Host Microbe Interactions in the Lactating Mammary Gland.

Area of Science:

• Microbiology
• Immunology
• Human Physiology

Background:

• The human milk microbiome (hMM) comprises bacteria found in breast milk.
• Previous studies indicate hMM is dominated by staphylococci and streptococci, with variable lactobacilli and low bifidobacteria.
• The hMM is increasingly recognized for its physiological role and potential health benefits.

Purpose of the Study:

• To review the composition and functions of the hMM.
• To explore the connection between hMM and mammary gland physiology and lactation.
• To investigate the role of hMM-host interactions in maternal health, particularly lactational mastitis.

Main Methods:

• Review of existing literature on human milk microbiome composition and function.
• Analysis of similarities between mammary gland and mucosal immune interfaces.
• Exploration of hMM's role in maternal health, focusing on mastitis.

Main Results:

• hMM composition is consistently dominated by staphylococci (e.g., *Staphylococcus epidermidis*) and streptococci.
• The role of hMM as an infant gut microbiome inoculum requires further demonstration.
• The mammary gland shares mucosal-like immune attributes, suggesting a role for hMM in local immune responses.

Conclusions:

• The hMM is a complex microbial community with potential implications for both infant and maternal health.
• Further research is needed to elucidate the precise mechanisms of hMM's influence on infant gut colonization.
• hMM-host interactions within the mammary gland may play a significant role in maintaining maternal health and preventing conditions like mastitis.