Blastocystis is a common polymorphic protozoan infecting human intestine with a zoonotic
potential. Despite the unclear pathogenicity, its existence may be linked to a wide range of
gastrointestinal disorders. The present cross sectional study was conducted to analyze Blastocystis
subtypes among 110 adolescents suffering from disturbing GIT symptoms in stool samples.
Positive samples (21 (19.1%)) by microscopy were subjected to DNA isolation and subtyped
by Sequence Tagged Site (STS)-PCR analysis, which successfully subtyped 10 (62.5%)
of 16 isolates. The dominant Blastocystis subtype was ST3 in 6 (40%) samples followed by 3
(30%) for ST2, but one sample (10%) was amplified for ST1. The results revealed significant
association between nausea and vomiting and Blastocystis infection. However, there was no
difference between the Blastocystis subtypes and demo-clinical characteristics.