Dientamoeba fragilis measures 9-12 uM and have 1-2 nuclei (nearly half have only 1 nucleus).

Important notice from RCPA 2015 concerning the (overall lack of) significance of Dientamoeba and Blastocystis detected in stool.  [Multiplex faecal PCR assays often include these species in the panel].

CDC resource page– FAQ and clinical relevance discussed.

Trophozoites are not visible in unstained preparations. Cytoplasm has fine granules, vacuolated and ingested bacteria are present.  This species was thought until recently to have no cyst stage. Most commonly missed during microscopy as it stains very pale and tends to be camouflaged in the background. Labs that don’t stain their samples miss this very common parasite.

Photo: Hemant Sharma, 2014