Blastocystis is a genus of single-celled parasites belonging to a group of organisms that are known as the Stramenopiles . Blastocystis consists of several species, living in the gastrointestinal tracts of humans and farm animals. Many different species can infect humans and would be identified as Blastocystis hominis depending on the sequencing of the gene encoding the 18S rRNA . Among the subtypes recognized, ST1-8 could colonize humans as well as animals.~Infection with B. hominis has a worldwide distribution with infection rate reaches up to 60% in developing countries. Initially B.hominis was accepted as a harmless commensal in the intestinal tract, but recently it was implicated as a pathogen. As it able to produce a cysteine protease which breaks up the mucosal IgA antibody. B.hominis infection has been associated with several gastrointestinal symptoms, Even though most cases are asymptomatic, it is also play a significant role in some chronic gastrointestinal illnesses as irritable bowel syndrome (IBS).~Blastocystis spp. are polymorphic parasites with multiple morphological forms including vacuolar, multivacuolar, granular, ameboid, and cystic forms. At least two out of three infections may be missed during microscopic detection of B.hominis due to their polymorphic nature, and the possibility of confusion with yeast, Cyclospora spp. or fat globules. . Different studies suggested that it multiply rapidly in culture medium and considered it a sensitive method for diagnosis of B.hominis . Recently Molecular diagnosis by polymerase chain reaction (PCR) is considered the most sensitive method for the detection of B.hominis.
Detection of the presence of Blastocystis hominis among outpatients presented with GIT symptoms at Assiut University Hospitals in comparison with those in control group.~Assessment of different culture techniques for detection, and isolation of Blastocystis hominis.~Molecular identification of Blastocystis hominis using polymerase chain reaction (PCR).