Further supporting the widespread notion that “breast is best” when it comes to infant feeding, a new study finds that a type of sugar present in breast milk could protect babies from the life-threatening infection group B streptococcus.

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Sugars in breast milk could protect babies from life-threatening group B streptococcus infection, say researchers.

According to the Centers for Disease Control and Prevention (CDC), group B streptococcus (GBS) infection is the most common cause of meningitis and sepsis in a newborn’s first week of life.

Around 1 in 4 expectant mothers carry GBS bacteria in their gastrointestinal tract or vagina. As such, early-onset infection in newborns most commonly occurs as a result of GBS bacteria being passed from mother to child during delivery.

Late-onset GBS infection – infection that occurs between the age of 1 week and 3 months – can arise as a result of the bacteria being passed from the mother, but it is more likely the infant has contracted the infection from elsewhere.

Now, researchers from Imperial College London in the United Kingdom have found that lacto-n-difucohexaose I – a type of naturally occurring sugar believed to be present in the breast milk of around half of women worldwide – could prevent babies from becoming infected with GBS.

Lead author Dr. Nicholas Andreas, of the Department of Medicine at Imperial, and colleagues publish their findings in the journal Clinical & Translational Immunology.

The researchers explain that the types of sugar in a woman’s breast milk – known as human milk oligosaccharides – are partly influenced by genetic makeup, primarily the Lewis antigen system, which is involved in producing the A, B, and O blood groups.

For their study, the researchers tested the breast milk of 183 mothers from Gambia for the presence of sugars known to be influenced by the Lewis genes.

Additionally, the mothers were tested for the presence of GBS through vaginal and rectal swabs collected at childbirth. At birth, 6 days after birth, and 60-89 days after birth, nasopharyngeal and rectal swabs were collected from their infants and tested for GBS.

Compared with mothers who did not have Lewis gene-related sugars in their breast milk, those who did had lower levels of GBS in their gut, the researchers report, and they were also less likely to pass the bacteria to their infants during childbirth.

What is more, the team found that infants born to mothers who had the sugar lacto-n-difucohexaose in their breast milk – also associated with the Lewis genes – were more likely to have cleared GBS bacteria from their body by 60-89 days of age.

On testing breast milk containing lacto-n-difucohexaose against GBS bacteria in the lab, the researchers found it was more effective at killing the bacteria than breast milk that did not contain this specific sugar.

Together, the researchers say their findings suggest naturally occurring sugars in breast milk – particularly lacto-n-difucohexaose – could prevent GBS infection in infants by boosting the presence of beneficial gut bacteria.

“Although this is early-stage research, it demonstrates the complexity of breast milk, and the benefits it may have for the baby. Increasingly, research is suggesting these breast milk sugars (human milk oligosaccharides) may protect against infections in the newborn, such as rotavirus and group B streptococcus, as well as boosting a child’s ‘friendly’ gut bacteria.”

Dr. Nicholas Andreas

The results could pave the way for new strategies to prevent GBS infection in mothers and their infants, the team notes. For mothers who do not produce the GBS-protective sugars, breast milk sugar supplements could be an option.

Furthermore, Dr. Andreas says the results also provide a basis for Lewis gene testing in new mothers.

“If we know whether a mother is colonized with group B streptococcus and know if she carries an active copy of the Lewis gene, it may give us an indication of how likely she is to pass the bacteria on to her baby, and more personalized preventive measures could be applied,” he explains.

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