Diagnostic contribution of anaerobic bottles in pediatric blood cultures: experience at a tertiary children’s hospital

Routine use of anaerobic bottles in pediatric blood cultures remains controversial because diagnostic yield must be balanced against limited sampling volume. We retrospectively analyzed paired pediatric aerobic–anaerobic blood cultures collected from patients younger than 18 years at a tertiary children’s hospital from January 2020 through December 2024. Accession-defined paired sets received within 15 min were grouped into culture episodes; episodes containing at least two paired sets comprised the primary cohort. Among 24,485 multi-set episodes from 8,658 patients, 999 (4.1%) were positive, and 387 (1.6%) were potential-contaminant episodes. Confirmed anaerobic-bottle contribution was observed in 208 positive episodes (20.8%), comprising additional organism recovery in 159 (15.9%) and detection more than 4 h earlier in 49 (4.9%); the absolute added yield was 8.5 per 1,000 episodes. Obligate anaerobes were identified in 11 positive episodes, whereas the majority of the contribution came from facultative organisms, particularly Staphylococcus aureus , Escherichia coli , and viridans group streptococci. Contribution was highest in the emergency room (28.2%) and neonatal intensive care unit (25.0%). Compared with the general ward, adjusted odds were higher in the emergency room (adjusted odds ratio, 1.83; 95% confidence interval, 1.23 to 2.73) and lower in the hemato-oncology ward (0.43; 0.21 to 0.85). Contribution was 21.8% among children younger than 4 years. The overall median within-accession time-to-positivity difference (anaerobic minus Peds Plus/F) was small (−0.17 h), although selected organisms showed earlier anaerobic detection. Anaerobic bottles provided complementary diagnostic information in approximately one-fifth of positive pediatric blood culture episodes, mainly through additional recovery rather than uniformly earlier detection.