Time to positivity of blood cultures in a level IV NICU varies based on organism category and population subgroups: is a 36-hour rule out safe?

Yo Nishihara; Christine E MacBrayne; Andrea Prinzi; Kelly Pearce; Diane Melara; Blair W Weikel; Jeanne Zenge; Theresa Grover; Sarah K Parker

doi:10.1038/s41372-024-02031-0

Time to positivity of blood cultures in a level IV NICU varies based on organism category and population subgroups: is a 36-hour rule out safe?

J Perinatol. 2024 Jun 20. doi: 10.1038/s41372-024-02031-0. Online ahead of print.

Authors

Yo Nishihara¹, Christine E MacBrayne², Andrea Prinzi³, Kelly Pearce⁴, Diane Melara⁵, Blair W Weikel⁵, Jeanne Zenge⁵, Theresa Grover⁵, Sarah K Parker⁶

Affiliations

¹ Department of Neonatology, Children's Hospital Colorado and School of Medicine, University of Colorado, Aurora, CO, USA. [email protected].
² Department of Pharmacy, Children's Hospital Colorado, Aurora, CO, USA.
³ Graduate School of Medicine, University of Colorado, Aurora, CO, USA.
⁴ Department of Epidemiology, Children's Hospital Colorado, Aurora, CO, USA.
⁵ Department of Neonatology, Children's Hospital Colorado and School of Medicine, University of Colorado, Aurora, CO, USA.
⁶ Department of Pediatric Infectious Diseases, Children's Hospital Colorado and School of Medicine, University of Colorado, Aurora, CO, USA.

PMID: 38902516
DOI: 10.1038/s41372-024-02031-0

Abstract

Background: Time to positivity (TTP) of blood cultures and organism characteristics may be different in a Level IV NICU population.

Methods: Retrospective study of 309 Level IV NICU positive blood cultures between January 2012 to December 2018 describing TTP and organism characteristics.

Results: Median TTP [IQR] was 21.1 [14.3, 25.2] hours, with 91.2% positive at 36 h, and 96.1% positive at 48 h. Gram negative definite pathogens had the shortest TTP (13.0 [11.4, 15.4] hours) compared to gram positive definite pathogens (16.3 [13.0, 22.4] hours). TTP for treated gram positive commensal organisms (22.3 [20.1, 30.4] hours) and those considered contaminants (23.6 [21.4, 26.0] hours), was significantly longer than both gram positive and negative definite pathogens.

Conclusion: When antimicrobials are initiated due to concern for bacteremia and blood cultures have not identified a causative pathogen at 36 h, antimicrobials may be safely discontinued in the majority of Level IV NICU patients.