Endocarditis prophylaxis revisited: experimental evidence of efficacy and new Swiss recommendations

Because of its severity, it is agreed that infectious endocarditis should b e prevented whenever possible. Determining adequate prophylactic measures i nvolves establishing (a) the patients at risk, (b) the procedures that migh t provoke bacteraemia, (c) the most effective prophylactic regimen, and (d) a balance between the risks of side effects from prophylaxis and of develo ping infectious endocarditis. Patients at risk and procedures inducing bact eraemia have been identified by clinical studies. On the other hand, the ef ficacy of prophylactic antibiotics has been based on animal studies. Random ised, placebo-controlled studies do not exist in humans because they would require large patient numbers and would raise ethical issues due to the sev erity of the disease. Case-control studies have indicated that infectious e ndocarditis prophylaxis is effective, but prevents only a limited number of cases. Animal experiments have revealed several key issues for human appli cation. First, antibiotics do not prevent the early stages of valve colonis ation, but rather kill the microorganisms after their attachment to the car diac lesions. Second, the duration of antibiotic presence in the serum is c ritical. Under experimental conditions, the drugs must remain above their m inimal inhibitory concentration for the organisms for greater than or equal to 10 h, to allow time for bacterial clearance from the valves. Third, ant ibiotic-induced killing is not the only mechanism allowing bacterial cleara nce. Other factors, such as platelet microbicidal proteins, may act in conc ert with the drugs to sterilise the lesions. Recommendations for prophylaxi s have recently been revised in Europe and the USA. New information has imp roved the definition of groups at risk. Since most cases of infectious endo carditis are not preceded by medical pro cedures, primary prevention of inf ectious endocarditis should target infected foci responsible for spontaneou s bacteraemia (e.g. poor dental hygiene). The purpose of this article is to update the existing recommendations in Switzerland, under the perspective of changing epidemiology, the availability of new drugs, and harmonisation with recommendations in other countries.