Acanthamoeba strains show reduced temperature tolerance after long-term axenic culture.

Acanthamoeba is a genus of free-living organisms that can be found in various habitats. We investigated the physiological characteristics of 15 Acanthamoeba isolates, representing five genotypes (T4, T5, T6, T7, and T11) of both clinical and nonclinical origins. Moreover, in order to evaluate possible alterations from long-term culture, old and fresh isolates were included, and results were compared to a previous study. We found that there is no significant difference in physiological characteristics between genotypes. However, Acanthamoeba strains that had been grown in axenic culture over long periods of time adapted to axenic growth. Overall growth rates under-agarose migration and particularly, temperature tolerance decrease after long-term axenic culture at room temperature. The only trait that remained rather constant was the cytopathic effect.