Molecular identification and subtypes analysis of Blastocystis sp. in South Khorasan province, Eastern Iran

Abstract Background Blastocystis sp. is a prevalent intestinal parasitic protest that infects both birds and animals. There are at least 17 subtypes (ST) of Blastocystis sp., with ST1-ST9 being found in humans. The correlation between specific subtypes and pathogenicity has not been definitively established. This study aimed to identify the genetic diversity within subtypes of Blastocystis sp. in stool samples collected from individuals who referred medical laboratories in the cities of Birjand, Darmian, Nehbandan, and Ferdows, Eastern Iran. Methods 1800 stool specimens were randomly collected from referred individuals randomly selected medical laboratories of South Khorasan province. DNA was extracted and PCR, sequencing and subtyping was performed for characterization and phylogenetic analysis. Results A total of 118 (6.5%) cases of Blastocystis sp. through microscopic observations was confirmed. A ~620-bp segment of the SSU rRNA gene of Blastocystis sp. was amplified and were genetically evaluated using MEGA6 and DnaSP. 30 samples of Blastocystis sp-positive cases were sequenced. BLAST analyses identified 3 distinct subtypes including ST1 (11, 36.66 %), ST2 (5, 16.68 %), ST3 (14, 46.66) within our samples. Intra-subtype discrimination showed the similarity of 95.88%, 91.56% and 92.14% for ST1 and ST2, ST1 and ST3, and ST2 and ST3, respectively.Additionally, allele 4 for ST1; allele 12 for ST2; alleles 34, 36 for ST3 were detected. Conclusions As results, ST1 exhibited the highest nucleotide diversity (π: 0.00113), suggesting a high degree of genetic diversity within this subtype. Phylogenetic analysis showed that, subtype 3 was clustered to animal isolates from cattle and cats, indicated the potential zoonotic transmission of Blastocystissp.