Abstract: Carbapenem derivatives of formula (I): ##STR1## wherein (a) R.sub.1 is a hydrogen atom, an alkyl group of from 1 to 6 carbon atoms, a hydroxy-lower alkyl group or a protected hydroxy-lower alkyl group of from 1 to 6 carbon atoms in its alkyl moiety, (b) COOR.sub.2 is a carboxyl group, a carboxylate anion or a protected carboxyl group, (c) R.sub.3 is an alkyl group of from 1 to 6 carbon atoms and (d) R.sub.4 is a substituted or unsubstituted heterobicyclic group of formula (II): ##STR2## in which the partial structure ##STR3## is a 5- or 6-membered, saturated or unsaturated, nitrogen-containing heterocycle containing 1 to 4 hereto atoms each selected from the group consisting of oxygen, sulfur and nitrogen, at least one hetero atom being nitrogen, and is which R.sub.5 and R.sub.6 each is a hydrogen atom or an appropriate substituent, any isomeric form thereof, and pharmacologically acceptable salts thereof are potent and stable antimicrobial agents.

Abstract: Carbapenem derivatives which may be utilized as antibiotics and which show strong antibacterial activity against various bacterial strains including Pseudomonas aeruginosa. The compounds containing the derivatives are quite safe and are also stable against hydrolases such as dehyropeptidase (DHP).