Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia

Abstract

Background: Infective endocarditis (IE) is a severe complication in patients with nosocomial Staphylococcus aureus bacteremia (SAB). We sought to develop and validate criteria to identify patients at low risk for the development of IE in whom transesophageal echocardiography (TEE) might be dispensable.

Methods: Consecutive patients with nosocomial SAB from independent cohorts in Europe (Invasive S. aureus Infection Cohort [INSTINCT]) and North America (S. aureus Bacteremia Group [SABG]) were evaluated for the presence of clinical criteria predicting an increased risk for the development of IE (ie, prolonged bacteremia of >4 days' duration, presence of a permanent intracardiac device, hemodialysis dependency, spinal infection, and nonvertebral osteomyelitis). Patients were observed closely for clinical signs and symptoms of IE during hospitalization and a 3-month follow-up period.

Results: IE was present in 13 (4.3%) of 304 patients in the INSTINCT cohort and in 40 (9.3%) of 432 patients in the SABG cohort. Within 14 days after the first positive blood culture result, echocardiography was performed in 39.8% and 57.4% of patients in the INSTINCT and SABG cohorts, respectively. In patients with IE, the most common clinical prediction criteria present were prolonged bacteremia (69.2% vs 90% for INSTINCT vs SABG, respectively) and presence of a permanent intracardiac device (53.8% vs 32.5%). In total, 13 of 13 patients in the INSTINCT cohort and 39 of 40 patients in the SABG cohort with documented IE fulfilled at least 1 criterion (sensitivity, 100% vs. 97.5%; negative predictive value, 100% vs 99.2%).

Conclusions: A simple criteria set for patients with nosocomial SAB can identify patients at low risk of IE. Patients who meet these criteria may not routinely require TEE.

Figure 1.

Flow diagram of patients recruited in the Invasive S. aureus Infection Cohort (INSTINCT) cohort.

Figure 2.

Flow diagram of patients recruited in the S. aureus Bacteremia Group (SABG) cohort.

Figure 3.

Relative frequency of infective endocarditis by number of positive criteria (error bars denote exact 95% confidence intervals) in the Invasive S. aureus Infection Cohort (INSTINCT; n = 304) and S. aureus Bacteremia Group (SABG; n = 432) cohorts. P values refer to intragroup (INSTINCT and SABG) comparisons of the relative frequency of infective endocarditis by the number of positive criteria (determined by the Fisher exact test).