Influenza-associated bacterial pneumonia; managing and controlling infection on two fronts

Abstract

Bacterial pneumonia complicating influenza is well-recognized as a severe manifestation of influenza, accounting for a substantial number of deaths from the 1918 influenza pandemic. Influenza-associated bacterial pneumonia remains a major contributor to the burden of influenza, and poses new challenges as antibiotic-resistant organisms such as methicillin-resistant Staphylococcus aureus spread. We provide an overview of the current state of knowledge of the epidemiology and co-pathogenesis of influenza-associated bacterial pneumonia, and outline management approaches and their limitations. We review preventative measures and discuss implications for pandemic planning. Knowledge gaps are underscored and future research directions are proposed.

Keywords:

• bacterial pneumonia
• control
• co-pathogenesis
• influenza virus
• transmission

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Bacterial pneumonia complicating influenza occurs in approximately one-third of patients with severe influenza, as defined by the need for intensive care unit admission.

• Influenza virus-mediated changes to respiratory tract epithelium, including mucociliary dysfunction and exposure of additional bacterial binding sites, and changes to the host immune response underlie the enhanced co-pathogenesis of bacterial infections associated with influenza.

• Diagnosis of influenza-associated bacterial pneumonia remains difficult and is often based upon a combination of clinical, laboratory and radiographic evidence.

• Increased morbidity is associated with S. aureus bacterial infection in the context of influenza, particularly when methicillin-resistant S. aureus is implicated, requiring empiric methicillin-resistant S. aureus coverage in the appropriate clinical/epidemiologic setting.

• A more profound understanding of the transmission of bacterial pathogens implicated in influenza pneumonia is required for the institution of more effective preventative measures to reduce their spread in healthcare settings. Similarly, the effect(s) of bacterial colonization and infection on the dispersion of influenza virus are largely undetermined and further insight may inform current policy and procedure.

• Influenza and S. pneumoniae vaccination remain important cornerstones of prevention.