PURPOSE:Pneumonia remains a major cause of morbidity and mortality in critically ill patients. The microbiology of non-nosocomial pneumonia (e.g. community-acquired (CAP) and healthcare-associated) necessitating mechanical ventilation (MV) at presentation may be shifting.
METHODS:Over the course of three years (2005–2007) we retrospectively identified all subjects admitted to the hospital for pneumonia, whom required MV on presentation, and had a positive culture. The culprit organism served as the primary endpoint. Pneumonia was diagnosed based on traditional clinical criteria. We made microbiologic diagnoses from invasive lower airway cultures, blood cultures, and urinary antigens. We grouped pathogens into traditional CAP organisms vs. antibiotic resistant pathogens. We also explored temporal changes in microbiology.
RESULTS:The sample included 328 subjects. The most frequently identified organisms included: S. pneumoniae (n=61, 18.6%), Methicillin-resistant Staphylococcus aureus (MRSA) (n=51, 15.5%), S. viridans (n=52, 15.9%), P. aeruginosa (PA)(n=38, 11.6%), and Methicillin-sensitive S. aureus (n=37, 11.3%). Organisms such as, Legionella spp, and Haemopholous influenzae were rarely implicated (aggregate n=46, 14.0%). Over the three year period, the proportion of severe pneumonia requiring MV due to MRSA remained unchanged while the proportion of pneumonias due to P. aeruginosa declined from 12% to 6% (p=0.044).
CONCLUSION:In patients presenting to the hospital with pneumonia and requiring MV, traditional community-acquired pathogens are infrequent. Shifting microbiology in this population indicates that healthcare-associated pneumonia may be supplanting community-acquired pneumonia in the ICU.
CLINICAL IMPLICATIONS:Physicians must adjust initial antibiotic therapy protocols for critically ill MV patients admitted with pneumonia to ensure these subjects receive initially appropriate treatment.
DISCLOSURE:Matthew Schreiber, Grant monies (from industry related sources) Astellas Pharma US, Ortho-MacNeil-Jansen, Pfizer; Consultant fee, speaker bureau, advisory committee, etc. Astellas Pharma US, Ortho-MacNeil-Jansen, Pfizer; No Product/Research Disclosure Information