Question 1

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

Accepted Answer

The drug should be toxic to the infecting microbe, but relatively harmless to the host’s cells.

Question 2

Which of the following is a major reason why bacteria produce antibiotics in nature?

Accepted Answer

To inhibit the growth of competing microorganisms in their environment.

Question 3

Which of the following drugs is most likely to be effective against Mycobacterium tuberculosis due to its ability to disrupt mycolic acid synthesis?

Accepted Answer

Isoniazid

Question 4

A patient is prescribed a broad-spectrum antibiotic. Which of the following is a potential risk associated with this treatment?

Accepted Answer

Development of secondary or superinfections due to killing of normal flora

Question 5

Which of the following best explains how beta-lactam antibiotics, such as penicillin, inhibit bacterial growth?

Accepted Answer

They bind to enzymes that cross-link NAM subunits in peptidoglycan, weakening the cell wall.

Question 6

A bacterial strain is resistant to penicillin due to the production of an enzyme. Which enzyme is responsible for this resistance?

Accepted Answer

β-lactamase

Question 7

Which of the following drugs acts by binding to ergosterol in fungal membranes, causing membrane leakage?

Accepted Answer

Amphotericin B

Question 8

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

Accepted Answer

Acquisition of R-plasmids via transformation, transduction, or conjugation

Question 9

A patient develops a white coating on her tongue and excessive vaginal discharge after taking antibiotics. What is the most likely explanation for these symptoms?

Accepted Answer

The antibiotics disrupted her normal microbiota, leading to a superinfection.

Question 10

Which of the following drugs inhibits bacterial DNA gyrase, thereby preventing DNA replication?

Accepted Answer

Ciprofloxacin

Question 11

Which of the following is a characteristic of an ideal antimicrobial drug?

Accepted Answer

It is non-allergenic and has a long shelf life.

Question 12

Which of the following best describes the mechanism of action of sulfonamide drugs?

Accepted Answer

They inhibit the synthesis of folic acid by acting as competitive inhibitors of para-aminobenzoic acid (PABA).

Question 13

Which of the following is the primary target of macrolide antibiotics?

Accepted Answer

50S subunit of the bacterial ribosome

Question 14

A patient is diagnosed with a Candida infection. Which of the following drugs would most likely be prescribed?

Accepted Answer

Fluconazole

Question 15

Which of the following is a common side effect of using broad-spectrum antibiotics?

Accepted Answer

Overgrowth of normal flora leading to superinfections

Question 16

Which of the following is NOT a mechanism by which bacteria can resist the effects of antibiotics?

Accepted Answer

Increasing the permeability of the cell membrane to the drug

Question 17

Which of the following drugs is used to treat tapeworm infections by preventing ATP generation?

Accepted Answer

Niclosamide

Question 18

A Kirby-Bauer test is performed to determine antibiotic susceptibility. What does a large zone of inhibition around an antibiotic disc indicate?

Accepted Answer

The bacteria are susceptible to the antibiotic.

Question 19

Which of the following antiviral drugs works by inhibiting neuraminidase, thus preventing the release of new influenza virus particles?

Accepted Answer

Oseltamivir (Tamiflu)

Question 20

Which of the following best explains why misuse of antibiotics in animal feed can promote antibiotic resistance?

Accepted Answer

It selects for resistant bacterial strains, which can spread to humans.

Control of Microorganisms in the Body: Antimicrobial Drugs

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