ORIGINAL ARTICLE Improved survival among ICU-hospitalized patients with community-acquired pneumonia by unidentified organisms: a multicenter case–control study J. Rello 1,2 & E. Diaz 2,3 & R. Mañez 4 & J. Sole-Violan 2,5 & J. Valles 2,6 & L. Vidaur 2,7 & R. Zaragoza 8 & S. Gattarello 9 & CAPUCI II Consortium Received: 2 September 2016 /Accepted: 2 September 2016 /Published online: 21 September 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract A retrospective analysis from prospectively collect- ed data was conducted in intensive care units (ICUs) at 33 hospitals in Europe comparing the trend in ICU survival among adults with severe community-acquired pneumonia (CAP) due to unknown organisms from 2000 to 2015. The secondary objective was to establish whether changes in anti- biotic policies were associated with different outcomes. ICU mortality decreased (p = 0.02) from 26.9 % in the first study period (2000–2002) to 15.7 % in the second period (2008– 2015). Demographic data and clinical severity at admission were comparable between groups, except for age over 65 years and incidence of cardiomyopathy. Over time, patients received higher rates of combination therapy (94.3 vs. 77.2 %; p < 0.01) and early (<3 h) antibiotic delivery (72.9 vs. 50.3 %; p < 0.01); likewise, the 2008–2015 group was more likely to receive adequate antibiotic prescription [as defined by the Infectious Diseases Society of America/American Thoracic Society (IDSA/ATS) guidelines] than the 2000–2002 group (70.7 vs. 48.2 %; p < 0.01). Multivariate analysis showed an independent association between decreased ICU mortality and early (<3 h) antibiotic administration [odds ratio (OR) 3.48 [1.70–7.15], p < 0.01] or adequate antibiotic prescription ac- cording to guidelines (OR 2.22 [1.11–4.43], p = 0.02). In con- clusion, our findings suggest that ICU mortality in severe CAP due to unidentified organisms has decreased in the last 15 years. Several changes in management and better compli- ance with guidelines over time were associated with increased survival. Introduction Community-acquired pneumonia (CAP) is a major cause of death worldwide and the foremost cause of death due to in- fectious diseases in western countries [1]. In its most severe forms of presentation, CAP is still associated with high mor- bidity and mortality, and entails a significant social cost [2]. Despite extensive studies, the management of several aspects of severe CAP remains controversial. For example, optimal antibiotic treatment in severe CAP is still an open issue. The administration of early antibiotic treatment seems to be associated with better outcomes, both in patients requiring vasopressors [3] and in those who underwent mechanical ven- tilation [4]. Combination antibiotic therapy has also been as- sociated with a decrease in mortality, although not all studies have reached similar conclusions [5]. Finally, compliance with international guidelines is associated with improved survival [6]. However, even with extensive sampling, the microorgan- ism responsible for CAP is identified in fewer than 50 % of cases [2]. CAPUCI II investigators are listed at the end of the text. * J. Rello jrello@crips.es CAPUCI II Consortium 1 Universitat Autonoma de Barcelona, Barcelona, Spain 2 CIBERES, Barcelona, Spain 3 Hospital Joan XXIII, Tarragona, Spain 4 Hospital de Bellvitge, Barcelona, Spain 5 Hospital Negrin, Las Palmas de Gran Canaria, Spain 6 Hospital Parc Tauli, Sabadell, Spain 7 Hospital de Donostia, Donostia, Spain 8 Hospital Peset, Valencia, Spain 9 Toronto General Hospital, Toronto, Canada Eur J Clin Microbiol Infect Dis (2017) 36:123–130 DOI 10.1007/s10096-016-2779-5