Primary isolation of a new strain of the TATLOCK/Pittsburgh pneumonia agent (Legionella micdadei).

Pneumonia, empyema and lung abscesses developed in a patient following a neurosurgical procedure and associated short-term corticosteroid therapy. An organism identical to the TATLOCK/Pittsburgh pneumonia agent (Legionella micdadei) was the only organism isolated from multiple specimens from lung aspirates and chest tube drainage. The organism was isolated directly on charcoal yeast extract (CYE) agar and classified as identical to the TATLOCK bacterium by direct immunofluorescent staining and by gas-liquid chromatography of cellular fatty acids. The patient's pulmonary infection improved during treatment with penicillin. Serum specimens obtained from the patient during convalescence showed an indirect fluorescent antibody reciprocal titer of 16,000 to his homologous antigen, but he also had titers that were potentially diagnostic against antigens of the six serogroups of Legionella pneumophila and three other Legionella-like organisms. Legionella can be isolated from clinical specimens by the routine use of CYE agar, which should be incorporated as the primary isolation medium for chest fluids and lung specimens. It appears that a large battery of antigens will be required for serological testing to diagnose infections caused by L micadei, L pneumophila and Legionella-like organisms.