Legionnaires' disease in patients with associated serious disease.

Of nine patients with Legionnaires' disease, seven were receiving corticosteroids, and all nine had serious underlying diseases. Direct immunofluorescent examination of respiratory secretions, including sputum and transtracheal aspirates, showed the Legionnaires' disease (LD) bacterium in five of seven patients who seroconverted and in a sixth patient with a single elevated titer to the LD bacterium. All nine patients received erythromycin therapy, and five survived. Two patients showed persistence of their infection after receiving 2 weeks of erythromycin therapy, and two patients developed pulmonary abscesses. These cases of Legionnaires' disease show the occurrence of pulmonary abscesses, the possibility of relapse after giving only 2 weeks of erythromycin therapy, and the utility of direct immunofluorescence for early diagnosis.