Blastocystis is a protozoan, specifically an amoeba. Blastocystis species are a common member of human and animal intestinal flora. These organisms are classified as stramenopiles, pathogenic species which include mildews, kelp, diatoms, and potato blight. This is a genetically diverse group of organisms, only some of which might cause illness. Many of the Blastocystis species have been isolated from animals, which caused researchers to conclude that humans are in fact inhabited by a number of zoonotic Blastocystis species.
Blastocystis species have no cell wall; they grows only in the presence of
bacteria and have a preference of alkaline pH; they reproduce by binary fission.
These protozoa species do not grow at 25 °C and are killed at 4 °C.
Infections with B. hominis are characterized by abdominal pain,
nausea, flatulence, diarrhea and constipation, and itchiness in the anal area.
Untreated, the organism may survive in the intestine from weeks to