Question 1

Which of the following best describes an attenuated vaccine, and why are such vaccines generally more effective than inactivated vaccines?

Accepted Answer

A vaccine containing live, weakened pathogens; they are more effective because they closely mimic a natural infection and induce a stronger, longer-lasting immune response.

Question 2

A patient receives a vaccine composed of a recombinant adenovirus expressing the malaria-CS protein. This vaccine is best classified as which type?

Accepted Answer

Recombinant vector vaccine

Question 3

Which of the following best explains why the oral (Sabin) polio vaccine could sometimes cause polio, but the injected (Salk) vaccine does not?

Accepted Answer

The Sabin vaccine contains live, attenuated virus that can rarely revert to a virulent form, while the Salk vaccine contains inactivated virus that cannot replicate.

Question 4

A diagnostic test for a viral infection yields a positive result in 95 out of 100 infected patients, but also gives a positive result in 10 out of 100 uninfected patients. What are the sensitivity and specificity of this test? Use the following formulas:

$$	ext{Sensitivity} = \frac{	ext{True Positives}}{	ext{True Positives} + 	ext{False Negatives}}$$

$$	ext{Specificity} = \frac{	ext{True Negatives}}{	ext{True Negatives} + 	ext{False Positives}}$$

Accepted Answer

Sensitivity: 95%, Specificity: 90%

Question 5

Which of the following best describes the mechanism of a precipitation reaction in immunology?

Accepted Answer

Soluble antigens and antibodies form visible complexes only when present in optimal proportions, resulting in a visible precipitate.

Question 6

A patient is diagnosed with hemolytic disease of the newborn (HDN). Which of the following best explains why HDN does not occur during the first pregnancy of an Rh-negative mother with an Rh-positive fetus?

Accepted Answer

The mother does not produce significant anti-Rh antibodies until after exposure to fetal blood during delivery.

Question 7

Which of the following is the most common mechanism by which bacteria develop resistance to penicillin?

Accepted Answer

Production of beta-lactamase enzymes that hydrolyze the beta-lactam ring

Question 8

A patient is prescribed both penicillin and tetracycline for a bacterial infection. However, the infection does not resolve as expected. Which of the following best explains this antagonism?

Accepted Answer

Tetracycline is bacteriostatic and inhibits bacterial growth, which reduces the effectiveness of penicillin, a bactericidal drug that requires actively growing cells.

Question 9

Which of the following best explains why sulfa drugs selectively inhibit bacterial growth without harming human cells?

Accepted Answer

Sulfa drugs inhibit the synthesis of folic acid, which bacteria must synthesize but humans obtain from their diet.

Question 10

A patient with a fungal infection is treated with amphotericin B. What is the primary target of this antifungal drug?

Accepted Answer

Ergosterol in the fungal cell membrane

Question 11

A 5-year-old child presents with a severe cough characterized by a 'whooping' sound. Laboratory tests confirm Bordetella pertussis infection. Which cells are primarily targeted by the pathogen to cause this symptom?

Accepted Answer

Ciliated epithelial cells of the respiratory tract

Question 12

Which of the following best explains why the lower respiratory tract is normally nearly sterile?

Accepted Answer

Ciliary escalator action and alveolar macrophages remove or destroy inhaled microorganisms.

Question 13

A patient is diagnosed with meningitis caused by Listeria monocytogenes after consuming refrigerated deli meats. Why is this pathogen frequently associated with refrigerated foods?

Accepted Answer

It is a psychrotroph capable of growing at low temperatures found in refrigerators.

Question 14

Which of the following best describes the function of an adjuvant in a vaccine formulation?

Accepted Answer

To enhance the immune response to the antigen

Question 15

A patient is given a direct fluorescent-antibody (FA) test to detect a pathogen. Which of the following best describes the principle of this test?

Accepted Answer

A fluorescent-labeled antibody binds directly to the antigen in the patient sample, and fluorescence indicates a positive result.

Question 16

Which of the following is the most common cause of cystitis, especially in females, and why?

Accepted Answer

Escherichia coli, due to its proximity to the urethra and its ability to adhere to uroepithelial cells

Question 17

A patient is diagnosed with Graves’ disease. Which organ is primarily affected in this autoimmune disorder?

Accepted Answer

Thyroid gland

Question 18

Which of the following best explains why acyclovir is effective against herpesvirus infections but has minimal toxicity to human cells?

Accepted Answer

Acyclovir is activated only by a viral-encoded enzyme (thymidine kinase), so it accumulates primarily in infected cells.

Question 19

Which of the following best describes the role of the human leukocyte antigen (HLA) complex in tissue transplantation?

Accepted Answer

The HLA complex encodes cell-surface proteins that are recognized as self or nonself by the immune system, influencing transplant compatibility.

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