Potent cephalosporinase inhibitors: 7 beta-[2-(1, 3-dithiolan-2-ylidene) acetamido] cephalosporins and related compounds.

Cephalosporins possessing a 1, 3-dithiolane, 1, 3-dithiane, or 1, 3-dithietane ring on their 7 beta-substituents showed potent inhibitory activity against cephaloridine hydrolysis by cephalosporinases purified from proteus morganii, Proteus rettgeri, and Proteus inconstans, which were not inhibited by clavulanic acid, a well-known beta-lactamase inhibitor. The mode of inhibition was competitive. The dithiolane cephalosporins themselves were stable against hydrolysis by the beta-lactamases tested. A combination of a dithiolane cephalosporin and cephaloridine synergistically inhibited in vitro growth of strains of P. morganii, P. rettgeri, P. inconstans, Enterobacter aerogenes, Enterobacter cloacae, and Serratia marcescens.