More <i>Acanthamoeba</i> Genotypes: Limits to Use rDNA Fragments to Describe New Genotype

Strains of the genus <i>Acanthamoeba</i> are usually assigned to sequence types or genotypes according to pair-wise similarity values of the nuclear gene for the small subunit of ribosomal RNA. This classification system was established by comparing full or nearly full gene sequences, > 2000 bp. For practical reasons, diagnostic fragments of smaller lengths have been identified and used for rapid and economic identification of large number of strains. While the use of these small fragments in diagnostics applications remains valid when and only if the reference full sequence-type is available, we contest their use to identify and describe new genotypes. We report herein the case of a new genotype described on the basis of solely a small partial sequence and discuss the poor reliability of this fragment to correctly infer phylogenetic relationships, and its limits in the description of new genotypes of <i>Acanthamoeba</i>.