Molecular and physiological differentiation between pathogenic and nonpathogenic Acanthamoeba.

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.