MLT 142 Intro into Parasitology and Protozoa

When concentrating specimens, one problem with the zinc sulfate flotation method is:

operculated eggs and some protozoans do not float.

An advantage of sedimenting stool specimens using formalin-ether concentration is:

all eggs and larvae can be concentrated using this method.

The trophozoite of Entamoeba histolytica:

may have ingested red cells or bacteria.

Which of the following is correct about Naegleria?

all of these are correct

Which intestinal flagellate’s trophozoite form has two nuclei with central karyosomes, a ventral sucking disk with a pointed anterior end, and bilateral symmetry

Giardia lamblia

The sexual cycle of Toxoplasma gondii occurs in:

cats.

Plasmodium falciparum:

has a present shaped gametocyte.

Chagas disease is diagnosed by observation of which of the following?

C-shaped tripomastigotes in blood smears.

The intestinal coccidians:

may be identified using the modified acid fast stain.

. The Plasmodium species that is the agent of a quartan malaria:

produces low levels of parasitism.

Trypanosoma cruzi:

is transmitted through infected reduviid bugs, causing Chagas disease.

An amoeba isolated from a patient with keratitis has spiny pseudopods and well-defined ectoplasm and endoplasm, but no flagellar phase noted. It is most likely:

Acanthamoeba.

Diagnosis of African sleeping sickness is based on the observation of:

trypomastigotes in peripheral blood.

Which of the following is the vector for Plasmodium?

Anopheles mosquitoes.

A coccidian parasite is isolated from the stool of an individual who was experiencing severe abdominal bloating and watery diarrhea in a suspected outbreak from contaminated blackberries. The sporocysts were very small, staining bright pink with the modified acid-fast stain. The sporocysts exhibited autofluorescence, appearing blue when exposed to ultraviolet light of 365 nm and green under 450–490 nm. This parasite is most likely:

Cyclospora.

True or False? The thick blood film is used to identify the parasitic species.

False

True or False? The sexual reproductive phase of the parasite occurs in the definitive host.

True

The asexual reproduction of Plasmodium in the red cells, where merozoites develop into ring forms, is known as erythrocytic

schizogony.

Babesia spp. is transmitted via the bite of a tick and can cause severe disease in patients who have been splenectomized or who are immunocompromised. To diagnose accurately these patient populations, the specimen of choice is:

blood.

A bone marrow aspirate is examined for the presence of parasites from a patient who has been traveling in Latin America for several months and who came in contact with a triatomid bug. Which parasite will most likely be identified?

Trypanosoma cruzi.

Some strains of leishmaniae have reservoir hosts, including dogs and wild rodents. Transmission is via the bite of a:

sandfly.

A 17-year-old male with a severe eye infection admits that he does not clean his contact lenses as often as he should. His eye infection is most likely the result of which parasite?

Acanthamoeba spp.

A 7-year-old girl was at summer camp and dove into the lake many times. She complained that water went up her nose a few times. Several days later she is unresponsive and comatose and rushed to the hospital. A cerebrospinal fluid (CSF) specimen is drawn, and several motile amebae are observed. She is most likely suffering from an infection with which of the following parasites?

Naegleria fowleri

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.

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

serologic means.

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

Entamoeba histolytica/dispar group

A patient has amebic colitis. A microscopic examination reveals the following:

ï    18 µm in diameter

ï    Fine granules

ï    Centrally located karyosome

ï    Cytoplasm with a “ground-glass” appearance

ï    RBC inclusions

This protozoan can be identified as:

E. histolytica.

An intestinal protozoan appeared 8 µm in diameter with a small, compact, centrally located karyosome. Four nuclei are present in the mature cyst. The organism is most likely:

E. hartmanni.

Which of the following intestinal protozoa has a cyst that ranges from 5 to 8 µm in diameter, a distinct cell wall with a clear zone, axostyle, flagellar axonemes, a costa, and has two nuclei with large central karyosomes?

Dientamoeba fragilis

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 resisting degradation by intestinal proteases. The organism is:

G. duodenalis.

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

C. mesnili

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.

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

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

tick,

Chagas disease is caused by:

Trypanosoma cruzi.

The vector Glossina palpalis group transmits the T. brucei gambiense organism. The diagnostic stage is the:

trypomastigote.

Stage I of trypanosomiasis characteristically involves systemic trypanosomiasis infection without central nervous system (CNS) involvement. Lymphadenopathy is also a feature of this disease. The trypomastigotes of which protozoa are involved

T. brucei gambiense

In T. brucei rhodesiense trypanosomiasis infections, CNS invasion occurs early. The disease progresses rapidly, and death may occur before extensive CNS involvement. Inflammation of which organ is more common and severe with this disease form?

heart.

Humans contract Chagas disease when the reduviid bug defecates while taking a blood meal and the parasites in the feces are rubbed or scratched into the bite wound or onto mucosal surfaces. Which stage in the blood infects the host cells?

Trypomastigote

The most frequent clinical signs of chronic Chagas disease involve the enlargement of which organ?

heart.

A 15-year-old male was diving in a lake when he inhaled some of the stagnate water. Five days later he was admitted to the hospital, comatose, and in critical condition. A cerebrospinal fluid (CSF) specimen was taken, and several motile amoebae were observed. The patient would most likely be diagnosed with which of the following conditions?

Primary amebic meningoencephalitis

The CSF would reveal which of the following results in infections caused by N. fowleri?

Decreased glucose, increased protein, and negative Gram stain

Trichomoniasis is the primary nonviral sexually transmitted disease worldwide. One complication of this infection is:

endometritis.

A 26-year-old woman has an odorous vaginal discharge, lower abdominal pain, and difficulty urinating. Vaginal secretions are collected and sent to the laboratory for examination 3 hours after collection. No motile organisms are observed on the wet preparation; however, T. vaginalis is suspected. Which one of the following statements explains this discrepancy?

The time between collection and the microscopic examination was prolonged, resulting in loss of motility.

Which of the following protozoans, is considered a causative agent in Primary Amoebic meningoencephalitis (PAM)?

N fowleri

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

Cats

Progressive, with hyaline, fingerlike pseudopodia

E. histolytica

Non-progressive; pseudopodia are angular, serrated, or broad lobed and almost transparent

D. fragilis

Sluggish, non-directional; blunt, granular pseudopodia

E. coli

rotary, boring; may be rapid

B. (N) coli

Sluggish, usually non-progressive

I. bütschlii

Falling leaf

D. fragilis

Stiff, rotary

C. mesnili