Question 1

Which of the following best describes the mechanism of action of beta-lactam antibiotics such as penicillin?

Accepted Answer

They bind to enzymes that cross-link NAM subunits, weakening the peptidoglycan layer and causing cell lysis.

Question 2

A patient is prescribed an antibiotic that binds to the 50S ribosomal subunit and prevents translocation during protein synthesis. Which class of antibiotic is most likely being used?

Accepted Answer

Macrolides

Question 3

Which of the following drugs is effective against mycobacteria due to its ability to disrupt mycolic acid synthesis?

Accepted Answer

Isoniazid

Question 4

A bacterial strain is found to be resistant to penicillin due to the production of an enzyme that breaks a specific bond in the antibiotic. What is the name of this enzyme and which bond does it break?

Accepted Answer

Beta-lactamase; it breaks the bond in the beta-lactam ring: $$\mathrm{C-N}$$

Question 5

Which of the following best explains why amphotericin B is effective against fungi but not bacteria?

Accepted Answer

It binds to ergosterol, which is present in fungal membranes but absent in bacterial membranes.

Question 6

Which of the following is a mechanism by which bacteria can acquire resistance to multiple antibiotics in a hospital setting?

Accepted Answer

Acquisition of R-plasmids via conjugation

Question 7

A patient is treated with a sulfonamide for a urinary tract infection. What is the primary mechanism by which sulfonamides inhibit bacterial growth?

Accepted Answer

They are metabolic antagonists that inhibit folic acid synthesis by competing with para-aminobenzoic acid (PABA).

Question 8

Which of the following scenarios best illustrates cross-resistance?

Accepted Answer

A bacterium resistant to one aminoglycoside is also resistant to other aminoglycosides due to a shared mechanism of action.

Question 9

Which of the following is NOT a common mechanism of antibiotic resistance in bacteria?

Accepted Answer

Inhibition of host immune response

Question 10

A hospital patient develops a urinary tract infection caused by a Gram-negative bacterium. Which of the following antibiotics would be most appropriate based on its extended spectrum of activity?

Accepted Answer

Ampicillin

Question 11

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

Accepted Answer

They inhibit prokaryotic DNA gyrase, preventing DNA replication.

Question 12

Which of the following is a consequence of using antibiotics for viral infections such as the common cold?

Accepted Answer

Selection for antibiotic-resistant bacterial mutants

Question 13

A new antibiotic is found to block the secretion of NAG and NAM from the cytoplasm. Which antibiotic does this mechanism most closely resemble?

Accepted Answer

Bacitracin

Question 14

Which of the following best explains why antibiotics that inhibit cell wall synthesis are only effective against growing bacterial cells?

Accepted Answer

They prevent the formation of new peptidoglycan but do not affect existing cell wall material.

Question 15

Which of the following is a real-world example of how misuse of antibiotics can lead to the development of 'superbugs'?

Accepted Answer

Using antibiotics in animal feed, which selects for resistant bacteria that can infect humans.

Question 16

Which of the following drugs is most likely to be used in combination with bacitracin and neomycin in an over-the-counter topical preparation?

Accepted Answer

Polymyxin B

Question 17

A patient with HIV is prescribed a drug that inhibits reverse transcriptase. Why does this drug not harm human cells?

Accepted Answer

Humans lack reverse transcriptase, so the drug targets only the viral enzyme.

Question 18

Which of the following best describes the action of tetracyclines?

Accepted Answer

They block the docking site of tRNA on the 30S ribosomal subunit, inhibiting protein synthesis.

Question 19

Which of the following is a likely outcome if a patient fails to complete the prescribed regimen of antibiotics?

Accepted Answer

The remaining bacterial population may become resistant to the antibiotic.

Antimicrobial Drugs: Mechanisms, Spectrum, and Resistance

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