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Severe community-acquired pneumonia due to Staphylococcus aureus, 2003-04 influenza season

Jeffrey C Hageman1, Timothy M Uyeki, John S Francis

  • 1Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. JHageman@cdc.gov

Emerging Infectious Diseases
|May 19, 2006
PubMed

Insights

Severe community-acquired pneumonia (CAP) during flu season is often linked to methicillin-resistant Staphylococcus aureus (MRSA). Early consideration of MRSA in treatment is crucial, especially in high-prevalence areas.

Area of Science:

  • Infectious Diseases
  • Pulmonology
  • Microbiology

Background:

  • Community-acquired pneumonia (CAP) poses a significant health burden.
  • Staphylococcus aureus, particularly methicillin-resistant strains (MRSA), is an emerging cause of severe CAP.
  • Influenza virus coinfection is increasingly recognized in severe bacterial pneumonia.

Purpose of the Study:

  • To investigate the characteristics and outcomes of Staphylococcus aureus CAP cases during the 2003-04 influenza season.
  • To identify risk factors and microbiological features associated with MRSA in severe CAP.
  • To inform clinical management strategies for severe CAP during influenza outbreaks.

Main Methods:

  • Retrospective analysis of 17 S. aureus CAP cases reported across 9 states during the 2003-04 influenza season.
  • Clinical data collection including patient demographics, underlying conditions, risk factors, and outcomes.
  • Microbiological characterization of S. aureus isolates, including antibiotic susceptibility, toxin gene profiling (Panton-Valentine leukocidin), and molecular typing (PFGE, SCCmec).
  • Laboratory confirmation of influenza virus infection.

Main Results:

  • 17 S. aureus CAP cases were identified; 15 (88%) were MRSA.
  • The median patient age was 21 years, with 29% having underlying diseases and 24% having MRSA risk factors.
  • Influenza virus infection was present in 71% of patients.
  • The overall mortality rate was 29% (5 deaths), with 4 deaths attributed to MRSA.
  • All S. aureus isolates carried toxin genes, predominantly Panton-Valentine leukocidin (85%).
  • MRSA isolates exhibited community-associated PFGE patterns and SCCmec type IVa.

Conclusions:

  • Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of severe community-acquired pneumonia (CAP), especially when associated with influenza virus infection.
  • The genotypic and phenotypic characteristics of these MRSA isolates are consistent with community-acquired strains.
  • Empiric antibiotic therapy for severe CAP during influenza seasons in areas with high MRSA prevalence should include coverage for MRSA.

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