Parasitology, mycology and virology

55 Lab technician recruitment practice questions on Parasitology, mycology and virology, part of Microbiology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Medium

   Which virus shows Negri bodies in neurons?

   1. AHerpes simplex virus
   2. BPoliovirus
   3. CJapanese encephalitis virus
   4. DRabies virus

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   Answer: D · Rabies virus

   Negri bodies are eosinophilic cytoplasmic inclusions in neurons, notably Purkinje cells and hippocampal neurons, in rabies. Herpes viruses give intranuclear Cowdry type A inclusions.

   • A: Herpes simplex forms intranuclear inclusions.
   • B: Poliovirus does not form Negri bodies.
   • C: JE virus does not form Negri bodies.

2. Question 2 · Medium

   Which stain is used to show oocysts of Cryptosporidium in stool?

   1. AGram stain
   2. BModified acid-fast stain
   3. CLugol's iodine
   4. DIron haematoxylin

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   Answer: B · Modified acid-fast stain

   Cryptosporidium oocysts (4-6 µm) stain pink-red with modified Ziehl-Neelsen (cold Kinyoun) using weak acid decolouriser. Cyclospora and Cystoisospora are also acid-fast.

   • A: Gram stain does not show oocysts reliably.
   • C: Iodine does not stain the oocysts well.
   • D: Iron haematoxylin is for amoebae and flagellates.

3. Question 3 · Hard

   A thick film is negative but RDT is positive for P. falciparum HRP-2 in a patient treated two weeks ago. Most likely explanation?

   1. AA lysed thick film
   2. BPersisting HRP-2 antigen
   3. CGametocytes in the film
   4. DWrong species on the RDT

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   Answer: B · Persisting HRP-2 antigen

   HRP-2 can stay in blood for several weeks after parasites are cleared, so an RDT may stay positive after successful treatment. Microscopy is used to judge cure and density.

   • A: Lysis of red cells is normal in thick films.
   • C: Gametocytes would be seen in the film.
   • D: HRP-2 is specific to P. falciparum.

4. Question 4 · Easy

   Heavy infection with which helminth may cause rectal prolapse in children?

   1. ATaenia saginata
   2. BAscaris lumbricoides
   3. CEnterobius vermicularis
   4. DTrichuris trichiura

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   Answer: D · Trichuris trichiura

   Whipworms embed their thin anterior ends in the caecal and rectal mucosa. Heavy loads cause dysentery, tenesmus and rectal prolapse in children.

   • A: Beef tapeworm causes mild abdominal symptoms.
   • B: Ascaris causes intestinal obstruction and lung migration.
   • C: Pinworm causes perianal itching, not prolapse.

5. Question 5 · Easy

   Schuffner's dots are seen in red cells infected with:

   1. AP. malariae
   2. BP. falciparum
   3. CP. vivax
   4. DP. knowlesi

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   Answer: C · P. vivax

   Schuffner's dots are fine red stippling in enlarged red cells infected by P. vivax (and P. ovale). P. falciparum shows coarser Maurer's clefts, and P. malariae may show Ziemann's dots.

   • A: P. malariae shows Ziemann's dots.
   • B: P. falciparum shows Maurer's clefts.
   • D: P. knowlesi does not cause Schuffner's dots.

6. Question 6 · Easy

   In which helminth are the larvae, rather than eggs, usually seen in fresh stool?

   1. AStrongyloides stercoralis
   2. BHymenolepis nana
   3. CAscaris lumbricoides
   4. DTrichuris trichiura

   Answer and explanation in LearnFree account

7. Question 7 · Easy

   Which stool protozoan has a pear-shaped trophozoite with two nuclei and falling-leaf motility?

   1. ATrichomonas hominis
   2. BEntamoeba histolytica
   3. CBalantidium coli
   4. DGiardia lamblia

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8. Question 8 · Easy

   Which medium is most widely used for routine isolation of fungi?

   1. AThiosulphate citrate bile salt sucrose agar
   2. BLowenstein-Jensen medium
   3. CSabouraud dextrose agar
   4. DMacConkey agar

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9. Question 9 · Easy

   Which yeast produces brown colonies on bird seed (niger seed) agar?

