Clinical and microbiological outcomes of maternal bacteremia: the role of intrapartum antibiotic use, insights from an 11-Year cohort study

Objectives: Maternal sepsis remains a leading cause of maternal mortality worldwide. However, it is unclear whether obstetrical, neonatal, and microbiological outcomes associated with maternal bacteremia differ based on the timing of bacteremia presentation. This study aimed to evaluate maternal, neonatal, and microbiological characteristics of bacteremia in pregnancy, with a specific focus on the association between intrapartum antibiotic use and bacteremia caused by ampicillin-resistant Enterobacteriaceae. Methods: A retrospective cohort study was conducted, including all women who delivered at Galilee Medical Center, a tertiary university-affiliated hospital, over an 11-year period (2012–2023). The maternal bacteremia rate, the primary outcome, was analyzed. The study included pregnant women from 24 weeks of gestation to 7 days postpartum, with bacteremia confirmed by positive blood cultures. The distribution of pathogens in blood cultures was compared according to timing of presentation (antepartum, intrapartum, or postpartum), and between women with preterm and term bacteremia. Maternal bactermia-related admission to the intensive care unit were characterized. Additionally, the impact of intrapartum antibiotic use on bacterial resistance profiles was assessed. Results: During the study period, 46,103 women gave birth, of whom 104 (2.2 per 1,000 deliveries) had confirmed maternal bacteremia from 24 weeks of gestation to 7 days postpartum. Over the 11-year period, the incidence of bacteremia decreased from 0.4% to 0.15%, with Enterobacteriaceae bacteremia consistently more frequent than Group B streptococcal (GBS) bacteremia. Antepartum bacteremia (21%) was primarily caused by pyelonephritis (82%), intrapartum bacteremia (45%) by chorioamnionitis (98%), and postpartum bacteremia (34%) by endometritis (94%). Overall, Enterobacteriaceae was the most commonly isolated pathogen (55%), followed by GBS (19%). The rate of Enterobacteriaceae-isolated bacteremia was significantly higher in preterm deliveries compared to term deliveries (68% vs. 47%, p = 0.039), while the rate of GBS-isolated bacteremia was significantly lower in preterm deliveries (0% vs. 30%, p < 0.001). Neonatal early onset sepsis occurred more frequently in preterm deliveries (16% vs. 2%, p = 0.027), with all preterm cases caused by ampicillin-resistant Escherichia coli. Among women with postpartum bactermia, the use of intrapartum ampicillin significantly increased the incidence of ampicillin-resistant Enterobacteriaceae bacteremia (92% vs. 52%, p = 0.023). Conclusions: Maternal bacteremia, predominantly caused by Enterobacteriaceae, poses a serious risk to both mothers and newborns. The study highlights the association between intrapartum ampicillin use and ampicillin-resistant Enterobacteriaceae bacteremia in both mothers and the neonates, emphasizing the need for optimized infection control measures and tailored antibiotic protocols in obstetric care. These findings support further research to improve management strategies and reduce adverse outcomes related to maternal bacteremia.