We report what we believe to be the first clinical isolation of Legionella rubrilucens from a pneumonia patient co-infected with Legionella pneumophila. L. rubrilucens strains were found in both a patient's sputum and the water of a hot spring in which the patient bathed, and DNA analysis by PFGE showed that they were indistinguishable. IntroductionSince Brenner et al. (1979) isolated the bacterium that caused pneumonia in patients with Legionnaires' disease and named it Legionella pneumophila, more than 20 species of Legionella have been implicated in human diseases (Stout et al., 2003). In 1980, an environmental strain of Legionella rubrilucens was isolated from tap water by G. W. Gorman (Brenner et al., 1985). However, to date, isolation of L. rubrilucens has not been described from patients coinfected with L. pneumophila.Here we report that L. rubrilucens strains were found in both a patient's sputum and the water of a hot spring in which the patient bathed, and DNA analysis performed by PFGE (Amemura-Maekawa et al., 2005) showed that they were indistinguishable. To our knowledge, this is the first report suggesting that L. rubrilucens can co-infect humans infected with L. pneumophila. Since the progress of Legionella pneumonia is very rapid in general, it can be fatal without early diagnosis and treatment. In this study, due to the early diagnosis, Legionella pneumonia was treated successfully. Case reportA 54-year-old Japanese man, height 165 cm, weight 72 kg, presented with a high fever, a feeling of weariness and pain in the joints. He had smoked 20 cigarettes a day for 34 years and had been drinking 350 ml beer and about 360 ml shouchu (Japanese liquor, alcohol concentration 25-30 %) daily for the past 10 years. He had been working as a caretaker for the elderly.After continuous high fever for 2 days, he was admitted for treatment and examination of the cause of the fever. He still complained of weariness throughout the body without signs of pains in the joints, cough or sputum. His vital signs were stable with blood pressure 120/70 mmHg, pulse rate 120 beats min 21 and body temperature 39.2 u C. No rale was audible in either of the lungs. The Influenza A and B Antigen test was negative. Laboratory data showed a white blood cell count of 17 100 cells ml 21 (neutrophils 87.7 %) and a Creactive protein value of 15.86 mg dl 21 in the serum. Urine analysis revealed that both a protein test and occult blood test were strongly positive (3+), assumingly due to an inflammatory response of the urinary tract from a bacterial infection. On the X-ray film, we observed minimal infiltrative shadows on the left middle and lower lobes.After admission, his febrile state did not change despite the administration of flomoxef at 2 g per day. On the 3rd day, he started to have a dry cough and fine crackles were audible in the left lower lobe. We found extended infiltrative shadows on the left middle and lower lobes in the chest X-ray (Fig. 1). The oxygen saturation by pulse oximetry (SpO 2 ) had declined to 93 % at this poi...