Does the degree of penicillin susceptibility of Streptococcus pneumoniae affect the bactericidal activity of co-amoxiclav versus oral cephalosporins at physiological concentrations? An in vitro pharmacodynamic simulation

An in vitro model simulating amoxicillin-clavulanic acid (co-amoxiclav) ver sus oral cephalosporin serum concentrations was used to explore activity ov er time against penicillin-susceptible and non-susceptible Streptococcus pn eumoniae. Initial inoculum reduction > 4 log cfu/ml (>99.9%) was obtained w ith co-amoxiclav against both strains. Cefuroxime, cefpodoxime and cefaclor achieved a similar reduction against the susceptible strain, but no reduct ion against the non-susceptible strain.