Abstract Background Rapid and accurate antimicrobial susceptibility testing (AST) is essential for managing Gram-negative bacteraemia. However, a major limitation of conventional phenotypic AST is its slow turnaround time, delaying targeted therapy. Objectives To evaluate the performance and turnaround time of direct-from-blood culture AST using an automated phenotypic system in paediatric patients with Gram-negative rod bacteraemia. Methods We retrospectively reviewed 135 positive blood cultures with Gram-negative rods from a tertiary paediatric hospital between January 2021 and December 2023. Blood cultures that yielded polymicrobial organisms were excluded from the study. Direct AST was performed by preparing bacterial suspensions directly from positive blood culture broth and analyzed using an automated phenotypic AST system (BD Phoenix™ M50). Conventional AST from isolated colonies served as the reference. Essential agreement (EA), categorical agreement (CA), and error rates very major error (VME), major error (ME), minor error (mE) were assessed. Time to AST result was compared between methods. Results The direct AST method reduced the median turnaround time by 24.0 h compared with conventional AST (P 0.0001). Overall EA and CA were 99.5% and 99.6%, respectively. No VMEs were observed. ME and mE rates were low at 0.25% and 0.25%, respectively, with discrepancies tending to indicate greater resistance by direct AST. Conclusions Direct-from-blood culture AST using an automated phenotypic system provides rapid, accurate susceptibility results in paediatric Gram-negative bacteraemia. This approach enables earlier reporting and may improve clinical outcomes and antimicrobial stewardship without additional resource burden.
Nanishi et al. (Thu,) studied this question.