Antibiotic Prophylaxis — Yes or No? — Endocarditis

Abstract

Antibiotic prophylaxis of subacute bacterial endocarditis before dental manipulations and other surgical procedures in patients with known heart disease has been widely used for over 25 years but its effectiveness has never been proved.(1) The basis of this practice is the observation that a small proportion of patients with endocarditis have a dental procedure before onset of the heart infection. However, among susceptible heart disease patients, the actual rate of development of endocarditis in association with operative procedures likely to produce bacteremia is extremely low. Therefore, it has not been possible to determine the value of antibiotic prophylaxis by clinical observation. Indeed, the presumed success of recommended antibiotics may be more due to inherently low infection rates than prophylaxis per se. Thus, even after administration of penicillin according to an approved regimen, cases of penicillin-sensitive endocarditis after tooth extractions are reported.(2) In our own hospital three such patients were seen in the past 20 years. An alternate explanation for the failure of antibiotic prophylaxis is that the “approved regimen was inadequate. This may relate to the basis for recommended schedules, namely, in vitro sensitivities of the organisms and serum concentrations achieved by the antibiotic. Although bacteremia is reduced, the frequency of lodgment and multiplication of bacteria on the endocardium under these conditions is not known. Since clinical observation cannot answer this dilemma, it recently was proposed by Durack and Petersdorf, (3) and also by Beeson, (4) that clinical recommendations be developed based on data derived from the prevention of bacterial endocarditis in a suitable animal model.