Q: Which of the following equations correctly represents the calculation of antibody titer in a serial dilution ELISA test?

$$Titer = \frac{1}{\text{highest dilution with positive result}}$$

Q: Which equation correctly represents the calculation of sensitivity in a diagnostic test?

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

Question 1

Which of the following best explains why attenuated vaccines generally provide longer-lasting immunity compared to inactivated vaccines?

Accepted Answer

Attenuated vaccines replicate in the host, mimicking natural infection and stimulating both humoral and cellular immune responses.

Question 2

A patient receives a blood transfusion and develops hemolysis due to ABO incompatibility. Which immunological mechanism is primarily responsible for this reaction?

Accepted Answer

Type II hypersensitivity (antibody-mediated cytotoxicity)

Question 3

Which of the following equations correctly represents the calculation of antibody titer in a serial dilution ELISA test?

Accepted Answer

$$Titer = \frac{1}{	ext{highest dilution with positive result}}$$

Question 4

A newborn is diagnosed with hemolytic disease due to Rh incompatibility. Which antibody class is most likely responsible for crossing the placenta and causing this condition?

Accepted Answer

IgG

Question 5

Which of the following best describes the mechanism of action of penicillin?

Accepted Answer

Inhibits peptidoglycan cross-linking by binding to transpeptidase enzymes

Question 6

A patient is exposed to Mycobacterium tuberculosis but does not develop active disease. Which immune response is most critical in containing the infection?

Accepted Answer

Cell-mediated immunity involving CD4+ helper T cells and macrophage activation

Question 7

Which of the following statements about the Sabin and Salk polio vaccines is correct?

Accepted Answer

The Sabin vaccine is a live attenuated vaccine administered orally, providing mucosal immunity.

Question 8

Which of the following is the most common cause of urinary tract infections (UTIs) in females?

Accepted Answer

Escherichia coli

Question 9

A patient develops a rash and joint pain after receiving a large dose of antiserum. Which type of hypersensitivity reaction is most likely responsible?

Accepted Answer

Type III (immune complex-mediated)

Question 10

Which of the following best explains the concept of herd immunity?

Accepted Answer

Protection of unvaccinated individuals due to a high proportion of immune individuals in the population

Question 11

Which equation correctly represents the calculation of sensitivity in a diagnostic test?

Accepted Answer

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

Question 12

Which of the following is a major reason why HIV infection is difficult to eradicate from the body?

Accepted Answer

HIV integrates its genome into host DNA, allowing latent infection.

Question 13

A patient with Graves' disease is found to have autoantibodies against the thyroid-stimulating hormone (TSH) receptor. What is the effect of these autoantibodies?

Accepted Answer

They stimulate the TSH receptor, causing hyperthyroidism.

Question 14

Which of the following best describes the role of the major histocompatibility complex (MHC) in transplantation?

Accepted Answer

MHC molecules present foreign antigens to T cells, leading to graft rejection if mismatched.

Question 15

Which of the following is the most common cause of bacterial meningitis in adults?

Accepted Answer

Streptococcus pneumoniae

Question 16

A patient is diagnosed with trichomoniasis. Which of the following symptoms is most likely to be present in the male reproductive system?

Accepted Answer

Painful urination and urethral discharge

Question 17

Which of the following best explains why antibiotics with a broad spectrum of activity may disrupt the normal microbiota and lead to superinfections?

Accepted Answer

Broad-spectrum antibiotics kill both pathogenic and beneficial bacteria, allowing opportunistic organisms to proliferate.

Question 18

Which of the following is the primary function of the blood-brain barrier in the context of infection?

Accepted Answer

To prevent pathogens and many drugs from entering the central nervous system

Question 19

Which of the following best describes the mechanism of action of acyclovir, an antiviral drug?

Accepted Answer

Inhibits synthesis of viral DNA by acting as a nucleoside analog

Microbiology: Immunology, Antimicrobial Drugs, and Infectious Diseases – Study Guide

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