1. A new era of medicine, even before birth

“In developed countries no one dies of tuberculosis, leprosy or syphilis anymore, but 20% of Europeans suffer from asthma, 5% will develop colon cancer and the number of cases of multiple sclerosis doubles every 10 years. Many of these non-transmittable chronic illnesses are increasing, we don't know what is going on,” explained Francisco Guarner, department head at the Vall d´Hebron University Hospital and one of the scientific leaders of this B·Debate.

He doesn't know, but he suspects it has something to do with the changes to the microbiome. It is, in part, what is been called the hygiene hypothesis: as we live in "cleaner" societies, have less contact with microorganisms and take more antibiotics, our defenses don't have as much practice, don't get the right stimuli and tend to behave incorrectly over time.

 “The bacteria that live with us are a window to discover the causes of this thing that's going on, and could be a new era in the history of medicine, as they were in Pasteur’s time (for other reasons)." They seem to be important even before birth.

A placental microbiome

Until very recently, pregnancy was considered a sterile process, free of microorganisms. The first contact the baby was thought to have with the bacterial world was at birth, in the mother's birth canal, for example. However, this theory seems to have fallen by the wayside. Dr. Kjersti Aagaard, vice-president of the Division of Maternal-Fetal Medicine at Houston’s Baylor College of Medicine, presented data from a study that has found that, long before birth, there is a placental microbiome that could have a significant impact on fetal development.

It could, for example, have an impact on the birth process. "We found differences in the placental microbiome of spontaneous and programmed pre-term births," said Aagaard. The interesting thing is that, when compared to other areas of the body, the microbiome of the placenta is most similar to that of the mouth. The hypothesis is that some of these bacteria may reach the placenta through the blood, and this would explain the links that have been seen for years between periodontal disease (infections of the mouth) and a greater risk of premature birth.

Aagaard called into question other theories that have been close to taking hold, like the importance of vaginal birth versus cesarean in establishing the newborn's microbiome. On one hand, because it could already be developing long before birth. On the other, because when you look at them just weeks after birth, data shows that "there's no lasting variation in the microbiome that correlates with type of birth." She even showed data, although preliminary, that suggests that an unhealthy, high-fat diet during pregnancy may alter the child's microbiome. In this case, the changes seem to persist, and may even be tied to increased anxiety. Whether this behavior is caused by bacteria is yet to be seen (it is important to remember that in this type of studies correlation does not imply causality).



“Asthma is the most common chronic childhood illness, we still don't know what causes it," explained Stuart Turvey, professor of Pediatric Immunology at the University of British Columbia in Vancouver, Canada. What is clear is that more and more children have asthma, and data points to the hygiene hypothesis: occurrence seems to increase in developed countries and with the use of antibiotics, but is lower in families with more siblings and children who spend time near farms with animals.

The CHILD study is a large-scale project that is following 5,000 children from birth for six years. Researchers, including Turvey, have analyzed their intestinal microbiome at several points and observed a curious, possibly revealing fact. Children with early symptoms of asthma have a different microbiome at three months, but not when they are one year old. This means that there seems to be a window of time that somehow predisposes them to developing the illness when we could intervene. In fact, in the laboratory, Turvey's team has prevented the onset of asthma in mice by administering a cocktail of four bacteria. Nevertheless, the scientist is cautious: “We don't know if it will work in humans yet. Or even if it's safe.”