Breastmilk Microbiome

Breastmilk Microbiome

Summary

            Human milk is the best food for children, and it has always been considered sterile. Human milk has complete nutrition for infants. Nevertheless, beyond its internal elements, human milk carries the majority of bioactive elements like microbes. The microbes and the other components are passed on to the baby through breastfeeding (Fernández et al. 2012). The dogma of viewing breast milk as the most sterile fluid has been reconsidered over the years. Culture-depended methods have been used to confirm the presence of microbes in human milk.

The policy that WHO has regarding the feeding of infants entails exclusive breastfeeding for the first six months. Many children who are not optimally breastfed die every year. The risk of death for children who are exclusively breastfed narrows down to 12% (Microbiology, Slide 4). Infants who are exclusively breastfed have a 13% reduction in the prevalence of being overweight and being obese (Microbiology, Slide 4). It should be noted that the variation and composition of human milk microbiota are intensely affected by a lot of maternal aspects. The origin of maternal milk microbiota is still under investigation. Nevertheless, three central hypotheses exist; backflow when suckling, areolar skin, and enteromammary pathway.

The mode that the baby was delivered affects the composition of the human microbiota, where high prevalence and diversity are found in milk following vaginal childbirth. The composition of breastmilk is also affected by the physiological status of the mother. Diet also has been known to influence the formation of lipids in human milk (Gomez-Gallego et al. 2016). Diet is seen as a grand strategy of modulating the microbes in maternal milk. Also, there has been proof that some particular probiotic strains are efficient in the treatment and the prevention of infectious illnesses in early life.

Literary Review

            Recently, the relevance of the gut microbiome for optimal health has been revealed just recently. Microbes have been viewed as the most relevant environmental aspects that give particular signals to guide the development of immune system maturation. Today, maternal microbiota is seen as an element that affects the development of the immune system of the infant. The literature review presents the implication of the maternal microbiota on the health of an infant while providing a broad overview of the activity and composition of the microbiota, together with factors that influence the structure and the biological importance.

Gomez-Gallego et al. (2016) provide evidence that human milk encompasses many immune substances like chemokines, cytokines, hormones, antibodies, and growth factors. Infants who are breastfed show reduced incidences of diarrhea, obesity, asthma, and allergies, among other issues. Fernández et al. (2012) show that breastmilk plays a vital metabolic role in infants. The glycobiome of specific bifidobacteria and lactobacilli may assist in creating a particular healthy microbiota in the gut of the infant. The elements result in an improvement in the intestinal habit, with an increase in the moisture of the feces and the volume and frequency of stool.

The origin of the human milk microbiome was considered in almost every sterile fluid. However, the concept has been revised over the past few years. According to Gomez-Gallego et al. (2016), studies that have been conducted on primates show that the milk of monkeys has cultural strains of not less than 19 bacteria species that belong to not less than five diverse genera. Turroni et al. (2018) confirm that similar results have been described in other mammals. Many reports have shown that the microbiota found in human milk can be found from colonization from the skin of the mother, the oral cavity of the infant when suckling, and the gut of the mother through the entero-mammary pathway (Fernández et al. 2012). With the application and development of culture-independent methods together with next-generation sequencing systems, there has been the affirmation of microbial DNA.

Human milk contains a unique microbial ecology that is different from any other that is found in humans. The microbiota in humans is not connected to any other in any human. Fernández et al. (2012) show that intestinal dendritic cells retain minimal sums of live commensal bacteria for a significant number of days in the mesenteric lymph nodes.  It is known that during the period of lactation, colonization of the mammary glands by cells of the immune system is a selective process that is managed by the lactogenic hormones.

Shotgun metagenomics analysis of human milk by complete sequencing of DNA has been conducted by using a coupled pooled milk samples. The study showed that human milk carries firmicutes, proteobacteria, and prokaryotic genera (Gomez-Gallego et al. 2016). Molecular methods have been viewed to carry some limitations. There have been reports of contamination of the DNA in extraction reagents and kits. Other factors that might be influencing the composition of milk microbiota might include the methods of sampling, the platforms of sequencing together with the used bioinformatics pipeline (Turroni et al. 2018).

