[Nosocomial legionellosis: study of 51 cases]

We report the features of 51 cases of hospital-acquired Legionella pneumophila pneumonia (HLP), diagnosed in our hospital during a period of about 5 years. Mean age was 64.6 years, and the male:female ratio 1.6. 29% of HLP involved patients who were not admitted to the hospital at the time of diagnosis. The monthly distribution showed a maximal incidence in July and August. Only 6% of cases involved patients without underlying diseases. The most common underlying diseases were chronic obstructive lung disease (COLD) (37%), heart disease (29%) and immunosuppressant therapy (29%). 21% of the patients with renal transplant had HLP. The only constant clinical feature was fever of 37.8 degrees C or higher. During the first 24-48 hours of illness, respiratory symptoms were not present in 41% of cases, and thoracic abnormalities in the physical examination were not present in 31%. The laboratory abnormalities were nonspecific and with incidence rates lower than 50%. In 41% of patients there was hypoxemia (60 mmHg or lower) with FiO2 of 0.21. The most common radiological finding was the initial unilateral and unilobar involvement. Pleural effusion and cavitation developed in 20% and 4%, respectively. Overall mortality rate was 12%. In the 43 patients treated early with intravenous erythromycin, mortality rate was 7%. We think that the relatively low incidence of severe underlying immunosuppression and the inclusion of hospital-acquired pneumonia in our institution influenced the low mortality rate of the present study, in contrast with other series of hospital-acquired legionellosis.