In a study published last week in the journal PLoS One, Dr. Kjersti Aagaard-Tillery, an obstetrician at Baylor College of Medicine, and her colleagues described the vaginal microbiome in pregnant women. Before she started the study, Dr. Aagaard-Tillery expected this microbiome to be no different from that of women who weren’t pregnant.
“In fact, what we found is the exact opposite,” she said.
Early in the first trimester of pregnancy, she found, the diversity of vaginal bacteria changes significantly. Abundant species become rare, and vice versa.
One of the dominant species in the vagina of a pregnant woman, it turns out, is Lactobacillus johnsonii. It is usually found in the gut, where it produces enzymes that digest milk. It’s an odd species to find proliferating in the vagina, to say the least. Dr. Aagaard-Tillery speculates that changing conditions in the vagina encourage the bacteria to grow. During delivery, a baby will be coated by Lactobacillus johnsonii and ingest some of it. Dr. Aagaard-Tillery suggests that this inoculation prepares the infant to digest breast milk.
The baby’s microbiome continues to grow during breast-feeding. In a study of 16 lactating women published last year, Katherine M. Hunt of the University of Idaho and her colleagues reported that the women’s milk had up to 600 species of bacteria, as well as sugars called oligosaccharides that babies cannot digest. The sugars serve to nourish certain beneficial gut bacteria in the infants, the scientists said. The more the good bacteria thrive, the harder it is for harmful species to gain a foothold.
Plus: viruses and fungi may be in on the action; strongly worded quotes suggesting that antibiotics could disrupt healthy bacteria in unhealthy ways; and fecal transplants seem to be gaining approval and could be coming to you in pill form someday. Oh and there’s a sweet graphic.
Researchers suspect that, by harming healthy microflora in children, antibiotics can lead to asthma and allergies later in life. Microbes could also influence the weight of the mammals that host them—scientists have made thin mice obese by giving them the gut bacteria of other obese mice. So where do these obesity-causing bacteria come from? Probably a variety of places. Even the food you eat can change your microflora. According to the Economist, a study found that a sugary, fat-laden diet could change a child’s gut bacteria profile, leading to an increased risk of asthma, allergies and other inflammatory diseases. Food for thought.