Impact of rapid identification by MALDI-TOF MS from positive blood cultures in Enterococcus spp. bloodstream infections.

Abstract

Purpose: Regarding bloodstream infections (BSI) Enterococcus spp. rank among the top five most common organisms. Due to enterococci intrinsic resistance, empiric antibiotic therapy is often inappropriate and early identification becomes crucial. Our objective was to assess the clinical impact of MALDI-TOF identification directly from positive blood cultures (BC) in Enterococcus spp. BSI (E-BSI).

Methods: A retrospective cohort study included all adult patients with E-BSI from 2010 to 2017 in a tertiary hospital. ID consultation within 48 h and MALDI-TOF identification directly from BC within 24 h were inclusion criteria. The primary outcome was antimicrobial treatment change following MALDI-TOF and secondary outcomes included 30-day and 1-year mortality, length of stay (LOS) and antimicrobial de-escalation.

Results: Among 267 BSI episodes, E. faecalis was isolated in 130 episodes (48.7%), E. faecium in 122 (45.7%), and 104 (39%) were polymicrobial. Empiric antibiotic therapy was inappropriate in 60.3% of patients. The LOS was 36 (IQR 20-64) days, 30-day and 1-year mortality were 16.1% and 43.4%, respectively. Enterococci identification with MALDI-TOF at the species level was possible in 66.3% cases and in 73% of monomicrobial cases. Antibiotics were changed in 85.3% of the former vs. 63.3% in remaining patients (p < 10^- 4), and de-escalation occurred in 35% of subjects (vs. 12.2%,p = 10^- 4). Changing antibiotics after correct identification was associated with a shorter LOS. In multivariate analysis, appropriate antibiotic therapy before MALDI-TOF was protective against 30-day mortality (aOR 0.40(0.08-1.96)), and appropriate antibiotic therapy afterwards against 1-year mortality (aOR 0.21(0.05-0.84)).

Conclusion: In E-BSI, direct MALDI-TOF identification from positive BC has a significant clinical impact due to a more frequent antibiotic spectrum correction and de-escalation. This may improve patient outcomes, reducing LOS and potentially mortality.

Clinical trial number: Not applicable.