Question 1

Which of the following best describes the concept of selective toxicity in antimicrobial drugs?

Accepted Answer

Destruction of structures present in bacteria, not present in host; no damage done to the host

Question 2

Which antibiotic class inhibits cell wall synthesis by blocking transpeptidation of peptidoglycan strands?

Accepted Answer

Beta-lactam antibiotics

Question 3

A patient is treated with an antibiotic that is bacteriostatic. What is the expected effect on bacterial cell counts over time?

Accepted Answer

Total and viable cell count remain constant

Question 4

Which of the following is the lowest concentration of an antibiotic that stops visible growth of a microorganism?

Accepted Answer

Minimal inhibitory concentration (MIC)

Question 5

What is the primary mechanism of action for vancomycin?

Accepted Answer

Inhibits cell wall synthesis by binding to D-Ala-D-Ala terminus of peptidoglycan precursors

Question 6

Which of the following antibiotics is primarily active against Gram-positive bacteria and interferes with the synthesis of linear sugar strands of peptidoglycan?

Accepted Answer

Bacitracin

Question 7

Which process is inhibited by cycloserine in bacterial cell wall synthesis?

Accepted Answer

Racemization of L-alanine to D-alanine

Question 8

A tube in a broth dilution test shows no growth after exposure to an antibiotic. When this culture is inoculated onto antibiotic-free media, no growth is observed. What does this indicate?

Accepted Answer

The minimal bactericidal concentration (MBC) has been reached

Question 9

Which of the following is a correct description of the action of bactericidal antibiotics?

Accepted Answer

Killing of bacteria; effect is non-reversible

Question 10

Which antibiotic inhibits the enzyme UDP-N-acetylglucosamine-3-enolpyruvyltransferase (MurA) in peptidoglycan biosynthesis?

Accepted Answer

Fosfomycin

Question 11

Which of the following is a real-world consequence of widespread vancomycin use in animal feed?

Accepted Answer

Emergence of vancomycin-resistant Enterococcus

Question 12

Which of the following antibiotics acts by binding to the 30S ribosomal subunit?

Accepted Answer

Streptomycin

Question 13

What is the role of transpeptidase in bacterial cell wall synthesis?

Accepted Answer

Crosslinking of peptidoglycan strands

Question 14

Which of the following best explains why antibiotics that target peptidoglycan are selectively toxic to bacteria?

Accepted Answer

Peptidoglycan is present in bacterial cell walls but absent in eukaryotic cells

Question 15

Which of the following is NOT a site of action for antibiotics?

Accepted Answer

Lipid biosynthesis in mitochondria

Question 16

Which of the following equations represents the calculation of the zone of inhibition in an antibiotic disk diffusion assay?

Accepted Answer

$$d = 2r$$

Question 17

A new antibiotic is found to inhibit both growing and resting bacteria. Which mode of action does this suggest?

Accepted Answer

Bactericidal

Question 18

Which of the following is a common mechanism of resistance against beta-lactam antibiotics?

Accepted Answer

Production of beta-lactamase enzymes

Question 19

Which antibiotic is used for initial therapy of severe infections due to its broad-spectrum activity?

Accepted Answer

Carbapenems

Question 20

Which of the following best describes the action of antimetabolite antimicrobials?

Accepted Answer

Structurally related to normal substrate of an enzyme; bind to enzyme like normal substrate but block active site

Antimicrobial Drugs: Mechanisms, Actions, and Resistance

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