Critical Importance of In Vivo Amoxicillin and Cefotaxime Concentrations for Synergy in Treatment of Experimental Enterococcus faecalis Endocarditis

The synergy between amoxicillin and cefotaxime against two strains of Enterococcus faecalis (JH2-2 and 6370) in vitro and in rabbit endocarditis was investigated. In vitro synergy was obtained only when amoxicillin concentrations were below the MBC and when cefotaxime concentrations were above 1 μg/ml. No synergy was observed in vivo, because of the short period of time during which these pharmacologic requirements were achieved.