Examkin

Question

Difficulty: HardInfectious Diseases

A 54-year-old man is evaluated in the hospital on hospital day 3 for ongoing management of a severe skin and soft tissue infection of the right lower extremity. He initially presented with high fever, chills, and a rapidly expanding area of erythema and induration. Blood cultures drawn on admission have now returned positive for methicillin-susceptible Staphylococcus aureus (MSSA). His empiric antimicrobial regimen since admission has consisted of intravenous vancomycin and cefepime. The patient's medical record indicates an allergy to penicillin, which he describes as a flat, red rash on his chest that occurred 20 years ago when taking amoxicillin. He explicitly denies any history of facial swelling, hives, or breathing difficulties. He is currently hemodynamically stable, his temperature is 37.4°C (99.3°F), and the erythema has significantly receded. Subsequent blood cultures drawn 48 hours after admission show no growth to date.

Which of the following is the most appropriate pharmacologic intervention at this time?

  1. A
    Stop cefepime and maintain intravenous vancomycin
  2. B
    Replace the current antimicrobials with intravenous ceftaroline
  3. Replace the current antimicrobials with intravenous cefazolinAnswer
  4. D
    Replace the current antimicrobials with intravenous daptomycin
  5. E
    Maintain the current regimen of intravenous vancomycin and cefepime

Answer

Replace the current antimicrobials with intravenous cefazolin
The patient has MSSA bacteremia secondary to a skin and soft tissue infection. The drug of choice for MSSA bacteremia is an anti-staphylococcal beta-lactam, such as cefazolin or nafcillin, because these agents have been shown to provide superior clinical outcomes, faster bacterial clearance, and lower mortality compared to vancomycin. A critical decision point in this vignette is the patient's reported penicillin allergy. He experienced a non-pruritic maculopapular rash to amoxicillin 20 years ago. This is a classic non-IgE-mediated, delayed-type hypersensitivity reaction that is generally benign. Furthermore, cefazolin has a unique R1 side chain that is structurally distinct from other penicillins and cephalosporins, making the rate of cross-reactivity virtually non-existent. Therefore, the most appropriate next step in antibiotic stewardship is to de-escalate his broad-spectrum empiric regimen and transition him to intravenous cefazolin monotherapy.

Step-by-Step Solution

1
Analyze the culture and susceptibility results.
The pathogen is identified as methicillin-susceptible Staphylococcus aureus (MSSA).
Guides targeted antimicrobial de-escalation from empiric broad-spectrum therapy.
2
Evaluate the patient's penicillin allergy history.
The history of a flat, red rash 20 years ago indicates a delayed, non-IgE-mediated reaction rather than anaphylaxis.
Determines the safety of administering beta-lactam antibiotics, which are the treatment of choice for MSSA.
3
Select the optimal targeted therapy for MSSA bacteremia.
Intravenous cefazolin is selected as the definitive therapy.
Anti-staphylococcal beta-lactams are superior to vancomycin for MSSA, and cefazolin poses virtually zero cross-reactivity risk given its unique side chain.

Key Concept

Patients with methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia should be treated with an anti-staphylococcal beta-lactam (e.g., cefazolin, nafcillin) rather than vancomycin due to superior clinical outcomes. A remote, non-IgE-mediated penicillin allergy is not a contraindication to cefazolin.
Estimated Time:1m 15s
Rate this question

Topics

Infectious Diseases

More questions from this topic