title: Polymicrobial intensive care unit-acquired pneumonia: prevalence, microbiology and outcome.
abstract: BACKGROUND
  Microbial aetiology of intensive care unit (ICU)-acquired pneumonia (ICUAP) determines antibiotic treatment and outcomes. The impact of polymicrobial ICUAP is not extensively known. We therefore investigated the characteristics and outcomes of polymicrobial aetiology of ICUAP.
  
  
  METHODS
  Patients with ICUAP confirmed microbiologically were prospectively compared according to identification of 1 (monomicrobial) or more (polymicrobial) potentially-pathogenic microorganisms. Microbes usually considered as non-pathogenic were not considered for the etiologic diagnosis. We assessed clinical characteristics, microbiology, inflammatory biomarkers and outcome variables.
  
  
  RESULTS
  Among 441 consecutive patients with ICUAP, 256 (58%) had microbiologic confirmation, and 41 (16%) of them polymicrobial pneumonia. Methicillin-sensitive Staphylococcus aureus, Haemophilus influenzae, and several Enterobacteriaceae were more frequent in polymicrobial pneumonia. Multi-drug and extensive-drug resistance was similarly frequent in both groups. Compared with monomicrobial, patients with polymicrobial pneumonia had less frequently chronic heart disease (6, 15% vs. 71, 33%, p = 0.019), and more frequently pleural effusion (18, 50%, vs. 54, 25%, p = 0.008), without any other significant difference. Appropriate empiric antimicrobial treatment was similarly frequent in the monomicrobial (185, 86%) and the polymicrobial group (39, 95%), as were the initial response to the empiric treatment, length of stay and mortality. Systemic inflammatory response was similar comparing monomicrobial with polymicrobial ICUAP.
  
  
  CONCLUSIONS
  The aetiology of ICUAP confirmed microbiologically was polymicrobial in 16% cases. Pleural effusion and absence of chronic heart disease are associated with polymicrobial pneumonia. When empiric treatment is frequently appropriate, polymicrobial aetiology does not influence the outcome of ICUAP.
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. miferrer@clinic.ub.es.|Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain. miferrer@clinic.ub.es.|Centro de Investigación Biomédica en Red-Enfermedades Respiratorias (CibeRes CB06/06/0028)-Instituto de Salud Carlos III (ISCiii), Madrid, Spain. miferrer@clinic.ub.es.
authors.forename: Miquel
authors.initials: M
authors.lastname: Ferrer
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. difrancescoleonardo@yahoo.it.|Department of Internal Medicine, Ospedale Sant'Andrea, "Sapienza" University, Via di Grottarossa 1035-1039, Rome, Italy. difrancescoleonardo@yahoo.it.
authors.forename: Leonardo Filippo
authors.initials: LF
authors.lastname: Difrancesco
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. mliapikou@yahoo.com.|Sotiria Chest Diseases Hospital, 6rd Respiratory Department, Mesogion 152, Athens, Greece. mliapikou@yahoo.com.
authors.forename: Adamantia
authors.initials: A
authors.lastname: Liapikou
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. marianorinaudo@gmail.com.
authors.forename: Mariano
authors.initials: M
authors.lastname: Rinaudo
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. marco.carbonara@gmail.com.|Department of Anesthesia, Università degli Studi di Milano, IRCCS Fondazione Ospedale Maggiore Policlinico Cà Granda Milano, Milan, Italy. marco.carbonara@gmail.com.
authors.forename: Marco
authors.initials: M
authors.lastname: Carbonara
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. glibassi@clinic.ub.es.|Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain. glibassi@clinic.ub.es.|Centro de Investigación Biomédica en Red-Enfermedades Respiratorias (CibeRes CB06/06/0028)-Instituto de Salud Carlos III (ISCiii), Madrid, Spain. glibassi@clinic.ub.es.
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Li Bassi
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. gabarrus@clinic.ub.es.|Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain. gabarrus@clinic.ub.es.
authors.forename: Albert
authors.initials: A
authors.lastname: Gabarrus
authors.affiliation: Department of Pneumology, Thorax Institute, Hospital Clinic, Villarroel 170, 08036, Barcelona, Spain. ATORRES@clinic.ub.es.|Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain. ATORRES@clinic.ub.es.|Centro de Investigación Biomédica en Red-Enfermedades Respiratorias (CibeRes CB06/06/0028)-Instituto de Salud Carlos III (ISCiii), Madrid, Spain. ATORRES@clinic.ub.es.
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
mesh_terms: D000328:Adult; D000368:Aged; D060085:Coinfection / Q000209:etiology* / Q000401:mortality; D003428:Cross Infection / Q000401:mortality* / Q000635:transmission; D005260:Female; D006801:Humans; D007049:Iatrogenic Disease; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000209:etiology / Q000382:microbiology / Q000401:mortality*; D015995:Prevalence; D011446:Prospective Studies