MLT GlobeParasitology: Intestinal protozoa – page 4
69 Parasitology MCQs on Intestinal protozoa with answers and explanations.
A cyst in an iodine wet mount has a single nucleus and a large, sharply outlined glycogen vacuole that stains brown. It is:
Iodamoeba cysts have one nucleus and a prominent glycogen mass that stains dark brown with iodine. Endolimax cysts have four small nuclei without a large vacuole.
A trichrome-stained stool shows round forms 6–20 µm, each with a large central body that pushes a thin rim of cytoplasm and small nuclei to the edge. The organism is:
The 'central body' form with peripheral nuclei is typical of Blastocystis. Iodamoeba cysts have a glycogen vacuole but only a single nucleus with a large karyosome.
A small (6–8 µm) oval cyst has four nuclei with large, blot-like karyosomes and no peripheral chromatin. It is most likely:
Endolimax nana cysts are small, with up to four nuclei that have large karyosomes and no peripheral chromatin. Entamoeba species show peripheral chromatin on the nuclear membrane.
In a stained smear, the nucleus of an Entamoeba histolytica trophozoite typically shows:
Fine even peripheral chromatin with a small central karyosome is typical of E. histolytica; coarse chromatin with an eccentric karyosome suggests E. coli.
A small lemon-shaped cyst with a single nucleus and a knob-like projection at one end is seen in stool. It belongs to a non-pathogenic flagellate called:
The lemon-shaped cyst with an anterior nipple is characteristic of the commensal flagellate Chilomastix mesnili.
Where in the human intestine does Cryptosporidium develop?
Cryptosporidium sits in an intracellular but extracytoplasmic vacuole at the microvillous surface of enterocytes, mainly in the small intestine.
In current protist classification, Trichomonas vaginalis belongs to which group?
Trichomonads are anaerobic flagellates with hydrogenosomes and parabasal bodies, grouped as Parabasalia. The older phylum Sarcomastigophora is outdated.
A trichrome-stained stool shows small trophozoites with one or two fragmented nuclei (chromatin in 4–6 granules) and no cyst stage is seen. The organism is:
Dientamoeba fragilis is a flagellate without external flagella, often binucleate with fragmented chromatin, and seen only in permanent stains. Endolimax nana has a single blot-like karyosome.
Stool from an HIV patient with chronic diarrhoea is stained with modified trichrome (chromotrope 2R). Tiny oval pinkish-red spores, 1–3 µm, some with a belt-like stripe, are seen. The organisms are:
Microsporidial spores are very small and stain pink-red with modified trichrome, often with a diagonal band. Cryptosporidium oocysts are larger (4–6 µm) and are shown with modified acid-fast stain.