[Descriptive study of a pneumonia episode due to Legionella]

Legionella is a gram negative aerobic bacillus. A total of 42 species with 64 serogroups have been described, Legionella pneumophila serogroup 1 being the one that causes the disease most frequently.

Describe an outbreak of legionellosis with some characteristics different from those communicated previously.

Descriptive study of the epidemiological and clinical characteristics of the patients affected by an outbreak of pneumonia due to Legionella pneumophila serogroup 1, that occurred in Vigo in September and October, 2000, seen in the Hospital Xeral-Cies.

A total of 33 patients, with a mean age of 61 years, were diagnosed. Fifty-nine percent had underlying diseases. The most frequent symptoms were fever, cough, dyspnea, diarrhea and awareness level alterations. Elevation of creatinphosphokinase in 79% and hyponatremia in 12%. The X-ray pattern observed most frequently was unilateral alveolar with predominant involvement of inferior lobes. A total of 77% received treatment with beta lactamics and macrolides, 13% beta lactamics and quinolones and 7% quinolones. Clinical and gasometric improvement were observed at a mean of 5 and 7 days, respectively. X-ray abnormalities improved in 62% in the first week. Eighteen percent had multiorgan failure and four patients died. In the analysis of the variables considered to have poor prognosis, only multiorgan failure demonstrated a significant association with mortality.

The characteristics of the patients affected by an episode of legionellosis in our health care area were similar to those described in other outbreaks, except for the rapid resolution of the pulmonary infiltrates and low presence of hyponatremia. Multiorgan failure was the only factor associated with poor prognosis.