Bilateral Acanthamoeba Keratitis in Synergeyes Contact Lens Wear: Clinical and Confocal Microscopy Findings

Differentiation of acanthamoeba keratitis from other non-acanthamoeba keratitis: Risk factors and clinical features

INTRODUCTION

Infectious Keratitis is one of the most common ocular emergencies seen by ophthalmologists. Our aim is to identify the risk factors and clinical features of Acanthamoeba Keratitis (AK).

METHODS

This retrospective chart review study was conducted at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia, and included all the microbial keratitis cases, male and female patients of all ages. The main outcome is the differentiation between various microbial keratitis types.

RESULTS

We included 134 consecutive eyes of 126 persons. We had 24 cases of acanthamoeba keratitis, 22 bacterial keratitis, 24 fungal keratitis, 32 herpetic keratitis, and 32 bacterial co-infection. Contact lens wear was found in 33 eyes (24.6%). Among acanthamoeba keratitis patients, 73% were ≤ 39 years of age, and 73% were females (P <0.001). Also, in AK cases, epithelial defect was found in all cases (100%), endothelial plaques were found in 18 eyes (69.2%), 12 cases had radial keratoneuritis (46.2%), and ring infiltrate was found in 53.8% of AK cases.

CONCLUSIONS

We determined the factors that increase the risk of acanthamoeba infection and the clinical characteristics that help distinguish it from other types of microbial keratitis. Our findings suggest that younger females and patients who wear contact lenses are more likely to develop acanthamoeba keratitis. The occurrence of epitheliopathy, ring infiltrate, radial keratoneuritis, and endothelial plaques indicate the possibility of acanthamoeba infection. Promoting education on wearing contact lenses is essential to reduce the risk of acanthamoeba infection, as it is the most significant risk factor for this infection.

Epidemiology of and Genetic Factors Associated with Acanthamoeba Keratitis

Acanthamoeba keratitis (AK) is a severe, rare protozoal infection of the cornea. Acanthamoeba can survive in diverse habitats and at extreme temperatures. AK is mostly seen in contact lens wearers whose lenses have become contaminated or who have a history of water exposure, and in those without contact lens wear who have experienced recent eye trauma involving contaminated soil or water. Infection usually results in severe eye pain, photophobia, inflammation, and corneal epithelial defects. The pathophysiology of this infection is multifactorial, including the production of cytotoxic proteases by Acanthamoeba that degrades the corneal epithelial basement membrane and induces the death of ocular surface cells, resulting in degradation of the collagen-rich corneal stroma. AK can be prevented by avoiding risk factors, which includes avoiding water contact, such as swimming or showering in contact lenses, and wearing protective goggles when working on the land. AK is mostly treated with an antimicrobial therapy of biguanides alone or in combination with diaminidines, although the commercial availability of these medicines is variable. Other than anti-amoeba therapies, targeting host immune pathways in Acanthamoeba disease may lead to the development of vaccines or antibody therapeutics which could transform the management of AK.

Diagnosing and monitoring the characteristics of Acanthamoeba keratitis using slit scanning and laser scanning in vivo confocal microscopy

INTRODUCTION

Acanthamoeba keratitis (AK) is a serious and potentially blinding ocular infection caused by the free-living amoeba, Acanthamoeba. In vivo confocal microscopy (IVCM) is a non-invasive device which has been proven of great use to diagnose Acanthamoeba infections immediately. The aim of this review was to establish different patterns and signs of AK that appear on the IVCM both before and after treatment.

METHODS

A systematic review of the literature from 1974 until September 2021 was performed using Embase and PubMed, following The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Twenty different signs of AK were observed using IVCM. The included studies used vastly different criteria to diagnose infections, ranging from just 1 to 13 of the signs, demonstrating the current lack of a standardised diagnosis of this infection using the IVCM. The appearance of double wall cysts, trophozoites, signet rings, target signs and clusters were shown to be pathognomonic to AK infections. Bright spots located in the corneal epithelium were demonstrated as non-reliable predictors of AK. The presence of cysts in clusters and single file can predict the need for corneal transplantation. The morphological changes in cysts using the IVCM following treatment were described as breaking down to hollow forms and occasionally surrounded by black cavities. Using this information, a visual guideline for identifying AK signs in diagnosis and follow-up using IVCM was created.

