Differentiating Giardia and Dientamoeba Cysts from those of the Commensal Flagellates

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Differentiating Giardia and Dientamoeba Cysts from those of the Commensal Flagellates

Table 7 outlines some key features in differentiating the cysts of the flagellates.
Table 7. Differentiating Giardia and Dientamoeba Cysts from those of the Commensal Flagellates.
OrganismImageNuclei #Other Features
Giardia duodenalis
Usually oval (can be round)
Usual size: 11-14 x 7-10 μm

(27)		 4 Deep staining median bodies lie across longitudinal fibers
Shrinkage gives a halo effect (arrow)
Dientamoeba fragilis
Oval to round
5-8 μm
 Cysts exist but are very rarely seen, and difficult to identify. 2 Can show shrinkage
Chilomastix mesnili
Lemon or pear shaped with hyaline knob
Usually 7-9 x 4-6 μm

(28)		 1 Cytostome with supporting fibrils
Pentatrichomonas hominis No cysts
27. DPDx. "Parasites - Giardia." CDC.gov, 9 Dec 2017, https://www.cdc.gov/dpdx/giardiasis/index.html
28. DPDx. "Parasites - Chilomastix mesnili - Figure E: Cyst of C. mesnili in a stool specimen, stained with trichrome. Image taken at 1000x magnification." CDC.gov, 5 Jun 2019, https://www.cdc.gov/dpdx/chilomastix/index.html