Impact of Blood Volume on Pathogen Detection and Time to Positivity in Paediatric Blood Cultures Using BACT/ALERT 3D Automated Systems.

Background Bloodstream infections (BSIs) are a major cause of morbidity and mortality in paediatric populations. Early and accurate pathogen detection is crucial for prompt therapy. Blood volume is a key factor influencing culture sensitivity and time to positivity (TTP). This study evaluated the impact of blood volume on microbial recovery and TTP in paediatric blood cultures using the BACT/ALERT 3D automated system (bioMérieux, Marcy-l'Étoile, France). Methods In this prospective study (April 2023-September 2024), 160 paediatric blood culture bottles were analysed. Blood volume was calculated using pre- and post-inoculation weights. Bottles were classified as optimal (>0.5 mL) or suboptimal (<0.5 mL). TTP and pathogen recovery were compared. Results Among 160 paediatric blood cultures, 78 (48.75%) flagged positive. Coagulase-negative Staphylococci (CoNS) were the most common isolates, followed by Candida spp. and Klebsiella pneumoniae. Median TTP was 18.13 h. No significant difference in pathogen recovery between optimal and suboptimal volume groups was observed. Gram-negative isolates had the shortest TTP (median: 11.39 h). Conclusion While adequate blood volume remains important, suboptimal volumes may still yield clinically significant pathogens with acceptable detection times, supporting the feasibility of low-volume cultures in neonates. TTP may serve as an adjunct marker for early identification of pathogenic organisms.