Deck 47: Intestinal Protozoa

Question 1

An intestinal protozoan appeared 8 microns in diameter with a small, compact, centrally located karyosome.Four nuclei were observed in the mature cyst.The organism can be identified as:

A) E. histolytica.
B) E. dispar.
C) E. hartmanni.
D) E. coli.

Answer 1

C
The above characteristics describe the cyst stage of the intestinal protozoan Entamoeba hartmanni.

Question 2

The presence of which of the following cells is diagnostic for the intestinal protozoan, Entamoeba histolytica, which measures 15 to 20 microns?

A) Yeast
B) White blood cells (WBCs)
C) Red blood cells (RBCs)
D) Bacteria

Answer 2

C
The presence of RBCs in E.histolytica is diagnostic.It is the only characteristic that allows the differentiation between pathogenic E.histolytica and nonpathogenic E.dispar.

Question 3

Highly active antiretroviral therapy (HAART)is the most effective prophylaxis and treatment in patients with acquired immunodeficiency syndrome (AIDS)with which type of infection?

A) Cyclospora
B) Sarcocystis
C) Cryptosporidium
D) Toxoplasma

Answer 3

C
In industrialized nations, the most effective prophylaxis and treatment for cryptosporidiosis in patients with AIDS is the use of HAART.The eradication and prevention of the infection are related to the replenishment of CD4+ cells in treated persons and the antiparasitic activities of the protease inhibitors used in HAART.A relapse of cryptosporidiosis is common in patients with AIDS who have stopped using HAART.

Question 4

The drug of choice for the parasite Blastocystis hominis, which is believed to produce proteases and is considered a virulence factor responsible for its pathogenesis, is:

A) metronidazole.
B) albendazole.
C) tetracycline.
D) nitazoxanide.

Question 5

This flagellate is pear-shaped with "falling leaf" motility.It contains variant-specific surface proteins (VSPs)on its surface, which provide a mechanism for the organism to survive in the small intestine as a result of its ability to resist intestinal proteases.The organism is:

A) Giardia lamblia.
B) Chilomastix mesnili.
C) Dientamoeba fragilis.
D) Enteromonas hominis.

Question 6

Entamoeba coli, a protozoan that ranges from 15 to 25 microns in diameter, can contain up to eight nuclei in mature cysts.How would the karyosome expect to appear on a stained slide?

A) Small, usually compact
B) Large, usually compact
C) Small, irregularly shaped
D) Large, not compact

Question 7

The cyst form of Balantidium coli is the infective stage.It has one large kidney-shaped macronucleus and one small, round micronucleus.The troph is quite large, measuring 50 to 150 microns in length and 40 to 70 microns in width.What single feature is associated with this organism?

A) Falling leaf motility
B) Shepherd's crook
C) Presence of oocytes
D) Cilia covering the troph

Question 8

The peripheral chromatin, which contains fine granules that are uniform in size and are evenly distributed, can be found in which one of the following protozoa?

A) Endolimax nana
B) Iodamoeba butschlii
C) Entamoeba coli
D) Entamoeba histolytica

Question 9

Outbreaks of infection with the organism Cyclospora are linked to contaminated raspberries, lettuce, and snow peas.The stain of choice to identify the oocysts in stool samples is:

A) trichrome.
B) Wright.
C) periodic acid-Schiff.
D) modified acid-fast.

Question 10

The polar tubule, which is responsible for the entrance of infective sporoplasm into the host cell, is found in which of the following genera?

A) Blastocystis
B) Sarcocystis
C) Enterocytozoon
D) Entamoeba

Question 11

Which of the following nonpathogenic protozoa has a very large glycogen vacuole in its cyst form and measures approximately 5 to 20 microns in diameter?

A) Entamoeba coli
B) Iodamoeba butschlii
C) Entamoeba dispar
D) Endolimax nana

Question 12

When cooking meat, an internal temperature of ____° C must be reached to kill organisms such as Toxoplasma and Sarcocystis.

A) 38
B) 48
C) 58
D) 68

Question 13

Which of the following flagellates has a single nucleus in the cyst and the typical curved, cytostomal fibril, which is called a shepherd's crook?

A) Giardia lamblia
B) Chilomastix mesnili
C) Dientamoeba fragilis
D) Enteromonas hominis

Question 14

Which of the following intestinal protozoa has no cyst stage, ranges from 9 to 12 microns in diameter, and has two nuclei in 60% of clinical specimens?

A) Giardia lamblia
B) Chilomastix mesnili
C) Dientamoeba fragilis
D) Enteromonas hominis

Question 15

A tissue sample is sent to the laboratory and microscopically examined for the presence of amebae.To differentiate between the host cells and the organism, _______ stain is used to allow the organisms to appear bright pink with a green-blue background.

A) trichrome
B) Giemsa
C) Wright
D) periodic acid-Schiff (PAS)

Question 16

A patient has amebic colitis.A microscopic examination reveals the following: • 18 microns in diameter
• Fine granules
• Centrally located karyosome
• Cytoplasm with a "ground glass" appearance
• RBC inclusions
This protozoan can be identified as:

A) Entamoeba dispar.
B) E. histolytica.
C) E. hartmanni.
D) E. coli.

Question 17

The organism Sarcocystis has an obligatory two-host life cycle-an intermediate host and definitive host.The sporocysts found in a stool specimen, which measure 9 to 16 microns, are broadly oval with slightly ___________ ends.

A) blunt
B) tapered
C) rounded
D) flattened

Question 18

The Isospora belli organism, which contains two sporocysts with four sporozoites each, is recovered from fecal specimens and has also been implicated in traveler's diarrhea.The drug of choice to treat infection caused by I.belli is:

A) trimethoprim-sulfamethoxazole combination.
B) tetracycline.
C) albendazole.
D) flagyl.

Question 19

A patient is diagnosed with a severe intestinal disease caused by Entamoeba histolytica.Which of the following treatments should be administered?

A) Diloxanide furoate
B) Metronidazole
C) Metronidazole plus iodoquinol
D) Iodoquinol and diloxanide furoate

Question 20

Asexual amplification, called merogony, is associated with the life cycle of which organism?

A) Cyclospora
B) Cryptosporidium
C) Toxoplasma
D) Sarcocystis