Disclosed are novel carbapenem derivatives characterized by a 2-substituent of the formula ##STR1## in which A represents a C.sub.1 -C.sub.6 straight or branched chain alkylene group; R.sup.5 represents an optionally substituted aliphatic, cycloaliphatic, cycloaliphatic-aliphatic, aryl, araliphatic, heteroaryl, heteroaraliphatic, heterocyclyl or heterocyclyl-aliphatic radial and ##STR2## represents a nitrogen-containing aromatic heterocycle attached to the alkylene group A at a ring carbon atom and quaternized by substituent R.sup.5. Such derivatives are useful as potent antibacterial agents.