Q: Which equation best represents the calculation of the minimum inhibitory concentration (MIC) in a broth dilution test?

MIC = $$\text{Lowest concentration of drug preventing visible growth}$$

Question 1

Which of the following best explains why fungal, protozoan, and helminthic infections are generally more difficult to treat than bacterial infections?

Accepted Answer

They possess eukaryotic cells, which share similarities with human cells, increasing the risk of host toxicity.

Question 2

A patient is diagnosed with a gram-negative bacterial infection. Which property of an antimicrobial drug would most likely increase its effectiveness against this pathogen?

Accepted Answer

The drug is small and hydrophilic.

Question 3

Which of the following mechanisms is responsible for the action of sulfonamides?

Accepted Answer

Competitive inhibition of folic acid synthesis by mimicking para-aminobenzoic acid (PABA).

Question 4

A bacterial strain produces penicillinase (β-lactamase). Which antibiotic would likely remain effective against this strain?

Accepted Answer

Semisynthetic penicillin

Question 5

Which of the following drugs inhibits protein synthesis by acting on 70S ribosomes?

Accepted Answer

Chloramphenicol

Question 6

A patient with tuberculosis is prescribed rifamycin. What is the primary mechanism of action for this drug?

Accepted Answer

Inhibition of mRNA synthesis

Question 7

Which equation best represents the calculation of the minimum inhibitory concentration (MIC) in a broth dilution test?

Accepted Answer

MIC = $$	ext{Lowest concentration of drug preventing visible growth}$$

Question 8

Which of the following is a plausible outcome when broad-spectrum antibiotics are used indiscriminately?

Accepted Answer

Increased risk of superinfection due to disruption of normal microbiota.

Question 9

A Kirby-Bauer disk-diffusion test is performed. After incubation, the zone of inhibition for Drug X is measured as 20 mm. What does this result most likely indicate?

Accepted Answer

The organism is sensitive to Drug X.

Question 10

Which of the following best describes the action of polyenes such as amphotericin B?

Accepted Answer

They combine with plasma membrane sterols, causing fungal cell death.

Question 11

A patient is prescribed a combination of two antibiotics. After treatment, both drugs are less effective than when used alone. What term best describes this interaction?

Accepted Answer

Antagonistic

Question 12

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

Accepted Answer

Enzymatic destruction of the drug

Question 13

Which of the following drugs is used primarily to treat skin infections caused by fungi by interfering with eukaryotic cell division?

Accepted Answer

Griseofulvin

Question 14

Which of the following statements about superbugs is correct?

Accepted Answer

They are bacteria resistant to several antibiotics.

Question 15

Which of the following is a correct description of the action of quinolones and fluoroquinolones?

Accepted Answer

They inhibit DNA gyrase, preventing DNA replication.

Question 16

A patient with a mycobacterial infection is prescribed isoniazid (INH). What is the primary target of this drug?

Accepted Answer

Cell wall synthesis in mycobacteria

Question 17

Which of the following equations best represents the calculation of the minimum bactericidal concentration (MBC) in a broth dilution test?

Accepted Answer

MBC = $$	ext{Lowest concentration of drug that kills bacteria}$$

Question 18

Which of the following is a major advantage of using semisynthetic penicillins over natural penicillins?

Accepted Answer

Semisynthetic penicillins are resistant to penicillinases and have a broader spectrum of activity.

Question 19

Which of the following statements about the use of antimicrobial agents is most accurate?

Accepted Answer

The risk versus benefit must be evaluated before antibiotics are used.

Antimicrobial Drugs: Mechanisms, Classes, and Resistance

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