TABLE A1.

Characteristics of intestinal protozoa, in particular, trophozoites of common amoebae^b

Organism(s)	Size (diam or length [μm])a	Motility	Visibility and no. of nuclei	Peripheral chromatin (stained) characteristic(s)	Karyosome (stained)	Cytoplasm appearance (stained)	Inclusions (stained)
Entamoeba histolytica	12–60 (usual range, 15–20; invasive forms may be over 20)	Progressive and directional, with hyaline, finger-like pseudopodia; motility may be rapid	Difficult to see in unstained preparations; 1 nucleus	Fine granules that are uniform in size are present and usually evenly distributed; may have beaded appearance	Small and usually compact; centrally located but may also be eccentric	Finely granular, “ground-glass” appearance; clear differentiation of ectoplasm and endoplasm; if present, vacuoles are usually small	Noninvasive organism may contain bacteria; the presence of RBCs is diagnostic
Entamoeba dispar/Entamoeba moshkovskii	Same as E. histolytica	Same as E. histolytica	Same as E. histolytica	Same as E. histolytica	Same as E. histolytica	Same as E. histolytica	Organisms usually contain bacteria; RBCs are usually not present in the cytoplasm
Entamoeba hartmanni	5–12 (usual range, 8–10)	Usually nonprogressive	Usually not seen in unstained preparations; 1 nucleus	Nucleus may stain more darkly than in E. histolytica/E. dispar and may be stain dependent, although morphologies are similar; chromatin may appear as a solid ring rather than beaded	Usually small and compact; may be centrally located or eccentric	Finely granular	May contain bacteria; no RBCs
Entamoeba coli	15–50 (usual range, 20–25)	Sluggish nondirectional, with blunt, granular pseudopodia	Often visible in unstained preparations; 1 nucleus	May be clumped and unevenly arranged on the membrane; may also appear as a solid, dark ring with no beads or clumps	Large, not compact; may or may not be eccentric; may be diffuse and darkly stained	Granular, with little differentiation into ectoplasm and endoplasm; usually vacuolated	Bacteria, yeasts, other debris are found in inclusion bodies
Endolimax nana	6–12 (usual range, 8–10)	Sluggish, usually nonprogressive	Occasionally visible in unstained preparations; 1 nucleus	Usually no peripheral chromatin; nuclear chromatin may be quite variable; perikaryosomal space is clear	Large, irregularly shaped; may appear “blot-like”; many nuclear variations are common; may mimic E. hartmanni or D. fragilis	Granular, vacuolated	Bacteria
Iodamoeba bütschlii	8–20 (usual range, 12–15)	Sluggish, usually nonprogressive	Usually not visible in unstained preparations; 1 nucleus	Usually no peripheral chromatin	Large, may be surrounded by refractile granules that are difficult to see (“basket nucleus”) and create a darker perikaryosomal space	Granular, may be heavily vacuolated	Bacteria

^aWet preparation measurements (on permanent stains, organisms usually measure 1 to 2 μm less).

^bAdapted from reference 5.