The first recognized patient with Legionella pneumophila serogroup 9 pneumonia in Japan

A 77-year-old female was admitted because of high fever, cough and sputum. She had been receiving corticosteroid therapy for 4 years for multiple myeloma and was immunosuppressed. A physical examination on admission showed coarse crackles in the right lower lung field, a chest radiograph showed consolidation in the right middle and lower lung fields, and a blood gas analysis revealed marked hypoxemia. The patient was diagnosed as having refractory pneumonia associated with acute respiratory failure and treated with intravenous cefmetazole followed by imipenem. On hospital day 5, erythromycin therapy was started because of a poor response to the previous antibiotics. The patient became afebrile on the tenth day and was in good health on day 15. A sputum culture on day 4 revealed a Legionella organism on Wadowsky-Yee-Okuda medium, which was subsequently confirmed to be Legionella pneumophila by a DNA hybridization test. This strain was identified at the Centers for Disease Control (Atlanta, GA, USA) by slide agglutination as L. pneumophila serogroup 9. Although our patient's symptoms are not apparently different from those caused by other serogroup strains of L. pneumophila, this is the first recognized patient with culture-proven L. pneumophila serogroup 9 pneumonia in Japan. The clinical course of the disease and the diagnostic difficulties in identifying this type of pneumonia are discussed.