Impact of rapid MALDI-TOF MS and susceptibilities on hospitalized children with Gram-negative bloodstream infections

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) offers fast identification to improve time to appropriate antibiotics in Gram-negative bloodstream infections (GN-BSIs). This retrospective study evaluated patients with GN-BSI PRE- and POST-implementation of rapid identification with and without direct antimicrobial susceptibility testing (AST). Patients aged 0–18 years with GN-BSI before and after implementation of direct blood culture broth MALDI-TOF MS and AST were evaluated. Cohorts were defined by methods of organism identification and AST: traditional culture and AST methods (PRE), direct from broth identification by MALDI-TOF MS with culture-dependent AST (MALDI + cAST) and direct from broth identification MALDI-TOF MS with direct AST (MALDI + dAST). A total of 246 pediatric patients were included, 78 PRE, 92 MALDI + cAST, and 76 MALDI + dAST. Both POST-implementation groups had decreased median time from blood culture collection to identification by over 24 h (16.1 h MALDI + cAST and 15.5 h MALDI + dAST vs 42.9 h PRE; P < 0.0001). MALDI + dAST had decreased median time to susceptibilities (34.3 h MALDI + dAST vs 44.4 h PRE and 51.4 h MALDI + cAST; P < 0.0001) and decreased time to optimal therapy (TTOT) compared with PRE and MALDI + cAST (51.4 h MALDI + dAST vs 57.1 h PRE and 58.2 h MALDI + cAST; P = 0.03). There was no significant difference in time to effective therapy (TTET). Time to discontinuation of Gram-positive coverage decreased in MALDI + cAST and MALDI + dAST cohorts (39.3 h MALDI + cAST and 37.1 h MALDI + dAST vs 49.1 PRE; P = 0.03). The implementation of a rapid ID and AST approach significantly reduced the time to identification and time to susceptibility. However, a 17-h gap in antibiotic optimization highlights the need for additional interventions. IMPORTANCE Rapid pathogen identification and susceptibility testing is essential for optimizing antimicrobial therapy in pediatric Gram-negative bloodstream infections. This study demonstrates that direct from blood culture broth identification with MALDI-TOF MS along with direct AST led to faster time to susceptibilities and time to optimal therapy in patients with GN-BSI. Despite this, there exists a 17-h gap between results and optimization of antibiotics. This suggests rapid diagnostic testing has not been effectively integrated into clinical practice and the need for active antimicrobial stewardship to improve the impact of these faster laboratory diagnostics.