Q: Which of the following equations correctly represents the therapeutic index (TI) of a drug?

$$TI = \frac{\text{Toxic Dose}}{\text{Therapeutic Dose}}$$

Question 1

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

Accepted Answer

The ability of a drug to kill harmful microbes without damaging the host

Question 2

A patient is prescribed a drug that inhibits the synthesis of peptidoglycan. Which type of microorganism will this drug most likely target?

Accepted Answer

Bacteria

Question 3

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

Accepted Answer

$$TI = \frac{	ext{Toxic Dose}}{	ext{Therapeutic Dose}}$$

Question 4

Which of the following is a major risk associated with the use of broad-spectrum antibiotics?

Accepted Answer

Development of superinfections such as those caused by Clostridioides difficile

Question 5

Aminoglycosides, such as streptomycin, exert their antibacterial effect by:

Accepted Answer

Changing the shape of the 30S subunit of the 70S ribosome

Question 6

Which of the following best explains why penicillin is more effective against Gram-positive bacteria than Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thicker peptidoglycan layer that is more accessible to penicillin

Question 7

A patient develops a yeast infection after taking antibiotics for a bacterial infection. This is an example of:

Accepted Answer

Superinfection

Question 8

Which of the following drugs is a semisynthetic penicillin designed to resist inactivation by penicillinase?

Accepted Answer

Methicillin

Question 9

Which mechanism of resistance allows bacteria to pump antibiotics out of the cell before they can act?

Accepted Answer

Rapid efflux of the antibiotic

Question 10

A patient is treated with a combination of trimethoprim and sulfamethoxazole. The combined effect is greater than either drug alone. This is an example of:

Accepted Answer

Synergism

Question 11

Which of the following statements about vancomycin is correct?

Accepted Answer

It is used as a last line of defense against MRSA

Question 12

Which of the following best describes the action of sulfonamides?

Accepted Answer

They competitively inhibit the enzyme that converts PABA to dihydrofolic acid

Question 13

Which of the following is a correct pairing of drug and its primary mode of action?

Accepted Answer

Polymyxin B – Injury to plasma membrane

Question 14

A patient with tuberculosis is prescribed isoniazid. What is the primary target of this drug?

Accepted Answer

Inhibition of mycolic acid synthesis in mycobacteria

Question 15

Which of the following is a potential adverse effect of chloramphenicol?

Accepted Answer

Aplastic anemia

Question 16

Which of the following best explains why using antibiotics for viral infections can contribute to antibiotic resistance?

Accepted Answer

Antibiotics select for resistant bacteria in the normal microbiota

Question 17

Which of the following is a correct statement about the Kirby-Bauer disk diffusion method?

Accepted Answer

It determines the sensitivity of an organism to an antibiotic by measuring the zone of inhibition

Question 18

Which of the following is a reason why healthcare workers should avoid unnecessary prescriptions of antibiotics?

Accepted Answer

To reduce the development of antibiotic-resistant bacteria

Question 19

Which of the following best describes the action of quinolones such as ciprofloxacin?

Accepted Answer

Inhibit DNA gyrase, interfering with DNA replication

Question 20

A patient is prescribed amphotericin B for a systemic fungal infection. Which of the following is a major concern with this drug?

Accepted Answer

It can cause severe kidney toxicity

Chemotherapeutic Agents: Principles and Applications in Microbiology

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