Successful treatment of Legionella micdadei (Pittsburgh pneumonia agent) pneumonia with erythromycin.

Optimal treatment of Legionella micdadei pneumonia has not been established, although in vitro studies have shown the pathogen to be sensitive to erythromycin. At our institution, L. micdadei pneumonia was diagnosed in six patients over a one and one-half year period. All patients were immunocompromised and had a typical clinical syndrome; in four of six, diagnosis was made by isolation of the pathogen. All patients received erythromycin (2 to 4 g daily) for 12 to 27 days, and five of six recovered completely. One patient improved initially but died four weeks later from Serratia marcescens pneumonia and septicemia. Although L. micdadei may cause life-threatening pneumonia in immunocompromised hosts, prompt diagnosis and institution of erythromycin therapy can result in a favorable outcome.