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

$$MIC = \text{lowest concentration of drug that inhibits visible growth}$$

Question 1

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

Accepted Answer

Drugs kill or inhibit microbial cells without simultaneously damaging host tissues.

Question 2

Which microbial genus is the primary source of penicillins used in clinical therapy?

Accepted Answer

Penicillium

Question 3

A patient is prescribed a broad-spectrum antibiotic for a mixed infection. Which drug is most likely to be chosen?

Accepted Answer

Tetracycline

Question 4

Which of the following drugs acts by inhibiting the synthesis of peptidoglycan in bacterial cell walls?

Accepted Answer

Penicillin

Question 5

Why are sulfonamides selectively toxic to bacteria but not to human cells?

Accepted Answer

Bacteria synthesize their own folic acid, while human cells obtain it from the diet.

Question 6

Which of the following is a mechanism by which bacteria acquire drug resistance?

Accepted Answer

Transfer of resistance (R) factors via plasmids

Question 7

A physician prescribes ampicillin for a patient with a Gram-negative infection. What property of ampicillin makes it suitable for this case?

Accepted Answer

It is a semisynthetic penicillin with a broader spectrum that can cross the outer membrane of Gram-negative bacteria.

Question 8

Which class of antibiotics works by binding to the 30S ribosomal subunit and causing misreading of mRNA?

Accepted Answer

Aminoglycosides

Question 9

A patient with tuberculosis is treated with streptomycin. What is the primary mechanism of action of this drug?

Accepted Answer

It interferes with protein synthesis by binding to the 30S ribosomal subunit.

Question 10

Which of the following is a synthetic drug that inhibits DNA gyrase, preventing DNA replication in bacteria?

Accepted Answer

Quinolone

Question 11

A patient is diagnosed with Mycoplasma pneumonia and is allergic to penicillin. Which antibiotic is most appropriate?

Accepted Answer

Erythromycin

Question 12

Which of the following best explains why antifungal drugs often have higher toxicity to humans than antibacterial drugs?

Accepted Answer

Fungal cells are eukaryotic and share many cellular features with human cells.

Question 13

Which of the following practices contributes most to the development of antibiotic resistance in bacteria?

Accepted Answer

Stopping antibiotic treatment early, before the full course is completed

Question 14

Which laboratory test is used to determine the minimum inhibitory concentration (MIC) of an antimicrobial drug?

Accepted Answer

Dilution test

Question 15

A new HIV drug acts as a competitive inhibitor by inserting into the viral DNA and preventing further addition of new bases. Which class does this drug belong to?

Accepted Answer

Nucleoside reverse transcriptase inhibitors (NRTIs)

Question 16

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

Accepted Answer

$$MIC = 	ext{lowest concentration of drug that inhibits visible growth}$$

Question 17

Which of the following is a real-world consequence of farmers adding antibiotics to animal feed?

Accepted Answer

It increases the prevalence of antibiotic-resistant bacteria in livestock populations.

Question 18

Which of the following drugs is most effective for treating both Gram-positive and Gram-negative urinary tract infections?

Accepted Answer

Quinolones

Question 19

Which of the following is a plausible reason for the failure of an antibiotic to treat a bacterial infection?

Accepted Answer

The bacteria have acquired resistance through spontaneous mutation or gene transfer.

Question 20

Which of the following best describes the action of interferons (IFN) in viral infections?

Accepted Answer

They are human-based glycoproteins that reduce healing time and complications, and slow the progress of certain cancers and viral infections.

Antimicrobial Therapy: Principles, Drug Types, and Microbial Sources

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