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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.

eg, illness acuity of the patient population. However, there is evidence that when these factors remain constant, a lowering of the infection rate can be the result of infection control efforts.' We wish to illustrate how a dramatic drop in infection rate may mislead infection control personnel into a false sense of accomplishment, when in reality it is an effect of changing medical practices. St. Vincent Hospital and Medical Center is a 450-bed tertiary care facility. Ongoing infection surveillance has been conducted in the same fashion and using the same criteria (NNIS) since 1969. For the past 10 years, the nosocomial infection rate (incidence) has fluctuated between 3.8% and 4.8%. The rates for the last 2 years, however, have shown unprecedented declines: 1982 = 4.7%, 1983 = 4.8%, 1984 = 4.0%, 1985 = 3.2%. Because considerable controversy regarding the significance of these figures existed among members of the Infection Control Committee, further analysis was attempted. Analysis of computer-generated demographic data collected by the medical records department showed two significant changes in the nature of the patient population between 1982 and 1985 (Table 1): 1) a significant increase in the proportion of obstetric and newborn patients, and 2) a significant decrease in the average length of stay. This decrease in stay occurred in all patient populations, but