Risk factors for infective endocarditis and outcome of patients with Staphylococcus aureus bacteremia

To investigate the risk factors for Staphylococcus aureus infective endocarditis (SAIE) and 6-month mortality in patients with S aureus bacteremia (SAB).

This study consisted of patients who were diagnosed as having nosocomial or community-acquired SAB or SAIE between June 1, 2000, and December 31, 2005. Clinical characteristics of patients with SAB were compared with those of patients with SAIE, and predictors of mortality in patients with SAB were analyzed.

The median age of the 132 randomly selected patients with SAB and the 66 patients with SAIE was 66 and 68 years, respectively. Univariable analysis showed that unknown origin of SAB, a valvular prosthesis, a pacemaker, persistent fever, and persistent bacteremia were significantly associated with SAIE. In multivariable analysis, unknown origin of SAB (odds ratio [OR], 4.2; 95% confidence interval [CI], 1.9-9.3; P=.001), a valvular prosthesis (OR, 9.2; 95% CI, 3.2-26.2; P<.001), persistent fever (OR, 3.1; 95% CI, 1.0-9.0; P=.04), and persistent bacteremia (OR, 6.8; 95% CI, 2.3-20.2- P=.001) were independently associated with SAIE. Six- month mortality was 8% in patients with SAB vs 35% in patients with SAIE (OR, 6.5; 95% CI, 2.9- 14.8; P<.001). In univariable analysis, methicillin- resistant S aureus (OR, 7.2; 95% CI, 1.7 - 29.4; P=.005) was significantly associated with 6-month mortality in patients with SAB.

Unknown origin of SAB, a valvular prosthesis, persistent fever, and persistent bacteremia were independently associated with SAIE in patients with SAB. In univariable analysis, methicillin-resistant S aureus was associated with 6-month mortality in patients with SAB. S aureus infective endocarditis had a significantly higher mortality than SAB. The optimal management of SAB and SAIE deserves further study.