Time to Blood Culture Positivity by Pathogen and Primary Service

Initiation and continuation of empirical antimicrobial agents for a 48-72-hour observation period is routine practice in the diagnosis and treatment of infants and children with concern for bacteremia. We examined blood cultures at a freestanding pediatric hospital over a 6-year period to determine the time to positivity.

Data were extracted for all patients who were hospitalized and had blood cultures drawn between January 2013 and December 2018. Time to positivity was calculated on the basis of date and time culture was collected compared with date and time growth was first reported.

Over a 6-year period, 89 663 blood cultures were obtained, of which 6184 had positive results. After exclusions, a total of 2121 positive blood culture results remained, including 1454 (69%) pathogens and 667 contaminants (31%). For all positive blood culture results, the number and percentage positive at 24, 36, and 48 hours were 1441 of 2121 (68%), 1845 of 2121 (87%) and 1970 of 2121 (93%), respectively. One hundred twenty-five (66 pathogens, 59 contaminants) of the 89 663 cultures (0.14%) yielded positive results between 36 and 48 hours, indicating that 719 patients would need to be treated for 48 hours rather than 36 hours to prevent 1 case of antibiotic termination before positive result. Median times to positive result by pathogen and service line are presented.

This study reveals that ≤36 hours may be a sufficient period of observation for infants and children started on empirical antimicrobial agents for concern for bacteremia. These findings highlight opportunities for antimicrobial stewardship to limit antimicrobial .