Influence of Acanthamoeba Genotype on Clinical Course and Outcomes for Patients with Acanthamoeba Keratitis in Spain

Abstract

Genotype T4 is by far the most frequent genotype of Acanthamoeba keratitis (AK) and therefore has been considered the most virulent. This study included 14 cases of AK of genotype T4 and three cases of non-T4 genotype. We found that cases of non-T4 genotype had a worse response to medical therapy, greater need for surgical intervention, greater risk of extracorneal involvement, and remarkably poorer final visual outcome than those of T4 genotype, suggesting an association between Acanthamoeba virulence and genotype that requires additional case investigation.A canthamoeba keratitis (AK) is a potentially blinding corneal infection in healthy immunocompetent individuals and is caused by free-living amoebae of the genus Acanthamoeba (1). Analysis of the 18S rRNA gene has identified 18 genotypes (T1 through T18) within this genus (2-4). Isolates from eight of the genotypic clades (T2, T3, T4, T5, T6, T10, T11, and T15) are confirmed causative agents of AK (4-12). Disease severity can range from relatively minor epithelial and subepithelial diseases, which respond well to treatment, to refractory disease that can provoke corneal melting and perforation requiring therapeutic or tectonic corneal grafts (13). Currently, the most important factors affecting the prognosis are disease severity at presentation and the interval between symptom onset and the start of effective therapy (14, 15); beginning therapy Ͼ3 weeks after symptom onset is associated with a worse prognosis.This study aimed to identify the genotypes of Acanthamoeba isolates from AK patients at our institution and to find any association between genotype and clinical outcomes.This revision was approved by the institutional review board at Hospital Universitario Ramón y Cajal. Seventeen amoebal isolates were obtained from the eyes of 17 patients with a clinical diagnosis of AK and who were followed prospectively at Hospital Universitario Ramón y Cajal, Madrid, Spain, from July 2009 to July 2013. The best spectacle-corrected visual acuity (BSCVA) in decimal Snellen fraction notation (1.0 indicates a normal value, and 0 indicates no vision at all), slit lamp and fundus examinations, and other events were recorded in the clinical notes. Tissue was obtained from each patient by epitheliectomy or by scraping the corneal ulcer when there was no epithelium left. A portion of the sample was routinely plated in blood agar, thioglycolate broth, or Sabouraud agar to rule out bacterial or fungal infection. The rest of the sample was submerged in a microcentrifuge tube with saline and sent together with the patient's contact lenses and cases to the laboratory at the University Institute of Tropical Diseases and Public Health of the Canary Islands; there it was cultured on 2% nonnutrient agar (NNA) plates and examined using an inverted microscope as previously described (16). Lenses were directly cultured in NNA and checked for amoebic growth. The contact lens cases were washed twice with 2 ml of sterile saline, and the saline was then filtered using a vacuum manifold sys...

Strategies for the prevention of contact lens‐related Acanthamoeba keratitis: a review

“…Both contact‐lens related and non‐contact‐lens related corneal isolates are most commonly associated with the T4 genotype which includes the species A. castellanii, A. polyphaga and A. culbertsonii . While one study has suggested that non‐T4 genotypes may be associated with a more severe manifestation of the disease, it does appear that non‐contact lens related Acanthamoeba keratitis, while also caused by T4 strains, is associated with a more advanced disease on delayed diagnosis and more severe disease presentation, evidenced by a greater need for surgery and poorer final visual outcome …”

“…Both contact-lens related and non-contact-lens related corneal isolates are most commonly associated with the T4 genotype [17][18][19][20][21][22] which includes the species A. castellanii, A. polyphaga and A. culbertsonii. 23 While one study has suggested that non-T4 genotypes may be associated with a more severe manifestation of the disease, 24 it does appear that non-contact lens related Acanthamoeba keratitis, while also caused by T4 strains, 21 is associated with a more advanced disease on delayed diagnosis and more severe disease presentation, evidenced by a greater need for surgery and poorer final visual outcome. 25 The pathogenesis of Acanthamoeba keratitis Compared with bacterial keratitis, there is relatively limited information on the pathogenesis of Acanthamoeba disease, including the role of virulence characteristics of the pathogen, the host response and the impact of the environment.…”

Translational and Reverse Translational Research Supporting Precision Medicine: Acanthamoeba Keratitis as a Model of Linkage between Clinical and Basic Research Focused on Personalized Ophthalmology

“…It is believed that an early start of a specific therapeutic procedure may increase the chances of restoring normal health conditions with minimal side effects and maximum patient's quality of life at the bedside [4,5]. For instance, laboratory assays of Acanthamoeba strains and clinical isolates on in vitro drug sensitivity tests [1,6,7] development of new therapeutic patterns [8,9] the characterization of differential virulence factors, as well as investigation of the cytopathic effects in cell culture and animal models [10][11][12] provide meaningful data.…”

“…Real-time PCRcan also give an estimate of parasite load through quantification of DNA copy number, which is associated with poor outcome [17]. Other possible applications of molecular techniques are detection of new species and genotypes of a specific microorganism [18,19] epidemiological survey, establishment of etiological link between source and infection [14,20] recognition of physiological differences (eg growth rate, metabolism) and screening of virulence profiles observed on in traspecific variations of pathogens [21,7]. However, the use of molecular diagnostics alone has not delivered the expected impact in clinical practice and patients' health.…”

“…Estimate of Acanthamoeba load by real-time PCR [17], providing data for personalized therapy Acanthamoeba phenotype associated with pathogenic strains: cytopathic effect, higher growth rate and temperature tolerance [21,55,56] Worse disease prognosis associated with non-T4 genotype [7,15] and genetic profile (eg phylogenetic clustering [21] and genes coding for differential virulence factors)…”