Which microbes live in a mother’s milk depends, in part, on whether she feeds her baby straight from the breast or gives the infant pumped milk from a bottle.
Human milk teems with a diverse population of microbes, some of which can take up residence in an infant’s gut. Meghan Azad at the Children’s Hospital Research Institute of Manitoba in Winnipeg, Canada, and her colleagues examined factors that influence the microbial content of breast milk by studying data from 393 mother–baby pairs. Some of the mothers exclusively nursed their infants at the breast; others used a mechanical breast pump to collect milk and feed it to their babies.
The team found that milk from mothers who pumped was lower in microbial diversity and richer in potential pathogens than milk from mothers who fed their infants directly from the breast. The research also showed that a species of Bifidobacterium, a group of bacteria commonly found in both human milk and infant digestive tracts, was less abundant in milk from mothers who pumped.
The results suggest that the microbes in a baby’s mouth might influence the microbial composition of a mother’s milk, but it remains unclear how this difference affects infant health, if at all.