Evaluation of Risk Factors in Enterococcal Bloodstream Infections

Objective: The aim of this retrospective case-control study was to determine the epidemiology and to evaluate risk factors for the development of enterococcal bloodstream infections and risk factors involved in mortality of adult patients in a tertiary care teaching hospital between February 2010 and February 2011. Methods: A total of 95 enterococcal bacteremia episodes were identified among 28 593 patients hospitalized during the study period. Control group was selected among patients who had no signs and symptoms of bacteremia and had negative blood cultures during the study period. In each case, there had to be two randomized control cases. Results: The most frequent isolates were Enterococcus faecalis (n=46, 48.4%) and E. faecium (n=45, 47.4%). There was only one vancomycin-resistant E. faecalis (vanA genotype) and one E. gallinarum. Eighty four (88.4%) patients were identified to have nosocomial infection. The most common primary sites were central venous catheter (32.7%) and urinary tract (14.7%). Six cases of infective endocarditis and two cases of meningitis due to enterococci were also identified. Polymicrobial bacteremia occurred in 39 (41%) patients. Immunosuppression, cardiovascular disease, chronic liver parenchymal disease, gastrointestinal tract disease, chronic renal failure, hemodialysis, an open wound, Foley catheter, surgery other than abdominal operation, antacid use, hospitalization in the last one month, prolonged hospitalization (> 15 days), exposure to antimicrobial therapy prior to bacteremia and inappropriate empirical therapy were the risk factors significantly associated with enterococcal bloodstream infections. In the multivariate logistic regression analysis, three factors were independently associated with mortality including high Charlson index (p=0.000), intensive care unit admission (p=0.016) and isolation of E. faecium from blood cultures (p=0.49). Conclusions: It should be considered that severely ill patients with prolonged hospitalization, those undergoing invasive procedures or receiving inappropriate antibiotic therapy have a high risk of enterococcal bacteremia and those with serious underlying comorbidities are likely to be unresponsive to treatment and have a higher mortality.