Subjects will be patients at high risk for infection including those with any one or more of the following characteristics: over 65 years old, poor heart function (ejection fraction <40), diabetes (insulin dependant or non-insulin dependant), peripheral vascular disease, kidney dysfunction (creatinine level >2mg/dl), obesity (body surface area > 2 m2), low serum protein levels (albumin < 2.5 mg/dl), infection of the heart valve (endocarditis), or on any antibiotics other than standard prophylaxis before surgery.