New genetic clues show why certain GBS types are particularly deadly in newborns

09 Jun 2020
New genetic clues show why certain GBS types are particularly deadly in newborns
New genetic clues from a leading cause of death in babies shows why certain types are particularly deadly, and links its origins with a bacterium in animals.   
Researchers can now identify why certain types of Group B Streptococcal (GBS) bacteria are particularly deadly in newborn babies, causing meningitis and sepsis. The new research has also given clues to the origin of GBS bacteria, linking it to bacteria found in animals.
The study was led by University College London in collaboration with the Malawi Liverpool Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, University of Oxford, University of Liverpool and University of Bristol, and was funded by Meningitis Research Foundation.
There are many different types of GBS bacteria harmlessly carried in the human body (the gut and the birth canal) or in animals. Some of these are much more likely to cause potentially fatal disease including meningitis, sepsis and pneumonia. Whether GBS is likely to be harmless, or cause serious disease, is in part determined by the bacteria’s genetics.
The study, published today (8th-9th June 2020) in mBio, identified different families of GBS bacteria with distinct genetic profiles which determine how harmful the bacteria are, and how well the bacteria is adapted to living in different environments within humans. Some, for example, live in the intestines and/or reproductive organs, where it is typically harmlessly carried, and others in the blood and brain where it causes GBS disease.

GBS is the leading cause of meningitis in newborn babies in the UK, the US and many other countries around the world, and it is increasingly recognised that it is most common in low-to-middle income countries, for example in sub-Saharan Africa - where around 20 percent of women carry GBS.
In most cases it is harmless but it can sometimes cause death or serious complications in babies that come into contact with the bacteria during or after birth.
The genetic make-up of almost 2,000 samples of GBS bacteria from both humans and animals living in various countries including Malawi, Kenya, USA, Canada and the Netherlands were analysed using cutting edge genome sequencing technology and computational analysis.
Researchers identified 279 genes that seem to explain why some families of GBS bacteria are so much more harmful than others.  The families of bacteria were not found to be geographically restricted.

Additionally, the authors suggest that the GBS bacteria now carried in humans first evolved in animals. But after managing to cross into humans they have managed to expand. These findings may help in the development of a vaccine against GBS disease.

“These findings are essential to help understand what is causing GBS disease and how the bacteria evolve and are transmitted. There is not yet a vaccine routinely available for pregnant women to protect their unborn babies against GBS disease, but with several vaccines currently in development these findings will enable researchers to target vaccines most effectively.” - Robert Heyderman, Professor of Infectious Diseases & International Health at University College London

Rob Dawson, Meningitis Research Foundation’s Director, added “GBS is a terrible problem around the world, causing not only meningitis in babies, but sepsis and pneumonia as well. Reducing neonatal meningitis is an international priority for us as a charity working towards a World-Health-Organization-led Global Roadmap to Defeat Meningitis by 2030. Preventing GBS by offering vaccination for pregnant women would be the best way to save lives. This research also demonstrates the power of genomics in helping us better understand disease, and will make key contributions to a new Global Meningitis Genome Partnership which will links resources for the four leading causes of acute bacterial meningitis to improve worldwide co-ordination of identification and tracking.”
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