CRISPRi Screening Identifies Essential E. coli Virulence Factors for Placental Barrier Breach in a Maternal–Fetal Infection Model

Early-onset neonatal sepsis caused by Escherichia coli (E. coli) threatens neonates’ lives due to the pathogen’s high virulence and multidrug resistance. The mechanisms that enable its placental barrier breach are poorly understood. Using a clinically isolated ST95 ExPEC strain from a neonatal sepsis case, along with a pregnant rat model and an in vitro placental barrier model, we performed CRISPR interference screening. This screen targeted 264 virulence factor genes and identified virulence factors for motility, iron acquisition, hemolysin secretion, and adherence/invasion as critical. We demonstrated that hlyB is essential for uterine infection, and we elucidated a mechanism for ibeA that facilitates syncytial trophoblast cell layer penetration by interacting with the host receptor(s) PSF/VIM to enhance bacterial internalization. Host cells countered ibeA+ E. coli infection via a novel host defense pathway involving upregulation of ASPHD1. This study systematically mapped the virulence factors required for E. coli placental translocation and delineated key host–pathogen interactions.