Blastocystis organisms isolated from humans have commonly been referred to as B. hominis. However, because of extensive genetic diversity ...SkipdirectlytositecontentSkipdirectlytopageoptionsSkipdirectlytoA-ZlinkDPDx-LaboratoryIdentificationofParasitesofPublicHealthConcernSectionNavigationCDCHomeFacebookTwitterLinkedInSyndicateBlastocystissp.MinusRelatedPages[Blastocystissp.][Blastocystishominis]ParasiteBiologyImageGalleryLaboratoryDiagnosisResourcesCausalAgentsBlastocystisisageneticallydiverseunicellularparasiteofunclearpathogenicpotentialthatcolonizestheintestinesofhumansandawiderangeofnon-humananimals.Onthebasisofmoleculardata,theorganismhasbeenclassifiedasastramenopile.Organismssuchasdiatoms,chrysophytes,watermolds,andslimenetsareotherexamplesofstramenopiles.BlastocystisorganismsisolatedfromhumanshavecommonlybeenreferredtoasB.hominis.However,becauseofextensivegeneticdiversity(evenamongorganismsisolatedfromhumans)andlowhostspecificity,thedesignationBlastocystissp.isconsideredmoreappropriate.Ifgenetictypingisperformed,thesubtype(ST)alsoshouldbenotedinaccordancewithconsensusterminology.*AmongthenineSTsfoundtodateinhumans,thefourmostprevalentSTsareST1,ST2,ST3,andST4;otherSTsoccursporadicallyandmayberelatedtozoonotictransmission.*Stensvold,C.R.,Suresh,G.K.,Tan,K.S.,Thompson,R.A.,Traub,R.J.,Viscogliosi,E.,Yoshikawa,H.andClark,C.G.,2007.TerminologyforBlastocystissubtypes–aconsensus.TrendsinParasitology,23(3),pp.93-96.LifeCycleViewLargerThelifecycleofBlastocystissp.isnotyetunderstood,includingtheinfectiousstageandwhether(andwhichofthe)variousmorphologicformsofthispolymorphicorganismthathavebeenidentifiedinstoolorcultureconstitutedistinctbiologicstagesoftheparasiteintheintestinaltractofhosts.Thecystform(3–5µm)ispostulatedtobeaninfectiousstage,butnotconfirmed.Thepredominantformfoundinhumanstoolspecimensisreferredtoasthevacuolar(orcentralbody)formandisofvariablesize(5–40µm,occasionallymuchlarger).Replicationappearstooccurviabinaryfission.Othermorphologicforms(e.g.,ameboida