Pneumonia and Multiple Lung Abscesses Caused by Dual Infection with Legionella micdadei and Legionella pneumophila

An immunocompromised patient developed pneumonia in which both Legionella micdadei and L. pneumophila, serogroup 6, were isolated from transtracheal aspirates in the absence of any other bacteria. Unusual features included the development of disseminated intravascular coagulation and multiple pulmonary abscesses during treatment with erythromycin, and relapse of the legionellosis after extended therapy with both erythromycin and rifampin, which was heralded by septic shock. Because simultaneous infection with two distinct species of Legionella occurs, concurrent increases in antibody titer to more than one Legionella may, in some instances, reflect multiple infection rather than cross-reacting antibody.