Failure of post-bacteraemia delayed antibiotic prophylaxis of experimental rabbit endocarditis.

Twenty-one rabbits had a cannula placed in the left ventricle and 48 h later 1 ml of a culture of Streptococcus sanguis NCTC 7864 was injected into an ear vein. Six hours later, 400 mg/kg of amoxycillin was administered intramuscularly to 17 animals, the others acting as non-antibiotic treated controls. Two of the 17 rabbits died during the experimental period, and the cannula was incorrectly placed in another two. Five of the remaining 13 animals developed endocarditis. All controls developed endocarditis. Amoxycillin administered 6 h after an induced bacteraemia failed to prevent endocarditis in five (38%) of 13 rabbits.