Escherichia coli résistant aux β-lactamines : étude de l'effet bactéricide des pénicillines associées aux inhibiteurs de β-lactamases

In all bactericidal tests, the addition of gentamicin to penicillins (amoxicillin, piperacillin, ticarcillin) enforced bactericidal power of penicillins. Bactericidal effects of piperacillin and ticarcillin varied when tested with or without β-lactamase inhibitors against a penicillinase producer. Against a high-level cephalosporinase producer, high amoxicillin concentration (256 mg/L) resulted in a short bactericidal effect only in the presence of gentamicin. In contrast, piperacillin presented a persistent bactericidal activity in the presence of tazobactam and gentamicin 2 mg/L, but regrowth occurred with gentamicin 1 mg/L. Ticarcillin showed the most rapid and persistent (> 24 h) bactericidal effect when associated with clavulanic acid and gentamicin 2 mg/L. The tests carried out in simulation of in vivo conditions provided similar bactericidal effects as in vitro. Synergistic effects of combination of a β-lactam plus gentamicin is confirmed all along the study.