Abstract: Compounds of formula (I) and (IA) have antibacterial or antiprotozoal activity: formula (1) formula (2) wherein: Z represents a radical of formula N(OH)CH(?O) or of formula C(?O)NH(OH); R1 represents hydrogen, methyl or trifluoromethyl, or, except when Z is a radical of formula N(OH)CH(?O), a hydroxy or amino group; R2 represents a radical of formula R10—(X)n-(ALK)m- wherein R10 represents hydrogen, or an optionally substituted c1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, cycloalkyl, aryl, or heterocyclyl group, 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; R3 represents hydrogen, C1-C6alkyl, or benzyl; and R4 is as defined in the specification.