Are enterococcal bloodstream infections an independent risk factor for a poorer 5-year survival or just a marker for severity of illness?—The Munich multicentric enterococci cohort
Authors: Rothe Kathrin , Bachfischer Tobias , Karapetyan Siranush , Hapfelmeier Alexander , Wurst Milena , Gleich Sabine , Dichtl Karl , Schmid Roland M. , Triebelhorn Julian , Wagner Laura , Erber Johanna , Voit Florian , Burgkart Rainer , Obermeier Andreas , Seibold Ulrich , Busch Dirk H. , Rämer Patrick C. , Spinner Christoph D. , Schneider Jochen 
Published: October 2023

To assess the long-term survival of patients with enterococcal bloodstream infections (BSI), encompassing various species and resistance patterns compared to
Escherichia coli
(
E. coli
) BSI. Between 2010–2019, 3,290 enterococcal and 3,415
E. coli
BSI were retrospectively screened in seven hospitals in Munich, Germany. All vancomycin-resistant (VRE), vancomycin/linezolid-resistant (LVRE), and linezolid-resistant (LRE)
Enterococcus faecium
(ECFM) BSI were included.
Enterococcus faecalis
(ECFA), vancomycin/linezolid-susceptible ECFM, and
E. coli
BSI were randomly assigned. Cox regression analysis was used to assess survival as the primary endpoint and was adjusted for limiting prognostic factors, which were measured for their importance using a random forest model (RFM). We analyzed 952 patients with 916 episodes of enterococcal BSI and 193 episodes of
E. coli
BSI. RFM identified multimorbidity and markers for disease severity as most indicative of low survival in enterococcal BSI. The 5-year survival was significantly lower for enterococcal BSI than for
E. coli
BSI (23.9% vs 42.3%;
P
< 0.001). This difference remained significant in the Cox regression analysis after adjusting for 17 prognostic factors and excluding patients with limited life expectancy (metastatic tumor disease, Charlson-Comorbidity-Index ≥5). Adjusted 5-year survival was similar for
E. coli
and ECFA but significantly different between ECFA and ECFM (29.2% vs 21.7%;
P
= 0.002). The analysis conducted on monomicrobial ECFM and VRE BSI indicated that their respective 5-year survival was similar (19.6% vs. 21.2%;
P
= 0.753). ECFM BSI seems to be an independent risk factor for poor long-term survival. However, additional vancomycin resistance does not appear to be a contributing factor.

IMPORTANCE

The present study provides a substantial contribution to literature, showing that patients with enterococcal bloodstream infections (BSI) have a lower survival rate than those with
Escherichia coli
(
E. coli
) bloodstream infections after adjusting for 17 limiting prognostic factors and excluding patients with a limited life expectancy [metastatic tumor disease, Charlson Comorbidity Index (CCI) (greater than or equal to) 5]. This difference in the 5-year long-term survival was mainly driven by
Enterococcus faecium
(ECFM) bloodstream infections, with vancomycin resistance not being a significant contributing factor. Our findings imply that
E. faecium
bloodstream infections seem to be an independent risk factor for poor long-term outcomes. As such, future research should confirm this relationship and prioritize investigating its causality through prospective studies.