443 - Impact of Antepartum Antibiotics Characteristics and Placental Pathology on Time to Positivity of Blood Culture in Neonatal Early Onset Sepsis

Publication Number: 2431.443

Michelle M. Nguyen, Loma Linda University Children's Hospital, San Bernardino, CA, United States; Shaina K. Lodhi, Loma Linda University Children's Hospital, Loma Linda, CA, United States; Larry Ngo, Loma Linda University Childrens Hospital, Loma Linda, CA, United States

Background: Early-onset sepsis (EOS) occurs in approximately 0.5 per 1,000 live births and remains a major cause of neonatal morbidity and mortality. Risk factors include prematurity, maternal infection, premature rupture of membranes, and maternal group B Streptococcus (GBS) colonization. The impact of maternal antenatal antibiotic administration on neonatal blood culture results and the incidence of culture-negative EOS remains unclear, thus it is worthwhile for stratifying risk to determine how significant these exposures influence blood culture time to positivity.

Objective: Empiric antibiotics are routinely initiated in neonates at risk for early-onset sepsis (EOS), with duration guided by blood culture results. Culture monitoring practices before antibiotic discontinuation vary across institutions. Recent studies demonstrate that neonatal culture positivity occurs within 36 hours for EOS. However, there are concerns that maternal risk factors and variables in antibiotic exposure may prolong time to positivity (TTP) for blood cultures. This study aimed to determine whether TTP is affected by maternal risk factors, antepartum antibiotic administration, and placental pathology findings.

Design/Methods: Neonates with positive blood cultures were retrospectively analyzed between 2013 to 2024. Data was collected on the time to positive blood culture result and blood culture pathogen. Additional factors assessed include gestational age, birth weight, delivery mode, maternal GBS status, chorioamnionitis (clinical and histologic), and intrapartum antibiotic exposure (timing and number of doses).

Results: A total of 93 infants were identified with positive blood culture results. 56 infants had pathogenic bacteria and 37 infants had contaminants. Among pathogenic cultures, the TTP was 13 hours with an interquartile range of 10-21 hours; 92% were positive by 36 hours and 98% by 48 hours. There was no statistically significant correlation between TTP and gestational age, delivery mode, birth weight, maternal GBS status, maternal chorioamnionitis, total maternal antepartum administration, or timing of antepartum administration. In addition, there was no significant difference in TTP when placental funisitis or chorioamnionitis was present.

Conclusion(s): Positive blood cultures in neonates with EOS typically resulted within 36 hours and were not affected by maternal risk factors, antenatal antibiotic administration characteristics or presence of placental findings. These results affirm the timing of pathogenic blood cultures and provide additional support for the consideration of a 36-48-hour evaluation for early onset sepsis.

Time To Positivity
92% of pathogenic blood cultures were positive by 36 hours and 98% were positive by 48 hours.

Impact of Number of Intrapartum Antibiotics on Time To Positivity
There is no statistically significant correlation between the number of intrapartum antibiotics received and blood culture's time to positivity.

Impact of the Timing of Intrapartum Antibiotics on Time to Positivity
There is no statistically significant correlation between the timing of intrapartum antibiotics and blood culture's time to positivity.