Compounds of formula (IA) or (IB) have antibacterial activity: wherein W is ═C(H)— or ═N—; R3 is a radical of formula -(Alk1)m-(Z1)p-(Alk2)n-Q wherein m, p and n are independently 0 or 1, provided that at least one of m, p and n is 1, Z1 is —O—, —S—, —S(O)—, —S(O2)—, —NH—, —N(CH3)—, —N(CH2CH3)—, —C(—O)—, —0—(C═O)—, —C(═O)—O—, or an optionally substituted divalent monocyclic carbocyclic or heterocyclic radical having 3 to 6 ring atoms; or an optionally substituted divalent bicyclic carbocyclic or heterocyclic radical having 5 to 10 ring atoms; Alk1 and Alk2 are optionally substituted C1-C6 alkylene, C2-C6 alkenylene, or C2-C6 alkynylene radicals, which may optionally terminate with or be interrupted by —O—, —S—, —S(O)—, —S(O2)—, —NH—, —N(CH3)—, Or —N(CH2CH3)—; and Q is hydrogen, halogen, nitrile, or hydroxyl, or an optionally substituted monocyclic carbocyclic or heterocyclic radical having 3 to 6 ring atoms; or an optionally substituted bicyclic carbocyclic or heterocyclic radical having 5 to 10 ring atoms; R4 and R5 are optional substituents; and R2, R6 and R7 are independently hydrogen or a radical of formula -(Alk3)x-(Z2)y-(Alk4)z-H wherein x, y and z are independently 0 or 1, Z2 is —O—, —S—, —S(O)—, —S(O2)—, —NH—, —N(CH3)—, —N(CH2CH3)—, —C(—O)—, —0—(C═O)— or —C(═O)—O—; Alk3 and Alk4 are optionally substituted C1-C3 alkylene, C2-C3 alkenylene, or C2-C3 alkynylene radicals, which may optionally terminate with or be interrupted by —O—, —S—, —S(O)—, —S(O2)—, —NH—, —N(CH3)—, or —N(CH2CH3)—.