PURPOSE: The incidence of Community Acquired Pneumonia (CAP) caused by Staphylococcus aureus, according to several worldwide prospective studies, is less than 5%. However recent clinical experience suggests it may be higher than previously noted, particularly in the medical intensive care unit (MICU) population. Minimal data exists at this time describing the percentage of severe CAP cases requiring MICU admission that are due to S. aureus.
METHODS: This was a retrospective chart review using an MICU log of admissions and diagnoses from the years 2005-2007 that was screened for cases potentially representing pneumonia. Of these, computerized discharge summaries as well as microbiologic and radiologic data were evaluated for those cases that were likely to be CAP. Candidate charts were reviewed for patient demographics, comorbidities, outcome, microbiology, and pneumonia characteristics. Incidence of S. aureus pneumonia was determined and multivariate analysis comparing it to other etiologic agents of pneumonia was performed.
RESULTS: 85 of the 1626 cases reviewed fully met criteria for CAP. Etiologic agents were determined in 66% of the cases. Of these, S. aureus accounted for 15 of 84 cases (18%), nine of which were Methicillin resistant (MRSA) and six of which were Methicillin sensitive (MSSA). There was an observed statistically significant difference in mortality in patients with CAP due to S. aureus compared to with other organisms.
CONCLUSION: Data from this retrospective study suggest a significantly higher percentage CAP cases due to S. aureus, particularly in with severe CAP necessitating MICU admission. Additionally, it appears that CAP due to MRSA is playing a more significant role than has been described in prior studies. Mortality in patients with severe CAP from S. aureus appears to be higher than severe CAP due to other organisms.
CLINICAL IMPLICATIONS: The prevalence of severe CAP from S. aureus pneumonia, including MRSA, appears to be significant and may impact empiric antibiotic selection under such clinical scenarios. Further evaluation, particularly prospective studies evaluating antibiotic selection and outcome in patients with severe CAP from S. aureus, is warranted.
DISCLOSURE: Jonathan Cooke, No Financial Disclosure Information; No Product/Research Disclosure Information