Sugars in human milk found to have antibacterial action

22 August 2017

Even as antibiotic-resistant "superbugs," threaten to make the most basic of infections, potentially lethal, there may be a way to counter the threat as researchers from Vanderbilt University have revealed a new class of antibiotic in human breast milk.

It has been known for long that breastfeeding is a vital part of healthy development, with the milk providing a nutritious mix of proteins, fats and sugars. But it is not limited to sustenance alone, as  due to the immature immune systems of infants, breast milk also serves to share the mother's immune function with her child.

These antibacterial properties were mostly thought to come from the proteins in the milk, but the Vanderbilt's team set out to investigate if sugars also played a part.

"For most of the last century, biochemists have argued that proteins are most important and sugars are an afterthought," says Steven Townsend, director of the new study, reported. "Most people have bought into that argument, even though there's no data to support it. Far less is known about the function of sugars and, as a trained glycoprotein chemist, I wanted to explore their role."

In order to test the antibacterial properties of the sugars, the team first extracted compounds called oligosaccharides from a few different samples of human breast milk. Using mass spectrometry, they created profiles of the compounds, and then introduced them to cultures of infectious bacteria in this case, Group B Strep, a common culprit of infections in newborns.

In the first experiment, the team tested five milk sugar samples against five strep colonies, of which three did not do much. One of the samples was moderately effective and one wiped out almost the whole bacterial colony.

In a second round of experiments which is still ongoing, the team is testing over two dozen samples. Two of the samples have so far been found to kill bacteria and destroy the biofilm that the bugs created to protect themselves. Two more killed the bacteria without breaking down the biofilm and four others destroyed the biofilm without killing the strep.

"This is the first example of generalised, antimicrobial activity on the part of the carbohydrates in human milk," said Townsend, assistant professor at the Vanderbilt University in Tennessee, US.

"One of the remarkable properties of these compounds is that they are clearly non-toxic, unlike most antibiotics," Townsend added.

The results were presented at the 254th National Meeting and Exposition of the American Chemical Society (ACS) in Washington, which showed that the sugars, sensitised the target bacteria and then they killed them.

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