Etiology of community-acquired pneumonia in a population-based study: link between etiology and patients characteristics, process-of-care, clinical evolution and outcomes.
BACKGROUND
The etiologic profile of community-acquired pneumonia (CAP) for each age group could be similar among inpatients and outpatients. This fact brings up the link between etiology of CAP and its clinical evolution and outcome. Furthermore, the majority of pneumonia etiologic studies are based on hospitalized patients, whereas there have been no recent population-based studies encompassing both inpatients and outpatients.


METHODS
To evaluate the etiology of CAP, and the relationship among the different pathogens of CAP to patients characteristics, process-of-care, clinical evolution and outcomes, a prospective population-based study was conducted in Spain from April 1, 2006, to June 30, 2007. Patients (age >18) with CAP were identified through the family physicians and the hospital area.


RESULTS
A total of 700 patients with etiologic evaluation were included: 276 hospitalized and 424 ambulatory patients. We were able to define the aetiology of pneumonia in 55.7% (390/700). The most frequently isolated organism was S. pneumoniae (170/390, 43.6%), followed by C. burnetti (72/390, 18.5%), M. pneumoniae (62/390, 15.9%), virus as a group (56/390, 14.4%), Chlamydia species (39/390, 106%), and L. pneumophila (17/390, 4.4%). The atypical pathogens and the S. pneumoniae are present in pneumonias of a wide spectrum of severity and age. Patients infected by conventional bacteria were elderly, had a greater hospitalization rate, and higher mortality within 30 days.


CONCLUSIONS
Our study provides information about the etiology of CAP in the general population. The microbiology of CAP remains stable: infections by conventional bacteria result in higher severity, and the S. pneumoniae remains the most important pathogen. However, atypical pathogens could also infect patients in a wide spectrum of severity and age.
Pneumology Service Hospital Galdakao, Galdakao, Bizkaia, Spain. alberto.capelasteguisaiz@osakidetza.net
Alberto
A
Capelastegui
Pedro P
PP
España
Amaia
A
Bilbao
Julio
J
Gamazo
Federico
F
Medel
Juan
J
Salgado
Iñaki
I
Gorostiaga
Maria Jose
MJ
Lopez de Goicoechea
Inmaculada
I
Gorordo
Cristobal
C
Esteban
Lander
L
Altube
Jose M
JM
Quintana
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001419:Bacteria / Q000145:classification* / Q000302:isolation & purification*; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000209:etiology* / Q000473:pathology; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000453:epidemiology* / Q000209:etiology* / Q000473:pathology; D011446:Prospective Studies; D013030:Spain / Q000453:epidemiology; D016896:Treatment Outcome; D055815:Young Adult