Infective endocarditis. Current recommendations for prophylaxis

Antibiotic prophylaxis is indicated for any patient with a predisposing cardiac lesion who undergoes a procedure likely to produce bacteraemia with an organism having the propensity to cause bacterial endocarditis. Cardiac abnormalities have been ranked according to their approximate risk and it is known that the organisms most likely to cause endocarditis are viridans streptococci, Group D streptococci and staphylococci. The procedures likely to induce bacteraemia with each of these are, respectively, dental and upper respiratory with bleeding, urinary and gastrointestinal, and cardiac valve surgery. Antibiotic prophylaxis is impractical when bacteraemia cannot be anticipated and is unnecessary when it is due to organisms such as anaerobes and Gram-negative bacilli which rarely colonise the endocardium. A variety of prophylactic antibiotic regimens, directed against the common aetiological organisms, have been evaluated in animal models of infective endocarditis and it is on the basis of this kind of indirect evidence that several expert committees have made and regularly update their recommendations. Because infective endocarditis is an uncommon disease, a controlled clinical trial to prove the efficacy of prophylaxis would require the enrolment of a prohibitive number of patients. Consequently, there is room for differences of opinion over what constitutes optimum prophylaxis in any particular situation. This review examines the rationale for prophylaxis and compares and contrasts several authoritative recommendations, among which the trend in recent years has been towards simpler oral regimens.