The First Microsatellite-based Characterisation of Blastocystis sp. ST3 Isolates and Population Structure Analysis.

Objective: Blastocystis sp. is an intestinal Stramenopile that can infect both humans and animals. Genetic variability of Blastocystis has been investigated with a variety of molecular methods and different subtypes (ST) have been identified. The present study aimed to characterize microsatellite loci and population structure for Blastocystis sp. ST3, the most common ST in human faecal samples.

Methods: The genome of Blastocystis sp. ST3 in GenBank was analyzed for the presence of microsatellites containing at least eight repeat units. Specific primers were designed for each locus and polymorphisms were identified using bioinformatics tools. The population structure was determined, and microsatellite typing was conducted on 18 Blastocystis sp. ST3 genomic DNA samples from the routine laboratory at Aydın Adnan Menderes University Hospital.

Results: The whole-genome scan of Blastocystis sp. ST3 revealed 12 microsatellite loci with at least eight repeats. All loci were successfully amplified with the designed primers and eight of them were selected for genotyping. Microsatellite polymorphism analysis showed that each isolate had a unique profile (18 isolates, 18 different microsatellite types). Furthermore, the isolates were grouped into two distinct population clusters.

Conclusion: Blastocystis sp. ST3 isolates exhibited significant variability in their microsatellite repeats. The polymorphic microsatellite loci offer a novel approach to study the detailed genetic diversity and population structure of Blastocystis sp. ST 3.