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Molecular and physiological differentiation between pathogenic and nonpathogenic Acanthamoeba
Naveed A Khan1, Edward L Jarroll, Timothy A Paget
1Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. nkhan@jhmi.edu
Abstract:
In this study, 14 isolates of Acanthamoeba from both clinical and environmental sources belonging to seven different species were assayed for tolerance of high osmotic pressure, temperature tolerance, extracellular proteases, and cytopathic effects (CPE) on immortalized rabbit corneal epithelial cells. On the basis of the results, amoeba isolates were divided into pathogenic and nonpathogenic groups. Ribosomal DNA sequencing was performed on these isolates. Phylogenetic relationships revealed that all the pathogenic strains tested clustered together as one group, while nonpathogenic strains clustered into other groups. Sequence comparisons with previously published sequences determined that among the six new pathogenic isolates used in this study, five belong to T4 genotype and one to T11. This is the first report of a T11 genotype being found in Acanthamoeba keratitis.
Insights
This study identified pathogenic Acanthamoeba strains, including a novel T11 genotype linked to Acanthamoeba keratitis. Pathogenic and nonpathogenic Acanthamoeba isolates were differentiated through various assays and genetic sequencing.
Area of Science:
- Microbiology
- Parasitology
- Genetics
Background:
- Acanthamoeba is an opportunistic protozoan parasite implicated in serious eye infections like Acanthamoeba keratitis.
- Distinguishing pathogenic from nonpathogenic Acanthamoeba strains is crucial for understanding disease pathogenesis and developing effective treatments.
Purpose of the Study:
- To characterize Acanthamoeba isolates from clinical and environmental sources.
- To differentiate pathogenic and nonpathogenic strains based on physiological and genetic markers.
- To identify the genotypes of pathogenic Acanthamoeba, particularly in relation to Acanthamoeba keratitis.
Main Methods:
- Assaying 14 Acanthamoeba isolates for tolerance to high osmotic pressure and temperature.
- Evaluating extracellular protease production and cytopathic effects (CPE) on rabbit corneal epithelial cells.
- Performing ribosomal DNA sequencing for phylogenetic analysis and genotype identification.
Main Results:
- Acanthamoeba isolates were successfully categorized into pathogenic and nonpathogenic groups.
- Phylogenetic analysis based on ribosomal DNA sequences clustered pathogenic strains separately from nonpathogenic ones.
- Five of six new pathogenic isolates belonged to the T4 genotype, and one belonged to the T11 genotype.
- This marks the first report of the T11 genotype associated with Acanthamoeba keratitis.
Conclusions:
- Acanthamoeba keratitis isolates exhibit distinct pathogenic characteristics and genotypes.
- The T4 genotype is prevalent among pathogenic Acanthamoeba, while the T11 genotype represents a newly identified risk factor for Acanthamoeba keratitis.
- Genotypic identification aids in understanding the epidemiology and pathogenicity of Acanthamoeba infections.