Characterization of extracellular proteases of Acanthamoeba genotype T4 isolated from different sources in Iran.

The members of the genus Acanthamoeba are ubiquitous, free-living amoebae found in various environments. The amoebae can cause severe complications in both, immunocompetent and immunocompromised individuals. The aim of this study was to characterize extracellular proteases of Acanthamoeba isolates from different sources belonging to genotype T4 as well as the determination of the pathogenicity potential to correlate pathogenicity with protease activity and protease banding pattern. A total of 19 isolates (11 clinical and 8 environmental) were cultured axenically, then the pathogenicity of the isolates was assessed by osmo- and thermo- tolerance tests. An applied colorimetric method using azocasein as a substrate was used for the extracellular protease activity assay. Protease characterization was carried out by zymography analysis with and without protease inhibitors. Assessment of the pathogenicity potential using physical parameters revealed that 2 (25%), 2 (25%), and 4 (50%) of the environmental isolates were potential pathogens, weak potential pathogens, and non-pathogens, respectively. According to our results, this protease activity assay can be a powerful tool for differentiating pathogenic and non-pathogenic strains of Acanthamoeba.