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Updated: May 26, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Factors associated with post-operative conversion to methicillin-resistant Staphylococcus aureus positivity or
Youmna Abi-Haidar1, Kalpana Gupta, Judith Strymish
1Department of Surgery, Management Research at the Veterans Affairs Boston Healthcare System, Boston, Massachusetts, USA.
Background:
Hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) is associated with morbid, invasive infections and has been implicated in nearly every type of nosocomial infection. Our aim was to identify the risk factors for patient conversion from MRSA negativity pre-operatively to MRSA positivity post-operatively.
Methods:
We retrospectively reviewed all patients at the Veterans Affairs-Boston Health Care System who underwent clean or clean-contaminated surgical procedures during the years 2008 and 2009 and had documented pre-operative nasal polymerase chain reaction (PCR) testing for MRSA. We abstracted post-operative MRSA microbiologic testing results, MRSA infections, surgical site infections (SSIs), surgical prophylaxis data, and SSI risk index, as calculated using the Veterans Affairs Surgical Quality Improvement Project (VASQIP) database variables. All patients who had a negative nasal MRSA PCR result in the 31-day pre-operative period and did not have any positive MRSA clinical swab or culture in the 1-year pre-operative period were defined as MRSA-negative. These patients were classified as converters to MRSA positivity if they had at least one documented positive nasal MRSA PCR swab, culture, nosocomial infection, or SSI within 31 days post-operatively.
Results:
Among 4,238 eligible patients, 3,890 (92%) qualified as MRSA-negative pre-operatively. A total of 1,432 (37%) of these patients were assessed in the VASQIP database, of whom 34 (2%) converted to MRSA positivity post-operatively. On multivariable logistic regression analysis of the VASQIP sample, age (odds ratio [OR] 1.049; 95% confidence interval [CI] 1.016, 1.083), SSI risk index (OR 2.863; 95% CI 1.251-6.554), and vancomycin prophylaxis alone or in combination (OR 3.223; 95% CI 1.174-8.845) were significantly associated with conversion to MRSA positivity.
Conclusion:
In pre-operatively MRSA-negative patients, age, SSI risk index, and vancomycin prophylaxis were significant factors for conversion to MRSA positivity post-operatively. Alternatives to vancomycin prophylaxis in non-colonized patients and optimization of patients' SSI risk factors should be considered before elective surgery.
Insights
Older age, higher surgical site infection risk, and vancomycin prophylaxis are key factors for methicillin-resistant Staphylococcus aureus (MRSA) conversion in pre-operatively negative patients. Strategies to mitigate these risks are crucial.
Area of Science:
- Infectious Disease Epidemiology
- Healthcare-Associated Infections
- Surgical Site Infections
Background:
- Hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections lead to significant morbidity.
- Identifying risk factors for post-operative MRSA conversion is critical for prevention.
- This study focuses on patients initially negative for MRSA before surgery.
Purpose of the Study:
- To identify risk factors associated with patient conversion from MRSA negativity to MRSA positivity post-operatively.
- To inform strategies for reducing MRSA acquisition in surgical patients.
Main Methods:
- Retrospective review of patients undergoing clean/clean-contaminated surgery (2008-2009) with pre-operative nasal MRSA PCR testing.
- Analysis of post-operative MRSA status, infections, surgical prophylaxis, and SSI risk index (VASQIP).
- Definition of 'converters' as MRSA-negative pre-operatively and positive within 31 days post-operatively.
Main Results:
- Of 4,238 eligible patients, 3,890 (92%) were MRSA-negative pre-operatively.
- Among 1,432 patients in the VASQIP database, 34 (2%) converted to MRSA positivity.
- Multivariable analysis identified older age (OR 1.049), higher SSI risk index (OR 2.863), and vancomycin prophylaxis (OR 3.223) as significant risk factors for conversion.
Conclusions:
- In pre-operatively MRSA-negative patients, age, SSI risk index, and vancomycin prophylaxis are significant predictors of post-operative MRSA conversion.
- Consideration of vancomycin prophylaxis alternatives for non-colonized patients is recommended.
- Optimizing patient SSI risk factors prior to elective surgery is essential for MRSA prevention.
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