ORIGINAL ARTICLE Risk factors and outcome of community-acquired pneumonia due to Gram-negative bacilli MIQUEL FALGUERA, 1 JORDI CARRATALÀ, 2 AGUSTÍN RUIZ-GONZALEZ, 1 CAROLINA GARCIA-VIDAL, 2 ISABEL GAZQUEZ, 1 JORDI DORCA, 3 FRANCESC GUDIOL 2 AND JOSÉ M. PORCEL 1 1 Internal Medicine Service, Institut de Recerca Biomèdica de Lleida (IRBLLEIDA), Hospital Universitari Arnau de Vilanova, University of Lleida, Lleida, 2 Infectious Diseases Service, and 3 Respiratory Service, Institut d’Investigació Biomèdica de Bellvitge (IDIBELL), Hospital Universitari de Bellvitge, University of Barcelona, Barcelona, Spain ABSTRACT 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 pneumo- nia 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 cor- ticosteroids (OR 2.8, 95% CI: 1.2–6.3), prior antibiotic therapy (OR 2.6, 95% CI: 1.4–4.8), tachypnoea 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 indepen- dently associated with Gram-negative bacilli pne- umonia. 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. Key words: community-acquired pneumonia, Gram- negative bacilli, outcome, Pseudomonas aeruginosa, risk factor. INTRODUCTION The ability of Gram-negative bacilli to cause pneumo- nia was demonstrated as early as 1880, when Kleb- siella pneumoniae was identified in autopsies of patients with community-acquired pneumonia. 1 Today Gram-negative bacilli are recognized as the predominant pathogens in nosocomial pneumonia, and studies suggest that they are also very common in health care-associated pneumonia. 2 In community- acquired pneumonia, aerobic Gram-negative bacilli play a decisive role in patients with neutropenia, or advanced HIV infection and those receiving immuno- suppressive treatment. 3–5 However, the true incidence of Gram-negative bacilli infection among immuno- competent patients with community-acquired pneu- monia is unclear. Correspondence: Miquel Falguera, Service of Internal Medi- cine, Hospital Universitari Arnau de Vilanova, Rovira Roure 80, Lleida 25197, Spain. Email: mfalguera@comll.cat *Correction added 12 November 2008 after online publication: Summary at a Glance has been inserted. Received 17 March 2008; Invited to revise 14 April 2008; Revised 27 April 2008; Accepted 6 May 2008 (Associate Editor: David Hui). SUMMARY AT A GLANCE* Community-acquired pneumonia due to Gram- negative bacilli is associated with high morbidity and mortality and consequently early recognition is crucial. This retrospective study showed that initial treatment was often inappropriate and disease carried a poor prognosis. The diagnosis of gram-negative pneumonia was significantly asso- ciated with tachypnoea, septic shock, COPD, con- current steroid use and prior antibiotics therapy. © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology Respirology (2009) 14, 105–111 doi: 10.1111/j.1440-1843.2008.01371.x