Objective: To survey the etiology and epidemiology of
community-acquired pneumonia (CAP) in relation to age, comorbidity, and
severity and to investigate prognostic factors.
Design: Prospective epidemiologic study, single
Setting: University hospital at Buenos Aires,
Patients: Outpatients and inpatients
fulfilling clinical criteria of CAP.
Systematic laboratory evaluation for determining the etiology, and
clinical evaluation stratifying patients into mild, moderate, and
severe CAP (groups 1 to 3), a clinical rule used for
Results: During a 12-month period,
343 patients (mean age, 64.4 years; range, 18 to 102 years) were
evaluated. We found 167 microorganisms in 144 cases (yield, 42%).
Streptococcus pneumoniae, the most common pathogen, was
isolated in 35 cases (24%). Mycoplasma pneumoniae,
present in 19 (13%), was second in frequency in group 1;
Haemophilus influenzae, present in 17 cases (12%), was
second in group 2; and Chlamydia pneumoniae, present in
12 cases (8%), was second in group 3. Etiology could not be determined
on the basis of clinical presentation; identifying the etiology had no
impact on mortality. Some findings were associated with specific
causative organisms and outcome. A significantly lower number of
nonsurvivors received adequate therapy (50% vs 77%).
Conclusions: Age, comorbidities, alcohol abuse, and smoking
were related with distinct etiologies. Pao2 to
fraction of inspired oxygen ratio < 250, aerobic Gram-negative
pathogen, chronic renal failure, Glasgow score < 15, malignant
neoplasm, and aspirative pneumonia were associated with mortality by
multivariate analysis. Local microbiologic data could be of help in
tailoring therapeutic guidelines to the microbiologic reality at
different settings. The stratification schema and the clinical
rule used for hospitalization were useful.