Detection of common neonatal sepsis pathogens using a contemporary pediatric blood culture system

OBJECTIVE: To evaluate recovery and time to positivity (TTP) of neonatal sepsis pathogens at low and ultra-low organism concentrations using a contemporary pediatric automated blood culture system. STUDY DESIGN: Six common neonatal sepsis pathogens were prepared in a 1:1 mixture of donor whole blood and saline-organism suspension at final concentrations ranging from ≤1 to 10-20 CFU/mL. Aliquots of 0.25-2.0 mL, containing 0.125-1.0 mL donor whole blood, were inoculated into BD BACTEC Peds Plus/F bottles. Recovery and TTP were assessed. RESULTS: Clinically important neonatal pathogens remained recoverable at very low inocula, including ≤1 CFU/mL. Median TTP ranged from 10 to 12 h for Escherichia coli and Streptococcus agalactiae to 20-26 h for coagulase-negative staphylococci. Increasing organism concentration shortened TTP for E. coli, Haemophilus influenzae, Staphylococcus capitis, and S. agalactiae. Inoculated suspension volume had relatively little effect on TTP among recovered cultures. Recovery improved across larger inoculated suspension volumes, particularly for staphylococcal organisms. CONCLUSIONS: A contemporary pediatric blood culture system demonstrated excellent recovery of common neonatal sepsis pathogens, including at very low organism concentrations. Larger inoculated suspension volumes primarily improved pathogen recovery rather than substantially faster detection. These findings support optimizing and documenting blood culture specimen volume as part of neonatal diagnostic stewardship. IMPACT: Common neonatal sepsis pathogens remained recoverable at very low organism concentrations, including ≤1 CFU/mL, using a contemporary pediatric blood culture system. Organism-specific differences in time to positivity were more pronounced than the generally modest effects of organism concentration or inoculated suspension volume. Larger inoculated suspension volumes primarily improved pathogen recovery rather than detection speed. Recovery of staphylococci was reduced at smaller inoculated suspension volumes, particularly at ultra-low organism concentrations. These findings support attention to specimen volume and documentation of the volume obtained as components of neonatal diagnostic and antimicrobial stewardship.