Acid-fast bacilli in sputum: a case of Legionella micdadei pneumonia

Legionella micdadei has been implicated as a cause of nosocomial pneumonia. There are no reports of L. micdadei pneumonia diagnosed by acid-fast stain of expectorated sputum. We report a case of L. micdadei pneumonia in which expectorated sputum harbored acid-fast bacteria that reacted specifically with fluorescent antiserum to L. micdadei, confirmed by culture. In a patient at risk for nosocomial infection, the differential diagnosis of a positive sputum stain for acid-fast bacilli should include L. micdadei in addition to mycobacteria. Therapy for L. micdadei infection should be considered pending confirmation of the diagnosis.