Page 76 - parasitology for medical and clinical laboratoryprofessionals

56 CHAPTER 3

MICROSCOPIC DIAGNOSTIC

FEATURE

General
Classification Amoeba
Source: Centers for Disease Control and Prevention (CDC) Stage Trophozoites most
Entamoeba coli
Organism
Specimen Required Stool specimen

diagnostic stage
Elongated trophozo-
Shape

ites and round cysts
Trophozoite—5–50 μm;
Size
cysts—15–25 μm
Motility
no progression
1 for trophozoites
Nucleus(i) Nondirectional with
FIGURE 3-14 Endolimax nana cysts from wet mount and up to 8 for cysts;
with iodine stain coarse and uneven
peripheral chromatin
Cytoplasm Vacuoles present
objective along with adjustment of the condenser. It is along with ingested
important to remember that E. coli is the only species of bacteria
Entamoeba with more than four nuclei in the cyst stage. Other Features Chromatoidal bars
The trophozoite stage of E. coli measures from 15 to with splintered
50 μm and the cytoplasm often appears “dirty” due to the terminal ends
coarse granulation as well as ingested bacteria and other Eccentric karyosome
fecal debris. A single nucleus is present with peripheral in nucleus of
nuclear chromatin that is distributed in clumps. A large trophozoite
eccentric (noncentered) karyosome in the solitary nucleus
Entamoeba coli
is characteristic of the trophozoite stage. The motility of
Trophozoite Cyst
the trophozoite is described as sluggish with little pro-
gression that is accomplished by blunt pseudopodia.
The nuclei of E. coli are best revealed by means
of an iodine stain. They have a dark circumference and
a dark central point (karyosome). The karyosome of
Entamoeba coli is not centrally located, but eccentric
(off-centered). Staining with an iodine solution (Lugol’s)
can also detect glycogen bodies or vacuoles (brown) in
Delmar/Cengage Learning
young cysts. Peripheral chromatin is present in the nuclei
of E. coli cysts and trophozoites but not in Endolimax
nana trophozoites (Figure 3-14).

Symptoms
Those infected with E. coli are generally asymptomatic
because these parasites are not considered pathogenic.