Risk factors and outcome of community-acquired pneumonia due to Gram-negative bacilli

Respirology. 2009 Jan;14(1):105-11. doi: 10.1111/j.1440-1843.2008.01371.x.


Background and objective: Several sets of guidelines have advocated initial antibiotic treatment for community-acquired pneumonia due to Gram-negative bacilli in patients with specific risk factors. However, evidence to support this recommendation is scarce. We sought to identify risk factors for community-acquired pneumonia due to Gram-negative bacilli, including Pseudomonas aeruginosa, and to assess outcomes.

Methods: An observational analysis was carried out on prospectively collected data for immunocompetent adults hospitalized for community-acquired pneumonia in two acute-care hospitals. Cases of pneumonia due to Gram-negative bacilli were compared with those of non-Gram-negative bacilli causes.

Results: Sixty-one (2%) of 3272 episodes of community-acquired pneumonia were due to Gram-negative bacilli. COPD (odds ratio (OR) 2.4, 95% confidence interval (CI): 1.2-5.1), current use of corticosteroids (OR 2.8, 95% CI: 1.2-6.3), prior antibiotic therapy (OR 2.6, 95% CI: 1.4-4.8), tachypnoea >or=30 cycles/min (OR 2.1, 95% CI: 1.1-4.2) and septic shock at presentation (OR 6.1, 95% CI: 2.5-14.6) were independently associated with Gram-negative bacilli pneumonia. Initial antibiotic therapy in patients with pneumonia due to Gram-negative bacilli was often inappropriate. These patients were also more likely to require admission to the intensive care unit, had longer hospital stays, and higher early (<48 h) (21% vs 2%; P < 0.001) and overall mortality (36% vs 7%; P < 0.001).

Conclusions: These results suggest that community-acquired pneumonia due to Gram-negative bacilli is uncommon, but is associated with a poor outcome. The risk factors identified in this study should be considered when selecting initial antibiotic therapy for patients with community-acquired pneumonia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / therapeutic use
  • Community-Acquired Infections / drug therapy
  • Community-Acquired Infections / epidemiology*
  • Female
  • Gram-Negative Bacterial Infections / drug therapy
  • Gram-Negative Bacterial Infections / epidemiology*
  • Humans
  • Incidence
  • Logistic Models
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Pneumonia, Bacterial / drug therapy
  • Pneumonia, Bacterial / epidemiology*
  • Pseudomonas Infections / drug therapy
  • Pseudomonas Infections / epidemiology
  • Risk Factors
  • Spain / epidemiology
  • Treatment Outcome


  • Anti-Bacterial Agents