[Blastocystis hominis--intestinal parasite or commensal?].

Blastocystis hominis has long been classified among Blastomycetes. It was considered to be an apathogenous fungal organism which was very frequently detected in routine stool examinations. Following the first studies with an electronic microscope in 1967, Zierdt et al. (34) classified Blastocystis hominis among the protozoa. Since then, there have been increasingly frequent reports that Blastocystis hominis can be an important cause of intestinal diseases especially diarrhea. For a definite taxonomic correlation and for an identification as pathogen, more investigations are greatly necessary.