A method for the treatment of bacterial infections in humans and non-human mammals, which comprises administering to a subject suffering such infection an antibacterially effective dose of a compound of formula (I) or a pharmaceutically or veterinarily acceptable salt thereof: wherein: R1 represents hydrogen, or C1-C6 alkyl or C1-C6 alkyl substituted by one or more halogen atoms; R2 represents a group R10—(X)n—(ALK)m— wherein R10 represents hydrogen, or a C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, cycloalkyl, aryl, or heterocyclyl group, any of which may be unsubstituted or substituted by (C1-C6)alkyl, (C1-C6)alkoxy, hydroxy, mercapto, (C1-C6)alkylthio, amino, halo (including fluoro, chloro, bromo and iodo), trifluoromethyl, cyano, nitro, —COOH, —CONH2, —COORA, —NHCORA, —CONHRA, NHRA, —NRARB, or —CONRARB wherein RA and RB are independently a (C1-C6)alkyl group, and ALK represents a straight or branched divalent C1-C6 alkylene, C2-C6 alkenylene, or C2-C6 alkynylene radical, and may be interrupted by one or more non-adjacent —NH—, —O— or —S—linkages, X represents —NH—, —O— or —S—, and m and n are independently 0 or 1; and A represents a group as defined in the specification.