Question 1

Which of the following best describes the principle of selective toxicity in antimicrobial chemotherapy?

Accepted Answer

The drug selectively destroys pathogens without harming host cells.

Question 2

Which of the following antibiotics is produced by the fungus Penicillium chrysogenum and is effective primarily against gram-positive bacteria?

Accepted Answer

Penicillin

Question 3

A patient develops a Clostridioides difficile infection after broad-spectrum antibiotic therapy. This is an example of:

Accepted Answer

Superinfection

Question 4

Which of the following drugs inhibits bacterial cell wall synthesis by preventing the cross-linking of peptidoglycans?

Accepted Answer

Penicillin

Question 5

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

Accepted Answer

Increased uptake of the drug into the cell

Question 6

Aminoglycosides, such as streptomycin, exert their antibacterial effect by:

Accepted Answer

Changing the shape of the 30S subunit of the 70S ribosome

Question 7

Which of the following statements about sulfonamides is correct?

Accepted Answer

They are structural analogs of para-aminobenzoic acid (PABA) and inhibit folic acid synthesis.

Question 8

Which of the following is a reason why combination therapy with trimethoprim and sulfamethoxazole is effective?

Accepted Answer

The drugs act synergistically to block sequential steps in folic acid synthesis.

Question 9

Which of the following best explains why vancomycin is considered a 'last line' antibiotic?

Accepted Answer

It is reserved for treating infections caused by multidrug-resistant gram-positive bacteria such as MRSA.

Question 10

A hospital is experiencing an outbreak of infections caused by a bacterium that produces beta-lactamase. Which class of antibiotics is most likely to be ineffective?

Accepted Answer

Beta-lactams (e.g., penicillins and cephalosporins)

Question 11

Which of the following is a potential adverse effect of chloramphenicol therapy?

Accepted Answer

Aplastic anemia

Question 12

Which of the following statements about the Kirby-Bauer disk diffusion method is correct?

Accepted Answer

It measures the zone of inhibition to assess the sensitivity of bacteria to antibiotics.

Question 13

Which of the following drugs is used to treat tuberculosis by inhibiting the synthesis of mycolic acid in mycobacteria?

Accepted Answer

Isoniazid

Question 14

A patient is prescribed a combination of two antibiotics, but the effect is less than when either drug is used alone. This is an example of:

Accepted Answer

Antagonism

Question 15

Which of the following is a mechanism by which antiviral drugs can inhibit viral replication?

Accepted Answer

Blocking viral entry or fusion with the host cell

Question 16

Which of the following best describes the action of quinolones such as ciprofloxacin?

Accepted Answer

Inhibit DNA gyrase, preventing DNA replication

Question 17

A patient with a fungal infection is prescribed amphotericin B. What is the primary mechanism of action of this drug?

Accepted Answer

Binds to ergosterol in fungal membranes, increasing permeability

Question 18

Which of the following is a recommended strategy to prevent the development of antibiotic resistance?

Accepted Answer

Completing the full prescribed course of antibiotics

Question 19

Which of the following best explains why tetracyclines can lead to superinfections?

Accepted Answer

They suppress normal intestinal microbiota, allowing resistant organisms to proliferate.

Question 20

Which of the following is a correct statement about the therapeutic index of an antibiotic?

Accepted Answer

It is the ratio of the toxic dose to the effective dose.

Antimicrobial Drugs: Mechanisms, Classes, and Resistance

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