$$\text{Therapeutic Index} = \frac{\text{Dose toxic to patient}}{\text{Dose typically used for treatment}}$$

Question 1

Which of the following best describes the term 'chemotherapeutics' in microbiology?

Accepted Answer

Molecules used to fight disease, including both natural and synthetic antimicrobials.

Question 2

Ehrlich's concept of the 'magic bullet' led to the discovery of which compound for treating syphilis?

Accepted Answer

Salvarsan (arsphenamine)

Question 3

Which microorganism is responsible for producing more than two-thirds of all natural antibiotics used today?

Accepted Answer

Streptomyces

Question 4

Why are semi-synthetic antibiotics often preferred over natural antibiotics?

Accepted Answer

They can be chemically modified to increase efficacy or alter spectrum of activity.

Question 5

A broad-spectrum antibiotic is most appropriately prescribed when:

Accepted Answer

The specific causative agent of infection is unknown.

Question 6

What is the main risk associated with the use of broad-spectrum antibiotics?

Accepted Answer

Development of antibiotic resistance and disruption of normal microbiota.

Question 7

Which equation best represents the therapeutic index of an antimicrobial drug?

Accepted Answer

$$	ext{Therapeutic Index} = \frac{	ext{Dose toxic to patient}}{	ext{Dose typically used for treatment}}$$

Question 8

Why is it inherently easier to treat bacterial infections with antibiotics compared to protozoan and fungal infections?

Accepted Answer

Bacterial cells are prokaryotic and have unique targets not found in human cells.

Question 9

Which mechanism of action is associated with beta-lactam antibiotics?

Accepted Answer

Interference with cell wall crosslinking.

Question 10

Polymyxin B is primarily used as a topical antibiotic because:

Accepted Answer

It is too toxic for systemic use due to its effect on plasma membranes.

Question 11

Sulfonamides (sulfa drugs) have a high therapeutic index because:

Accepted Answer

Humans do not synthesize folic acid; we absorb it from food.

Question 12

Which of the following drugs inhibits bacterial DNA replication by interfering with the gyrase enzyme?

Accepted Answer

Quinolones (e.g., ciprofloxacin)

Question 13

A synergistic drug combination is best exemplified by:

Accepted Answer

Amoxicillin and potassium clavulanate (Augmentin)

Question 14

Which of the following is NOT a mechanism by which bacteria acquire antibiotic resistance?

Accepted Answer

Direct destruction of human immune cells

Question 15

Which of the following is a major consequence of inappropriate prescription and use of antibiotics?

Accepted Answer

Rise in antibiotic resistance among pathogens

Question 16

Why are systemic fungal infections difficult to treat?

Accepted Answer

Fungal cells are eukaryotic and similar to human cells, making selective toxicity challenging.

Question 17

Which antifungal drug is traditionally used for systemic infections but is limited by kidney toxicity?

Accepted Answer

Polyenes (e.g., Amphotericin)

Question 18

Flagyl (metronidazole) is prescribed for certain protozoan infections because it targets:

Accepted Answer

Anaerobic metabolism

Question 19

Acyclovir is an antiviral drug that acts as a nucleoside analog. What is its primary mechanism of action?

Accepted Answer

Incorporates into viral DNA and blocks further replication

Question 20

AZT was the first drug used for HIV treatment. What is its mechanism?

Accepted Answer

Blocks the activity of reverse transcriptase as a nucleoside analog

Antimicrobial Drugs: Mechanisms, Resistance, and Clinical Applications

Study Guide - Practice Questions