Does the Degree of Penicillin Susceptibility ofStreptococcus pneumoniaeAffect the Bactericidal Activity of Co-Amoxiclav Versus Oral Cephalosporins at Physiological Concentrations? AnIn VitroPharmacodynamic Simulation

An in vitro model simulating amoxicillin-clavulanic acid (co-amoxiclav) versus oral cephalosporin serum concentrations was used to explore activity over time against penicillin-susceptible and non-susceptible Streptococcus pneumoniae. Initial inoculum reduction > 4 log cfu/ml (>99.9%) was obtained with co-amoxiclav against both strains. Cefuroxime, cefpodoxime and cefaclor achieved a similar reduction against the susceptible strain, but no reduction against the non-susceptible strain.