In vitro antibacterial activity and mechanism of action of J-111,225, a novel 1β-methylcarbapenem, against transferable IMP-1 metallo-β-lactamase producers

IMP-1 β-lactamase, a class B zinc metallo-enzyme encoded by the transferable bla IMP gene, is known to confer high-level resistance to carbapenems as well as to penicillins and cephalosporins. J-111,225 is a novel 1β-methylcarbapenem with a structurally unique side chain comprising a trans-3,5-disubstituted pyrrolidinylthio moiety at the C2 position. It inhibited 17 Serratla marcescens and two Pseudomonas aeruginosa IMP-1-producing clinical Isolates at a concentration of 32 mg/L (range 4-32 mg/L). It showed synergy with imipenem against IMP-1-producing S. marcescens BB5886 and P. aeruglnosa GN17203 with minimal FIC indices of 0.38 and 0.5, respectively. J-111,225 was more resistant than imipenem to hydrolysis by class B metallo-β-lactamases. In kinetic studies, J-111,225 inhibited the IMP-I enzyme with a K 1 of 0.18 μM when Imipenem was used as a substrate. In contrast, J-111,225 was the substrate for hydrolysis by other class B β-lactamases such as Bacteroldes fragllls CcrA, Stenotrophomonas maltophilia L1 and Bacillus cereus type II enzyme with respective K m values of 11, 10 and 148 μM. The greater antibacterial activity of J-111,225 against IMP-1-producing bacteria may result from its unique interaction with the β-lactamase.