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Updated: Apr 12, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Improving Clinical Outcomes in Patients With Methicillin-Sensitive Staphylococcus aureus Bacteremia and Reported
Kimberly G Blumenthal1, Robert A Parker2, Erica S Shenoy3
1Division of Rheumatology, Allergy, and Immunology, Department of Medicine Medical Practice Evaluation Center, Massachusetts General Hospital Harvard Medical School.
Background:
Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a morbid infection. First-line MSSA therapies (nafcillin, oxacillin, cefazolin) are generally avoided in the 10% of patients reporting penicillin (PCN) allergy, but most of these patients are not truly allergic. We used a decision tree with sensitivity analyses to determine the optimal evaluation and treatment for patients with MSSA bacteremia and reported PCN allergy.
Methods:
Our model simulates 3 strategies: (1) no allergy evaluation, give vancomycin (Vanc); (2) allergy history-guided treatment: if history excludes anaphylactic features, give cefazolin (Hx-Cefaz); and (3) complete allergy evaluation with history-appropriate PCN skin testing: if skin test negative, give cefazolin (ST-Cefaz). Model outcomes included 12-week MSSA cure, recurrence, and death; allergic reactions including major, minor, and potentially iatrogenic; and adverse drug reactions.
Results:
Vanc results in the fewest patients achieving MSSA cure and the highest rate of recurrence (67.3%/14.8% vs 83.4%/9.3% for Hx-Cefaz and 84.5%/8.9% for ST-Cefaz) as well as the greatest frequency of allergic reactions (3.0% vs 2.4% for Hx-Cefaz and 1.7% for ST-Cefaz) and highest rates of adverse drug reactions (5.2% vs 4.6% for Hx-Cefaz and 4.7% for ST-Cefaz). Even in a "best case for Vanc" scenario, Vanc yields the poorest outcomes. ST-Cefaz is preferred to Hx-Cefaz although sensitive to input variations.
Conclusions:
Patients with MSSA bacteremia and a reported PCN allergy should have the allergy addressed for optimal treatment. Full allergy evaluation with skin testing seems to be preferred, although more data are needed.
Insights
For methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia, evaluating penicillin (PCN) allergy is crucial. Allergy testing and cefazolin treatment yield better outcomes than vancomycin for patients with reported PCN allergy.
Area of Science:
- Infectious Diseases
- Clinical Pharmacology
- Allergy and Immunology
Background:
- Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a significant clinical challenge.
- Many patients with MSSA bacteremia report penicillin (PCN) allergy but are not truly allergic, leading to avoidance of first-line therapies.
- Optimal management strategies for these patients are needed.
Purpose of the Study:
- To determine the optimal evaluation and treatment strategy for patients with MSSA bacteremia and a reported PCN allergy.
- To compare outcomes of vancomycin, history-guided cefazolin, and skin test-guided cefazolin treatment.
- To assess cure rates, recurrence, and adverse events associated with different treatment approaches.
Main Methods:
- A decision tree model with sensitivity analyses was developed to simulate three treatment strategies.
- Strategies included: no allergy evaluation (vancomycin), history-guided cefazolin, and complete allergy evaluation with penicillin skin testing followed by cefazolin.
- Outcomes measured were 12-week MSSA cure, recurrence, death, allergic reactions, and adverse drug reactions.
Main Results:
- Vancomycin resulted in the lowest MSSA cure rates and highest recurrence rates compared to cefazolin strategies.
- The complete allergy evaluation with skin testing followed by cefazolin (ST-Cefaz) strategy showed the best outcomes.
- ST-Cefaz also demonstrated the lowest frequency of allergic reactions and comparable adverse drug reactions to other strategies.
Conclusions:
- Addressing reported penicillin allergy in patients with MSSA bacteremia is essential for optimal treatment outcomes.
- Full allergy evaluation, including penicillin skin testing, appears to be the preferred strategy.
- Further research is warranted to validate these findings and refine management guidelines.
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