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 amoxicillin (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 most prevalent in Spain, was explored. Despite a greater initial inocula decrease observed with cefotaxime against the resistant strains at the first sampling time, a decrease greater than or equal to 99.9% was obtained with both beta-lactams from 6h onwards against the penicillin-susceptible strains; the same was observed for the penicillin-resistant strains with amoxicillin but not with cefotaxime.