Cefazolin versus cephalothin in β-lactamase-producing Staphylococcus aureus endocarditis in a rabbit experimental model

The effectiveness of cefazolin and cephalothin was compared in endocarditis in rabbits produced by two strains of beta-lactamase-producing Staphylococcus aureus. Cefazolin and cephalothin given intramuscularly for four days significantly protected against mortality and significantly reduced counts of Staph aureus in vegetations when compared with untreated controls. At four days the mortality rates with Strain 1 were: 94% in untreated controls, 20% in cefazolin treated rabbits and 55% in cephalothin treated animals. At four days the mortality rates with Strain 2 were: 95% in untreated rabbits, 43% in cefazolin treated rabbits and 50% in cephalothin treated animals. There were no significant differences in mortality or efficacy of treatment between cefazolin or cephalothin.