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Relationship between Milk Microbiota, Bacterial Load, Macronutrients, and Human Cells during Lactation.

Boix-Amorós A, Collado MC, Mira A - Front Microbiol (2016)

Bottom Line: Fat, protein, lactose, and dry extract of milk as well as the number of somatic cells were also analyzed.We observed that milk bacterial communities were generally complex, and showed individual-specific profiles.The median bacterial load was 10(6) bacterial cells/ml through time, higher than those numbers reported by 16S gene PCR and culture methods.

View Article: PubMed Central - PubMed

Affiliation: Department of Health and Genomics, Center for Advanced Research in Public Health, FISABIO FoundationValencia, Spain; Department of Biotechnology, Institute of Agrochemistry and Food Technology, Spanish National Research CouncilValencia, Spain.

ABSTRACT
Human breast milk is considered the optimal nutrition for infants, providing essential nutrients and a broad range of bioactive compounds, as well as its own microbiota. However, the interaction among those components and the biological role of milk microorganisms is still uncovered. Thus, our aim was to identify the relationships between milk microbiota composition, bacterial load, macronutrients, and human cells during lactation. Bacterial load was estimated in milk samples from a total of 21 healthy mothers through lactation time by bacteria-specific qPCR targeted to the single-copy gene fusA. Milk microbiome composition and diversity was estimated by 16S-pyrosequencing and the structure of these bacteria in the fluid was studied by flow cytometry, qPCR, and microscopy. Fat, protein, lactose, and dry extract of milk as well as the number of somatic cells were also analyzed. We observed that milk bacterial communities were generally complex, and showed individual-specific profiles. Milk microbiota was dominated by Staphylococcus, Pseudomonas, Streptococcus, and Acinetobacter. Staphylococcus aureus was not detected in any of these samples from healthy mothers. There was high variability in composition and number of bacteria per milliliter among mothers and in some cases even within mothers at different time points. The median bacterial load was 10(6) bacterial cells/ml through time, higher than those numbers reported by 16S gene PCR and culture methods. Furthermore, milk bacteria were present in a free-living, "planktonic" state, but also in equal proportion associated to human immune cells. There was no correlation between bacterial load and the amount of immune cells in milk, strengthening the idea that milk bacteria are not sensed as an infection by the immune system.

No MeSH data available.


Related in: MedlinePlus

Relationships between bacterial composition and nutritional or cellular content of human breastmilk. The figure shows a heatmap where samples have been clustered according to its compositional profile. Bacterial genera appear color-coded according to their under- (red) or over-representation (blue) in the samples, and its proportion is correlated to the amount of protein content (indicated as “prot” in the figure), fat content (Fat), lactose content (Lact), and non-fatty solid content (NFS), as well as the density of bacterial and human somatic cells. n = 30.
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Figure 5: Relationships between bacterial composition and nutritional or cellular content of human breastmilk. The figure shows a heatmap where samples have been clustered according to its compositional profile. Bacterial genera appear color-coded according to their under- (red) or over-representation (blue) in the samples, and its proportion is correlated to the amount of protein content (indicated as “prot” in the figure), fat content (Fat), lactose content (Lact), and non-fatty solid content (NFS), as well as the density of bacterial and human somatic cells. n = 30.

Mentions: After comparing the number of somatic cells and bacterial load in the same samples, no significant correlation was found (Figure 4). Given that the number of somatic cells in milk is considered the gold standard for detecting infection (e.g., lactational mastitis) in farm animals (Olechnowicz and Jaśkowski, 2012), the absence of a somatic cell increase in our samples suggests a lack of significant immune response. Thus, the data presented in the current work suggest that high counts of bacteria in milk are not associated with infection in these healthy mothers without lactation problems. However, a positive correlation was found between the proportion of the common mastitis pathogen Staphylococcus and the number of somatic cells (Pearson correlation coefficient: 0.48, p = 0.0457). Given that a negative relationship was found between the proportion of Staphylococcus and the total bacterial load (correlation coefficient: −0.456, p = 0.056), the data suggest that it is not the number of bacteria but the specific composition of the milk microbiota that could be inducing an immune response in the mammary gland, although the major mastitis pathogen S. aureus was not detected in our samples (Table 1). Other bacteria appeared to show a positive relationship with the number of somatic cells were Peptoniphilus and Finegoldia (Figure 5), although the correlations were not statistically significant in these cases. It has to be kept in mind that breast milk contains several anti-inflammatory (He et al., 2016) that could partly reduce somatic cells counts.


