[Bacterial growth delay in E. coli: demonstration and evaluation of the beta-lactamase post-inhibitor effect on 6...

Six E. coli, whose phenotypes of resistance were different, were tested in vitro in order to evaluate a regrowth delay, the post beta-lactamases inhibitor effect (PLIE). This PLIE was investigated after a brief incubation in contact with clavulanic acid (CA) alone or associated with amoxicillin (AMX). After removal of the drugs used during the pre-exposure phase, the bacteria were incubated with AMX at different concentrations. The PLIE was shown not to be in association with any other regrowth delay (post-antibiotic effect or effect inherent to the technical procedures used). A PLIE was evaluated on the five intermediary or high-level beta-lactamases-producing strains. Generally, the duration of the PLIE was prolonged after the CA alone pre-exposure phase and could reach values up to 22 hours. The concentrations of AMX added in cultures previously exposed to sufficient CA concentrations were related to an extended PLIE.