Abstract Background Bacterial infection at the maternal-fetal interface contributes to adverse pregnancy outcomes, including preterm birth, chorioamnionitis, and sepsis. Despite evolving obstetric practices that may influence microbial patterns, recommended clinical algorithms for prophylaxis and treatment rely on outdated data. Furthermore, the pathogenic organisms associated with adverse outcomes remain incompletely characterized. Methods We conducted a retrospective study of placental cultures from a high-risk obstetric cohort from a single hospital system between 2014-2019 (n=714). Placental cultures were obtained from deliveries at high risk for infection: eg. preterm birth, suspected chorioamnionitis. Placental cultures were stratified into pathogenic and nonpathogenic. Associated clinical outcomes, histopathology and antimicrobial susceptibility patterns were compared. Results Pathogenic organisms were identified in 69% (492/714) of cultures. Group B Streptococcus (n=161; 22.5% total isolates) and Escherichia coli (n=53; 7.4% total isolates) were the most common pathogens isolated, we also identified additional pathogens including Enterococcus faecalis (n=44), Haemophilus (n=37), Prevotella (n=32), and Bacteroides species (n=23). Pathogenic cultures correlated with significantly higher rates of composite adverse maternal (27.0% vs. 17.6%, p=0.006) and neonatal outcomes (78.9% vs. 60.6%, p=0.0002), as well as histopathologic chorioamnionitis (72.5% vs. 60.9%, p=0.003). Antimicrobial resistance for recommended empiric regimens ranged from 47.1%-87.8%. Conclusion Bacterial pathogens isolated from the placenta in high-risk pregnancies are associated with perinatal morbidity. GBS and E. coli remain common and E. faecalis, Haemophilus spp., and anaerobes such as Prevotella, may represent emerging pathogens underrecognized in contemporary obstetric practice. Placental cultures may serve as a valuable surveillance tool for informing empiric antibiotic strategies in pregnancy.
Liu et al. (Sat,) studied this question.