Abstract: The present invention relates to carbapenems and provides a compound of the formula (I) ##STR1## wherein: R.sup.1 is 1-hydroxyethyl, 1-fluoroethyl or hydroxymethyl;R.sup.2 is hydrogen or C.sub.1-4 alkyl;R.sup.3 is hydrogen or C.sub.1-4 alkyl;A is a 5-membered heteroaryl ring containing one nitrogen atom and up to two additional heteroatoms selected from nitrogen, oxygen and sulphur; and is bonded to the nitrogen of the linking carbamoyl group by a carbon atom in the ring, is substituted with the carboxy group on a carbon atom in the ring and is optionally further substituted on a carbon atom in the ring; andin any ring --NH--, H is optionally replaced by C.sub.1-4 alkyl; or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof. Processes for their preparation, intermediates in their preparation, their use as therapeutic agents and pharmaceutical compositions containing them are also described.

Abstract: A cephalosporin derivative of the formula I: ##STR1## in which X is S, O, CH.sub.2 or SO, ##STR2## represents one of C-7 acyl groups known in the cephalosporin art, R3 is hydrogen or methoxy, R4 is hydrogen, optionally substituted alkyl or allyl, and R5 is an aromatic heterocyclic ring system which is linked via carbon, and which contains a quaternized nitrogen atom.

Abstract: Cephalosporin antibiotics having a 3-position substituent of the formula:--CH.sub.2 NR.sup.1 --Y--A--Z--Qare described, wherein R.sup.1 is hydrogen or certain optionally substituted alkyl groups; Y is --CO-- or --SO.sub.2 --; A is optionally substituted phenylene or heterocyclylene; Z is a linking group and Q is a catechol or related ring system. Processes for their preparation and use are described.

Abstract: Cephalosporin antibiotics having a 3-position substituent of the formula:--CH.sub.2 NR.sup.1 --Y--A--Z--Qare described, wherein R.sup.1 is hydrogen or certain optionally substituted alkyl groups; Y is --CO-- or --SO.sub.2 --; A is optionally substituted phenylene or heterocyclylene; Z is a linking group and Q is a catechol or related ring system. Processes for their preparation and use are described.

Abstract: A cephalosporin derivative of the formula I: ##STR1## in which X is ##STR2## represents one of C-7 acyl groups known in the cephalosporin art, R3 is hydrogen or methoxy, R4 is hydrogen, optionally substituted alkyl or allyl, and R5 is an aromatic heterocyclic ring system which is linked via carbon, and which contains a quaternized nitrogen atom.

Abstract: A cephalosporin derivative of the formula I: ##STR1## in which X is S, O, CH.sub.2 or SO, ##STR2## represents one of the C-7 acyl groups known in the cephalosporin art, R3 is hydrogen or methoxy, R4 is hydrogen, optionally substituted alkyl, allyl, furfuryl or benzyl, and R5 is an aromatic heterocyclic ring system which is linked via carbon, and which contains a quaternized nitrogen atom.