Human milk contains sugars that may protect against group B strep, which is a leading cause of severe infection in newborn babies. The scientists behind the discovery suggest that the sugars might also prevent biofilms, which are a particularly stubborn form of infection.
The study is the first to show that carbohydrates in human milk could work against biofilms, say the researchers, who are from Vanderbilt University in Nashville, TN.
If their findings are confirmed by further studies, the sugars might form part of antimicrobial treatments for babies and adults. They might also reduce reliance on some common antibiotics, says senior investigator Steven Townsend, Ph.D., who is an assistant professor of chemistry.
The team recently presented the study at the American Chemical Society’s 254th National Meeting & Exposition, held in Washington, D.C., and they reported it in the journal ACS Infectious Diseases.
Group B Streptococcus (group B strep) is a type of bacteria that is commonly found in the gut (including the stomach, intestines, and rectum) and genital tract without causing any symptoms. Occasionally, however, group B strep causes illness – especially when it infects the bloodstream and soft tissue.
In babies, group B strep infection can result in severe illnesses such as sepsis (infection in the blood), pneumonia (infection in the lungs), and meningitis (infection of the fluid and lining of the brain and spinal cord).
There are two main types of group B strep disease in babies: those that occur during the first week of life (termed early-onset) and those that occur between that period and age 3 months (late-onset).
In the United States, there are around 26,500 severe cases of group B strep infection every year in all age groups.
The rate of early-onset infection in babies has fallen dramatically since “active surveillance” began in the mid-1990s; between 1993 and 2014, the rate fell from 17 to 0.24 cases per 1,000 live births.
In their study report, the researchers explain that group B strep can infect the fetal membranes during pregnancy. Another route of infection from the mother is thought to be from the vagina during childbirth.
“In most women, the group B strep that is present will not cause illness,” notes Prof. Townsend.
“But for newborn babies,” he explains that infection by group B strep “often leads to sepsis or pneumonia, and in severe cases death, because they don’t have fully developed defense mechanisms.”
Much of the success in reducing early-onset infection is the result of giving women who test positive for group B strep in their last trimester a course of antibiotics during labor. This does not necessarily prevent late-onset cases, however.
Around 10 years ago, researchers discovered that in some late-onset cases of group B strep in babies, the route of infection was breast milk, despite the fact that it also has antibacterial properties.
However, because most babies do not become infected, the Vanderbilt University team wondered if human milk might also contain some compounds that specifically protect against group B strep.
Prof. Townsend explains, “As carbohydrate chemists, we knew from previous research that milk carbohydrates are protective against other bacteria, so we figured there would be a chance they would be active against group B strep, too.”
So, he and his colleagues set up a pilot study wherein they collected samples of breast milk from five donor mothers. They did not know whether the donors were positive or negative for group B strep.
The team then separated out compounds called oligosaccharides – a group of complex sugars – from the human milk samples and used them to grow group B strep.
The results showed that sugars from the breast milk of one donor nearly wiped out all the cultured bacteria. Sugars from another donor had a moderate effect, while those of the other three showed minimal effect.
The researchers found that in the case of the effective sample, the sugars also destroyed biofilms of group B strep.
Bacteria form biofilms – which can be very hard to treat – by surrounding themselves with a “gooey substance” that they excrete.
The team is currently testing human milk samples from another 12 donors to see if they produce the same results.
The results so far show that two of the samples are active against both microbial and biofilm forms of group B strep. Another two appear to work for microbial but not biofilm forms, while a further four appear to work against biofilm but not microbial forms.
Initial findings also suggest that some of the samples contained sugars that make group B strep more vulnerable to erythromycin, penicillin, and other common antibiotics.
The team says that should further research confirm their findings, these human milk sugars could form part of treatment for bacterial infections in both adults and babies. They might also help to reduce our reliance on antibiotics, says Prof. Townsend. He concludes:
“The great thing about these sugars is that if they’re safe for babies, they should be safe for everyone.”