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. 2017 Dec 23;10(1):14.
doi: 10.3390/nu10010014.

Physiological Translocation of Lactic Acid Bacteria during Pregnancy Contributes to the Composition of the Milk Microbiota in Mice

Javier de Andrés  1 , Esther Jiménez  2 , Isabel Chico-Calero  3 , Manuel Fresno  4 , Leónides Fernández  5 , Juan Miguel Rodríguez  6
Affiliations

Physiological Translocation of Lactic Acid Bacteria during Pregnancy Contributes to the Composition of the Milk Microbiota in Mice

Javier de Andrés et al. Nutrients. .

Abstract

The human milk microbiota is a complex and diverse ecosystem that seems to play a relevant role in the mother-to-infant transmission of microorganisms during early life. Bacteria present in human milk may arise from different sources, and recent studies suggest that at least some of them may be originally present in the maternal digestive tract and may reach the mammary gland through an endogenous route during pregnancy and lactation. The objective of this work was to elucidate whether some lactic acid bacteria are able to translocate and colonize the mammary gland and milk. For this purpose, two lactic acid bacteria strains (Lactococcus lactis MG1614 and Lactobacillus salivarius PS2) were transformed with a plasmid containing the lux genes; subsequently, the transformed strains were orally administered to pregnant mice. The murine model allowed the visualization, isolation, and Polymerase Chain Reaction (PCR)-detection of the transformed bacteria in different body locations, including mammary tissue and milk, reinforcing the hypothesis that physiological translocation of maternal bacteria during pregnancy and lactation may contribute to the composition of the mammary and milk microbiota.

Keywords: Lactobacillus salivarius; bioluminescence; human milk; lactation; lux; pregnancy; translocation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Transformation of E. coli with the lux operon. (A) LB agar plate showing non-transformed E. coli cells (negative control). (B) LB agar plate showing E. coli cells transformed with pMG36e::luxABCDE. (C) Microtiter plate showing E. coli cells transformed with pMG36e::luxABCDE; Column 1: non-inoculated LB medium (negative control); Column 2: files b to f: serial dilutions of E. coli cells transformed with pMG36e::luxABCDE.
Figure 2
Figure 2
In vitro and in vivo detection of L. lactis MG1614 transformed with pMG36::luxABCDE. (A) GM17 agar plate with transformed (left) and non-transformed (right) L. lactis MG1614 cells. (B) Mouse immediately (left) and 20 min (right) after being fed with L. lactis pMG36e::luxABCDE.
Figure 3
Figure 3
Isolation of transformed L. lactisMG1614 cells on GM17 agar plates from different maternal biological samples and organ biopsies: 1: milk; 2: feces; 3: small intestine; 4: large intestine; 5: kidney; 6: liver; 7: spleen; 8: stomach; 9: Peyer’s patch; 10: urine; and 11: mammary gland.
Figure 4
Figure 4
Transmission electron microscopy (TEM) images. Bacteria (black arrows) and mitochondria (white arrows) present in samples from a mesenteric lymph node (A) and spleen (B).
See this image and copyright information in PMC

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