http://www.the-scientist.com/?articles.view/articleNo/40038/title/The-Matern
al-Microbiome/

 

Mother’s microbial milk

“The overwhelming dogma before the microbiome world really started was that
milk was sterile, that the only time you could culture an organism out of
milk was when a woman had mastitis,” an infection of the breast tissue, said
Mark McGuire, <http://www.uidaho.edu/cals/avs/faculty/markmcguire>  a milk
researcher at the University of Idaho. So when Complutense University’s
Rodríguez first began examining breast milk in the 1990s and found evidence
that it served as a potential source of microbes in infant feces, many
people didn’t believe him. They assumed that his samples were contaminated,
“maybe from the mother’s skin or maybe the mouth of baby,” he said, but the
bacterial strains he found in breast milk didn’t exist in the mouth or on
the skin. And later, his group confirmed that these breast-milk bacteria
were finding their way into the infant gut.

In 2011, McGuire’s team characterized
<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0021313>
the microbiome of human breast milk from 16 women. “It’s quite a diverse
[microbial] community,” McGuire told The Scientist. The most abundant
bacteria were Streptococcus, Staphylococcus, Serratia, and Corynebacteria,
although each woman’s sample was different. “It was very personalized,” said
McGuire. “Part of that personalization means she’s sampling her environment
and providing that environment to her offspring, and maybe that’s a way to
train the immune system and help the infant expand what it’s going to be
exposed to early in life.”

 

For mom’s sake

Several years ago, Rodríguez stumbled upon the idea that the microbiome of
breast milk is important for the health of the mother. Mastitis, which can
cause such severe pain and is often treated with antibiotics, is
characterized by a “huge dysbiosis” of the breast-milk microbiome, said
Rodríguez. A single strain of pathogenic bacteria would dominate the sample,
while Lactobacillus would disappear.

McGuire’s wife and colleague, Michelle (Shelley) McGuire
<http://sbs.wsu.edu/faculty/?faculty/154> , a lactation researcher at
Washington State University, recently got a similar result in when she and
her colleagues collected breast milk samples from a group of women. Once in
a while the researchers would find a bacterial community that was dominated
by a single strain, and in those cases, “nine times out of 10 [the woman
with the dysbiosis] had taken an antibiotic or complained there was a little
discomfort in that breast,” Shelley McGuire said. “We could see it in her
milk.” (The results of this work are still unpublished.)

The lack of Lactobacillus levels in the milk that Rodríguez observed offered
him an opportunity to test whether bacteria in breast milk originate in the
gut. He designed a study in which women took supplements containing the
missing bacteria, and found that, sure enough, the same strains of
Lactobacillus showed up in their breast milk. Unexpectedly, after about
three weeks on the supplements, the women reported that their mastitis had
cleared up. “For the first time we said, Maybe this is important for the
treatment of mastitis or painful breastfeeding,” said Rodríguez, whose team
is now wrapping up subsequent trials to treat mastitis during breastfeeding
with bacteria, rather than antibiotics.

And even when not lactating, the breast itself has its own microbiome,
according to the work of Gregor Reid
<http://theafricainstitute.uwo.ca/about/affiliated_faculty/gregor_reid.html>
, a microbiologist at Western University and Lawson Health Research
Institute in London, Ontario, who suspects that the bacteria in the breast
might play a role in disease, such as cancer. But to look for a link between
the breast microbiome and health requires characterizing what’s normal,
which is not so easy, researchers agree. One thing that is becoming clear,
however, is that a healthy microbiome, whether it’s in the baby or the
mother, harbors a diversity of bacteria. “In the big picture of life, we’re
just appreciating that diversity is a really good thing to have,” said
Aagaard. “The more diversity we can pick up, probably the healthier we’ll be
over time.”

Judy


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