Parasitology Exam

This parasite has the following characteristics:

stains red with acid fast stain

zoonotic transer to humans

spread by fecal oral route

Chryptosporidium

This parasite has the following characteristics:

banana shaped gametocytes in RBCs

multiple ring forms in RBCs

all RBCs are infected

Plasmodium falciparum

Individuals who lack the Duffy antigen on the surface of their red blood cells are protected against which species of Plasmodium?

P. vivax

Where do Plasmodium sporozoites proliferate?

liver

A Wright-stained peripheral smear reveals the following:

erythrocytes enlarged 1.5x to 2x normal size

Schüffner’s dots

parasites with irregular "spread out" trophozoites, golden brown pigment

12-24 merozoites

wide range of stages

This is consistent with:

vivax

A 44-year-old man was admitted to the hospital following a 2-week history of low-grade fever, malaise and anorexia. Examination of a Giemsa stain revealed many intraerythrocytic parasites.

Further history revealed frequent camping trips near Martha's Vineyard and Nantucket Island,

but no travel outside the continental United States. This parasite could easily be confused with:

Plasmodium falciparum

This parasite is transmitted by accidental ingestion of cat feces that contain oocysts and by ingestion of undercooked meat that has tissue cysts. The parasite is:

Toxoplasma godii

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

Cryptosporidium

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

Cryptosporidium

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:

modified acid-fast.

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:

trimethoprim-sulfamethoxazole combination.

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.

tapered

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

68

A stool specimen is sent to the laboratory and microscopically examined for the presence of Cryptosporiudium. To differentiate between the host cells and the organism, _______ stain is used to allow the organisms to appear bright red to purple with a blue or green background.

Ziehl-Neelsen

This organism evolved from fungi and demonstrates characteristics of both prokaryotes and eukaryotes.

Microsporidia

In cases of malaria, the primary exoerythrocytic cycle occurs in the:

liver.

Delicate ring forms and crescent-shaped gametocytes are the only forms normally observed in the peripheral blood of which Plasmodium spp.?

P. falciparum

A thick ring, large nucleus, and bands across the cell and 6 to 12 merozoites in a mature schizont are all characteristics of which Plasmodium spp.?

P. malariae

Cerebral malaria is considered to be the most serious complication and major cause of death with which species of Plasmodium spp.?

P. falciparum

P. vivax is suspected in a patient who has been traveling for months in the tropics. Blood was collected in a lavender top tube; however, the slide was not prepared for examination until the next day because the specimen came in on the night shift. Once the slide was prepared and examined, Schüffner dots were not visible. Which one of the following statements explains this discrepancy?

The blood remained in the tube too long, yielding false-negative results.

Resistance to chloroquine and mefloquine has been identified in which Plasmodium spp.?

P. falciparum

Ring forms and a “Maltese cross” were observed in a blood smear. The vector that transmits this disease is a(n):

tick

Laboratory diagnosis of T. gondii is confirmed by:

serologic testing

What is the only known definitive host for the causative agent of Toxoplamosis?

Cats

A liquid stool specimen is collected at 10:00 PM and brought to the laboratory for culture and ova and parasite examination. It is refrigerated until 10:10 AM the next day, when the physician requests that the technologist look for amoebic trophozoites. The best course of action would be to:

request a fresh specimen

What diagnostic methodology has been used to differentiate a N. fowleri from Acanthamoeba spp.?

Flow cytometry

The advantage of thick blood smears for malarial parasites is to:

improve detection of the organisms

A formed stool is received in the laboratory at 3 AM for ova and parasite exam. The night shift technologist is certain that the workload will prevent examination of the specimen until 6 AM

when the next shift arrives. The technologist should:

?

The method of choice to detect Acanthamoeba species from corneal ulcer scrapings is:

blood agar flooded with a 24-hour growth of E coli

Polyvinyl alcohol used in the preparation of permanently stained smears of fecal material:

serves as an adhesive

Artifacts found in a stool specimen that can be confused with ova or cysts are:

pollen grains

Which of the following is currently the only fixative available that does not contain formalin, polyvinyl alcohol (PVA), or mercury?

TOTAL-FIX

The concentration protocol of the ova and parasite (O&P) examination:

is designed to allow the detection of protozoan cysts, coccidian oocysts, microsporidial spores, and helminth eggs and larvae.

The permanent stained smear protocol of the O&P examination:

is designed to facilitate the identification of intestinal protozoa.

The Entero-Test Capsule technique involves the collection of duodenal contents to examine the presence of which of the following parasites?

Giardia duodenalis

A urine sample from a 26-year-old woman is examined, and an organism is observed that displays “jerky” motility. This organism is classified as a(n):

flagellate.

A modified acid-fast stain is performed on lung tissue. The most likely organism that will be observed is:

Cryptosporidium spp.

A medical laboratory scientist (MLS) is examining a thin blood film from a patient suspected of having a Plasmodium infection. After examining the slide for 5 minutes and viewing approximately 100 oil immersion fields, the MLS does not observe any structures associated with Plasmodium. Which one of the following statements explains this discrepancy?

---

The MLS may have missed the organism; more than 300 fields should be viewed.

The PARA-TECT Cryptosporidium/Giardia test kit uses which of the following formats for detection?

Direct fluorescent antibody (DFA)

The parasite T. gondii is acquired via the ingestion of infected oocysts from cat feces. A diagnosis is primarily made through:

serologic means.

The only medically significant ciliate organism is:

Balantidium coli