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Thanks to Joe Alcock for this fascinating commentary on Marty Blaser’s plenary lecture.


Marty Blaser of NYU delivered the second plenary lecture of the conference, entitled “Human Evolution 201: Our early life microbial metagenome guides developmental phenotypes”

Blaser points out that the Yanomami, an Amerindian group of hunter horticulturalists, have the highest microbiota diversity yet discovered on the planet. Most modern industrialized populations have lost 50% of this diversity, suffering increased losses with each of the last few generations in stepwise fashion. Blaser proposes that the ecological destruction of the microbiome is responsible for worldwide epidemics of obesity and autoimmune disease. Birth by cesarean section, formula feeding of babies, and modern diets are all responsible for the disappearing microbiome. But the biggest culprits, says Blaser, are antibiotics.

Millions of antibiotics prescriptions are filled each year in the US. In other countries, such as Peru, antibiotics are available over the counter, along with antacids and batteries. We have long known that antibiotics fatten farm animals from cows to chickens. In the same way, people too are fattened by early antibiotics. Our youngest patients are the group most exposed to antibiotics, which is a problem because it interrupts the normal dialog with microbes that guides developmental decisions. One mechanism involves depletion of gut microbes from antibiotics, leading to a change in Th17 immune cells and antimicrobial peptides in the gut. This causes durable changes in the gut microbiota predisposing to obesity. Transferring these microbes into germ free mice makes recipient mice obese, cementing the link between obesity and antibiotic depleted microbiome.

What can we do about this? Blaser argues that the next steps should focus on arresting or slowing the decline in microbiota diversity. This can be accomplished by choosing antibiotics more carefully. Macrolide antibiotics cause a durable destruction of microbiome diversity, while amoxicillin treated microbiomes bounce back pretty quickly. Childhood antibiotics appear to be particularly destructive and should be avoided when possible.

Better yet, Blaser imagines a day in which doctors restore microbiome species richness. Babies in the future might undergo a microbiome analysis, and then receive lost microbes, which would act like a vaccine to prevent obesity and autoimmune disease.