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Updated: May 23, 2025
Preparation of a Blood Culture Pellet for Rapid Bacterial Identification and Antibiotic Susceptibility Testing
Published on: October 15, 2014
Impact of rapid identification by MALDI-TOF MS from positive blood cultures in Enterococcus spp. bloodstream
Diogo Lopes1, Bruno Grandbastien2, Christina Orasch3
1Intensive Care Unit, Curry Cabral Hospital - Central Lisbon University Hospital Centre, Lisboa, Portugal. diogo.lopes@ulssjose.min-saude.pt.
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.
Insights
Rapid MALDI-TOF identification of Enterococcus bloodstream infections (E-BSI) significantly improves antibiotic treatment. This leads to more frequent spectrum correction and de-escalation, potentially reducing patient length of stay and mortality.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Medical Diagnostics
Background:
- Enterococcus species are a leading cause of bloodstream infections (BSI).
- Intrinsic resistance in Enterococcus necessitates accurate and timely identification for effective empiric antibiotic therapy.
- Early identification is crucial to guide appropriate antimicrobial treatment and improve patient outcomes.
Purpose of the Study:
- To evaluate the clinical impact of Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) mass spectrometry for direct identification of Enterococcus species from positive blood cultures (BC).
- To assess the effect of MALDI-TOF identification on antimicrobial treatment changes, de-escalation, length of stay (LOS), and mortality in patients with Enterococcus BSI (E-BSI).
Main Methods:
- Retrospective cohort study of adult patients with E-BSI from 2010-2017.
- Inclusion criteria: ID consultation within 48 hours and MALDI-TOF identification from BC within 24 hours.
- Primary outcome: antimicrobial treatment change post-MALDI-TOF; secondary outcomes: mortality, LOS, and de-escalation.
Main Results:
- MALDI-TOF identified Enterococcus species in 66.3% of cases, enabling antibiotic changes in 85.3% of identified cases.
- Antimicrobial de-escalation occurred in 35% of patients with MALDI-TOF identification versus 12.2% without.
- Appropriate antibiotic therapy post-identification was associated with reduced 1-year mortality (aOR 0.21).
Conclusions:
- Direct MALDI-TOF identification from positive blood cultures significantly impacts clinical management of E-BSI.
- This method facilitates more frequent antibiotic spectrum correction and de-escalation.
- Improved identification accuracy can lead to better patient outcomes, including reduced LOS and potentially lower mortality.
