Q: Which of the following equations correctly expresses the therapeutic index of an antimicrobial drug?

$$\text{Therapeutic Index} = \frac{\text{Dose toxic to patient}}{\text{Dose used for therapy}}$$

Question 1

Which of the following best describes Paul Ehrlich's contribution to antimicrobial therapy?

Accepted Answer

He synthesized arsenic compounds, such as Salvarsan, to selectively kill microbial pathogens without harming the human host.

Question 2

Which of the following statements about chemotherapeutic agents is correct?

Accepted Answer

They are chemicals used to treat disease, including antimicrobial drugs.

Question 3

Gerhard Domagk's discovery of Prontosil led to the development of which important class of drugs?

Accepted Answer

Sulfa drugs, such as sulfanilamide

Question 4

Which of the following best explains why Prontosil was effective in animals but not in test tubes?

Accepted Answer

It required activation by enzymes in the blood to produce the active compound sulfanilamide.

Question 5

What is the principle of selective toxicity in antimicrobial therapy?

Accepted Answer

The drug should cause greater harm to microbes than to the human host by targeting structures unique to microbes.

Question 6

Which of the following equations correctly expresses the therapeutic index of an antimicrobial drug?

Accepted Answer

$$	ext{Therapeutic Index} = \frac{	ext{Dose toxic to patient}}{	ext{Dose used for therapy}}$$

Question 7

A patient is prescribed an antimicrobial drug that is only effective if the patient’s immune system eliminates the pathogen after growth is inhibited. Which type of drug is this?

Accepted Answer

Bacteriostatic

Question 8

Why are broad-spectrum antimicrobials sometimes problematic for patients?

Accepted Answer

They can disrupt normal microbiota, leading to secondary infections.

Question 9

Which of the following mechanisms is NOT a common way bacteria acquire resistance to antimicrobial drugs?

Accepted Answer

Acquisition of resistance genes from viruses

Question 10

A laboratory is testing a new antibiotic. They determine the minimum inhibitory concentration (MIC) by serially diluting the drug and observing bacterial growth. What does the MIC represent?

Accepted Answer

The lowest concentration that prevents visible bacterial growth

Question 11

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

Accepted Answer

They competitively inhibit enzymes that catalyze the formation of peptide bridges in peptidoglycan, weakening the cell wall.

Question 12

A strain of Staphylococcus aureus is resistant to methicillin. Which of the following best explains this resistance?

Accepted Answer

The bacterium has altered penicillin-binding proteins (PBPs) that have low affinity for all beta-lactam drugs.

Question 13

Which of the following is a reason why combination therapy is often used to treat Mycobacterium tuberculosis infections?

Accepted Answer

To decrease the chance that resistant mutants will emerge, since simultaneous resistance to multiple drugs is less likely.

Question 14

Which of the following best describes the Kirby-Bauer disc diffusion test?

Accepted Answer

It assesses bacterial susceptibility to antibiotics by measuring zones of inhibition around antibiotic discs on an agar plate.

Question 15

Which of the following is a mechanism by which bacteria can decrease the uptake of an antimicrobial drug?

Accepted Answer

Changes in porin proteins of the outer membrane

Question 16

Which of the following equations correctly represents the calculation of the minimum bactericidal concentration (MBC)?

Accepted Answer

$$	ext{MBC} = 	ext{Lowest concentration that kills 99.9\% of cells in vitro}$$

Question 17

Which of the following is a real-world consequence of the misuse of antibiotics in animal feed?

Accepted Answer

It selects for drug-resistant microbes, which can be transferred to humans.

Question 18

Which of the following best explains why antibiotics are ineffective against viral infections such as the common cold?

Accepted Answer

Viruses lack the structures targeted by antibiotics, such as cell walls and ribosomes.

Antimicrobial Medications: History, Importance, and Development

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