Performance and Impact on Initial Antibiotic Choice of Direct Identification of Pathogens from Pediatric Blood Culture Bottles Using an In-House MALDI-TOF MS Protocol

The performance and early therapeutic impact of direct identification by matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF; DIMT) on pediatric blood culture bottles using in-house-developed methods to obtain microbial pellets for spectrometric analysis have seldom been studied. During a 2-year period (June 2018 to May 2020), DIMT was performed on broths from positive pediatric blood culture bottles using an in-house-developed method. Organism identifications with a score of ≥1.6 were notified to treating clinicians. Therapeutic modifications that occurred after the communication of DIMT were reviewed through the electronic medical records. DIMT was performed on 530 pediatric positive blood culture bottles. Among 505 monomicrobial bottles, identifications from 298 (97.7%) deemed as bloodstream infections (BSI) and 189 (94.5%) as contaminations had DIMT notified to clinicians. All identifications were correct except for one Streptococcus mitis incorrectly reported as Streptococcus pneumoniae. Therapy modifications resulting from DIMT occurred in 27 (8.3%) patients with BSI. Deescalation from effective or ineffective broad-spectrum regimens occurred mainly in Enterococcus faecalis bacteremia, whereas appropriate escalation from an ineffective regimen with narrower spectrum occurred mainly in bacteremia caused by AmpC-β-lactamase-producing Enterobacterales. Escalation therapy was instituted significantly faster than deescalation therapy (median time, 0.75 versus 10.5 h [P = 0.01]). DIMT also enabled clinicians to confirm contamination in nearly one-half of patients with contaminated blood cultures. Our DIMT method applied to positive pediatric blood culture bottles demonstrated reliable performance for the rapid identification of pathogens. Our DIMT approach allowed therapeutic optimization in BSI, especially involving microorganisms with intrinsic antibiotic resistance, and was helpful in the early identification of likely contaminants. IMPORTANCE We demonstrate the performance and early impact on the antimicrobial management of bloodstream infections of an inexpensive, in-house preparation method for direct identification of bloodstream pathogens in pediatric blood culture bottles by matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry.