Antibacterial compounds of the formula ##STR1## wherein R is a mononuclear carbocyclic aromatic group, a 5-membered aromatic heterocyclic group which contains as the hetero (non-carbon) ring member(s) an oxygen or sulphur atom or an imino or lower alkylimino group and, optionally, one or two nitrogen atoms, or a 6-membered aromatic heterocyclic group which contains one to three nitrogen atoms as the hetero ring member(s); R.sup.1 is hydrogen or a 3-substituent which is usable in cephalosporin chemistry; A is lower alkylene or C.sub.3-7 cycloalkylene which is optionally substituted with carboxy, carbamoyl, lower alkylcarbamoyl or di-(lower alkyl)carbamoyl; Q is lower alkylene or C.sub.3-7 cycloalkylene which is optionally substituted with carboxy, carbamoyl, lower alkylcarbamoyl or di(lower alkyl)carbamoyl, or the group --NR.sup.2 -- or --NR.sup.2 NR.sup.3 --; R.sup.2 and R.sup.3 are independently hydrogen or lower alkyl; p and m are the zero or 1, n is zero, 1 or 2; R.sup.4 is hydrogen, lower alkanoyl or tri(lower alkyl)silyl; two R.sup.4 groups together represent diphenylmethylene; R.sup.5 is hydrogen, lower alkyl, hydroxy, lower alkoxy, halogen, nitro, --OCOR.sup.7, --OCOOR.sup.71, --N(R.sup.7).sub.2, --NHCOR.sup.7, --NHCOOR.sup.71, --COR.sup.7, --SR.sup.7, --SOR.sup.7, --SO.sub.2 R.sup.7, --SO.sub.3 H, --COOR.sup.7 or --CON(R.sup.7).sub.2 R.sup.6 is hydrogen, lower alkyl or halogen, R.sup.7 is hydrogen or lower alkyl; R.sup.71 is lower alkyl, and the two --OR.sup.4 groups are attached to the phenyl ring via adjacent carbon atoms,as well as readily hydrolyzable esters and pharmaceutically acceptable salts of these compounds and hydrates of compounds of formula I and of their esters and salts.