   1. ACandida albicans
   2. BCandida tropicalis
   3. CRhodotorula
   4. DCryptococcus neoformans

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10. Question 10 · Medium

    Which hookworm feature separates Ancylostoma duodenale from Necator americanus in adult worms?

    1. AAbsence of a copulatory bursa
    2. BTwo pairs of teeth in the buccal capsule
    3. CPresence of cutting plates
    4. DA barrel-shaped egg

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11. Question 11 · Medium

    In a thin smear, which finding suggests P. falciparum rather than P. vivax?

    1. ASchizonts with 16 merozoites
    2. BEnlarged pale red cells
    3. CAmoeboid trophozoites
    4. DMultiple rings in normal-sized cells

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12. Question 12 · Hard

    A diabetic with ketoacidosis has a black nasal crust. KOH mount of tissue shows broad aseptate hyphae. Which culture finding fits?

    1. ASlow waxy heaped colonies
    2. BSmooth cream yeast colonies
    3. CRapid woolly growth filling the plate
    4. DGreen velvety colonies with a white rim

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13. Question 13 · Easy

    Which cells are the main target of HIV?

    1. ANeutrophils
    2. BB lymphocytes
    3. CCD8 cytotoxic T cells
    4. DCD4 T cells

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14. Question 14 · Easy

    Which stain is used to show the capsule of Cryptococcus neoformans in CSF?

    1. AIndia ink
    2. BGram stain
    3. CLactophenol cotton blue
    4. DGiemsa stain

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15. Question 15 · Medium

    Which antigen do most rapid malaria tests detect to identify P. falciparum?

    1. AAldolase only
    2. BCircumsporozoite protein
    3. CHRP-2
    4. DpLDH of P. vivax

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16. Question 16 · Hard

    A thin smear shows 50 infected red cells among 2,000 red cells counted. What is the parasitaemia?

    1. A25%
    2. B0.25%
    3. C2.5%
    4. D5%

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17. Question 17 · Medium

    Which marker shows immunity after hepatitis B vaccination alone?

    1. AAnti-HBs and anti-HBc
    2. BHBsAg and anti-HBc
    3. CAnti-HBs only
    4. DIgM anti-HBc

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18. Question 18 · Medium

    Which fungus shows broad, ribbon-like, mostly aseptate hyphae branching at right angles in tissue?

    1. ATrichophyton
    2. BRhizopus
    3. CCandida
    4. DAspergillus

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19. Question 19 · Easy

    Which solution is used for a wet mount to show trophozoites and cysts in fresh stool?

    1. ATen percent formalin
    2. BAbsolute alcohol
    3. CDistilled water
    4. DNormal saline

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20. Question 20 · Easy

    Lactophenol cotton blue is used mainly to:

    1. AShow acid-fast bacilli
    2. BMount and stain fungal growth from culture
    3. CStain malaria parasites
    4. DClear keratin in skin scrapings

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21. Question 21 · Easy

    Which mosquito transmits human malaria?

    1. AFemale Culex
    2. BMale Anopheles
    3. CAedes aegypti
    4. DFemale Anopheles

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22. Question 22 · Easy

    Which reagent is used in a direct mount of skin scrapings to look for fungal hyphae?

    1. ASodium chloride
    2. BCrystal violet
    3. CPotassium hydroxide
    4. DHydrogen peroxide

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23. Question 23 · Hard

    A patient from Kerala has watery diarrhoea and eosinophilia. Stool shows rhabditiform larvae with a short buccal canal. The next best test?

    1. AKOH mount
    2. BNight blood smear
    3. CAgar plate culture
    4. DCellophane tape swab

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24. Question 24 · Medium

    Why are operculated eggs such as those of Fasciola and Diphyllobothrium poorly recovered by zinc sulphate flotation?

    1. AThey are heavy and may open
    2. BThey float only in saline
    3. CZinc dissolves their shells
    4. DThey are too small to float

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25. Question 25 · Medium

    Under the national HIV testing strategy, an adult is reported positive when:

    1. AThree different tests are reactive
    2. BOne ELISA is reactive
    3. CTwo runs of the same kit are reactive
    4. DWestern blot alone is reactive

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