Disclosed are a novel pyridine thio derivative, and a pharmaceutical composition using the novel pyridine thio derivative, particularly a pharmaceutical composition having selective antibacterial activity against Helicobacter pylori. Specifically disclosed is a pyridine thio derivative represented by general formula (I) (wherein R 1 and R 2 each represents a hydrogen atom, a C 1-8 alkyl group or the like； R 3 and R 4 each represents a hydrogen atom, a C 1-8 alkyl group or the like； X represents -O-, -S- or the like； Y represents a C 1-12 alkyl group which may be substituted by a substituent or -(R S -O) n -R 6 (wherein R 5 represents a C 1-5 alkylene group； R 6 represents a C 1-8 alkyl group which may be substituted by a substituent, and n represents an integer of 1-10)； and Z represents a hydrogen atom or the like), or a pharmacologically acceptable salt thereof. Also specifically disclosed is a pharmaceutical composition containing the pyridine thio derivative or a salt thereof.
