Comparison of the Clinical Characteristics and Outcomes Associated with Vancomycin-Resistant Enterococcus faecalis and Vancomycin-Resistant E. faecium Bacteremia

Abstract

eIn published studies, cohorts of patients with bacteremia due to vancomycin-resistant Enterococcus (VRE) have predominantly been infected with Enterococcus faecium. Little is known about the epidemiology and outcomes associated with bacteremia due to VR Enterococcus faecalis. A retrospective study of isolates obtained from January 2008 to October 2010 was conducted at Detroit Medical Center (DMC). Unique patients with blood cultures positive for VRE were reviewed. Outcomes were analyzed using logistic regression. During the study period, 105 cases of bacteremia due to VR E. faecalis and 197 cases of bacteremia due to VR E. faecium were identified. The mean age in the study cohort was 61.5 ؎ 15 years; 162 subjects (53.6%) were male. After controlling for a propensity score, bacteremia due to VR E. faecalis was associated with >2-fold-lower in-hospital mortality than bacteremia due to VR E. faecium. Interestingly, bacteremia due to VR E. faecalis was associated with longer hospital stay after VRE isolation, although total length of stay was similar for groups with VR E. faecalis and VR E. faecium. Bacteremia due to VR E. faecalis was associated with a >2-fold-lower risk for mortality than bacteremia due to VR E. faecium, possibly due to the availability of ␤-lactam therapeutics for treatment of VR E. faecalis. Enterococci are the third most common type of health careassociated pathogen in the United States (17). The two most common species responsible for enterococcal infections in humans are Enterococcus faecalis and Enterococcus faecium. Enterococci are inherently resistant to several antimicrobials and also have an ability to acquire mobile genetic resistance determinants (22). The emergence of resistance to various antimicrobial agents, specifically to vancomycin, has become a major clinical and epidemiological threat. Vancomycin-resistant Enterococcus (VRE) infections are associated with increased morbidity, mortality, and costs compared to vancomycin-susceptible enterococcal infections (3).VRE infections impose a huge burden on facilities in metropolitan Detroit. At Detroit Medical Center (DMC) in 2009, 530 of 4,377 (12.1%) isolates of E. faecalis and 846 of 1,150 (73.6%) isolates of E. faecium were VRE (16). Both the proportion of total VREs accounted for by VR E. faecalis and the total absolute number of unique clinical isolates of VR E. faecalis increased significantly from 2003 to 2009 (16). The prevalence of VR E. faecalis at DMC is much higher than in other regions in North America and worldwide. According to National Healthcare Safety Network (NHSN) data, 6.9% of E. faecalis isolates reported in 2006 and 2007 were VRE, compared to over 12% of E. faecalis isolates reported at DMC (17).Past studies of the epidemiology and outcomes associated with VRE infections were conducted with cohorts consisting predominantly of E. faecium, and relatively little is known about the epidemiology of vancomycin-resistant E. faecalis (5). Only a few studies with small sample sizes have compared the epidemiology of infec...

Epidemiology of Vancomycin-Resistant Enterococcus faecalis: a Case-Case-Control Study

“…Exposure to cephalosporins was reported as a VRE risk factor in past studies, although none of these studies evaluated VR E. faecalis exclusively (16,17). We recently reported that patients with bacteremia due to VR E. faecalis were exposed to cephalosporins more frequently than were patients with VR E. faecium bacteremia (18). Fluoroquinolones were also independently associated with isolation of VR E. faecalis, and this association was demonstrated by other investigators with regard to VRE (16).…”

Stewardship Approach for Optimizing Antimicrobial Therapy through Use of a Rapid Microarray Assay on Blood Cultures Positive for Enterococcus Species

“…nterococci are facultative anaerobic Gram-positive cocci that exist as a major component of normal colonic flora and represent the third most common type of health care-associated pathogen in the United States (1,2). Although enterococci possess intrinsic resistance to several antibiotics, they have acquired additional resistance determinants, such as that for vancomycin resistance (3,4).…”

Impact of Different Antimicrobial Therapies on Clinical and Fiscal Outcomes of Patients with Bacteremia Due to Vancomycin-Resistant Enterococci

“…Such comparisons have not been previously performed. We previously reported that VR E. faecalis bacteremia was independently associated with decreased in-hospital mortality compared to VR E. faecium (20). In this study, patients with VR E. faecalis bacteremia also had decreased in-hospital mortality compared to that of VR E. faecium (n ϭ 18 cases [20.9%] versus n ϭ 46 cases [33.1%], P ϭ 0.07).…”