Relationship between Milk Microbiota, Bacterial Load, Macronutrients, and Human Cells during Lactation.

Boix-Amorós A, Collado MC, Mira A - Front Microbiol (2016)

Relationships between bacterial composition and nutritional or cellular content of human breastmilk. The figure shows a heatmap where samples have been clustered according to its compositional profile. Bacterial genera appear color-coded according to their under- (red) or over-representation (blue) in the samples, and its proportion is correlated to the amount of protein content (indicated as “prot” in the figure), fat content (Fat), lactose content (Lact), and non-fatty solid content (NFS), as well as the density of bacterial and human somatic cells. n = 30.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4837678&req=5

Figure 5: Relationships between bacterial composition and nutritional or cellular content of human breastmilk. The figure shows a heatmap where samples have been clustered according to its compositional profile. Bacterial genera appear color-coded according to their under- (red) or over-representation (blue) in the samples, and its proportion is correlated to the amount of protein content (indicated as “prot” in the figure), fat content (Fat), lactose content (Lact), and non-fatty solid content (NFS), as well as the density of bacterial and human somatic cells. n = 30.
Mentions: After comparing the number of somatic cells and bacterial load in the same samples, no significant correlation was found (Figure 4). Given that the number of somatic cells in milk is considered the gold standard for detecting infection (e.g., lactational mastitis) in farm animals (Olechnowicz and Jaśkowski, 2012), the absence of a somatic cell increase in our samples suggests a lack of significant immune response. Thus, the data presented in the current work suggest that high counts of bacteria in milk are not associated with infection in these healthy mothers without lactation problems. However, a positive correlation was found between the proportion of the common mastitis pathogen Staphylococcus and the number of somatic cells (Pearson correlation coefficient: 0.48, p = 0.0457). Given that a negative relationship was found between the proportion of Staphylococcus and the total bacterial load (correlation coefficient: −0.456, p = 0.056), the data suggest that it is not the number of bacteria but the specific composition of the milk microbiota that could be inducing an immune response in the mammary gland, although the major mastitis pathogen S. aureus was not detected in our samples (Table 1). Other bacteria appeared to show a positive relationship with the number of somatic cells were Peptoniphilus and Finegoldia (Figure 5), although the correlations were not statistically significant in these cases. It has to be kept in mind that breast milk contains several anti-inflammatory (He et al., 2016) that could partly reduce somatic cells counts.

Bottom Line: Fat, protein, lactose, and dry extract of milk as well as the number of somatic cells were also analyzed.We observed that milk bacterial communities were generally complex, and showed individual-specific profiles.The median bacterial load was 10(6) bacterial cells/ml through time, higher than those numbers reported by 16S gene PCR and culture methods.

View Article: PubMed Central - PubMed

Affiliation: Department of Health and Genomics, Center for Advanced Research in Public Health, FISABIO FoundationValencia, Spain; Department of Biotechnology, Institute of Agrochemistry and Food Technology, Spanish National Research CouncilValencia, Spain.

ABSTRACT
Human breast milk is considered the optimal nutrition for infants, providing essential nutrients and a broad range of bioactive compounds, as well as its own microbiota. However, the interaction among those components and the biological role of milk microorganisms is still uncovered. Thus, our aim was to identify the relationships between milk microbiota composition, bacterial load, macronutrients, and human cells during lactation. Bacterial load was estimated in milk samples from a total of 21 healthy mothers through lactation time by bacteria-specific qPCR targeted to the single-copy gene fusA. Milk microbiome composition and diversity was estimated by 16S-pyrosequencing and the structure of these bacteria in the fluid was studied by flow cytometry, qPCR, and microscopy. Fat, protein, lactose, and dry extract of milk as well as the number of somatic cells were also analyzed. We observed that milk bacterial communities were generally complex, and showed individual-specific profiles. Milk microbiota was dominated by Staphylococcus, Pseudomonas, Streptococcus, and Acinetobacter. Staphylococcus aureus was not detected in any of these samples from healthy mothers. There was high variability in composition and number of bacteria per milliliter among mothers and in some cases even within mothers at different time points. The median bacterial load was 10(6) bacterial cells/ml through time, higher than those numbers reported by 16S gene PCR and culture methods. Furthermore, milk bacteria were present in a free-living, "planktonic" state, but also in equal proportion associated to human immune cells. There was no correlation between bacterial load and the amount of immune cells in milk, strengthening the idea that milk bacteria are not sensed as an infection by the immune system.

No MeSH data available.


Related in: MedlinePlus