Antibiotic prophylaxis of experimental endocarditis due to methicillin-resistant Staphylococcus epidermidis

Antibiotic prophylaxis for the prevention of endocarditis due to methicillin-resistant Staphylococcus epidermidis (MRSE) was evaluated in a modified rabbit endocarditis model and compared with results obtained with methicillin-sensitive S. epidermidis (MSSE). One dose of nafcillin, cefamandole, cephalothin, or vancomycin neither prevented endocarditis nor sterilized the blood of rabbits challenged with each of two MRSE or two MSSE isolates. One dose of gentamicin protected greater than or equal to 80% of animals challenged with three of the four isolates, and one dose of rifampin protected greater than or equal to 90% challenged with any of the four isolates. Multiple doses of any of the antibiotics prevented endocarditis in greater than or equal to 80% of rabbits challenged with MSSE, and four doses of vancomycin protected rabbits challenged with MRSE. However, MRSE endocarditis was prevented in less than or equal to 25% of animals given six doses of nafcillin or cephalosporins. Thus, nafcillin and cephalosporins were ineffective prophylaxis for MRSE endocarditis, whereas vancomycin, gentamicin, and rifampin were effective.