Bacterial threat to newborns from mothers

Cambridge researchers found that one in 200 newborns is admitted to a neonatal unit with a bacterial infection caused by bacteria commonly carried by their mothers. This is a higher rate than previously thought. The research team created a susceptible test to improve the detection of this bacteria, which is often overlooked in most cases. This discovery suggests that the risks and benefits of universal screening for this bacteria in mothers must be reconsidered in the UK.

Group B Streptococcus (GBS) is found in the genital tract of about one in five women. Previous research from the University of Cambridge and Rosie Hospital showed that GBS is present in the placenta of around 5% of women before labor begins. GBS can cause a severe infection in newborns, leading to sepsis. 

With screening, carriers will know they have it. Worldwide, GBS contributes to around 50,000 stillbirths and up to 100,000 infant deaths annually. In a recent study published in Nature Microbiology, the researchers explored the connection between GBS in the placenta and the risk of newborns being admitted to a neonatal unit. They confirmed their findings in two groups of infants, totaling 1,361 pregnancies.

The researchers found that having Group B Streptococcus (GBS) in the placenta increased the risk of a baby being admitted to a neonatal unit two to three times. This means one in 200 babies with GBS-related sepsis is permitted, which is almost ten times higher than previous estimates. Current tests in the USA identify GBS in all pregnant women, and those positive receive antibiotics. 

In the UK, only a few pregnant women are tested for GBS, typically those with complications. Reasons include the difficulty in detecting GBS in mothers and the belief that only a small number of exposed babies get sick. The UK is conducting a trial to assess GBS screening and antibiotic treatment.

Dr Francesca Gaccioli from the Department of Obstetrics & Gynaecology at the University of Cambridge said: “In the UK, we’ve traditionally not screened mothers for GBS, but our findings – that significantly more newborns are admitted to the neonatal unit as a result of GBS-related sepsis than was previously thought – profoundly changes the risk/benefit balance of universal screening.”

Researchers created a susceptible PCR test to improve detection that amplifies tiny amounts of DNA or RNA to check for Group B Streptococcus (GBS). They’ve filed a patent for this test with Cambridge Enterprise. Professor Gordon Smith from the University of Cambridge states that the current clinically detected GBS cases may be the tip of the iceberg, and the new test could lead to point-of-care testing for immediate neonatal care.

The study also found that when analyzing serum from babies’ umbilical cords, over a third showed significantly increased levels of cytokines, indicating a ‘cytokine storm’ or an extreme immune response that contributes to the increased risk of disease. The Medical Research Council funded the research and was supported by the National Institute for Health and Care Research (NIHR) Cambridge Biomedical Research Centre.

This study underscores the importance of addressing the risks associated with GBS in newborns, highlighting disparities in screening practices and the potential impact of an ultrasensitive PCR test on improving detection and informing neonatal care decisions.

Journal reference:

1. Gaccioli, F., Stephens, K., Sovio, U. et al. Placental Streptococcus agalactiae DNA is associated with neonatal unit admission and fetal pro-inflammatory cytokines in term infants. Nature Microbiology. DOI: 10.1038/s41564-023-01528-2.