New Carbapenem Antibiotics Iv. Inhibitory Activity against /3-lactamases

New carbapenern antibiotics, C-19393 S2 and H2, have been found to be potent and broadspectrum inhibitors of /3-lactamases. Among 11 types of /3-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 jS-lactamase by C-19393 S2 was irreversible, while that by C-19393 H2 was reversible.