Legionnaires' disease in South Australia. Prevalence and diagnosis.

Legionella pneumophila was successfully isolated from sputum, and from respiratory secretions obtained by tracheal aspiration, of two patients with Legionnaires' disease by means of guinea pigs and charcoal yeast extract agar. Direct culture of lung tissue from one of these patients gave a pure growth of L. pneumophila. In both cases, legionellas were isolated from specimens which were collected several days after treatment with erythromycin began. Direct fluorescent antibody tests on these specimens gave positive results. This test can result in the rapid diagnosis of legionellosis in carefully selected patients. Serological diagnosis by demonstrating a greater than fourfold rise in antibody level, particularly that of IgM antibody, is the method of choice for making the diagnosis of legionellosis in patients who do not have life-threatening infections or in whom a definitive bacteriological diagnosis cannot be made. Serological studies suggest that infection with L. pneumophila is endemic in South Australia.