Although a short time to positivity (TTP) was a significant predictor of mortality in patients with bloodstream infections (BSI) caused by Enterococcus spp, it was not an independent predictor of death in survival analysis, according to study results published in Diagnostic Microbiology and Infectious Disease.
In this single-center retrospective study conducted at a university hospital in Germany, researchers investigated the role of TTP as a prognostic and diagnostic tool for patients with BSIs caused by E faecalis vancomycin-susceptible E faecium (VSEfm), and vancomycin-resistant E faecium (VREfm). Since appropriate antimicrobial therapy can interfere with TTP, only patients who received inappropriate antimicrobial therapy on the day of positive blood culture were included in the study. In addition, data from only patients with monomicrobial BSIs were analyzed. The primary outcome was mortality.
Of the 244 patients with monomicrobial BSIs, 22.1% (n=54) of cases were caused by E faecalis, 55.3% (n=135) were caused by VSEfm, and 22.5% (n=55) were caused by VREfm. No vancomycin resistance was recorded with the E faecalis isolates. In addition, mortality rates were 16.7% with E faecalis, 26.7% with VSEfm, and 38.2% with VREfm.
The median TTP was 9.2 hours with E faecalis, 12.1 hours with VSEfm, and 11.8 hours with VREfm. Analysis of TTP and its cutoffs showed no significant associations with risk of death or BSIs caused by E faecalis (area under the curve [AUC], 0.64; P =.18), VSEfm (AUC, 0.59; P =.11), or VREfm (AUC, 0.50; P =1.00). However, in patients with BSIs caused by E faecalis and VSEfm, a shorter TTP (≤4.35 and ≤10.05 hours, respectively) was associated with significantly increased mortality rates compared with a delayed TTP (66.7% [P =.047] and 55.6% [P =.02], respectively).
As a diagnostic tool, TTP was a significant indicator for cardiovascular sources of infection in patients with BSI caused by E faecalis (AUC, 0.76; P =.01).
In a multivariate analysis of only patients with BSIs caused by E faecium, there were 2 independent predictors of death: appropriate antimicrobial therapy, and a positive quick sequential organ failure assessment (qSOFA) score. Appropriate antimicrobial therapy was significantly associated with increased survival among patients with BSIs caused by VSEfm (adjusted hazard ratio, [aHR], 0.42; P =.04) or VREfm (aHR, 0.15; P =.00). Likewise, positive qSOFA scores were a significant predictor of mortality among patients with BSIs caused by VSEfm (aHR, 12.3; P =.00) or VREfm (aHR, 9.17; P =.04).
The limitations of this study included its small sample size, as well as TTP being prone to disturbances, including, “the possibility of insufficient blood samples, the delay to incubation, or contamination of blood culture,” noted the researchers.
“Overall, these findings prove the discrepancy between the entities E faecalis and E faecium,” concluded the researchers.
Michelson K, Löffler B, Höring S. Time to positivity as a prognostic factor in bloodstream infections with Enterococcus spp. Diagn Microbiol Infect Dis. 2021;101(3):115396. doi:10.1016/j.diagmicrobio.2021.115396