice patterns and opinions in the treatment of acanthamoeba keratitis

PURPOSE

Management of acanthamoeba keratitis remains challenging for ophthalmologists. We conducted a survey of members of The Cornea Society to elicit expert opinions on the diagnosis and treatment of acanthamoeba keratitis.

METHODS

An online survey was sent to all subscribers of The Cornea Society via the kera-net listserv. Descriptive statistics were performed.

RESULTS

Eighty-two participants completed the online survey. Of the 82 respondents, 76.8% included the combination of clinical examination and culture in their diagnostic strategy and 43.9% used confocal microscopy. Most respondents (97.6%) had used combination therapy with multiple agents to treat acanthamoeba keratitis at some point in the past, whereas a smaller proportion (47.6%) had ever used monotherapy. Respondents most commonly chose polyhexamethylene biguanide as the ideal choice for monotherapy (51.4%), and dual therapy with a biguanide and diamidine as the ideal choice for combination therapy (37.5%). The majority of respondents (62.2%) reported using topical corticosteroids at least some of the time for acanthamoeba keratitis. Keratoplasty was an option considered by most respondents (75.6%), although most (85.5%) would only perform surgery after medical treatment failure.

CONCLUSIONS

There was a wide range of current practice patterns for the diagnosis and treatment of acanthamoeba keratitis. The lack of sufficiently powered comparative effectiveness studies and clinical trials makes evidence-based decision-making for this disease difficult.

Prescribing trends in infectious keratitis: a survey of New Zealand ophthalmologists

PURPOSE

To obtain an overview of the treatment of infectious diseases of the cornea by New Zealand ophthalmologists and to analyse the data in the context of evidence-based treatment recommendations.

METHODS

A questionnaire was sent to all New Zealand ophthalmologists. It comprised 23 multiple-choice questions pertaining to the characteristics of the respondents, the nature of their practice and their prescribing preferences in infectious conjunctivitis and keratitis.

RESULTS

Of the 93 ophthalmologists surveyed, 80.6% returned the questionnaire. Of those in clinical practice, 91.4% regularly treated patients with corneal disease. A subspecialty interest in cornea was stated by 12.5% of these. This paper reports observations for adenoviral conjunctivitis and adenoviral, Herpes simplex, varicella zoster, bacterial, acanthamoebal and fungal keratitis. In some conditions prescribing practice varied dramatically, such as in adenoviral conjunctivitis where 50% of respondents prescribed a corticosteroid and 51.6% an antibiotic, whereas 37.5% prescribed only lubrication or no topical treatment. In other conditions there was a high degree of agreement between ophthalmologists; indeed, all ophthalmologists treated Herpes simplex dendritic keratitis with topical acyclovir. No statistically significant differences in prescribing habits were identified between subspecialist and non-subspecialist groups, although some important clinical differences emerged. There were occasional marked differences in response when the age group of respondents was considered, particularly in relation to the management of adenoviral infections and bacterial keratitis.

CONCLUSIONS

The findings of this survey suggest that the majority of New Zealand ophthalmologists generally follow international guidelines for the management of infectious keratitis. The identified variations in management provide a foundation for informed clinical debate and the development of treatment guidelines, in line with evidence-based recommendations.

Corneal co-infection with Scedosporium apiospermum and Acanthamoeba after sewage-contaminated ocular injury

PURPOSE

To describe a corneal co-infection with the fungus Scedosporium apiospermum and Acanthamoeba that result in spontaneous corneal perforation.

METHODS

A 27-year-old man presented due to severe ocular pain in his left eye caused by a corneal ulcer. The patient was injured 7 days before presentation by metallic thread contaminated by sewage. Corneal scrapping and deep stromal biopsy were obtained and stained for microscopic evaluation with periodic acid-Schiff, Giemsa, and Gomori's methenamine silver stains. Samples were sent for aerobic and anaerobic bacterial and fungal cultures.

RESULTS

Corneal biopsy and corneal scrapping showed viable Acanthamoeba cysts in the corneal stroma and S. apiospermum micelle, respectively. The fungal culture was sensitive to ketoconazole, miconazole, econasole, and traconazole. Devastating corneal perforation occurred despite aggressive antifungal and antiamoebic topical and systemic treatment initiated after diagnosis. The corneal button showed a necrotic tissue devoid of inflammatory cells and microorganisms.

CONCLUSION

S. apiospermum and Acanthamoeba may co-infect immune privilege sites, such as the cornea, in immunocompetent hosts. Compromised corneal surface, e.g., after trauma by sewage-contaminated objects, may increase the susceptibility for such devastating coinfection. Prevention may be possible by use of protective eyewear by high-risk individuals. Treatment should be initiated promptly with broad-spectrum antimicrobial agents after ocular injury by sewage-contaminated objects. Repeated corneal cultures and biopsies, if the cultures are negative, are warranted. Corticosteroids should be withheld until the causative agents are identified and targeted treatment is initiated.

