PROJECT SUMMARY Bacterial infections leading to morbidity and mortality of human newborns remain significant public health concerns. Group B Streptococci (GBS) are Gram-positive bacteria that cause preterm births, stillbirths and early onset infections in human newborns. Although GBS normally reside as commensal organisms in the lower genital tract (LGT) of healthy women, the events that promote transmission of GBS from the LGT to the amniotic cavity and fetus during pregnancy are unknown. The objective of this proposal is to define the role of the human cervical mucus plug in prevention of GBS growth and to determine if GBS sense CMP and modify virulence factor expression leading to ascending infection and fetal injury.