Composition of Human Breast Milk Microbiota and Its Role in Children's Health

Human milk contains a number of nutritional and bioactive molecules including microorganisms that constitute the so-called Human Milk Microbiota (HMM). Recent studies have shown that not only bacterial but also viral, fungal, and archaeal components are present in the HMM. Previous research has established, a core microbiome, consisting of Firmicutes (i.e., Streptococcus, Staphylococcus), Proteobacteria (i.e., Serratia, Pseudomonas, Ralstonia, Sphingomonas, Bradyrhizobium), and Actinobacteria (i.e., Propionibacterium, Corynebacterium). This review aims to summarize the main characteristics of HMM and the role it plays in shaping a child's health. We reviewed the most recent literature on the topic (2019-2021), using the PubMed database. The main sources of HMM origin were identified as the retrograde flow and the entero-mammary pathway. Several factors can influence its composition, such as maternal body mass index and diet, use of antibiotics, time and type of delivery, and mode of breastfeeding. The COVID-19 pandemic, by altering the mother-infant dyad and modifying many of our previous habits, has emerged as a new risk factor for the modification of HMM. HMM is an important contributor to gastrointestinal colonization in children and therefore, it is fundamental to avoid any form of perturbation in the HMM that can alter the microbial equilibrium, especially in the first 100 days of life. Microbial dysbiosis can be a trigger point for the development of necrotizing enterocolitis, especially in preterm infants, and for onset of chronic diseases, such as asthma and obesity, later in life.

Automated summary

Human Milk Microbiota (HMM) is a microbiota present in human milk, consisting of bacteria, viruses, fungi, and archaea. The composition of HMM is influenced by various factors such as maternal body mass index, diet, antibiotic use, delivery time and type, and breastfeeding mode. The COVID-19 pandemic has emerged as a new risk factor for the modification of HMM. HMM plays a crucial role in gastrointestinal colonization in children, and perturbations in HMM can lead to microbial dysbiosis and the development of chronic diseases later in life.