Revisiting time to blood culture positivity: can we decrease antibiotic exposure in the NICU?

We aimed to investigate the time to positivity of blood cultures in our NICU to determine if we can better inform empiric antibiotic duration decisions in both early-onset (≤72 h) and late-onset (>72 h) sepsis evaluations.

Retrospective review of all positive blood cultures isolated from infants admitted to the Rainbow Babies and Children's Hospital NICU from July 1, 2018 to July 1, 2023.

There were 264 positive blood cultures from 125 infants with a median postmenstrual age of 30.9 weeks. The vast majority (86%) of positive cultures were obtained during the late-onset sepsis period. Gram-negative bacteria grew faster than gram-positive bacteria. Overall, 84% of blood cultures for all pathogenic bacteria (excluding coagulase-negative staph, fungi, and likely contaminants) were positive by 24 h.

Our data do not support discontinuing empiric antibiotics at 24 h as our a priori target of 90% positivity was not met. These results underline the importance of evaluating an individual NICU's data before implementing a practice change.