Deck 46: Intestinal Protozoa

Question 1

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

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

Answer 1

B
Cryptosporidium infections begin with the ingestion of viable oocysts.Upon contact with gastric and duodenal fluids,four sporozoites are released from each oocyst.They invade the epithelial cells and develop to trophozoites,surrounded by a parasitophorous vacuole.Within the epithelial cells,trophozoites undergo two or three generations of asexual amplification,called merogony,leading to the formation of different types of meronts that contain four to eight merozoites.The latter differentiate into sexually distinct stages in a process called gametogony.

Question 2

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

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

Answer 2

C
D.fragilis has no cyst stage and ranges from 9 to 12 µm.Two nuclei are observed in 60% of clinical specimens.

Question 3

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

Answer 3

D
Cooking meat until an internal temperature of higher than 67°C is reached will kill Toxoplasma gondii tissue cysts in meat.This temperature should also kill tissue cysts of Sarcocystis in meat.

Question 4

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 5

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's.
C)periodic acid-Schiff.
D)modified acid-fast.

Question 6

An intestinal protozoan appeared 8 µm 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.

Question 7

A patient has amebic colitis.A microscopic examination reveals the following:
·18 µm 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)Entamoeba hartmanni.
D)E.coli.

Question 8

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

A)E.coli
B)I.butschlii
C)E.dispar
D)E.nana

Question 9

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 10

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)G.duodenalis.
B)C.mesnili.
C)D.fragilis.
D)E.hominis.

Question 11

The Cystoisospora 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 C.belli is:

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

Question 12

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 µm,are broadly oval with slightly ___________ ends.

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

Question 13

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 µm in length and 40 to 70 µm 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 14

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

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

Question 15

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)G.duodenalis
B)C.mesnili
C)D.fragilis
D)E.hominis

Question 16

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

Question 17

E.coli,a protozoan that ranges from 15 to 25 µm 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 18

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 19

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's
D)periodic acid-Schiff (PAS)