Examkin

Question

Difficulty: MediumInfectious Diseases

A 54-year-old man is hospitalized for a 3-day history of high fever, severe back pain, and chills. He has a history of type 2 diabetes mellitus and intravenous drug use. Temperature is 39.2°C (102.6°F), blood pressure is 110/70 mm Hg, and pulse is 112/min. Physical examination reveals point tenderness over the L3-L4 vertebrae and a new soft systolic murmur heard at the left lower sternal border. Blood cultures are drawn, and he is started empirically on intravenous vancomycin and piperacillin-tazobactam. Magnetic resonance imaging of the spine reveals L3-L4 osteomyelitis with an associated anterior epidural abscess. On day 3 of hospitalization, blood cultures grow Staphylococcus aureus. Susceptibility testing shows the organism is resistant to penicillin and susceptible to oxacillin, cefazolin, and vancomycin. Which of the following is the most appropriate next step in the patient's pharmacotherapy?

  1. A
    Continue vancomycin and discontinue piperacillin-tazobactam
  2. B
    Discontinue vancomycin and continue piperacillin-tazobactam
  3. C
    Continue both vancomycin and piperacillin-tazobactam
  4. Discontinue vancomycin and piperacillin-tazobactam, and start intravenous cefazolinAnswer
  5. E
    Discontinue vancomycin and piperacillin-tazobactam, and start oral linezolid

Answer

Discontinue vancomycin and piperacillin-tazobactam, and start intravenous cefazolin
The patient has a severe, invasive methicillin-susceptible Staphylococcus aureus (MSSA) infection (bacteremia, osteomyelitis, epidural abscess, and possible endocarditis). When susceptibility testing confirms MSSA (indicated by susceptibility to oxacillin or cefazolin), the standard of care is to de-escalate from empiric broad-spectrum antibiotics to a targeted intravenous beta-lactam, such as cefazolin, nafcillin, or oxacillin. These agents possess superior bactericidal activity against MSSA compared to vancomycin, resulting in lower rates of treatment failure and mortality. Continuing vancomycin or piperacillin-tazobactam violates antimicrobial stewardship principles and provides suboptimal therapy.

Step-by-Step Solution

1
Analyze the culture and susceptibility results.
The patient has bacteremia and invasive infection caused by methicillin-susceptible Staphylococcus aureus (MSSA).
The organism is susceptible to oxacillin and cefazolin, confirming it is not MRSA.
2
Determine the optimal targeted antimicrobial therapy for MSSA.
Narrow-spectrum intravenous beta-lactams (e.g., cefazolin, nafcillin, oxacillin) are the treatment of choice.
Beta-lactams have superior bactericidal activity against MSSA compared to vancomycin, leading to lower mortality and failure rates.
3
Apply antimicrobial stewardship principles to the current empiric regimen.
Discontinue broad-spectrum empiric therapy (vancomycin and piperacillin-tazobactam) and initiate targeted therapy (intravenous cefazolin).
De-escalation reduces toxicity, prevents the emergence of multidrug-resistant organisms, and provides the most effective treatment for the specific pathogen.

Key Concept

De-escalation to targeted intravenous beta-lactam therapy for methicillin-susceptible Staphylococcus aureus (MSSA) infections
Rate this question

Topics

Infectious Diseases

More questions from this topic