CONCLUSION

Increased awareness of the different signs and patterns of AK that appear on the IVCM is crucial in order to correctly identify an infection and increase the potential of this device. Our guidelines presented here can be used, but further studies are needed in order to determine the relationship and aetiology of these signs and cellular changes on the IVCM both before and after anti-amoeba treatment.

The global epidemiology and clinical diagnosis of Acanthamoeba keratitis

Acanthamoeba keratitis is a rare parasitic infection of the cornea that can lead to permanent blindness if not diagnosed and treated promptly. We collected data on the incidences of Acanthamoeba keratitis from 20 countries and calculated an annual incidence of 23,561 cases, with the lowest rates in Tunisia and Belgium, and the highest in India. We analyzed 3755 Acanthamoeba sequences from the GenBank database across Asia, Europe, North America, South America, and Oceania and genotyped them into T1, T2, T3, T4, T5, T10, T11, T12, and T15. Many genotypes possess different characteristics, yet T4 is the most prevalent genotype. As efficient treatment against Acanthamoeba remains lacking, prevention from early diagnosis via staining, PCR, or in vivo confocal microscopy (IVCM) becomes significant for the condition's prognosis. IVCM is the most recommended approach for the early detection of Acanthamoeba. If IVCM is unavailable, PCR should be used as an alternative.

Use of Amniotic Membrane Transplant and Deep Anterior Keratoplasty in a Patient with Bilateral Acanthamoeba Infectious Keratitis: A Case Report

The aim of this study was to report a case with the use of amniotic membrane transplant and deep anterior keratoplasty in a patient with bilateral Acanthamoeba infectious keratitis as a treatment. A 20-year-old male presented with bilateral Acanthamoeba keratitis (AK) who was initially diagnosed with herpetic keratitis receiving full antiviral and corticosteroid topical treatment without any improvement. Corneal biopsy was performed to confirm the suspected diagnosis, and Acanthamoeba stromal cysts were identified in the sample. Treatment was initiated with 0.02% chlorhexidine, 0.1% propamidine isethionate, neomycin, and tropicamide/phenylephrine. Symptoms and clinical improvement were achieved between the 8th and 10th weeks, so corticosteroids were initiated. Treatment was continued until we observed a poor response in the left eye; therefore, an epithelial scraping and amniotic membrane placement were performed. Lately, the right eye underwent a deep anterior lamellar keratoplasty. A challenging case of bilateral AK managed with topical medications, amniotic membrane, and corneal keratoplasty. The earlier the disease is diagnosed, the better the outcome. If the diagnosis is delayed, the amoebas have penetrated deep into the corneal stroma, and successful therapy becomes difficult. A surgical option can be an early solution with a good prognosis for these cases.

Biological characteristics and pathogenicity of Acanthamoeba

Acanthamoeba is an opportunistic protozoa, which exists widely in nature and is mainly distributed in soil and water. Acanthamoeba usually exists in two forms, trophozoites and cysts. The trophozoite stage is one of growth and reproduction while the cyst stage is characterized by cellular quiescence, commonly resulting in human infection, and the lack of effective monotherapy after initial infection leads to chronic disease. Acanthamoeba can infect several human body tissues such as the skin, cornea, conjunctiva, respiratory tract, and reproductive tract, especially when the tissue barriers are damaged. Furthermore, serious infections can cause Acanthamoeba keratitis, granulomatous amoebic encephalitis, skin, and lung infections. With an increasing number of Acanthamoeba infections in recent years, the pathogenicity of Acanthamoeba is becoming more relevant to mainstream clinical care. This review article will describe the etiological characteristics of Acanthamoeba infection in detail from the aspects of biological characteristic, classification, disease, and pathogenic mechanism in order to provide scientific basis for the diagnosis, treatment, and prevention of Acanthamoeba infection.

