MICROBIOTA OF BREASTMILK
Dr.E.Pradeep Kumar,
Director, Gheeth Kids Clinic, Marthandam
PUBLICATION
MICROBIOTA OF BREASTMILK
Introduction
Did you know that the bacterial diversity is higher in Breast milk than in infant faeces? Bacterial presence in something as holy as breast milk might come as a shocker to few. Breast milk is home to a variety of microbes. The most frequently found are Staphylococcus, Streptococcus, Lactobacillus, Pseudomonas, Bifidobacterium, Corynebacterium, Enterococcus, Acinetobacter, Rothia, Cutibacterium, Veillonella and Bacteroides.
There are 10 ^1 to 10 ^7 colony forming units per ml of bacteria in breast milk. The infant recieving 300–700 ml of milk per day gets a large amount of these bacteria. Breastmilk microbiota is individual and changeable. Recently, probiotic bacteria have often been touted as a Panacea for all infant ailments. Adding probiotics to breast milk offers an exciting avenue for future interventions to improve infant health.
How do microbes reach the breast milk?
Mammaryducts become colonised by the infant oral microbiota during suckling. Retrograde flow ofbreast milk into mammary ducts has been documented. Bacteria from the skin (such as Corynebacterium, Cutibacterium and Staphylococcus) also colonise the mammary ducts.
The pathway by which Lactobacilli is received into the milk is enteromammary transport through the dendritic cells. Bacterial Translocation from the intestine increases in pregnant and lactating women.

Factors influencing breast milk microbiota
- Gestational age : The macronutrients and immunological components of breast milk of women who deliver at term orpreterm differ. Bifidobacterium are predominant in women who delivered at term.
- Delivery mode : Normal labour leads to a higher transfer of bacteria into breast milk. Women who delivered by Caesarian Section have abundance of environmental bacteria in breast milk like Proteobacteria Carnobacteriaceae. Vaginal delivery is associated with higher Bifidobacterium & Lactobacillus.
- Intrapartum antibiotics : Women who received intrapartum antibiotics have lower totalbacterial loads (10^4 vs. 10^6 CFU/ml). Also healthy bacteria like Bifidobacterium could not be found in them.
- Lactation stage : The composition of breast milk changes during lactation. Colostrum contains many immune active substances, such as antibodies, complement factors, cytokines, lysozyme,oligosaccharides and antimicrobial peptides. Anaerobic bacteria are abundant in mature milk compared with colostrum.
- Body mass index: Obese mothers have a less diverse bacterial community in the breast milk with higher total bacterial loads.
- Body Human Milk Oligosaccharides (HMOs) were positively associated with abundant Bifidobacterium.
- Probiotic supplementation during pregnancy did not affect the composition of the breast milk microbiota
- Geography: One study found that women in the USA might have less Lactobacillus and Bifidobacterium in their breast milk compared with women in Europe.
- Mastitis : During acute mastitis, S.aureus dominated the microbiota of breast milk. while during subacute mastitis it was S.epidermidis which was dominating.
- Collection and feeding method : Breast milk obtained by breast pump had a lower diversity, but Higher pathogenic Enterobacteriaceae and Pseudomonas. Manually expressed milk had abundance of Gemellaceae, Nocardioides and Vogesella. Women who exclusively breastfed had a higher S. parasanguis compared with women who used mixed infant feeding.
Health implications
Breast milk gives protection to not only infants (intestinal colonisation and protection against pathogens, maturation of the immune system and digestion of nutrients) but also to Mothers (mammary gland health.) Disruption of intestinal microbiota, known as Dysbiosis has many adverse health outcomes like atopy, inflammatory bowel diseases, obesity, diabetes mellitus and even diminished vaccine responses.
- Lactic acid bacteria (LAB) and Parabacteroides inhibit growth of pathogenic bacteria by production of bacteriocins (e.g. nisin), organic acids or hydrogen peroxide. They improve nutritional value of food and even stimulate the immune system.
- Parabacteroides has been observed to reduce intestinal inflammation in animals models.
- Weissella inhibits biofilm formation and acts as an anti inflammatory.
- Alloiococcus protects against colonisation with pathogenic bacteria.
- C.acnes produces glycerol, which inhibits growth of S. aureus, S. epidermidis, a major cause of mastitis.
In addition to the abundance of microbes, the interactions between them, is important.
- A higher abundance of Bacteroides and Clostridium, and lower levels of Bifidobacterium and Lactobacillus is associated with allergic sensitisation, eczema and asthma.
- A higher Bacteroides has been associated with lower vaccine responses to oral rotavirus vaccine and a higher Bifidobacterium produces higher vaccine responses to polio and tetanus.
Interventional Studies
- In a study, in which Lactobacillus reuteri was administered for 3 months in 336 healthy children, it was shown that during the administration and for the next 3 months, the number of episodes of diarrhea significantly decreased. Respiratory tract infections in the 336 children has also significantly decreased at 3 and 6 months after the administration of the probiotics.
- In a 6-month study with 91 infants given L. fermentum, a reduction in the total number of infections, especially gastrointestinal tract and respiratory infections, was observed.
- A multicenter, randomized, double-blind, placebo-controlled trial on 126 healthy children aged 12–48 months with Lactobacillus paracasei showed a lower incidence of respiratory and gastrointestinal tract infections
- The results of 14 studies involving controlled trials and one systematic review indicate that the use of L. reuteri may be considered in the management of acute gastroenteritis as an adjunct to rehydration. L. reuteri produce reuterin, a broad-spectrum antibacterial substance that can inhibit the growth of a wide spectrum of microorganisms. They also regulate immune response..
- Lactobacillus rhamnosus can promote the recovery from rotavirus diarrhea and can reduce the incidence of diarrhea associated with the use of antibiotics. In a randomized, double-blind, placebo-controlled study with 571 healthy children aged 1–6 years, there was 17% relative reduction in the number of children with respiratory infections with complications and lower respiratory tract infections and a 19% relative reduction in antibiotic treatments for respiratory infection.
- Mastitis is difficult to treat with antibiotics and is one of the main reasons to cease breastfeeding. L. fermentum demonstrated better clinical effect than conventional antibiotics. After 21 days, a reduction in the number of the main etiological agents causing mastitis (S. epidermidis, S. aureus, and Streptococcus mitis) was observed. The women also experienced greater pain reduction.
- Probiotics & obesity : Obese mothers transfer bacteria which predispose to obesity to their babies. Probiotic supplement might hamper this and prevent against obesity.
Conclusion
Breast milk microbiota has important implications for maternal and infant health. Several bacteria isolated from breast milk have been evaluated for use as probiotics. After decades of research, probiotics are still an enigma. Influencing the mucosal microflora is a promising and exciting adventure and might hold the key to treating modern civilization’s hard to manage diseases.