The identification of free-living environmental isolates of amoebae from Bulgaria

A survey was carried out in Bulgaria to determine the presence of free-living amoebae (FLA) from environmental sources. In 171 (61.1%) of 280 samples, isolates of Acanthamoeba with group II or III morphology, as well as Hartmannella spp. were recovered. Five isolates named 6 (artificial lake), Ep (lake), G2 (soil), R4* (river) and PK (spring water)—all exhibiting a highly efficient proliferation in axenic cultures—were subsequently cloned and subjected to molecular analyses for identification and genotyping In accordance with morphological findings, PCR-based analyses identified four isolates (6, Ep, G2, R4*) belonging to the genus Acanthamoeba. Confirmation of these findings was obtained by phylogenetic analysis using partial sequencing of the 18S rDNA (ASA.S1) Acanthamoeba-gene. Comparison of these sequences with corresponding regions from other Acanthamoeba strains available from GenBank sorted all four isolates into the sequence type group T4 that contains most of the pathogenic Acanthamoeba strains already identified. The fifth isolate (PK) exhibited morphological characteristics matching those of Hartmannella, and scored negative in the Naegleria fowleri and Acanthamoeba PCRs.