Compounds of formula (I): ##STR1## .[.[.]. wherein: R.sup.1 .[.represents a hydrogen atom, an alkyl group, an alkoxy group or various substituted alkyl groups.]. .Iadd.is hydroxyethyl; .Iaddend.R.sup.2 represents a group of formula ##STR2## in which ##STR3## .[.represents an alicyclic amine group having from 4 to 8 ring atoms, optionally having a single double bond, optionally containing an additional hetero-atom and optionally having an oxo group on the ring;.]. .Iadd.is a 3-pyrrolidinyl group; .Iaddend.X represents a hydrogen atom.[.; an alkyl group, an alkoxy group, an alkylthio group, an alkylsulphinyl group, an alkylsulphonyl group, a hydroxy group, a halogen atom or various substituted alkyl groups.].;Y represents .[.a hydrogen atom, an alkyl group, an aliphatic acyl group or an acylimidoyl.]. .Iadd.an acetylimidoyl .Iaddend.group; andR.sup.3 represents a carboxy group or a protected carboxy group.[.].].and pharmaceutically acceptable salts thereof have valuable antibacterial activity, especially in vivo.