Bacterial regrowth delays against E-coli: demonstration and evaluation of the post-beta-lactamases inhibitor effect (PLIE) on six strains with various resistance phenotypes.

Six E. coil, whose phenotypes of resistance were different, were tested in vitro in order to evaluate a regrowth delay, the post beta-lactamases inhib itor 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 bacte ria were incubated with AMX at different concentrations. The PLIE was shown not to be in association with any other regrowth delay (post-antibiotic ef fect or effect inherent to the technical procedures used). A PLIE was evalu ated on the five intermediary or high-level beta-lactamases-producing strai ns. Generally, the duration of the PLIE was prolonged after the CA alone pr e-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. (C) 2000 Editions scientifiques et medic ales Elsevier SAS.