What are the possible etiologies of community-acquired pneumonia (CAP) in patients admitted to the ICU?

Updated: Oct 31, 2019
  • Author: Stephanie L Baer, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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In certain patients admitted to the ICU, the microbial etiology of pneumonia may be complex. In a study by Cilloniz et al, 11% of cases were polymicrobial. The most frequently identified pathogens in polymicrobial infections were S pneumoniae, respiratory viruses, and P aeruginosa. Chronic respiratory disease and acute respiratory distress syndrome (ARDS) criteria were independent predictors of a polymicrobial infection. [39] Bacterial and viral co-infection may portend a worse prognosis. [40, 41]

Other gram-negative pathogens (eg, Enterobacter species, Serratia species, Stenotrophomonas maltophilia, Burkholderia cepacia) rarely cause CAP in patients without underlying lung disease or immunosuppression.

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