Acanthamoeba keratitis

Acanthamoeba species are an important cause of microbial keratitis that may cause severe ocular inflammation and visual loss. The first cases were recognized in 1973, but the disease remained very rare until the 1980s, when an increase in incidence mainly associated with contact lens wear was reported. There is an increased risk when contact lens rinsing and soaking solutions are prepared with nonsterile water and salt tablets. The clinical picture is often characterized by severe pain with an early superficial keratitis that is often treated as herpes simplex infection. Subsequently a characteristic radial perineural infiltration may be seen, and ring infiltration is common. Limbitis and scleritis are frequent. Laboratory diagnosis is primarily by culture of epithelial samples inoculated onto agar plates spread with bacteria. Direct microscopy of samples using stains for the cyst wall or immunostaining may also be employed. A variety of topically applied therapeutic agents are thought to be effective, including propamidine isethionate, clotrimazole, polyhexamethylene biguanide, and chlorhexidine. Various combinations of these and other agents have been employed, often resulting in medical cure, especially if treatment is commenced early in the course of the disease. Penetrating keratoplasty is preferably avoided in inflamed eyes, but may be necessary in severe cases to preserve the globe or, when the infection has resolved, to restore corneal clarity for optical reasons.

Outbreak of keratitis presumed to be caused by Acanthamoeba

PURPOSE

A sharp increase of Acanthamoeba keratitis from two cases per year to 30 cases per year at our institution prompted this study to determine whether there was a change in the clinical characteristics, basic epidemiology, and outcome of this disease.

METHODS

We reviewed all cases of Acanthamoeba keratitis diagnosed at the University of Iowa Hospitals and Clinics from mid-1993 through 1994.

RESULTS

We screened 217 patients with keratitis by tandem scanning confocal microscopy and suspected Acanthamoeba in 51 patients. Diagnosis was confirmed by cytology in 43 patients (48 eyes). There were no positive cultures. Patients examined within four weeks of onset of symptoms were younger (mean age, 32.6 +/- 15.4 years) and wore contact lenses (11 of 18 patients), and infrequently herpes simplex keratitis (four of 18 patients) was diagnosed. Patients examined after four weeks were older (mean age, 54.0 +/- 19.5 years), infrequently wore contact lenses (six of 25 patients), and often had herpes simplex keratitis (12 of 25 patients).

CONCLUSIONS

Corneal examination with tandem scanning confocal microscopy was associated with a marked increase in the detection of Acanthamoeba, strongly suggesting that the disease is more prevalent than suspected. Acanthamoeba may account for many cases of clinically presumed herpes simplex keratitis, the leading cause of corneal blindness in the United States. Acanthamoeba should be considered in the differential diagnosis of any unexplained keratitis, even those of short duration.

Ecology of free-living amoebae

Small free-living amoebae (FLA) are the main predators controlling bacterial populations in soils. They are distributed in the rhizospheric zone and the surrounding bulk soil; however, they may spread deeper, reaching the vadose zone of groundwater systems, especially where bacterial populations get to high densities. Soil texture is the physical factor controlling the distribution of FLA because it determines the mean bore pore of soil aggregates and other important physical factors. FLA help maintain the high bacterial mineralization rate of organic matter through predation. As attachment onto a surface is necessary for feeding, the quantity of available surfaces is very important for developing this activity. However, the role of protozoa on plant growth promotion is still unclear because they may increase this effect by feeding on both fungi and bacteria. Small FLA are found in soils or sediments, as well as attached to suspended particulate matter in water columns, in the first 30 microns of water surface, or on the bodies of submerged animals and plants. These microorganisms do not distinguish between terrestrial or aquatic environments because they live in the interfaces between them. However, their importance in aquatic systems has been considered as negligible because they are outcompeted by free swimmers. The water conditions affecting amoebae survival are pH, temperature, concentration of sulfhydric acid and salinity. These factors have a strong influence on the structure of amoebae communities in aquatic environments. FLA are considered cosmopolitan as a group, and they live inside vertebrates, in soils, freshwater, marine waters, and on the aerial parts of plants and animals. These microbes, are spread by wind and water currents. Once in the air, cysts and trophozoites behave like any other suspended particulate matter. Therefore, suspension transportation, and removal depend on atmospheric dynamics rather than on their own mechanisms. Ultraviolet light and drought are the main causes of losing viability, but much needs to be learned about the effects of air contaminants on amoebal survival. Naked amoebae also live in the phyllosphere as part of phylloplane community, but their importance and participation in this environment remain unknown. Some species belonging to the genera Acanthamoebae, Naegleria, and Balamuthia cause fatal diseases in humans and are carriers of other pathogens such as Legionella pneumophilia. However, FLA communities can be of some utility in sewage treatment works based in soil filters. FLA's predatory activity in the root zone method may be of greater importance than previously thought, because this is their natural or more favorable environment.(ABSTRACT TRUNCATED AT 400 WORDS)

Acanthamoeba keratitis. A masquerade of presentation in six cases

Acanthamoeba keratitis is an uncommon but devastating complication of contact lens wear causing significant ocular morbidity. Six consecutive cases occurring in Western Australia in an 18-month period are reported. In all cases either poor contact lens hygiene or an association with swimming pools and contact lens use is a feature. There is invariably a delay in making the diagnosis, with the appearance frequently mistaken for herpes simplex keratitis. In all cases corneal biopsy was required to confirm the diagnosis. Of the six patients, four responded to medical therapy alone, one required a corneal graft and one required enucleation. We suggest that earlier rather than later corneal biopsy is important in unresponsive cases of culture-negative keratitis, especially in contact lens wearers. We would agree that the treatment of choice is intensive topical propamidine and neosporin. Prevention by strict adherence to contact lens care and hygiene is urged.