Question 1

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

Accepted Answer

The drug targets differences between host and pathogen to minimize host damage.

Question 2

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

Accepted Answer

Alexander Fleming; Penicillium chrysogenum

Question 3

Beta-lactam antibiotics, such as penicillins, inhibit bacterial growth by:

Accepted Answer

Inhibiting the cross-linking of NAM subunits in peptidoglycan

Question 4

Which of the following drugs is most likely to be nephrotoxic and is used primarily as a topical antibiotic for Gram-negative skin infections?

Accepted Answer

Polymyxin

Question 5

A patient with tuberculosis is prescribed a drug that disrupts mycolic acid synthesis. Which drug is most likely being used?

Accepted Answer

Isoniazid

Question 6

Which of the following best explains why broad-spectrum antibiotics can lead to superinfections?

Accepted Answer

They kill normal microbiota, reducing microbial antagonism and allowing resistant pathogens to thrive.

Question 7

Which of the following is a mechanism by which bacteria can acquire resistance to antimicrobial drugs?

Accepted Answer

By acquiring R plasmids through conjugation, transformation, or transduction

Question 8

A Kirby-Bauer test is performed to determine the susceptibility of a bacterial isolate to various antibiotics. What does the 'zone of inhibition' represent?

Accepted Answer

The region where bacterial growth is inhibited by the antibiotic

Question 9

Which of the following equations correctly represents the therapeutic index (TI) of an antimicrobial drug?

Accepted Answer

$$TI = \frac{Toxic\ dose}{MIC}$$

Question 10

Which of the following drugs acts by inhibiting the synthesis of folic acid in bacteria, and what is its mechanism?

Accepted Answer

Sulfonamides; competitive inhibition of the enzyme that converts PABA to dihydrofolic acid

Question 11

Which of the following is a reason why antiviral drugs are generally more limited in number compared to antibacterial drugs?

Accepted Answer

Viruses use host cell machinery for replication, making selective toxicity difficult.

Question 12

Which of the following statements about the use of combination antimicrobial therapy is correct?

Accepted Answer

Synergism occurs when one drug enhances the effect of another.

Question 13

Which of the following is a common side effect of tetracycline antibiotics, especially in children and pregnant women?

Accepted Answer

Permanent discoloration of teeth

Question 14

Which of the following best describes the action of amphotericin B?

Accepted Answer

It binds to ergosterol in fungal membranes, forming pores that disrupt membrane integrity.

Question 15

A patient is prescribed an oral antibiotic for a skin infection. Which route of administration is being used?

Accepted Answer

Oral

Question 16

Which of the following mechanisms is NOT a way bacteria can resist the effects of antibiotics?

Accepted Answer

Increasing uptake of the antibiotic into the cell

Question 17

Which of the following statements about minimum inhibitory concentration (MIC) is correct?

Accepted Answer

MIC is the lowest concentration of drug that inhibits visible growth of a microorganism.

Question 18

Which of the following is a unique target for antifungal drugs that is not found in human cells?

Accepted Answer

Ergosterol

Question 19

Which of the following best explains why drugs that inhibit protein synthesis can have side effects in humans?

Accepted Answer

Human mitochondria contain 70S ribosomes, which are similar to bacterial ribosomes.

Controlling Microbial Growth in the Body: Antimicrobial Drugs (Chapter 10 Study Notes)

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