Antimicrobial quinolonyl lactam compounds comprising a lactam-containing moiety linked, by a non-ester linking moiety, to the 3-carboxy group of a quinolone moiety. These compounds are of the formula:
wherein
(1) R 3 , R 4 , and R 5 , together with bonds "a" and "b", form any of a variety of lactam-containing moieties similar to those known in the art to have antimicrobial activity; (2) A, R 6 , R 7 , and R 8 form any of a variety of quinolone or naphthyridine structures similar to those known in the art to have antimicrobial activity; and (3) Y, together with R 5 , form a variety of non-ester linking moieties between the lactam-containing moiety and the quinolone moiety.