Short-term bactericidal activity of amoxicillin and cefotaxime against penicillin-susceptible and -resistant pneumococcal strains: an in vitro pharmacodynamic simulation

The 8-hour in vitro activity of serum-simulated concentrations of amoxicill in (obtained after 875 mg oral dose) and cefotaxime (obtained after a 1 g i .v. dose), against 20 strains of the 5 Streptococcus pneumoniae serotypes m ost prevalent in Spain, was explored. Despite a greater initial inocula dec rease observed with cefotaxime against the resistant strains at the first s ampling time, a decrease greater than or equal to 99.9% was obtained with b oth beta-lactams from 6h onwards against the penicillin-susceptible strains ; the same was observed for the penicillin-resistant strains with amoxicill in but not with cefotaxime.