Legionella species community-acquired pneumonia. A review of 56 hospitalized adult patients.

BACKGROUND

In a prospective study, Legionella species (Lsp) was identified as the causative agent in 56 (16.2%) of 346 adult patients hospitalized over the course of 1 year with community-acquired pneumonia (CAP), in the Soroka Medical Center, Beer-Sheva, Israel.

OBJECTIVE

To characterize patients with Lsp CAP in our study.

METHODS

The diagnosis of infection with Lsp was based on serologic testing of antibodies using the indirect immunofluorescent method.

RESULTS

In 35 (62.5%) of the patients, at least one other etiologic agent for CAP was identified in addition to Lsp. The patient population was relatively young, with relatively low rates of chronic comorbidity, and a broad spectrum of disease severity compared with previously published studies. No single epidemiologic, clinical, laboratory, or radiographic characteristic differentiated between Lsp CAP and other CAP patients in our study. Three patients (5.4%) who were not treated with erythromycin died. However, in contrast, nine patients who were treated with beta-lactam antibiotics recovered completely.

CONCLUSIONS

Lsp is a common cause of CAP in our region, usually as a coinfection with another causative agent. Lsp CAP, which cannot be characterized on the basis of clinical, routine laboratory, or radiographic data, requires specific microbiologic or serologic diagnosis. Treatment with erythromycin appears to be important to reduce mortality from this disease, but in a significant number of patients, the disease may be self-limited.