The invention relates to the compounds of formula Iwherein A is N or CH; and n is 0 or 1; or the pharmaceutically acceptable salts thereof, for preventing or treating intestinal diseases which are caused by bacteria selected fromClostridium difficile,Clostridium perfringens or Staphylococcus aureus.本發明係關於式I化合物其中A係N或CH;且n係0或1;或其醫藥上可接受之鹽,其係用來預防或治療由選自難辨梭菌(Clostridium difficile)、產氣莢膜梭菌(Clostridium perfringens)或金黃色葡萄球菌(Staphylococcus aureus)之細菌引起之腸疾病。