The etiology of community-acquired pneumonia in Australia: why penicillin plus doxycycline or a macrolide is the most appropriate therapy.
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.
Charles
Patrick G P
PG
Department of Infectious Diseases, Austin Health, Heidelberg, VIC, Australia. patrick.charles@austin.org.au
Whitby
Michael
M
Fuller
Andrew J
AJ
Stirling
Robert
R
Wright
Alistair A
AA
Korman
Tony M
TM
Holmes
Peter W
PW
Christiansen
Keryn J
KJ
Waterer
Grant W
GW
Pierce
Robert J P
RJ
Mayall
Barrie C
BC
Armstrong
John G
JG
Catton
Michael G
MG
Nimmo
Graeme R
GR
Johnson
Barbara
B
Hooy
Michelle
M
Grayson
M L
ML
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
D000900:Anti-Bacterial Agents; D018942:Macrolides; D010406:Penicillins; D002443:Ceftriaxone; D004318:Doxycycline