Does maternal intrapartum antibiotic treatment prolong the incubation time required for blood cultures to become positive for infants with early-onset sepsis?

Background: We hypothesized that maternal intrapartum antibiotic treatment delays the growth of the organism in the blood culture obtained during the work-up for infants with suspected early-onset sepsis (EOS).

Methods: Single center, retrospective review of infants with blood culture-proven EOS over 13.5 years period. EOS was defined by isolation of a pathogen from blood culture obtained within 72 hours of birth and antibiotic treatment for  ≥ 5 days.

Results: Among 81 infants with positive blood cultures, 38 were deemed to have EOS and 43 were deemed contaminants. The organisms grown were as follows: Escherichia coli in 17 infants, Group B streptococcus in 10 infants, and others in 11 infants. Overall, 17 infants with EOS did not receive intrapartum antibiotics and had blood cultures drawn for being symptomatic after birth. The other 21 infants who received intrapartum antibiotics had blood culture drawn primarily for maternal chorioamnionitis. The median (interquartile range [IQR]) incubation time to blood culture positivity was not different in infants who received intrapartum antibiotics compared with infants who did not (19.6 hours, IQR 16-28 hours vs. 19.5 hours, IQR 17.2-21.6 hours, p = 0.7489).

Conclusion: Maternal intrapartum antibiotic treatment did not delay the time to blood culture positivity in infants with EOS.