Atypical presentation of acanthamoeba keratitis resembling central toxic keratopathy

PURPOSE

To describe an atypical case of acanthamoeba keratitis with positive in vivo confocal microscopy in a non-contact lens user who presented with signs and symptoms suggestive of central toxic keratopathy.

OBSERVATIONS

The patient presented with bilateral, though sequential, decreased visual acuity with mild pain. Examination showed stromal haze with corneal flattening and thinning without epithelial defects. Optical coherence tonometry of the right eye revealed an inverse dome-shaped appearance of the opacity and in-vivo confocal imaging showed double-walled cysts consistent with acanthamoeba. Corneal haze, stromal loss, resolved and visual acuity improved over time.

CONCLUSION AND IMPORTANCE

Acanthamoeba is a rare cause of infectious keratitis that is most often associated with contact lens wear in developed countries. Typically, it presents with a unilateral decrease in visual acuity, photophobia, watering, and pain that is out of proportion to slit lamp examination findings. However, many atypical presentations have been reported in the literature. Consequently, it may be misdiagnosed, especially early in the course of the disease. This delay in diagnosis can lead to progressive ulceration and visual impairment. In addition, cyst formation can make eradication with anti-amoebic treatment especially difficult.Central toxic keratopathy is a non-inflammatory clinical syndrome of unknown etiology that is most often associated with excimer laser ablation, though other associated causes have been reported. It is characterized by a central or paracentral opacity with corneal stromal loss and resultant hyperopic shift. The opacification and stromal loss mostly resolve over the course of months with an improvement in visual acuity. This report may help physicians broaden their differential and correctly diagnose atypical presentations of amoebic infection.

Clinical course of Acanthamoeba keratitis by genotypes T4 and T8 in Hungary

Genus Acanthamoeba is an opportunistic protozoan that is widely distributed in the environment. Within this genus, numerous species are recognized as human pathogens, potentially causing Acanthamoeba keratitis (AK). AK is a corneal disease, associated predominantly with contact lens (CL) wear; its epidemiology is related to the specific Acanthamoeba genotypes. This study reports seven CL wearer, Acanthamoeba PCR-positive patients with AK, diagnosed between January 2015 and 2018. Patients had the diagnosis of AK 1.36 months after first symptoms. Genotyping allowed the identification of six isolates of the T4 and one of the T8 genotypes. At first presentation, pseudendritiformic epithelopathy/dirty epithelium (four eyes, 57.1%), multifocal stromal infiltrates (five eyes, 71.4%), ring infiltrate (three eyes, 42.8%), and perineuritis (one eye, 14.3%) were observed. AK was healed without later recurrence in two eyes (28.5%) using triple-topical therapy, in three eyes (42.8%) following additional penetrating keratoplasty. In one patient (14.3%), AK recurred following successful application of triple-therapy and was treated successfully with repeated triple-topical therapy and in one patient (14.3%), no follow-up data were available after diagnosis. We could not observe correlation of genotype and clinical course or the necessity of corneal transplantation in our case series.

Biofilm testing of microbiota: An essential step during corneal scrap examination in Egyptian acanthamoebic keratitis cases

PURPOSE

To detect co-infections in the culture-proven acanthamoebic keratitis (AK) cases, and to test the capability of biofilm formation in the isolated microbiota. The clinical findings, habit of wearing contact lens and in-vitro antibiotic resistance were analyzed further according to the biofilm formation capability.

METHODS

After clinical examination, corneal scraps and swabs were taken from 240 clinically suspected AK cases, for Acanthamoeba and microbiological cultures. In cases of keratoplasty, trimmed corneal tissue was collected and sent for histopathological examination. Scanning electron microscopy was done for some samples. Biofilm formation capability was investigated using a tissue culture plate method. Antibiotic resistance pattern was determined using a modified-Kirby-Bauer disc diffusion method.

RESULTS

In 102 AK culture proven cases, 11 had no co-infection, 74 had a single co-infection and 17 had double co-infections. Enterobactericae and Aspergillus were the commonest bacterial and fungal isolates, respectively. Regarding the biofilm formation, 64.7% of Enterobactericae, 50% of Pseudomonas aeuroginosa, 43.75% of Staph aureus, 76.92% of Streptococcus pneumoniae, 28.57% of Corynebacterium, 60% of α-haemolytic streptococci, 40% of Acinetobacter, 100% of Candida and 77.8% Aspergillus isolates were biofilm producers. Severe manifestations were more frequently reported in cases co-infected with biofilm producers than with non-biofilm producers. Generally, high percentages of the biofilm forming bacterial isolates were sensitive to antibiotics in-vitro.

