Novel pandemic influenza A (H1N1) and community-associated methicillin-resistant Staphylococcus aureus pneumonia

Abstract

Postinfluenza bacterial pneumonia is a leading cause of influenza-associated death, and Staphylococcus aureus and Streptococcus pneumoniae have been important pathogens that have caused pneumonia since the influenza pandemic in 1919. Emergence of novel influenza A (H1N1) pdm09 and the concomitant global spread of community-associated methicillin-resistant S. aureus (CA-MRSA) have led to increasing prevalence of CA-MRSA pneumonia following influenza infection. Such an epidemiologic change poses a therapeutic challenge due to a high risk of inappropriate empiric antimicrobial therapy and poor clinical outcomes. Early diagnosis and initiation of appropriate antimicrobial therapy for post-influenza bacterial pneumonia have become even more important in the era of CA-MRSA. Therefore, novel molecular diagnostic techniques should be applied to more readily diagnose MRSA pneumonia.

Keywords:

• anti-bacterial agents
• bacterial drug resistance
• bacterial pneumonia
• coinfection
• linezolid
• vancomycin

Financial & competing interests disclosure

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education (2012R1A1A2006672). The authors have no other 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 apart from those disclosed.

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

Key issues

• Secondary bacterial pneumonia is a leading cause of death associated with influenza infection.

• Incidence of Staphylococcus aureus pneumonia during different influenza seasons has been varied, but no significant deviation from previous trend was observed in the 2009–2010 influenza season when novel influenza A (H1N1) pdm09 was prevalent.

• Methicillin-resistant S. aureus (MRSA) pneumonia, including cases caused by community-associated methicillin-resistant S. aureus (CA-MRSA), is closely associated with prior influenza-like illness or laboratory-confirmed influenza infection.

• Proposed mechanisms for secondary bacterial pneumonia after influenza include virus-mediated lung tissue damage, increased bacterial adherence due to influenza neuraminidase and upregulation of platelet-activating factor receptor, suppression of innate immune function through overexpression of IFN-γ and IL-10 and subsequent inhibition of the IL-17 pathway.

• Pneumonia caused by CA-MRSA is clinically distinct entity characterized by severe manifestation, necrotizing pneumonia, leukopenia, rapid progression to shock, frequent requirement of ventilatory support and high risk of death.

• Novel molecular diagnostic techniques including real-time PCR and matrix-assisted laser desorption/ionization-time of flight are being developed to enable more rapid diagnosis of MRSA infection.

• The antimicrobial agent of choice for MRSA pneumonia has been vancomycin. Linezolid can be considered as a safe alternative.

• Early clinical diagnosis of CA-MRSA pneumonia and initiation of appropriate antibiotics are necessary in patients with bacterial pneumonia following influenza.