Pazufloxacin投与中に再燃を来したレジオネラ肺炎の1例

Recurrence of Legionella Pneumonia Despite Pazufloxacin Mesilate Treatment:A case report

要旨

　患者は59歳，男性．温泉に入湯後，発熱，湿性咳嗽，呼吸苦を訴え，胸部X線写真で右下肺野に浸潤影と胸水を認め，尿中レジオネラ抗原が陽性を示し，レジオネラ肺炎と診断した．基礎疾患に慢性腎不全があり，pazufloxacin mesilate(PZFX)を300mg/日で投与した．一時的に改善したが，13病日から再び呼吸苦を訴え，胸部X線写真で右下肺野に浸潤影とスリガラス状陰影の混在した病変を認めた．レジオネラ肺炎の再燃と考え，PZFXを1日2回600mgに増量したところ速やかに改善し，重症化を回避できた．入院当初著明な腎機能低下があり，低用量のPZFXを投与していたが，腎機能の改善に伴いPZFXの血中濃度が徐々に低下したことが再燃の原因と考えた．

　A 59-year-old man developed pyrexia, productive cough, and dyspnea after visiting some hot-spring resorts. His chest computed tomography showed consolidation and pleural effusion in the right lung. Because Legionella antigen was detected in his urine, Legionella pneumonia caused by Legionella pneumophila serotype 1 was diagnosed. He developed chronic renal failure, and his renal function deteriorated due to severe infection. Therefore, we administered low dose pazufloxacin mesilate(300mg/day) as a treatment for Legionella pneumonia. His condition improved temporally, but he complained of dyspnea and cough on the 13^th day. Chest radiograph also showed aggravated findings in the bilateral lung fields. Under suspicion of recurrence of Legionella pneumonia, we increased the daily dose of pazufloxacin mesilate from 300mg to 600mg/day, which proved to be effective in controlling the recurred pneumonia and preventing further worsening of the illness. In this case, Legionella pneumonia recurred despite treatment with low dose pazufloxacin mesilate, which is known to be effective against Legionella. After the increase in the dose of pazufloxacin mesilate, the symptoms improved within some days. Therefore, we speculated that a gradual decrease in the concentration of pazufloxacin, which was brought about as a result of the improvement in renal function, caused the recurrence of Legionella pneumonia. In this patient with renal dysfunction, the use of therapeutic drug monitoring could have enabled better regulation of the antibiotic dose.