Q: A patient is prescribed an antibiotic with a therapeutic index (TI) of 2. Another drug has a TI of 10. Which statement is correct regarding the safety of these drugs?

The drug with TI = 10 is safer because $$TI = \frac{\text{toxic dose}}{\text{effective dose}}$$ and a higher TI means a wider margin of safety.

Question 1

Which of the following best describes the main goal of antimicrobial chemotherapy?

Accepted Answer

To administer a drug that destroys the infective agent without harming the host’s cells

Question 2

Which of the following is a characteristic of an ideal antimicrobial drug?

Accepted Answer

It is microbicidal rather than microbiostatic

Question 3

A patient is prescribed an antibiotic with a therapeutic index (TI) of 2. Another drug has a TI of 10. Which statement is correct regarding the safety of these drugs?

Accepted Answer

The drug with TI = 10 is safer because $$TI = \frac{	ext{toxic dose}}{	ext{effective dose}}$$ and a higher TI means a wider margin of safety.

Question 4

Which method is commonly used to determine the minimum inhibitory concentration (MIC) of an antibiotic?

Accepted Answer

Tube dilution test

Question 5

Which of the following drugs acts by inhibiting bacterial cell wall synthesis?

Accepted Answer

Penicillin

Question 6

A patient develops a vaginal yeast infection after a course of antibiotics for a urinary tract infection. This is an example of:

Accepted Answer

Superinfection

Question 7

Which of the following mechanisms is NOT a common way bacteria develop resistance to antibiotics?

Accepted Answer

Increasing the rate of host cell apoptosis

Question 8

Which of the following statements about broad-spectrum antibiotics is correct?

Accepted Answer

They are effective against a wide variety of microbial types, including both gram-positive and gram-negative bacteria.

Question 9

Which of the following is a major adverse effect associated with the use of polymyxins?

Accepted Answer

Kidney damage (nephrotoxicity)

Question 10

Which of the following best explains why it is difficult to develop vaccines against helminths (worms)?

Accepted Answer

Helminths have complex life cycles and can evade the host immune system.

Question 11

Which of the following drugs is used to treat infections caused by Mycobacterium tuberculosis and acts only against growing cells?

Accepted Answer

Isoniazid

Question 12

A hospital patient develops diarrhea after antibiotic treatment, and laboratory tests confirm Clostridioides difficile overgrowth. What is the most likely explanation?

Accepted Answer

A superinfection due to disruption of normal microbiota

Question 13

Which of the following is a mechanism of action for sulfonamide antibiotics?

Accepted Answer

They interfere with folic acid synthesis by blocking enzymes required for tetrahydrofolate production.

Question 14

Which of the following is a real-world consequence of the overuse of antibiotics in livestock?

Accepted Answer

The spread of drug-resistant bacteria from animals to humans

Question 15

Which of the following is a correct pairing of an antibiotic and its cellular target?

Accepted Answer

Ciprofloxacin – DNA gyrase

Question 16

Which of the following is a plausible reason for treatment failure in a patient receiving an antibiotic?

Accepted Answer

The drug cannot diffuse into the infected body compartment

Question 17

Which of the following is a novel approach to antimicrobial therapy currently under investigation?

Accepted Answer

CRISPR technology targeting bacterial genes

Question 18

Which of the following statements about selective toxicity is correct?

Accepted Answer

Selective toxicity refers to the ability of a drug to target microbial cells without harming host cells.

Question 19

Which of the following is a correct statement about the Kirby–Bauer technique?

Accepted Answer

It measures the zone of inhibition around antibiotic discs to assess bacterial susceptibility.

Question 20

Which of the following is a reason why antifungal drugs can be toxic to humans?

Accepted Answer

Fungal cells are eukaryotic and share similarities with human cells.

Chapter 12: Antimicrobial Treatment – Principles, Drug Groups, and Resistance

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