Comparison of in vivo and in vitro pharmacodynamics of a humanized regimen of 600 milligrams of Ceftaroline Fosamil every 12 hours against Staphylococcus aureus at initial inocula of 106 and 108 CFU per milliliter.

In light of the in vivo/in vitro discordance among beta-lactams against Gram-negative pathogens, we compared the in vivo pharmacodynamics of humanized ceftaroline against 9 Staphylococcus aureus strains (MICs of 0.13 to 1 mg/liter) from published in vitro studies using standard and high inocula in the murine thigh infection model. Consistent with the in vitro findings, mean reductions of ≥1 log10 CFU were observed for ceftaroline against all strains using both standard and high inocula. These results suggest in vivo/in vitro concordance with no observed inoculum effect.