Staphylococcal
infective endocarditis is a severe event requiring aggressive
therapy.
Antibiotic regimen depends mainly on (1) the species of Staphylococcus (Staphylococcus aureus versus
coagulase-negative staphylococci) and its resistance pattern (resistance to
penicillin, to
methicillin, to multiple classes of
antibiotics); (2) the type of infected valve (native versus prosthetic); (3) the site of
infection (left side versus right side
endocarditis); (4) some underlying conditions of the host, in particular the presence or not of
intravenous drug abuse. Based on in vitro susceptibility results, animal models and clinical trials, the following regimens are currently recommended. For native valve
endocarditis,
penicillin G 20 million units per day i.v. for 4-6 weeks for
penicillin-susceptible strains; a
penicillinase-resistant
penicillin (
oxacillin) 2 g i.v. q 4 h for 4-6 weeks plus an
aminoglycoside (
gentamicin) 1.0 mg.kg-1 i.v. q 8 h for 1 week, for
penicillin-resistant,
methicillin-susceptible strains; for methicillin resistant strains,
vancomycin 30 mg.kg.day-1 i.v. in 2-4 doses for 4-6 weeks with the addition or not of
rifampin 600-900 mg.day-1 orally. For a prosthetic valve
endocarditis, a three-
drug regimen (
oxacillin or
vancomycin, plus
gentamicin and
rifampin) and a longer duration (6 weeks or more) are generally recommended. Shorter (2 weeks) treatment could be delivered to uncomplicated cases of right-sided
endocarditis. In view of an increased resistance to classic drugs and suboptimal efficacy of some of them, new therapeutic modalities should be looked at, in particular for
endocarditis cases due to methicillin-resistant strains.