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To determine the incidence of endocarditis in bacteremic patients with prosthetic heart valves and the risk factors for and the effect of duration of antibiotic therapy on development of endocarditis in such patients.Multicenter, prospective observational study.Six university teaching hospitals with high-volume cardiothoracic surgery.One hundred seventy-one consecutive patients with prosthetic heart valves who developed bacteremia during hospitalization.Patients were evaluated when they were identified as having bacteremia and 1, 2, 6, and 12 months after its occurrence. Of 171 patients, 74 (43%) developed endocarditis: Fifty-six (33%) had prosthetic valve endocarditis at the time bacteremia was discovered ("endocarditis at outset"), whereas 18 (11%) developed endocarditis a mean of 45 days after bacteremia was discovered ("new endocarditis"). Mitral valve location and staphylococcal bacteremia (Staphylococcus aureus or S. epidermidis) were significantly associated with the development of "new" endocarditis. All 18 cases of new endocarditis were nosocomial, and in 6 of these cases (33%) bacteremia was acquired via intravascular devices. Twenty-one patients without evidence of endocarditis at the time of bacteremia received short-term antibiotic therapy (14 days); 1 patient (5%) developed endocarditis. Eleven of 70 patients (16%) who received long-term antibiotic therapy (14 days) developed endocarditis (P0.2).Bacteremic patients with prosthetic heart valves were at notable risk for developing endocarditis, even when they received antibiotic therapy before endocarditis developed and regardless of the duration of such therapy. Intravascular devices were a common portal of entry.

One hundred fifty Hickman right atrial catheters were inserted into 143 patients and were followed prospectively until removal. Primary indications for their use were: cancer chemotherapy (45), parenteral nutrition (35), antibiotic therapy (63), and miscellaneous (7). The overall catheter-associated infection rate was 12.0%. Since the mean duration of catheterization was 125 days, the infection/duration rate was 1.0/1,000 days of use. The risk of infection differed significantly according to the primary indication for catheterization: parenteral nutrition > antibiotic therapy > cancer chemotherapy. The increased risk of catheter-associated infection attributable to duration of catheterization was additive, and the per day risk of such infections remained constant regardless of duration. Nearly two-thirds of patients were discharged home with catheters in place, without adversely affecting infection risk.