Time to Positive Blood and Cerebrospinal Fluid Cultures in Febrile Infants ≤60 Days of Age.

Objectives: To determine the time to positivity for bacterial pathogens and contaminants in blood and cerebrospinal fluid (CSF) cultures in a cohort of febrile infants ≤60 days of age.

Methods: This was a secondary analysis of prospective observational multicenter study of noncritically ill infants ≤60 days of age with temperatures ≥38°C and blood cultures (December 2008 to May 2013). The main outcome was time to positivity for bacterial pathogens and contaminants.

Results: A total of 256 of 303 (84.49%) patients with positive blood cultures, and 73 of 88 (82.95%) with positive CSF cultures met inclusion criteria. Median time (interquartile range [IQR]) to positivity for blood cultures was 16.6 hours (IQR 12.6-21.9) for bacterial pathogens ( = 74) and 25.1 hours (IQR 19.8-33.0) for contaminants ( = 182); < .001. Time to bacterial pathogen positivity was similar in infants 0 to 28 days of age (15.8 hours [IQR 12.6-21.0]) and 29 to 60 days of age (17.2 [IQR 12.9-24.3]; = .328). Median time to positivity for CSF was 14.0 hours (IQR 1.5-21.0) for bacterial pathogens ( = 22) and 40.5 hours (IQR 21.2-62.6) for contaminants ( = 51); < .001. A total of 82.4% (95% confidence interval, 71.8-90.3) and 81.8% (95% confidence interval, 59.7%-94.8%) of blood and CSF cultures showed bacterial pathogen positivity within 24 hours.

Conclusions: Among febrile infants ≤60 days of age, time to blood and CSF positivity was significantly shorter for bacterial pathogens than contaminants. Most blood and CSF cultures for bacterial pathogens were positive within 24 hours. With our findings, there is potential to reduce duration of hospitalization and avoid unnecessary antibiotics.