Background: Community-associated methicillin-resistant Staphylococcus aureus (MRSA) has typically been distinguished from healthcare-associated MRSA by staphylococcal cassette chromosome mec (SCCmec) type. However, the impact of SCCmec type on mortality in MRSA infections remains unclear. The objective of this study was to determine the association between SCCmec type and mortality in MRSA bacteremia, specifically SCCmec II as opposed to SCCmec IV.
Methods: A cohort study of patients who were hospitalized from May 2007 to December 2009 with S. aureus bacteremia was conducted within a university health system. A multivariable logistic regression model was developed to evaluate the association of SCCmec type with 30-day in-hospital mortality.
Results: 188 patients had bacteremia due to MRSA during the study period. A total of 34 patients died while hospitalized for MRSA bacteremia, resulting in a crude mortality rate of 18.5%. Adjusted risk factors for 30-day in-hospital mortality included APRDRG Risk of Mortality score (odds ratio [OR], 5.33; 95% confidence interval [CI], 2.28-12.4; P<0.001), WBC count (OR, 1.09; 95% CI, 1.03-1.15; P=0.002), and malignancy (OR, 3.25; 95% CI, 1.17-9.02; P=0.02). On multivariable analyses, SCCmec II was not significantly associated with increased mortality in patients with MRSA bacteremia (OR, 1.85; 95% CI, 0.69-4.92; P=0.22).
Conclusion: After adjustment for relevant confounders, mortality in MRSA bacteremia was independent of SCCmec type. It is possible that SCCmec type II is a marker for illness severity in serious infections due to MRSA. Further research is needed to elucidate the microbiologic and host factors associated with poor clinical outcomes in MRSA infections.
W. Bilker, None
E. Lautenbach, Merck: Grant Investigator, Grant recipient
AstraZeneca: Grant Investigator, Grant recipient
Cubist: Grant Investigator, Grant recipient
3M: Grant Investigator, Grant recipient