In vitro effectiveness of biapenem against IMP-producing Enterobacteriaceae

The options available for treating infections with carbapenemase-producing Enterobacteriaceae (CPE) are limited; with the increas- ing threat of these infections, new treatments are urgently needed. Biapenem (BIPM) is a carbapenem, and limited data confirming its in vitro killing effect against CPE are available. In this study, we examined the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of BIPM for 14 IMP-1-producing Enterobacteriaceae strains isolated from the Okayama region in Japan. The MICs against almost all the isolates were lower than 0.5 ?g ml?1, indicating susceptibility to BIPM, while approxi- mately half of the isolates were confirmed to be bacteriostatic to BIPM. However, initial killing to a 99.9% reduction was observed in seven out of eight strains in a time–kill assay. Despite the small data set, we concluded that the in vitro efficacy of BIPM suggests that the drug could be a new therapeutic option against infection with IMP-producing CPE.