Revisiting theAcanthamoebaspecies that form star-shaped cysts (genotypes T7, T8, T9, and T17): characterization of seven new Brazilian environmental isolates and phylogenetic inferences

Abstract

SUMMARYFree-living amoebae of the genusAcanthamoebaare the agents of both opportunistic and non-opportunistic infections and are frequently isolated from the environment. Of the 17 genotypes (T1–T17) identified thus far, 4 (T7, T8, T9, and T17) accommodate the rarely investigated species of morphological group I, those that form large, star-shaped cysts. We report the isolation and characterization of 7 new Brazilian environmentalAcanthamoebaisolates, all assigned to group I. Phylogenetic analyses based on partial (∼1200 bp) SSU rRNA gene sequences placed the new isolates in the robustly supported clade composed of the species of morphological group I. One of the Brazilian isolates is closely related toA. comandoni(genotype T9), while the other 6, together with 2 isolates recently assigned to genotype T17, form a homogeneous, well-supported group (2 0% sequence divergence) that likely represents a newAcanthamoebaspecies. Thermotolerance, osmotolerance, and cytophatic effects, features often associated with pathogenic potential, were also examined. The results indicated that all 7 Brazilian isolates grow at temperatures up to 40°C, and resist under hyperosmotic conditions. Additionally, media conditioned by each of the newAcanthamoebaisolates induced the disruption of SIRC and HeLa cell monolayers.