Pharmacology Antimicrobial and Chemotherapeutic Agents Questions and Answers

Question 1

A patient is prescribed penicillin for a gram-positive bacterial infection. What is the primary mechanism by which this antibiotic exerts its bactericidal effect?

Accepted Answer

Inhibition of transpeptidase, preventing peptidoglycan cell wall cross-linking.

Answer

Inhibition of DNA gyrase, preventing bacterial DNA replication.

Answer

Binding to the 30S ribosomal subunit to disrupt protein synthesis.

Answer

Creation of pores in the bacterial cell membrane, causing leakage of intracellular contents.

Question 2

A 68-year-old male with a history of atrial fibrillation, well-controlled on warfarin, is diagnosed with oropharyngeal candidiasis and is prescribed a course of oral fluconazole. What is the most significant potential interaction the pharmacist should be concerned about?

Accepted Answer

Inhibition of warfarin metabolism, leading to a supratherapeutic INR and increased risk of bleeding.

Answer

Increased metabolism of warfarin, leading to a subtherapeutic INR and risk of thrombosis.

Answer

Decreased absorption of fluconazole, leading to antifungal treatment failure.

Answer

Displacement of warfarin from plasma proteins by fluconazole, causing a transient increase in free drug.

Question 3

Which of the following statements most accurately describes the mechanism of action of acyclovir in treating a herpes simplex virus (HSV) infection?

Accepted Answer

It is a guanosine analog that, after phosphorylation by viral thymidine kinase, inhibits viral DNA polymerase and causes chain termination.

Answer

It acts as a neuraminidase inhibitor, preventing the release of newly formed virions from the host cell.

Answer

It directly inhibits the fusion of the viral envelope with the host cell membrane.

Answer

It prevents the uncoating of the viral genome after it enters the host cell.

Question 4

A patient undergoing chemotherapy with a regimen that includes cisplatin is closely monitored for adverse effects. Which of the following is a well-known and often dose-limiting toxicity of this agent?

Accepted Answer

Nephrotoxicity

Answer

Cardiotoxicity

Answer

Pulmonary fibrosis

Answer

Hemorrhagic cystitis

Question 5

A patient is admitted with a severe skin and soft tissue infection. Cultures grow Staphylococcus aureus that is resistant to oxacillin. This resistance is conferred by the mecA gene. What is the primary mechanism of resistance in this organism?

Accepted Answer

Alteration of the drug's target site, the penicillin-binding protein (PBP).

Answer

Increased production of beta-lactamase enzymes that hydrolyze the antibiotic.

Answer

Efflux pumps that actively transport the antibiotic out of the bacterial cell.

Answer

Modification of the antibiotic molecule by bacterial enzymes.

Question 6

Metronidazole is a unique antimicrobial agent prescribed for a variety of infections. Its spectrum of activity is primarily limited to which of the following classes of organisms?

Accepted Answer

Anaerobic bacteria and certain protozoa

Answer

Aerobic gram-positive cocci

Answer

Atypical bacteria (e.g., Mycoplasma, Chlamydia)

Answer

Fungi and yeasts