Importance of legionella pneumophila in the etiology of severe community-acquired pneumonia in Santiago, Chile

Abstract

Background: In US and European literature, Legionella pneumophila is reported as an important etiologic agent of severe community-acquired pneumonia (CAP), but in Chile this information is lacking. The aim of this study was to determine the incidence and identify predictors of severe CAP caused by L pneumophila in Santiago, Chile. Methods: A multicenter, prospective clinical study lasting 18 months was conducted; it included all adult patients with severe CAP admitted to the ICUs of four hospitals in Santiago. We excluded patients who were immunocompromised, had been hospitalized in the previous 4 weeks, or presented with another disease during their hospitalization. All data for the diagnosis of severe CAP were registered, and urinary antigens for L pneumophila serogroup 1 were determined. Results: A total of 104 patients with severe CAP were included (mean SD age, 58.3 19.3 years; men, 64.4%; APACHE (Acute Physiology and Chronic Health Evaluation) II score, 16.7 6.3; Sepsisrelated Organ Failure Assessment score, 6.1 3.2; Pitt Bacteremia Score, 3.4 2.5; Pa O 2 /F IO 2 , 170.8 87.1). An etiologic agent was identifi ed in 62 patients (59.6%), with the most frequent being Streptococcus pneumoniae (27 patients [26%]) and L pneumophila (nine patients [8.6%]). Logistic regression anal ysis showed that a plasma sodium level of 130 mEq/L was an independent predictor for L pneumophila severe CAP (OR, 11.3; 95% CI, 2.5-50.5; P 5 .002). Global mortality was 26% and 33% for L pneumophila . The Pitt bacteremia score and pneumonia score index were the best predictors of mortality. Conclusions: We found that in Santiago, L pneumophila was second to S pneumoniae as the etiologic agent of severe CAP. Severe hyponatremia at admission appears to be an indicator for L pneumophila etiology in severe CAP.