[Measure by turbidimetry and bactericidal effect of the speed of action of clavulanic acid, amoxicillin and their combinations on a Haemophilus influenzae producer of beta-lactamase].

The amoxicillin-acid clavulanic acid combination is known to be active on H. influenzae beta-lactamase producer. Clavulanic acid possesses its own antibacterial activity at high concentrations. As the combination of two beta-lactams is sometimes antagonist, we studied the action of amoxicillin, clavulanic acid alone and in combination on H. influenzae beta-lactamase producer by kinetic turbidimetry and time-kill curve. Clavulanic acid alone has slowed down the growth at 8 micrograms/ml, has inhibited at 32 micrograms/ml and was bactericidal at 128 micrograms/ml. The amoxicillin-clavulanic acid combination (proportion 4/1) was bactericidal at 2-0.5 micrograms/ml. The speed of bactericidal activity was only slightly dependent on concentrations. The increase in biomass measured by turbidimetry has been important. As for all beta-lactams it was due to the formation of spheroplasts, non viable after 24 h.