A compound represented by general formula (1) (wherein R 1 represents a hydrogen atom, an optionally substituted C 1-6 alkyl group or the like； R 2 represents a hydrogen atom, an optionally substituted C 1-6 alkyl group or the like； R 3 represents a hydrogen atom or an optionally substituted C 1-6 alkyl group； R 4 represents a hydrogen atom, an optionally substituted C 1-6 alkyl group or the like； X 1 represents an optionally substituted C 2-6 alkynylene group or the like； A represents an optionally substituted bivalent aromatic hydrocarbon group or the like； X 2 represents an optionally substituted C 1-6 alkylene group or the like； Y 1 represents an oxygen atom or the like； and R 5 represents a hydrogen atom or the like) or a salt thereof is useful as an antibacterial agent.
