Q: Which equation best represents the therapeutic index for an antibiotic?

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

Question 1

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

Accepted Answer

Alexander Fleming; Penicillium

Question 2

What is the primary mechanism by which penicillins exert their antibacterial effect?

Accepted Answer

Inhibition of cell wall synthesis by preventing cross-linking of peptidoglycan

Question 3

Which equation best represents the therapeutic index for an antibiotic?

Accepted Answer

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

Question 4

A patient develops a superinfection after prolonged antibiotic therapy. Which organism is most likely responsible?

Accepted Answer

Candida albicans

Question 5

Why is it difficult to target pathogenic viruses without damaging host cells?

Accepted Answer

Viruses replicate inside host cells, using host cell machinery

Question 6

Which antimicrobial drug is most effective against Mycobacterium tuberculosis by inhibiting mycolic acid synthesis?

Accepted Answer

Isoniazid

Question 7

A bacterium is resistant to penicillin due to the production of an enzyme that breaks the $$\beta-$$lactam ring. What is this enzyme called?

Accepted Answer

Penicillinase (or $$\beta-$$lactamase)

Question 8

Which antibiotic is known to cause aplastic anemia by suppressing bone marrow?

Accepted Answer

Chloramphenicol

Question 9

What is the mode of action for sulfonamides in bacterial cells?

Accepted Answer

Competitive inhibition of folic acid synthesis by mimicking PABA

Question 10

Which of the following is a broad-spectrum antibiotic that interferes with tRNA attachment to the ribosome and is effective against rickettsias and chlamydias?

Accepted Answer

Tetracycline

Question 11

A patient is prescribed a combination of trimethoprim and sulfamethoxazole (TMP-SMZ). What is the expected effect of this drug combination?

Accepted Answer

Synergism: the effect is greater than either drug alone

Question 12

Which antifungal drug targets ergosterol in fungal cell membranes, causing increased permeability?

Accepted Answer

Amphotericin B

Question 13

What is the primary reason for the development of antibiotic resistance in bacteria?

Accepted Answer

Overuse and misuse of antibiotics

Question 14

Which mechanism of resistance is most commonly seen in Gram-negative bacteria?

Accepted Answer

Prevention of penetration to the target site via modified porins

Question 15

Why can’t you use a bacteriostatic and bactericidal chemotherapeutic at the same time?

Accepted Answer

Bacteriostatic drugs inhibit bacterial growth, preventing bactericidal drugs from killing actively growing cells

Question 16

Which drug is used to treat malaria by killing Plasmodium species?

Accepted Answer

Artemisinin

Question 17

A disk-diffusion test shows a large zone of inhibition around an antibiotic disk. What does this indicate?

Accepted Answer

The organism is sensitive to the antibiotic

Question 18

Which of the following is NOT a mode of action for antimicrobial drugs?

Accepted Answer

Inhibition of viral envelope formation

Question 19

Which equation describes the competitive inhibition of folic acid synthesis by sulfonamides?

Accepted Answer

$$	ext{Sulfonamide} + 	ext{Enzyme} ightarrow 	ext{Inactive Complex}$$

Question 20

Which of the following drugs is used to treat tapeworms by preventing ATP production?

Accepted Answer

Niclosamide

Antimicrobial Drugs: Mechanisms, Classes, and Resistance

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