Practice Based Learning: Influenza and S Aureus Co-infection

Jane Stremming, MD

Presented by Jane Stremming, MD

Questions:

  • What is the incidence of co-infection of influenza and Staph aureus?
  • Who is at risk for co-infection?

Key points:

  • Co-infection with Staph increases risk of morbidity and mortality
  • Patients with co-morbidities have higher risk of developing S. aureus CAP
  • S. aureus CAP should be considered in ill patients with radiographically confirmed pneumonia

Reed C, Kallen AJ, Patton M, Arnold KE, Farley MM, Hageman J, Finelli L. Infection with community-onset Staphylococcus aureus and influenza virus in hospitalized children. Pediatr Infect Dis J. 2009 Jul;28(7):572-6.

Article summary:

  • S. aureus was the most common organism associated with co-infection with influenza
  • Children with co-infection had longer hospital stay and higher risk of PICU admission, mechanical intubation, and death
  • Children with co-infection were older than those with influenza alone
  • Limitations
    • Small study
    • Included Cystic Fibrosis patients

Kallen AJ, Reed C, Patton M, Arnold KE, Finelli L, Hageman J. Staphylococcus aureus community-onset pneumonia in patients admitted to children’s hospitals during autumn and winter of 2006-2007. Epidemiol Infect. 2010 May;138(5):666-72.

Article summary:

  • Patients admitted with positive respiratory culture for S. aureus
    • Cystic fibrosis patients excluded
  • 274 episodes of positive cultures
    • 86 (31%) pneumonia, 79 (29%) primary pneumonia
    • 46 with primary S. aureus CAP (16 excluded due to CF)
    • 30 positive culture as an outpatient or within 3 days of admission with S. aureus CAP
      • 67% with comorbidity
  • Of those 30 patients:
    • Age <1-23.8
    • 20 patients (67% with comorbidities)
      • Developmental delay, neuromuscular disease, seizures, asthma, CLD, prematurity
  • 8 patients (33%) lived with a smoker
    • Most commonly reported signs/symptoms – cough (67%), reported fever (60%), dyspnea (57%), leukocytosis (62%)
    • 29 patients had abnormal CXR on admission
      • 2 patients had cavitation
      • 7 patients had pleural effusion
  • 18 patients tested for influenza – 3 positive
  • Conclusion – patients with co-morbidities are at highest risk of S. aureus CAP

Finelli L, Fiore A, Dhara R, Brammer L, Shay DK, Kamimoto L, Fry A, Hageman J, Gorwitz R, Bresee J, Uyeki T. Influenza-associated pediatric mortality in the United States: increase of Staphylococcus aureus coinfection. Pediatrics. 2008 Oct;122(4):805-11.

Article summary:

  • Susceptibility of bacterial co-infection
    • Virus damages the epithelial layer of the tracheobronchial tree, which allows for better bacterial adherance – possibly due to neuraminidase activity?
      • “Even delayed treatment with neuraminidase inhibitors could prevent influenza associated bacterial complications” although it may not change the course of influenza
    • Virus suppresses phagocytic function of neutrophils and macrophages
  • Increasing prevalence of nasal colonization?
    • 0.8% in 2001 vs >9% in 2005

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