What is already known on this topic
Changes in the bacterial composition of breast milk can disrupt the infant gut microbiota, resulting in increased risk of chronic diseases such as allergy and asthma. However, the factors that contribute to shaping the milk microbiota remain unclear.
What this research adds
The milk microbiota composition is influenced by several factors, including feeding strategies – whether the milk is pumped or fed to an infant directly from the breast. Milk from breast pumps contains higher levels of potentially harmful bacteria such as Stenotrophomonas and Pseudomonadaceae.
The findings suggest that the microbes present in the infant’s mouth play a critical role in determining the bacteria found in mothers’ milk, but more research is needed to understand the effects of pumping on milk microbiota composition and infants’ health.
Once considered sterile, breast milk is now known to have its own microbiota, which helps to establish the community of bacteria of the infant’s gut. A new study found that one of the most important factors associated with the bacterial makeup of breast milk is the feeding strategy – whether the milk is pumped or fed to an infant directly from the breast.
The research, led by Shirin Moossavi at the University of Manitoba, is among the largest studies yet of human milk microbes, and adds new evidence to the hypothesis that the milk microbiota is influenced by the bacteria present in the infant’s mouth. The results were published in the journal Cell Host & Microbe.
Zeroing in on milk microbes
Although recent studies suggest that the milk microbiota is affected by different factors, the key determinants of its composition remain unknown.
To fill this gap in knowledge, the researchers analyzed the breast milk microbiota from nearly 400 mother-infant pairs enrolled in the Canadian Healthy Infant Longitudinal Development (CHILD) study.
Overall, the most common bacteria in breast milk belonged to the Proteobacteria,
Firmicutes, Actinobacteria, and Bacteroidetes families, whereas the top genera were Streptococcus, Ralstonia, and Staphylococcus.
Pumping changes milk microbes
Mothers who fed their infants pumped milk had lower bacterial richness and diversity in their milk than mothers who fed infants directly at the breast.
What’s more, the two feeding strategies were associated with different abundance of specific bacteria. Gemellaceae, Vogesella, and Nocardioides, which are usually found in infants’ mouth, were frequent in direct breastfeeding, whereas environmental bacteria such as Enterobacteriaceae, Enterococcaceae, and Pseudomonas were more common with indirect breastfeeding.
Pumped milk also had higher levels of potential pathogens such as Stenotrophomonas and Pseudomonadaceae.
The findings suggest that direct breastfeeding fosters the acquisition of bacteria from the infant’s mouth microbiota, while indirect breastfeeding results in the enrichment of bacteria associated with the environment, or breast pumps. However, further research is needed to understand the effects of pumping on milk microbiota composition and infants’ health.