title: The etiology of community-acquired pneumonia in Australia: why penicillin plus doxycycline or a macrolide is the most appropriate therapy.
abstract: BACKGROUND
  Available data on the etiology of community-acquired pneumonia (CAP) in Australia are very limited. Local treatment guidelines promote the use of combination therapy with agents such as penicillin or amoxycillin combined with either doxycycline or a macrolide.
  
  
  METHODS
  The Australian CAP Study (ACAPS) was a prospective, multicenter study of 885 episodes of CAP in which all patients underwent detailed assessment for bacterial and viral pathogens (cultures, urinary antigen testing, serological methods, and polymerase chain reaction). Antibiotic agents and relevant clinical outcomes were recorded.
  
  
  RESULTS
  The etiology was identified in 404 (45.6%) of 885 episodes, with the most frequent causes being Streptococcus pneumoniae (14%), Mycoplasma pneumoniae (9%), and respiratory viruses (15%; influenza, picornavirus, respiratory syncytial virus, parainfluenza virus, and adenovirus). Antibiotic-resistant pathogens were rare: only 5.4% of patients had an infection for which therapy with penicillin plus doxycycline would potentially fail. Concordance with local antibiotic recommendations was high (82.4%), with the most commonly prescribed regimens being a penicillin plus either doxycycline or a macrolide (55.8%) or ceftriaxone plus either doxycycline or a macrolide (36.8%). The 30-day mortality rate was 5.6% (50 of 885 episodes), and mechanical ventilation or vasopressor support were required in 94 episodes (10.6%). Outcomes were not compromised by receipt of narrower-spectrum beta-lactams, and they did not differ on the basis of whether a pathogen was identified.
  
  
  CONCLUSIONS
  The vast majority of patients with CAP can be treated successfully with narrow-spectrum beta-lactam treatment, such as penicillin combined with doxycycline or a macrolide. Greater use of such therapy could potentially reduce the emergence of antibiotic resistance among common bacterial pathogens.
authors.affiliation: Department of Infectious Diseases, Austin Health, Heidelberg, VIC, Australia. patrick.charles@austin.org.au
authors.forename: Patrick G P
authors.initials: PG
authors.lastname: Charles
authors.forename: Michael
authors.initials: M
authors.lastname: Whitby
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Fuller
authors.forename: Robert
authors.initials: R
authors.lastname: Stirling
authors.forename: Alistair A
authors.initials: AA
authors.lastname: Wright
authors.forename: Tony M
authors.initials: TM
authors.lastname: Korman
authors.forename: Peter W
authors.initials: PW
authors.lastname: Holmes
authors.forename: Keryn J
authors.initials: KJ
authors.lastname: Christiansen
authors.forename: Grant W
authors.initials: GW
authors.lastname: Waterer
authors.forename: Robert J P
authors.initials: RJ
authors.lastname: Pierce
authors.forename: Barrie C
authors.initials: BC
authors.lastname: Mayall
authors.forename: John G
authors.initials: JG
authors.lastname: Armstrong
authors.forename: Michael G
authors.initials: MG
authors.lastname: Catton
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Nimmo
authors.forename: Barbara
authors.initials: B
authors.lastname: Johnson
authors.forename: Michelle
authors.initials: M
authors.lastname: Hooy
authors.forename: M L
authors.initials: ML
authors.lastname: Grayson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001315:Australia / Q000453:epidemiology; D001419:Bacteria / Q000187:drug effects / Q000302:isolation & purification; D002443:Ceftriaxone / Q000627:therapeutic use; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology* / Q000401:mortality / Q000821:virology*; D004318:Doxycycline / Q000627:therapeutic use*; D005260:Female; D019983:Guideline Adherence / Q000706:statistics & numerical data; D006801:Humans; D018942:Macrolides / Q000627:therapeutic use*; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010406:Penicillins / Q000627:therapeutic use*; D018410:Pneumonia, Bacterial / Q000453:epidemiology / Q000382:microbiology* / Q000401:mortality; D011024:Pneumonia, Viral / Q000453:epidemiology / Q000401:mortality / Q000821:virology*; D011446:Prospective Studies; D016896:Treatment Outcome; D014780:Viruses / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D010406:Penicillins; D002443:Ceftriaxone; D004318:Doxycycline