[Comparison of the growth curves of Escherichia coli and Haemophilus influenzae subjected to ampicillin and amoxicillin].

Results of conventional techniques indicate that most non-beta-lactamase producing Haemophilus influenzae strains are "susceptible" to ampicillin and amoxicillin. A previous study of growth curves established using the MS-2 system has demonstrated a faster bacteriolytic activity on Escherichia coli of amoxicillin as compared to ampicillin. A similar study on Haemophilus influenzae ATCC 9795 showed a) significant residual growth subsequent to contact of cultures with antibiotics in concentrations approximating minimal inhibitory concentrations; b) persistent residual growth for all concentrations from 1 to 500 micrograms/ml, with little concentration-dependency. Concentrations of amoxicillin needed to achieve identical inhibition of Haemophilus growth curves were twice those of ampicillin.