PENICILLIN PROPHYLAXIS (PP) FOR EXPERIMENTAL STREPTOCOCCAL ENDOCARDITIS IS EARLY PENICILLIN TREATMENT

Abstract

The aim of PP for endocarditis due to viridans streptococci (VS) is to prevent the onset of bacteremia. However, the incidence of postextraction bacteremia in children with cardiac disease after dental extraction under PP has been shown to be 21% (Hess et al, Ped 71: 554-558, 1983). Since the adherence of VS onto vegetations is recognized as an initial step in the pathogenesis of endocarditis, we studied the effect of P on adherence of VS in experimental endocarditis. 107-CFU penicillin-sensitive VS (MIC .01μg/ml, MBC .02μg/ml) were injected iv 30 min after im injection of procaine penicillin G (PPG) 250 mg/kg into Chinchilla rabbits with a left heart catheter in situ for 24 hrs. The rabbits were sacrificed 5 min, 0.5 hr, 2 hr, 4 hr and 48 hr after the injection of the VS, and the cardiac vegetations, induced by the catheter, were excized and cultured to determine whether or not colonization of the vegetations had been prevented by P. Results were: We conclude that PP does not prevent the colonization of cardiac vegetations by reducing the bacterial adherence, but sterilizes initially infected vegetations. Therefore, PP for experimental streptococcal endocarditis is in fact early treatment.