Answer to Case 437

Answer:BlastocystisspeciesI had posed the question about nomenclature to see how labs are currently reporting this parasite when it is identified in stool specimens by microscopic examination.Originally, onlyB. hominiswas thought to infect humans, while other species infected other animals. However, we now know that humans can be infected with the same organisms as many other hosts, and differentiation between these species is not possible by morphologic examination alone. Therefore,the most accurate way to report this organism when observed in human stool specimens is "Blastocystissp. "rather than "Blastocystis hominis" .This may cause some confusion among clinicians and therefore, providing some education about the change is recommended.Some other fun taxonomic facts aboutBlastocystisspp.:It was first described by Alexeev in 1911It was thought to be a yeast due to its morphologic appearanceLater,Blastocystiswas re-classified as a sporozoan protozoal parasite Blastocystis spp. is now believed to be a stramenopile - a group that includes diatoms, brown algae and mildew. The only other stramenopile to infect humans isPythium. (HERE is a nice article in the Journal of Clinical Microbiology about human infection withP. insidiosum)For more information aboutBlastocystisspp., check out the excellentBLOG by Dr. Christen Rune Stenvold. Many thanks to Dr. Graham Clark for his assistance with describingBlastocystis taxonomy is a comprehensible fashion.
Source: Creepy Dreadful Wonderful Parasites - Category: Parasitology Source Type: blogs