Bacteria known as group B Streptococcus (GBS) are a common cause of blood infections, meningitis and stillbirth in newborns. Although GBS infections can often be treated or prevented with antibiotics, the bacteria are becoming increasingly resistant.
Now, researchers have discovered that human milk oligosaccharides (HMOs) –– short strings of sugar molecules abundant in breast milk –– can help prevent GBS infections in human cells and tissues. Someday, HMOs might be able to replace antibiotics for treating infections in infants and adults, they say.
The researchers presented their results at the fall meeting of the American Chemical Society (ACS).
“Our lab has previously shown that mixtures of HMOs isolated from the milk of several different donor mothers have antimicrobial and antibiofilm activity against GBS,” says Rebecca Moore, who is presenting the work at the meeting. “We wanted to jump from these in vitro studies to see whether HMOs could prevent infections in cells and tissues from a pregnant woman, and in pregnant mice.” Moore is a graduate student in the labs of Steven Townsend, Ph.D., at Vanderbilt University and Jennifer Gaddy, Ph.D., at Vanderbilt University Medical Center.
According to the U.S. Centers for Disease Control and Prevention, about 2,000 babies in the U.S. get GBS each year, and 4-6% of them die from it. The bacteria are often transferred from mother to baby during labor and delivery. An expectant mother who tests positive for GBS is usually given intravenous antibiotics during labor to help prevent early-onset infections, which occur during the first week of life. Interestingly, the incidence of late-onset infections (which happen from one week to three months after birth) is higher in formula-fed than breastfed infants, which suggests that factors in breast milk could help protect against GBS. If so, the sugars could perhaps replace antibiotics, which, in addition to killing beneficial bacteria, are becoming less effective because of the rise in antibiotic resistance.
The researchers studied the effects of combined HMOs from several mothers on GBS infection of placental immune cells (called macrophages) and of the gestational membrane (the sac surrounding the fetus). “We found that HMOs were able to completely inhibit bacterial growth in both the macrophages and the membranes, so we very quickly turned to looking at a mouse model,” Moore says.