Pharmacology Antimicrobial Therapy Principles Questions and Answers

Question 1

A patient with infective endocarditis caused by Enterococcus faecalis is treated with a combination of ampicillin and gentamicin. What is the primary rationale for using this specific combination?

Accepted Answer

To achieve a synergistic bactericidal effect.

Answer

To cover for potential anaerobic co-pathogens.

Answer

To reduce the nephrotoxic effects of gentamicin.

Answer

To prevent the emergence of resistance to ampicillin.

Question 2

A bacterial strain isolated from a wound culture is found to be resistant to ampicillin but susceptible to amoxicillin-clavulanate. What is the most likely mechanism of resistance to ampicillin in this strain?

Accepted Answer

Production of a beta-lactamase enzyme.

Answer

Alteration of the drug's target site (penicillin-binding proteins).

Answer

An active efflux pump that removes the antibiotic from the cell.

Answer

Impaired drug entry due to a porin channel mutation.

Question 3

Which of the following best describes the primary pharmacodynamic property of beta-lactam antibiotics, such as piperacillin, which dictates their dosing strategy?

Accepted Answer

Their efficacy is best correlated with the duration that the drug concentration remains above the minimum inhibitory concentration (T > MIC).

Answer

Their bactericidal activity is primarily dependent on achieving a high peak concentration relative to the MIC (Cmax/MIC).

Answer

They exhibit a long and significant post-antibiotic effect (PAE) against most pathogens.

Answer

They are most effective when dosed intermittently to minimize the risk of target site saturation.

Question 4

Sulfonamide antibiotics, such as sulfamethoxazole, exhibit selective toxicity against bacteria. Why are human cells typically unaffected by this mechanism?

Accepted Answer

Human cells utilize pre-formed folic acid from dietary sources.

Answer

Human cells possess an active efflux pump that removes sulfonamides.

Answer

Human cells have an 80S ribosome, while bacteria have a 70S ribosome.

Answer

Human cells lack a peptidoglycan cell wall.

Question 5

A physician notes that an aminoglycoside has a significant post-antibiotic effect (PAE). Which of the following statements best describes the clinical implication of the PAE?

Accepted Answer

Bacterial growth suppression continues for a period after the plasma concentration has fallen below the MIC.

Answer

The drug is likely to cause a disulfiram-like reaction with alcohol.

Answer

The drug must be administered via continuous infusion to be effective.

Answer

The drug is safe to use in patients with renal impairment without dose adjustment.

Question 6

A 68-year-old patient with a complicated urinary tract infection is being treated with ciprofloxacin, a fluoroquinolone. This class of antibiotics achieves its bactericidal effect by targeting which of the following?

Accepted Answer

DNA gyrase and topoisomerase IV.

Answer

The 50S ribosomal subunit to inhibit protein translocation.

Answer

Peptidoglycan cross-linking in the bacterial cell wall.

Answer

Dihydropteroate synthase in the folic acid pathway.

A patient with infective endocarditis caused by Enterococcus faecalis is treated with a combination of ampicillin and gentamicin.What is the primary rationale for using this specific combination?

A patient with infective endocarditis caused by Enterococcus faecalis is treated with a combination of ampicillin and gentamicin.
What is the primary rationale for using this specific combination?