Group B strep (group B streptococcus, or GBS) is a common bacteria present in the vagina of about 1 in 4 women. In the US and other developed countries, pregnant women are tested for GBS—those who test positive are given antibiotics to help protect babies from infection. In low-resource settings where GBS testing and treatment is often not accessible, invasive GBS infection leads to a large percentage of still births and an estimated 3.5 million preterm births each year.

Despite the substantial impact on pregnancy outcomes, scientists know little about how GBS establishes an in utero infection. In a paper published in the Journal of Clinical Investigation, Dr. Lakshmi Rajagopal, a principal investigator in Seattle Children’s Research Institute’s Center for Global Infectious Disease Research describes a newly uncovered mechanism by which GBS gains access to a woman’s uterus.

Rajagopal’s lab found that GBS takes advantage of exfoliation, a response to infection previously thought to protect against invasive infection. Rather than preventing infection by shedding infected cells from tissue, GBS-induced exfoliation activates a signaling pathway that allows the bacteria to permeate the vaginal barrier and infect the uterus. The discovery could yield new treatment options that prevent GBS-induced loss of barrier function, or stop GBS from colonizing in the vagina, to significantly reduce the risk of infection to the baby.