title: Polybacterial aetiology and outcomes in patients with community-acquired pneumonia.
abstract: METHODS
  Community-acquired pneumonia (CAP) is a common cause of morbidity and mortality worldwide. While interactions among bacterial pathogens in the respiratory tract have been studied, the impact of polybacterial aetiology on mortality has not been fully elucidated.
  
  
  OBJECTIVE
  To investigate the impact of polybacterial aetiology on mortality, prevalence, microbial patterns and clinical characteristics among CAP patients.
  
  
  METHODS
  Retrospective data analysis.
  
  
  RESULTS
  Bacterial aetiology was established in 711 (46.0%) of 1544 enrolled hospitalised CAP patients. Of these, polybacterial aetiology was identified in 89 (12.5%): Streptococcus pneumoniae was the most frequently identified pathogen (n = 55, 61.8%). The most prevalent microbial combination was S. pneumoniae and Haemophilus influenzae (n = 19, 21.3%). Alcoholism and lack of previous antibiotic therapy were independent predictors of polybacterial aetiology. The proportion of patients with severe pneumonia was significantly higher in the polybacterial aetiology group than in the monobacterial group. Multivariate analysis showed that polybacterial aetiology was a predictor of 30-day mortality (OR 2.14, 95%CI 1.07-4.24, P = 0.030), independently of severe pneumonia status, pneumonia severity index, chronic obstructive pulmonary disease and inappropriate empirical therapy.
  
  
  CONCLUSIONS
  Polybacterial CAP tends to advance in severity, and indicates adverse outcomes.
authors.affiliation: Department of Respiratory Medicine, Ohara Memorial Kurashiki Healthcare Foundation, Kurashiki Central Hospital, Kurashiki, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kumagai
authors.affiliation: Department of Respiratory Medicine, Ohara Memorial Kurashiki Healthcare Foundation, Kurashiki Central Hospital, Kurashiki, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ishida
authors.affiliation: Department of Respiratory Medicine, Ohara Memorial Kurashiki Healthcare Foundation, Kurashiki Central Hospital, Kurashiki, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tachibana
authors.affiliation: Department of Respiratory Medicine, Ohara Memorial Kurashiki Healthcare Foundation, Kurashiki Central Hospital, Kurashiki, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ito
authors.affiliation: Department of Respiratory Medicine, Ohara Memorial Kurashiki Healthcare Foundation, Kurashiki Central Hospital, Kurashiki, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Respiratory Medicine, Ohara Memorial Kurashiki Healthcare Foundation, Kurashiki Central Hospital, Kurashiki, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hashimoto
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D060085:Coinfection; D017714:Community-Acquired Infections / Q000150:complications / Q000453:epidemiology* / Q000382:microbiology / Q000401:mortality; D005260:Female; D006193:Haemophilus influenzae / Q000302:isolation & purification; D006760:Hospitalization; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009026:Mortality; D018410:Pneumonia, Bacterial / Q000150:complications / Q000453:epidemiology* / Q000382:microbiology / Q000401:mortality; D015995:Prevalence; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013296:Streptococcus pneumoniae / Q000302:isolation & purification; D055815:Young Adult