A compound represented by formula (I):
wherein X1 and X2 each represent a halogen atom; R1 represents a hydrogen atom or a substituent; R2 represents a substituted or unsubstituted bicyclic heterocyclic substituent; A represents a nitrogen atom or a substituted carbon atom; and R represents a hydrogen atom or a substituent, or a salt thereof is disclosed. The compound exhibits potent antimicrobial activity and also high safety due to reduced lipophilicity.