Question 1

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

Accepted Answer

Drugs are toxic to the target microbe but not to the host.

Question 2

Paul Ehrlich is credited with introducing the concept of the 'magic bullet' in antimicrobial therapy. What disease did his first antimicrobial drug cure?

Accepted Answer

Syphilis

Question 3

Alexander Fleming's discovery of penicillin was significant because:

Accepted Answer

He discovered a mold that inhibited bacterial growth on a petri plate.

Question 4

Why is bacterial protein synthesis a good target for selective toxicity?

Accepted Answer

Bacterial 70S ribosomes are structurally different from eukaryotic 80S ribosomes.

Question 5

A doctor is unsure of the source of a patient's infection. Which type of antimicrobial drug is most likely to be prescribed and why?

Accepted Answer

Broad-spectrum, because they are effective against a more diverse group of bacteria.

Question 6

Which chemical modification to penicillin would make it broader spectrum?

Accepted Answer

Addition of an amino group to make the molecule more polar, allowing it to pass through porins in Gram-negative membranes.

Question 7

Which of the following best explains why Candida albicans is a common superinfection after antibiotic use?

Accepted Answer

Candida albicans is a fungus and is not killed by antibiotics, allowing it to cause infection after antibiotic use.

Question 8

Which of the following is an example of possible synergism between two antimicrobial drugs?

Accepted Answer

Sulfamethoxazole and trimethoprim, which block different steps of the same bacterial metabolic pathway.

Question 9

The therapeutic index of a drug is given by the formula:

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

If a $$drug has a therapeutic index of 100, what does this mean?

Accepted Answer

It takes 100 times the effective dose to be toxic.

Question 10

Which of the following is a major shortcoming of penicillin V and penicillin G?

Accepted Answer

They are susceptible to common enzymes (i.e., β-lactamase) that can inhibit them.

Question 11

Amoxicillin is often prescribed with clavulanic acid. How does clavulanic acid work synergistically with amoxicillin?

Accepted Answer

Clavulanic acid binds to the active site of beta-lactamase, deactivating the enzyme.

Question 12

Why are carbapenems typically reserved for severe, multi-drug-resistant infections?

Accepted Answer

Overuse of carbapenems could promote widespread resistance.

Question 13

Which of the following drugs is available without a prescription in the US and targets cell wall synthesis?

Accepted Answer

Bacitracin

Question 14

A patient presents with a cough, blood in the sputum, and fever. The pathogen is only visible with an acid-fast stain. Which antibacterial drug would be appropriate?

Accepted Answer

Isoniazid

Question 15

Which of the following drugs most directly affect the binding of tRNA to the mRNA?

Accepted Answer

Tetracycline & gentamycin

Question 16

Which of the following correctly matches the drug with its target?

Accepted Answer

Rifamycin → RNA polymerase

Question 17

Why are sulfa drugs & trimethoprim often used together?

Accepted Answer

They exhibit synergism by inhibiting different steps of the same metabolic pathway.

Question 18

Which of the following drugs target ergosterols in fungal cell membranes?

Accepted Answer

I & II (Nystatin and Miconazole)

Question 19

Which of the following best describes why the use of antibiotics in agriculture is a significant concern for the spread of antibiotic resistance in human diseases?

Accepted Answer

Horizontal transfer allows resistance genes in animals to be passed to human pathogens.

Question 20

Which of the following resistance mechanisms would NOT result in a lower concentration of the drug inside a cell?

Accepted Answer

Enzymatic inactivation

Antimicrobial Drugs: Mechanisms, Spectrum, Resistance, and Clinical Applications

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