C-19393 S2 and H2, new carbapenem antibiotics. IV. Inhibitory activity against beta-lactamases

New carbapenem antibiotics, C-19393 S2 and H2, have been found to be potent and broad-spectrum inhibitors of beta-lactamases. Among 11 types of beta-lactamases tested, those from Escherichia coli (plasmid-bearing), Klebsiella pneumoniae, Proteus vulgaris, Serratia marcescens and Bacteroides fragilis were especially sensitive. They also inhibited cephalosporinases insensitive to clavulanic acid. The inhibition by C-19393 S2 and H2 was of progressive type, except for the inhibition of E. coli enzyme (plasmid-mediated type I) by C-19393 H2. The inhibition of E. coli beta-lactamase by C-19393 S2 was irreversible, while that by C-19393 H2 was reversible.