CONCLUSIONS

Routine investigations for co-infection and biofilm formation in addition to Acanthamoeba culture are strongly recommended in suspected AK cases. Co-infection with biofilm producers may precipitate extrinsic in-vivo drug resistance despite of the in-vitro sensitivity. Designing a biofilm-dissolving topical drug is highly recommended to enhance the response to the standard therapeutic regimen especially in the resistant AK cases.

Occurrence of Acanthamoeba genotypes in Central West Malaysian environments

Acanthamoeba species are ubiquitous free-living protozoa that can be found worldwide. Occasionally, it can become parasitic and the causative agent of acanthamoebic keratitis (AK) and Granulomatous Amoebic Encephalitis (GAE) in man. A total of 160 environmental samples and 225 naturally-infected animal corneal swabs were collected for Acanthamoeba cultivation. Acanthamoeba was found to be high in samples collected from environments (85%, 136/160) compared to infected animal corneas (24.89%, 56/225) by microscopic examination. Analysis of nucleotide sequence of 18S rRNA gene of all the 192 cultivable Acanthamoeba isolates revealed 4 genotypes (T3, T4. T5 and T15) with T4 as the most prevalent (69.27%, 133/192) followed by T5 (20.31%), T15 (9.90%) and T3 (0.52%). Genotype T4 was from the strain of A. castellanii U07401 (44.27%), A. castellanii U07409 (20.83%) and A. polyphagaAY026243 (4.17%), but interestingly, only A. castellanii U07401 was detected in naturally infected corneal samples. In environmental samples, T4 was commonly detected in all samples including dry soil, dust, wet debris, wet soil and water. Among the T4, A. castellanii (U07409) strains were detected high occurrence in dry (45%) followed by aquatic (32.50%) and moist (22.50%) samples but however A. castellanii (U07401) strains were dominant in dry samples of soil and dust (93.10%). Subsequently, genotype T5 of A. lenticulata (U94741) strains were dominant in samples collected from aquatic environments (58.97%). In summary, A. castellanii (U07401) strains were found dominant in both environmental and corneal swab samples. Therefore, these strains are possibly the most virulent and dry soil or dusts are the most possible source of Acanthamoeba infection in cats and dogs corneas.

Non-contact lens related Acanthamoeba keratitis

The purpose of the study is to describe epidemiology, clinical features, diagnosis, and treatment of Acanthamoeba keratitis (AK) with special focus on the disease in nonusers of contact lenses (CLs). This study was a perspective based on authors' experience and review of published literature. AK accounts for 2% of microbiology-proven cases of keratitis. Trauma and exposure to contaminated water are the main predisposing factors for the disease. Association with CLs is seen only in small fraction of cases. Contrary to classical description experience in India suggests that out of proportion pain, ring infiltrate, and radial keratoneuritis are seen in less than a third of cases. Majority of cases present with diffuse infiltrate, mimicking herpes simplex or fungal keratitis. The diagnosis can be confirmed by microscopic examination of corneal scraping material and culture on nonnutrient agar with an overlay of Escherichia coli. Confocal microscopy can help diagnosis in patients with deep infiltrate; however, experience with technique and interpretation of images influences its true value. Primary treatment of the infection is biguanides with or without diamidines. Most patients respond to medical treatment. Corticosteroids play an important role in the management and can be used when indicated after due consideration to established protocols. Surgery is rarely needed in patients where definitive management is initiated within 3 weeks of onset of symptoms. Lamellar keratoplasty has been shown to have good outcome in cases needing surgery. Since the clinical features of AK in nonusers of CL are different, it will be important for ophthalmologists to be aware of the scenario wherein to suspect this infection. Medical treatment is successful if the disease is diagnosed early and management is initiated soon.