Delayed blood culture positivity in Fusobacterium nucleatum bacteremia: A retrospective comparative study

This is the authors' abstract. We don't add key points for this paper.

Objectives Blood culture time to positivity (TTP) in Fusobacterium nucleatum bacteremia remains poorly characterized at the species level. We aimed to characterize TTP in F. nucleatum bacteremia and compare it with that of representative anaerobes and common bloodstream pathogens. Methods We conducted a single-center retrospective study of all F. nucleatum bacteremia episodes detected between December 2020 and March 2026. Episodes of Bacteroides fragilis, Clostridium perfringens, Escherichia coli, and Staphylococcus aureus bacteremia served as comparators. Episode-level TTP was defined as the shortest TTP among blood culture bottles from which the index organism was recovered. Overall differences were assessed using the Kruskal-Wallis test, followed by pairwise Mann-Whitney U tests with Holm adjustment. Results Nine F. nucleatum bacteremia episodes were identified, with TTP available for eight. The median TTP was 79.3 h, substantially longer than that of B. fragilis (32.1 h), C. perfringens (12.8 h), E. coli (11.7 h), and S. aureus (15.4 h). All pairwise comparisons remained significant after Holm adjustment (adjusted P < 0.001 for each). Six of eight episodes signaled positive after 48 h. Conclusions F. nucleatum bacteremia was associated with substantially longer TTP than the comparator organisms. A negative blood culture at 48 h should be interpreted cautiously when F. nucleatum bacteremia remains clinically plausible.