The treatment of staphylococcal endocarditis.

Staphylococcus aureus may attack normal or damaged native valves, or prosthetic valves, and has a predilection for the tricuspid valve in drug addicts. S. epidermidis most frequently attacks prosthetic valves, but occasionally damaged native valves. There have been few clinical trials of antibiotic regimens in staphylococcal endocarditis. It has a better prognosis in drug addicts than in non-addicts and addicts seldom require valve surgery. In non-addicts staphylococcal endocarditis can be a devastating infection with a significant mortality rate; emergency valve replacement may be required, sometimes early in the antibiotic course. Failure of medical treatment can occur whatever antibiotic regimen is given. Most strains of S. aureus are resistant to penicillin and sensitive to flucloxacillin which is the mainstay of treatment, given intravenously in large doses. Combination therapy is usual but, although it may achieve more rapid clearance of bacteraemia, has not been shown to affect morbidity or mortality. Penicillin should be used for sensitive strains and vancomycin for patients allergic to penicillins and staphylococci resistant to flucloxacillin. Whether rifampicin confers additional benefit to vancomycin is unproven. The optimum length of treatment for staphylococcal endocarditis is unknown but at least 4 weeks is suggested, possibly less in drug addicts.