title: Community-acquired Legionella pneumonia: new insights from the German competence network for community acquired pneumonia.
abstract: BACKGROUND
  The Competence Network for Community Acquired Pneumonia (CAPNETZ) offers a unique opportunity to study the epidemiology of legionellosis throughout Germany, applying sophisticated diagnostic tools.
  
  
  METHODS
  The incidence, clinical characteristics, and outcome of Legionella pneumonia in 2503 adult patients with community-acquired pneumonia, participating in the German Multicenter Study of the CAPNETZ, were studied.
  
  
  RESULTS
  Legionella pneumonia was diagnosed in 94 patients (3.8%), thus identifying Legionella species as one of the most common pathogens to cause community-acquired pneumonia. It was equally common among ambulatory and hospitalized patients (3.7% and 3.8%, respectively). The predominant species causing community-acquired pneumonia was Legionella pneumophila; however, 10% of cases were caused by other species not detectable by the urinary antigen test. Patients whose disease was diagnosed by urinary antigen testing experienced a more severe clinical course. Compared with hospitalized patients, ambulatory patients with Legionella pneumonia showed an equal sex distribution, were younger, had fewer comorbidities, fewer cases of discordant initial antimicrobial treatment, and a milder clinical course without fatalities. Thirty percent of patients with Legionella pneumonia received discordant initial antimicrobial treatment without increased mortality.
  
  
  CONCLUSIONS
  Legionella is a leading cause of community-acquired pneumonia in Germany. It needs to be considered equally in hospitalized and ambulatory patients. A positive result of a urine antigen test is associated with a more severe clinical course and leads to a potentially relevant underrecognition of species other than L. pneumophila. Legionella pneumonia in outpatients differs significantly from that in hospitalized patients in terms of clinical presentation and outcome. There was an unacceptably high rate of discordant initial antimicrobial treatment.
authors.affiliation: Institute for Medical Microbiology and Hygiene, University Hospital of Ulm, Germany. heike.von-baum@uniklinik-ulm.de
authors.forename: Heike
authors.initials: H
authors.lastname: von Baum
authors.forename: Santiago
authors.initials: S
authors.lastname: Ewig
authors.forename: Reinhard
authors.initials: R
authors.lastname: Marre
authors.forename: Norbert
authors.initials: N
authors.lastname: Suttorp
authors.forename: Susanne
authors.initials: S
authors.lastname: Gonschior
authors.forename: Tobias
authors.initials: T
authors.lastname: Welte
authors.forename: Christian
authors.initials: C
authors.lastname: Lück
mesh_terms: D000328:Adult; D000368:Aged; D017714:Community-Acquired Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007875:Legionella / Q000235:genetics / Q000302:isolation & purification*; D007876:Legionellosis / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000175:diagnosis* / Q000453:epidemiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S