PROBLEM TO BE SOLVED: To relate to a composition and a method for treating infectious diseases by bacteria, to provide a method for treating cystic fibrosis (CF), non-CF bronchiectasis, and acute exacerbation in chronic obstructive pulmonary disease, and to provide a pharmaceutical composition used for the same.SOLUTION: Provided is the powder composition administered to lung which contains ciprofloxacin betaine, porous long chain saturated phosphatidylcholine, and calcium chloride, and contains a particle having an aerodynamic mass median diameter of about 1 to about 5 &mu；m. The fluoroquinolone concerned has a half-life of pulmonary retention of at least 1.5 hours. It is useful for the treatment of infectious disease in a bronchus by Pseudomonas aeruginosa or the like, particularly cystic fibrosis.【課題】バクテリアによる感染症を治療するための組成物、及び方法に関連し、また嚢胞性線維症（ＣＦ）、非ＣＦ気管支拡張症、及び慢性閉塞性肺疾患における急性増悪の治療する方法及びそのために用いる医薬組成物の提供。【解決手段】シプロフロキサシンベタイン、多孔質長鎖飽和ホスファチジルコリン及び塩化カルシウムを含む、約１～約５μｍの空気動力学的質量中央径を有する粒子を含有し、当該フルオロキノロンが、少なくとも１．５時間の肺中半減期を有する、緑膿菌等による気管支内感染症、特に嚢胞性線維症の治療に有用である、肺に投与する粉末組成物。【選択図】なし
