Reacción a "Reactions to the study exploring how the microbiome is transmitted by social contact"

The study is very robust, because the authors have used all the resources already available in public databases and have also generated their own sequences. They have taken into account many factors such as the nationality of the people in the study, their lifestyle habits, etc. The methodology is based on bioinformatics, and solid conclusions are reached through the application of biostatistics. This work has a high scientific quality due to the large amount of data used, and this has allowed the authors to reach solid conclusions for different ethnic groups and conditions. 

We already knew that most of the micro-organisms in a newborn baby come from its mother, or from a shared family environment through cohabitation. The study demonstrates this with state-of-the-art techniques and, more interestingly, looks at the transmission of micro-organisms between unrelated people. 

Just like all bioinformatic (in silico) analyses, this kind of study may not fully capture reality. That is why the researchers added biostatistical controls that ensure the validity of the process. Very few papers are as robust as this one, which includes so many people and so many sequences. 

Microbiology has always focused on the study of micro-organisms that cause acute infections. But with new studies of the microbiome, we have discovered that we are colonised, from birth and throughout our lives, by many more micro-organisms of which we weren’t aware with classical culture techniques. The potential of these ecosystems for our health is becoming increasingly clear, not because of the bacteria directly, but because of our continuous exposure to their metabolites. For this reason, prevalent diseases such as cancer or cardiovascular disease are increasingly being analysed from a microbiota perspective. In addition to the fact that bacteria can excrete active substances in our cells, there is also evidence that these bacteria can degrade human metabolites and disable their function. Very few studies have included the joint perspective of micro-organisms and humans in global metabolism. Since there is a transmission of microorganisms between people who live together and in the general population, perhaps we should identify microbiota associated with diseases that have never been considered transmissible, such as cancer or cardiovascular accidents like myocardial infarction. 

Finally, I would like to highlight the contribution of Dr. María Carmen Collado, from IATA in Valencia, to this research. She is one of the world's leading experts on the establishment of the microbiota in newborns.