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harr 5TH: parasitology EXAM STUDY GUIDE NEWEST REVIEW
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harr 5TH: parasitology EXAM STUDY GUIDE NEWEST REVIEW
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harr 5TH: parasitology EXAM STUDYGUIDE NEWEST REVIEW
1. The incorrect match between organism and the appropriate diagnostic procedure is:
A. Onchocerca volvulus—examination of skin snips
B. Cryptosporidium spp.—modified acid-fast stain
C. Enterobius vermicularis—routine ova and parasite examination
D. Schistosoma haematobium—examination of urine sedimen - ANS 1. C The appropriate
procedure for the diagnosis of E. vermicularis would involve the microscopic examination of a
series of consecutive cellulose tapes. Typical eggs and/or a rare adult pinworm could be
identified under the microscope
2. In a patient with diarrhea, occasionally Entamoeba histolytica/E. dispar (four nucleated cysts,
no chromatoidal bars) are identified as being present; however, these cells, which are
misdiagnosed as protozoa, are really:
A. Macrophages
B. Polymorphonuclear leukocytes (PMNs)
C. Epithelial cells
D. Eosinophil - ANS 2. B As PMNs in stool begin to fragment and appear to have four nuclei,
they will resemble E. histolytica/E. dispar cysts. However, E. histolytica/E. dispar cysts are rarely
seen in cases of diarrhea. The species name E. histolytica is reserved for the true pathogen,
whereas E. dispar is used for the nonpathogenic species. Unfortunately, they look identical
morphologically. The only time E. histolytica could be identified morphologically would be from
trophozoites containing ingested RBCs. Nonpathogenic E. dispar would not contain ingested
RBCs. The correct way to report these organisms is E. histolytica/E. dispar (no trophozoites
containing ingested RBCs) or E. histolytica (trophozoites seen that contain ingested RBCs).
Physicians may base the treatment on patient symptoms
3. Charcot-Leyden crystals in stool may be associated with an immune response and are
thought to be formed from the breakdown products of:
A. Neutrophils
B. Eosinophils
C. Monocytes
D. Lymphocytes - ANS 3. B When eosinophils disintegrate, the granules reform into
Charcot-Leyden crystals.
4. Parasitic organisms that may be transmitted sexually do not include:
A. Entamoeba gingivalis
B. Dientamoeba fragilis
C. Trichomonas vaginalis
,D. Diphyllobothrium latum - ANS 4. D Of the organisms listed, Diphyllobothrium latum cannot
be transmitted sexually; this infection is acquired from the ingestion of infected raw or poorly
cooked freshwater fish
5. The incorrect match between the organism and one method of acquiring the infection is:
A. Trypanosoma brucei rhodesiense—bite of sand fleas
B. Giardia lamblia (G. intestinalis, G. duodenalis)—ingestion of water contaminated with cysts
C. Hookworm—skin penetration of larvae from soil
D. Toxoplasma gondii—ingestion of infected raw or rare meats - ANS 5. A East and West
African trypanosomiasis (T. B. rhodesiense and T. B. gambiense) are acquired when infective
forms are introduced into the human body through the bite of the tse-tse fly, not sand fleas.
6. Upon examination of stool material for Cystoisospora belli, one would expect to see:
A. Cysts containing sporozoites
B. Precysts containing chromatoidal bars
C. Oocysts that are modified acid-fast positive
D. Sporozoites that are hematoxylin positive - ANS 6. C C. belli oocysts in various stages of
maturity would be seen in the concentrate sediment or possibly the direct, wet preparation;
these oocysts would stain positive with modified acid-fast stains.
7. Which specimen is the least likely to provide recovery of Trichomonas vaginalis?
A. Urine
B. Urethral discharge
C. Vaginal discharge
D. Feces - ANS 7. D T. vaginalis is site-specific. The organisms are found in the urogenital
tract; thus, the intestinal tract is not the normal site for these organisms
8. Which of the following is the best technique to identify Dientamoeba fragilis in stool?
A. Formalin concentrate
B. Trichrome-stained smear
C. Modified acid fast-stained smear
D. Giemsa stain - ANS 8. B The best technique to recover and identify D. fragilis trophozoites
and rare cysts would be the trichrome-stained smear.
9. One of the following protozoan organisms has been implicated in waterborne and foodborne
outbreaks within the United States. The suspect organism is:
A. Pentatrichomonas hominis
B. Dientamoeba fragilis
C. Giardia lamblia (G. intestinalis, G. duodenalis)
D. Balantidium coli - ANS 9. C For a number of years, G. lamblia (G. intestinalis, G.
duodenalis) has been implicated in both waterborne and foodborne outbreaks from the ingestion
of infective cysts within contaminated water and food.
, 10. Gram staining of a sample from a gum lesion showed what appeared to be amoebae. A
trichrome smear showed amoebae with a single nucleus and partially digested PMNs. The
correct identification is:
A. Trichomonas tenax
B. Entamoeba histolytica/Entamoeba dispar
C. Entamoeba gingivalis
D. Entamoeba polecki - ANS 10. C E. gingivalis is known to be an inhabitant of the mouth
and is characterized by morphology that resembles E. histolytica/E. dispar. However, E.
gingivalis tends to ingest PMNs, whereas E. histolytica/E. dispar do not.
11. An E. histolytica (true pathogen) trophozoite has the following characteristics:
A. Compact karyosome in the nucleus, ingested RBCs, and clear pseudopodia
B. Ingested RBCs, clear pseudopodia, and uneven chromatin on the nuclear membrane
C. Ingested RBCs, clear pseudopodia, and large glycogen vacuoles in cytoplasm
D. Large, blotlike karyosome, ingested white blood cells (WBCs), and granular pseudopods -
ANS 11. A The trophozoite of E. histolytica has evenly arranged chromatin on the nuclear
membrane; a central, compact karyosome in the nucleus; clear pseudopodia; and ingested
RBCs in the cytoplasm.
12. A 12-year-old girl is brought to the emergency room with meningitis and a history of
swimming in a warm-water spring. Motile amoebae that measure 10 μm in size are seen in CSF
and are most likely:
A. Iodamoeba bütschlii trophozoites
B. Endolimax nana trophozoites
C. Dientamoeba fragilis trophozoites
D. Naegleria fowleri trophozoites - ANS 12. D N. fowleri are free-living soil and water
amoebae that cause primary amebic meningoencephalitis (PAM). The number of cases reported
is few; however, the infection is very acute and almost always fatal.
13. Characteristics of the rhabditiform (noninfective) larvae of Strongyloides stercoralis include
a:
A. Short buccal capsule and large genital primordium
B. Long buccal capsule and pointed tail
C. Short buccal capsule and small genital primordium
D. Small genital primordium and notch in tail - ANS 13. A The rhabditiform larvae of S.
stercoralis are characterized by the short buccal capsule (mouth) and large genital primordium,
whereas hookworm larvae have a long buccal capsule and very small genital primordium
14. Visceral larva migrans is associated with which of the following organisms and diagnostic
method?
A. Toxocara—serology
B. Onchocerca—skin snips
C. Dracunculus—skin biopsy
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