PSA Antimicrobial Prescribing 2 — Questions and Answers
Question 1: A patient with confirmed MRSA bacteremia requires IV antibiotic therapy. Which agent is the first-line choice?
- Vancomycin (Correct answer)
- Oxacillin
- Cefazolin
- Ampicillin-sulbactam
Correct answer: Vancomycin
Vancomycin is the first-line agent for MRSA bacteremia due to its reliable activity against methicillin-resistant strains.
Question 2: A patient with a severe penicillin allergy (anaphylaxis) develops a skin and soft tissue infection caused by Staphylococcus aureus (MSSA). Which antibiotic is most appropriate?
- Cephalexin
- Vancomycin (Correct answer)
- Amoxicillin-clavulanate
- Cefazolin
Correct answer: Vancomycin
Vancomycin is the safest option in true penicillin anaphylaxis, as cross-reactivity with beta-lactams remains a concern despite being low with cephalosporins.
Question 3: A healthy 35-year-old presents with community-acquired pneumonia (CAP) requiring outpatient treatment with no comorbidities. What is the preferred first-line regimen?
- Amoxicillin 500 mg three times daily (Correct answer)
- Levofloxacin 750 mg once daily
- Azithromycin 500 mg then 250 mg daily
- Doxycycline 100 mg twice daily
Correct answer: Amoxicillin 500 mg three times daily
Current US guidelines recommend amoxicillin as first-line monotherapy for outpatient CAP in patients without comorbidities or risk factors for drug-resistant organisms.
Question 4: A premenopausal woman presents with an uncomplicated lower urinary tract infection. Urine culture grows E. coli susceptible to all agents tested. Which antibiotic is preferred due to stewardship concerns?
- Ciprofloxacin
- Nitrofurantoin (Correct answer)
- Trimethoprim-sulfamethoxazole
- Amoxicillin
Correct answer: Nitrofurantoin
Nitrofurantoin is preferred for uncomplicated UTI to preserve fluoroquinolones and avoid broader-spectrum agents when susceptibility is not known at initiation.
Question 5: Which antibiotic class provides the most reliable coverage against anaerobic organisms, making it useful for intra-abdominal infections?
- Fluoroquinolones
- Aminoglycosides
- Metronidazole (Correct answer)
- Macrolides
Correct answer: Metronidazole
Metronidazole has excellent anaerobic coverage and is a cornerstone agent in the treatment of intra-abdominal and pelvic infections.
Question 6: A hospitalized patient develops Clostridioides difficile colitis classified as non-severe. What is the first-line treatment?
- Oral vancomycin 125 mg four times daily (Correct answer)
- IV metronidazole 500 mg three times daily
- Oral fidaxomicin 200 mg twice daily
- Oral metronidazole 500 mg three times daily
Correct answer: Oral vancomycin 125 mg four times daily
Current IDSA guidelines recommend oral vancomycin (or fidaxomicin) over metronidazole as first-line therapy for non-severe C. difficile infection due to superior outcomes.
Question 7: A patient requires eradication therapy for Helicobacter pylori. Which regimen is recommended as first-line in areas with clarithromycin resistance >15%?
- Clarithromycin triple therapy (PPI + amoxicillin + clarithromycin)
- Bismuth quadruple therapy (PPI + bismuth + tetracycline + metronidazole) (Correct answer)
- Metronidazole dual therapy (PPI + metronidazole)
- Amoxicillin dual therapy (PPI + high-dose amoxicillin)
Correct answer: Bismuth quadruple therapy (PPI + bismuth + tetracycline + metronidazole)
Bismuth quadruple therapy is preferred in regions with high clarithromycin resistance, as it avoids clarithromycin and achieves superior eradication rates.
PSA Antimicrobial Prescribing 2
A patient with confirmed MRSA bacteremia requires IV antibiotic therapy.
Which agent is the first-line choice?