title: Community-acquired polymicrobial pneumonia in the intensive care unit: aetiology and prognosis.
abstract: BACKGROUND
  The frequency and clinical significance of polymicrobial aetiology in community-acquired pneumonia (CAP) patients admitted to the ICU have been poorly studied. The aim of the present study was to describe the prevalence, clinical characteristics and outcomes of severe CAP of polymicrobial aetiology in patients admitted to the ICU.
  
  
  METHODS
  The prospective observational study included 362 consecutive adult patients with CAP admitted to the ICU within 24 hours of presentation; 196 (54%) patients had an established aetiology.
  
  
  RESULTS
  Polymicrobial infection was present in 39 (11%) cases (20% of those with defined aetiology): 33 cases with two pathogens, and six cases with three pathogens. The most frequently identified pathogens in polymicrobial infections were Streptococcus pneumoniae (n = 28, 72%), respiratory viruses (n = 15, 39%) and Pseudomonas aeruginosa (n = 8, 21%). Chronic respiratory disease and acute respiratory distress syndrome criteria were independent predictors of polymicrobial aetiology. Inappropriate initial antimicrobial treatment was more frequent in the polymicrobial aetiology group compared with the monomicrobial aetiology group (39% vs. 10%, P < 0.001), and was an independent predictor of hospital mortality (adjusted odds ratio = 10.79, 95% confidence interval = 3.97 to 29.30; P < 0.001). The trend for higher hospital mortality of the polymicrobial aetiology group compared with the monomicrobial aetiology group (n = 8, 21% versus n = 17, 11%), however, was not significantly different (P = 0.10).
  
  
  CONCLUSIONS
  Polymicrobial pneumonia occurs frequently in patients admitted to the ICU. This is a risk factor for inappropriate initial antimicrobial treatment, which in turn independently predicts hospital mortality.
authors.affiliation: Department of Pneumology, Institut Clinic del Tórax, Hospital Clinic of Barcelona-Institut d'Investigacions Biomèdiques August Pi i Sunyer, University of Barcelona-SGR 911-Ciber de Enfermedades Respiratorias, Villarroel 170, Barcelona 08036, Spain.
authors.forename: Catia
authors.initials: C
authors.lastname: Cillóniz
authors.forename: Santiago
authors.initials: S
authors.lastname: Ewig
authors.forename: Miquel
authors.initials: M
authors.lastname: Ferrer
authors.forename: Eva
authors.initials: E
authors.lastname: Polverino
authors.forename: Albert
authors.initials: A
authors.lastname: Gabarrús
authors.forename: Jorge
authors.initials: J
authors.lastname: Puig de la Bellacasa
authors.forename: Josep
authors.initials: J
authors.lastname: Mensa
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
mesh_terms: D000368:Aged; D060085:Coinfection / Q000453:epidemiology* / Q000382:microbiology; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000453:epidemiology* / Q000382:microbiology; D011379:Prognosis; D011446:Prospective Studies; D012720:Severity of Illness Index