CHAPTER 22: Serological and Molecular Diagnosis of Parasitic and Fungal Infections

Question 1

Compared with a host’s response to the mumps virus, overcoming a parasitic infection is more difficult for the host because of which of the following characteristics of parasites?
a. Large size
b. Complex antigenic structures
c. Elaborate life cycle
d. All of the above

Answer 1

d. All of the above

Question 2

Which of the following is indicative of a recent infection with Toxoplasma gondii?
a. Anti-Toxoplasma IgM
b. Anti-Toxoplasma IgE
c. High avidity anti-Toxoplasma IgG
d. Low avidity anti-Toxoplasma IgG

Answer 2

d. Low avidity anti-Toxoplasma IgG

Question 3

Parasites are able to evade host defenses by which of the following means?
a. Production of antigens similar to host antigens
b. Changing surface antigens
c. Sequestering themselves within host cells
d. All of the above

Answer 3

d. All of the above

Question 4

The chronic nature of parasitic infections is caused by the host’s
a. inability to eliminate the infective agent.
b. type I hypersensitivity response to the infection.
c. ability to form a granuloma around the parasite.
d. tendency to form circulating immune complexes.

Answer 4

a. inability to eliminate the infective agent.

Question 5

The presence of both IgM and IgG antibody in toxoplasmosis infections suggests that the infection
a. occurred more than 2 years ago.
b. occurred more recently than 18 months ago.
c. is chronic.
d. has resolved itself.

Answer 5

b. occurred more recently than 18 months ago.

Question 6

Which of the following is indicative of a parasitic infection?
a. Increased IgA levels
b. Increased IgE levels
c. Increased IgG levels
d. Increased IgM levels

Answer 6

b. Increased IgE levels

Question 7

In congenital toxoplasmosis, which class of antibodies is the most sensitive in detecting infection?
a. IgA
b. IgG
c. IgM
d. IgE

Answer 7

a. IgA

Question 8

The most significant defense against fungal infections is
a. cellular immunity.
b. humoral immunity.
c. phagocytosis.
d. complement activation.

Answer 8

a. cellular immunity.

Question 9

Clinical manifestations of fungal-related illness include
a. hypersensitivity caused by fungal spores.
b. poisoning caused by ingestion of mycotoxins.
c. growth of fungi in or on tissue.
d. all of the above.

Answer 9

d. all of the above.

Question 10

Which of the following assay formats are increasingly being adopted by clinical laboratories for serological detection of fungal infections because of their ease of use?
a. ELISA assays
b. Lateral flow assays
c. Radial immunodiffusion assays
d. Indirect immunofluorescence assays

Answer 10

b. Lateral flow assays

Question 11

The presence of anti-H antibodies indicates which of the following?
a. A previous infection with Coccidioides immitis
b. A previous exposure to Histoplasma capsulatum
c. An active infection with Cryptococcus neoformans
d. An active infection with Histoplasma capsulatum

Answer 11

d. An active infection with Histoplasma capsulatum

Question 12

A limiting factor in reliably being able to detect anti-fungal antibodies in an acute infection is
a. the lack of humoral response to fungal agents caused by immunosuppression.
b. current assays lack specificity.
c. antibodies are not normally formed against most fungi.
d. antibodies tend to remain at low titer as a mycosis develops.
a. the lack of humoral response to fungal agents caused by immunosuppression.

Answer 12

a. the lack of humoral response to fungal agents caused by immunosuppression.

Question 13

False positives may be observed in latex agglutination tests for the capsular antigen of Cryptococcus neoformans because of
a. the use of serum instead of CSF.
b. the presence of rheumatoid factor in the specimen.
c. cross-reactivity with other fungal antigens.
d. the low specificity of the assay.

Answer 13

b. the presence of rheumatoid factor in the specimen.

Question 14

A 27-year-old man from Ohio, diagnosed with AIDS, developed chest pains. After a short period of time he also developed severe headaches with dizziness. In his free time, his hobby was exploring caves (a spelunker). His physician ordered a sputum culture and spinal tap and both were positive for a yeastlike fungus. These findings are most consistent with infection by

a. Candida albicans.
b. Coccidioides immitis.
c. Cryptococcus neoformans.
d. Histoplasma capsulatum.

Answer 14

d. Histoplasma capsulatum.

Question 15

Which of the following serological tests detects the polysaccharide capsule antigen in serum and CSF of patients with suspected infection with Cryptococcus neoformans?
a. Complement fixation (CF)
b. India ink test
c. Latex agglutination (LA)
d. Hemagglutination test

Answer 15

c. Latex agglutination (LA)

Question 16

Which of the following is a nondimorphic fungus that is found in concentrated bird droppings and can readily cause meningitis in immunocompromised individuals?
a. Coccidioides immitis
b. Candida albicans
c. Cryptococcus neoformans
d. Histoplasma capsulatum

Answer 16

c. Cryptococcus neoformans