INOCULUM EFFECT OF BETA-LACTAMASE-PRODUCI NG HAEMOPHILUS-INFLUENZAE ISOLATES ON AMOXICILLIN, AMOXICILLIN-CLAVULANIC ACID AND AMPICILLIN-SULBACTAM COMBINATIONS, CEFUROXIME AND CEFPODOXIME

Minimal inhibitory concentrations (MICs) of amoxycillin, amoxycillin-c lavulanate, ampicillin-sulbactam, cefuroxime and cefpodoxime were meas ured in the presence of increasing bacterial inoculum of beta-lactamas e producing strains of Haemophilus influenzae (5.10(6) to 10(8) cfu/ml ). For a standard inoculum, cefpodoxime and amoxycillin-clavulanate ha ve the best inhibitory activity against the H. influenzae strains test ed. However, for an increasing inoculum, results are different. Amoxyc illin-clavulanate and ampicillin-sulbactam are minimally affected by t he inoculum size, while a significant ''inoculum effect'' is observed with amoxycillin, cefuroxime and cefpodoxime.