The reported incidence of Legionella sp as a cause of community-acquired pneumonia ranges from 1 to 30 percent of cases in various series. But despite these widely divergent data, most studies have demonstrated the great importance of this agent in the etiology of community-acquired pneumonias, especially in severe cases. There are some factors that increase the frequency of this infection (advanced age, alcoholism, cigarette smoking, chronic disease, immunosuppression, patients receiving organ transplants) and people with these risk factors are more likely to develop a severe disease with respiratory failure and other systemic complications.
Our working team is carrying out a prospective follow-up of community-acquired pneumonias, and we have noticed a considerable increase in the incidence of pneumonia caused by L pneumophila. It is for this reason and also for the severity that usually accompanies this disease that we conducted a prospective study of all patients admitted for community-acquired pneumonia in our hospital in order (1) to know the real incidence of pneumonia caused by L pneumophila in our community, (2) to find clinical features and laboratory data that would allow us to differentiate community-acquired pneumonia caused by L pneumophila from pneumococcal pneumonia, (3) to identify clinical, radiologic or laboratory data that would be suggestive of pneumonia caused by L pneumophila and would lead to earlier therapy, and (4) to determine the utility of culture techniques in the diagnosis of pneumonia due to L pneumophila.