The implementation of rapid microbial identification via MALDI-ToF as a tool for improving patients outcome

Background: Prompt identification of bloodstream infections (BSI) pathogen is essential for the selection of appropriate treatment. Several studies have tried to provide technical solutions for rapid microbial identification (RMI). Since January 2016, we initiated RMI of positive blood cultures at the Tel-Aviv Sourasky Medical Center by analyzing “young” bacterial colonies using MALDI-ToF. Our goal was to study the effect of RMI of positive blood culture on patient outcome measures.

Methods: This was a retrospective-cohort study of hospitalized, adult patients with bacteremia. The outcome of patients with bacteremia episodes was compared before vs. after the initiation of RMI. RMI was done by matrix-assisted laser desorption/ionization time-of-flight testing of microcolonies.

Results: The study included 1460 and 2710 cases in the pre- and post-intervention periods, respectively. There were similar rates of gram-negative, gram-positive, anaerobes and polymicrobial infections, but higher rate of contaminants in the intervention period (39.9 vs. 43.7%, p=0.019). The median time-to-identification decreased from 47.5 to 21.3 hours (p<0.001). Post-intervention, the median LOS declined from 10.83 to 9.79 days (p=0.016), the rate of ICU transfer declined from 13.8% to 11.6% (p=0.054) and the mortality rate declined from 20.9% to 18.3% (p=0.047). The improvement in outcome variables remained statistically significant in multivariate analysis when performed for all episodes and non-contaminants but not for contaminants. The mortality declined in gram-negative bacteremia (20% vs. 15.5%, p=0.005 in multivariate analysis) but not in gram-positive bacteremia (18.1% vs. 18.5%).

Conclusions: RMI reduces mortality from gram-negative but not gram-positive bacteremia.