Question 1

Which scientist is credited with the discovery of penicillin, and what was the source organism?

Accepted Answer

Alexander Fleming; Penicillium chrysogenum

Question 2

Why are antibiotics generally ineffective against the common cold?

Accepted Answer

The common cold is caused by viruses, which lack the structures targeted by antibiotics.

Question 3

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

Accepted Answer

They prevent cross-linkage of NAM subunits in peptidoglycan, weakening the cell wall.

Question 4

Which equation best represents the osmotic lysis of a bacterial cell after exposure to beta-lactam antibiotics?

Accepted Answer

$$\Delta P = P_{in} - P_{out}$$, where $$\Delta P is $$the osmotic pressure difference across the cell wall.

Question 5

Which of the following drugs is most likely to be effective against Mycobacterium tuberculosis due to its mechanism of action?

Accepted Answer

Isoniazid, because it disrupts mycolic acid synthesis.

Question 6

Which of the following statements about semisynthetic antibiotics is correct?

Accepted Answer

They are natural antibiotics that have been chemically modified to improve their properties.

Question 7

A patient is prescribed mupirocin for a Gram-positive skin infection. What is the drug’s mechanism of action?

Accepted Answer

It binds to isoleucyl-tRNA synthetase, preventing isoleucine incorporation during protein synthesis.

Question 8

Which of the following antimicrobials is produced by a fungus and is effective against Gram-positive bacteria?

Accepted Answer

Penicillin G

Question 9

Which of the following best explains why polymyxin is not used to treat Gram-positive bacterial infections?

Accepted Answer

Gram-positive bacteria lack the outer membrane targeted by polymyxin.

Question 10

Which of the following drugs acts by inhibiting folic acid synthesis in bacteria, and what is the consequence for the cell?

Accepted Answer

Sulfonamides; the cell cannot synthesize nucleotides for DNA and RNA.

Question 11

Which of the following is a reason why there are fewer antiviral drugs compared to antibacterial drugs?

Accepted Answer

Viruses use host cell machinery, making selective toxicity difficult.

Question 12

Which of the following best describes the action of quinolones and fluoroquinolones?

Accepted Answer

They inhibit DNA gyrase, preventing DNA replication in prokaryotes.

Question 13

A new drug is found to inhibit the enzyme responsible for glucan synthesis in fungal cell walls. To which class does this drug most likely belong?

Accepted Answer

Echinocandins

Question 14

Which of the following is a plausible reason why beta-lactam antibiotics are only effective against actively growing bacterial cells?

Accepted Answer

They inhibit the synthesis of new peptidoglycan, which only occurs during cell growth.

Question 15

Which of the following best explains why amphotericin B is selectively toxic to fungi but not to bacteria?

Accepted Answer

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

Question 16

Which of the following is a correct pairing of antimicrobial and its source organism?

Accepted Answer

Vancomycin; Amycolatopsis orientalis

Question 17

Which of the following drugs would be most appropriate to inhibit HIV replication by targeting an enzyme not found in humans?

Accepted Answer

Reverse transcriptase inhibitors

Question 18

A patient is treated with a drug that blocks the movement of mRNA through the ribosome by binding to the 50S subunit. Which class of drugs is this?

Accepted Answer

Lincosamides or macrolides

Question 19

Which of the following best describes the action of protease inhibitors in the treatment of HIV?

Accepted Answer

They interfere with an enzyme required for viral protein processing.

Question 20

Which of the following is a likely outcome if a bacterium is exposed to a beta-lactam antibiotic during the stationary phase of growth?

Accepted Answer

The bacterium will likely survive because beta-lactams do not affect existing peptidoglycan.

Controlling Microbial Growth in the Body: Antimicrobial Drugs

Study Guide - Practice Questions