It has been proved that mode of delivery, genetic factors, lactation stage, geographical location, and time of day affect the composition of human milk. The aspect that could moderate the microbiota of the oral cavity, skin, intestine, and vagina of the mother and the infant’s microbiota has the capability of potentially modulating the microbiota of human milk (Gomez-Gallego et al. 2016). Consequently, the nutritional status, maternal dietary habits, lactation period, gestational period, delivery mode, and the use of medicines and antibiotics influences the composition of the milk microbiota (Fernández et al. 2012).

Greater diversity of microbes has been reported in the samples of colostrum as compared to mature milk. The stage of lactation is seen as a factor that impacts the microbes that are found in milk. At first, the microbiota is dominated by staphylococcus, leuconostac, lactococcus sp, and streptococcus milk (Gomez-Gallego et al. 2016). Later, the milk microbiota carries intense levels of Provotella, lactobacillus, veilonella, and lactobacillus and streptococcus spp milk (Gomez-Gallego et al. 2016). The method that is used in delivery impacts the composition of milk microbiota. Milk and colostrum following vaginal delivery carry high microbial prevalence and diversity of Lactobacillus spp. And Bifidobacterium (Fernández et al. 2012). The contrary is, however, seen in cesarean delivery.

The composition of milk is also affected by the age of gestation with notable differences between preterm and term delivered mothers. Moreover, changes in the composition of milk microbiota are related to the maternal status of the mothers encompassing celiac disease, obesity, and HIV (Gomez-Gallego et al. 2016). Mothers who have celiac disease have minimal levels of Bacteroides spp and cytokines in their milk (Turroni et al. 2018). The milk from mothers who are HIV positive, and especially those from Africa, has been discovered to present higher bacterial prevalence and diversity of Lactobacillus spp — compared to the milk of mothers who are not HIV positive.

Analysis of the microbiota in maternal milk generally shows that Streptococcus spp. and staphylococcus, together with strains of lactic bacteria, are available in liquid. Nevertheless, large-scale researches with maternal milk samples from various geographical regions are required. It has been proved that perinatal antibiotic use carries implications on maternal microbiota. Chemotherapy has been linked to affecting milk microbiota through alteration (Fernández et al. 2012). Additionally, the diet has been known to influence the profile of human milk, modulating the concentration of long-chain polyunsaturated fatty acids (Gomez-Gallego et al. 2016). The use of prebiotics and probiotics in pregnancy could affect maternal milk microbiota even though more studies are required to support the potential transfer of gut bacteria to the mammary glands (Gomez-Gallego et al. 2016). There is an urgent need for more studies to scrutinize the relations among nutrients in the maternal diet and the breast-milk microbiota and the health implications that are on infants.

Diet is the most powerful method that can be used in altering gut microbiota. According to Gomez-Gallego et al. (2016), strategies regarding diet could be devised to moderate the microbial composition to impact human physiology and minimize the risk of illnesses that are linked to imbalances of the composition of the microbiota. Also, it has been established that particular probiotic strains are efficient in the treatment and prevention of infectious illnesses in early life and that they minimize the risk of eczema in infants in populations that are at risk. In a study that is placebo-controlled ingestions of probiotics in pregnancy has been established to control colonization of Bifidobacteria in infants and also to modulate the microbiome in breastmilk.

There is the possibility that selective pressure has implicated breastmilk nature in the process of human evolution to give the child the utmost benefit. Sharing of nutrients and competition is a vital determinant of microbial dynamics in the microbiota gut. The capability of particular Bifidobacterium strains to use HMO effectively implies that there may be a strategy for making sure that the bacteria group is present in the gut of the infant. Modulation of the maternal microbiota can have a direct influence on the health of the infants, creating new perspectives for probiotics and bacteriotherapy.