Determinants of vancomycin resistance and mortality rates in enterococcal bacteremia. a prospective multicenter study.

BACKGROUND

Enterococcus species are major nosocomial pathogens and are exhibiting vancomycin resistance with increasing frequency. Previous studies have not resolved whether vancomycin resistance is an independent risk factor for death in patients with invasive disease due to Enterococcus species or whether antibiotic therapy alters the outcome of enterococcal bacteremia.

OBJECTIVE

To determine whether vancomycin resistance is an independent predictor of death in patients with enterococcal bacteremia and whether appropriate antimicrobial therapy influences outcome.

DESIGN

Prospective observational study.

SETTING

Four academic medical centers and a community hospital.

PATIENTS

All patients with enterococcal bacteremia.

MEASUREMENTS

Demographic characteristics; underlying disease; Acute Physiology and Chronic Health Evaluation (APACHE) II scores; antibiotic therapy, immunosuppression, and procedures before onset; and antibiotic therapy during the ensuing 6 weeks. The major end point was 14-day survival.

RESULTS

Of 398 episodes, 60% were caused by E. faecalis and 37% were caused by E. faecium. Thirty-seven percent of isolates exhibited resistance or intermediate susceptibility to vancomycin. Twenty-two percent of E. faecium isolates showed reduced susceptibility to quinupristin-dalfopristin. Previous vancomycin use (odds ratio [OR], 5.82 [95% CI, 3.20 to 10.58]; P < 0.001), previous corticosteroid use (OR, 2.43 [CI, 1.22 to 4.86]; P = 0.01), and total APACHE II score (OR, 1.06 per unit change [CI, 1.02 to 1.10 per unit change]; P = 0.003) were associated with vancomycin-resistant enterococcal bacteremia. The mortality rate was 19% at 14 days. Hematologic malignancy (OR, 3.83 [CI, 1.56 to 9.39]; P = 0.003), vancomycin resistance (OR, 2.10 [CI, 1.14 to 3.88]; P = 0.02), and APACHE II score (OR, 1.10 per unit change [CI, 1.05 to 1.14 per unit change]; P < 0.001) were associated with 14-day mortality. Among patients with monomicrobial enterococcal bacteremia, receipt of effective antimicrobial therapy within 48 hours independently predicted survival (OR for death, 0.21 [CI, 0.06 to 0.80]; P = 0.02).

CONCLUSIONS

Vancomycin resistance is an independent predictor of death from enterococcal bacteremia. Early, effective antimicrobial therapy is associated with a significant improvement in survival.