A medicament for preventive and/or therapeutic treatment of a microbial infection which comprises as an active ingredient a compound represented by the following general formula (I): wherein, R1 and R2 represent hydrogen atom, a halogen atom, hydroxyl group or the like, W1 represents —CH═CH—, —CH2O—, —CH2CH2— or the like; R3 represents hydrogen atom, a halogen atom, hydroxyl group or an amino group; R4 represents hydrogen atom, a group of —OZ0-4R5 (Z0-4 represents an alkylene group, a fluorine-substituted alkylene group or a single bond, and R5 represents a cyclic alkyl group, an aryl group or the like); W2 represents a single bond or —C(R8)═C(R9)−(R8 and R9 represent hydrogen atom, a halogen atom, a lower alkyl group or the like, Q represents an acidic group, but W2 and Q may together form vinylidenethiazolidinedione or an equivalent heterocyclic ring; m and n represent an integer of 0 to 2, and q represents an integer of 0 to 3.