Bacterial infection increases risk of illness for newborns

British researchers have proposed screening pregnant women for a bacterial infection linked to risk of neonatal sepsis.

Placental Group B Streptococcus (GBS) is associated with a two- to three-fold increased risk of neonatal unit admission, with one in 200 babies admitted with GBS-associated sepsis – almost 10 times the previous estimate, researchers found.

A team at the University of Cambridge and Rosie Hospital, Cambridge University Hospitals NHS Foundation Trust, UK, examined the link between the presence of GBS in the placenta and the risk of admission of the baby to a neonatal unit.

Data from their previous study, which identified GBS in the placenta of around 5% of women prior to the onset of labour, was re-analysed data available from their previous study of 436 infants born at term and confirmed their findings in a second cohort of 925 pregnancies.

The results, published in Nature Microbiology, estimate that placental GBS was associated with a two- to three-fold increased risk of neonatal unit admission, with one in 200 babies admitted with sepsis associated with GBS.

They found the clinical assessment of these babies using the current diagnostic testing identified GBS in less than one in five of these cases.

While all pregnant women in the USA are routinely screened for GBS and treated with antibiotics if found to be positive, only a small number in the UK are screened as only those who experience complications or have other risk factors are targeted.

However, a randomised controlled trial of screening for GBS for treatment with antibiotics is taking place in the UK.

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.”

The team have developed an ultrasensitive PCR test, which amplifies tiny amounts of DNA or RNA from a suspected sample to check for the presence of GBS.

Professor Gordon Smith, head of obstetrics & gynaecology at the University of Cambridge, said: “Using this new test, we now realise that the clinically detected cases of GBS may represent the tip of the iceberg of complications arising from this infection. We hope that the ultra-sensitive test developed by our team might lead to viable point-of-care testing to inform immediate neonatal care.”

When the researchers analysed serum from the babies’ umbilical cords, they found that more than one third showed increased levels of several cytokines. This suggests that a ‘cytokine storm’ was behind the increased risk of disease.

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 29 November 2023; doi: 10.1038/s41564-023-01528-2


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