Disclosed are novel carbapenem derivatives characterized by a 2-substituent of the formula ##STR1## in which A represents cyclopentylene, cyclohexylene or C.sub.2 -C.sub.6 alkylene optionally substituted by one or more C.sub.1 -C.sub.4 alkyl groups and ##STR2## represents a quaternized nitrogen-containing aromatic heterocycle. Such derivatives are useful as potent antibacterial agents. Also disclosed are processes for the preparation of such derivatives and novel intermediates utilized in these processes.