Newborn breastfed babies’ saliva combines with breastmilk to release antibacterial compounds including hydrogen peroxide that help to shape the oral and gut microbiota Queensland scientists have found.
The growth of both pathogenic microorganisms and commensals was inhibited rapidly and for up to 24 hours following breastmilk and saliva mixing in a study led by Dr Emma Sweeney and Adjunct Associate Professor Christine Knox, from QUT’s Institute of Health and Biomedical Innovation.
Their in vitro studies examined the influence of breastmilk and saliva mixing on microorganisms such as S. epidermidis, S. aureus (MRSA), S. pyogenes, E. faecalis, E. faecium, P. aeruginosa, K. pneumoniae, E. coli and C. albicans.
Growth of pathogenic and commensal species was inhibited at different levels, with recovery depending on the quantities of micro-organism and concentrations of hydrogen peroxide and used.
These findings add to evidence that the neonatal microbiome is highly dynamic and influenced by breastfeeding, the researchers say.
They note that breastmilk is high in the enzyme xanthine oxidase which acts on two substrates, found in neonate’s saliva to release hydrogen peroxide. The enzyme interaction also activates the ‘lactoperoxidase system’ that produces other reactive oxygen species (ROS) and reactive nitrogen species (RNS) that have antibacterial activity and are capable of regulating the growth of microorganisms.
“[Our] study adds to the body of evidence that breastfeeding plays more than a simple nutritional function during infancy, and expands the evidence that breast-milk saliva interactions play an important role in the establishment of the infant’s microbiota,” they report in Nature Scientific Reports.
“While adult oral microbiota are stable, our studies have shown that the microbiota in the mouths of newborns is much more dynamic and seems to be altered by the mode of feeding within the first few months of life,”Dr Sweeney said.
The changes in the composition of neonatal oral microbiota would have important implications for infection or disease early in life, particularly for babies who have nasogastric tubes, she added.
“In these cases, the mixing of breastmilk and babies’ saliva does not occur and so they do not receive the benefits of the antibacterial compounds released during breastfeeding.”
“Other researchers have shown that hydrogen peroxide can remain active at pH levels similar to that of a baby’s stomach, so we think that this antimicrobial activity seen in the mouth may also continue within the baby’s stomach and intestines,” she noted.