Thursday, September 19, 2019 - Getting up close – and a little dirty – with farm animals just might help us fend off illness, say researchers who’ve further demonstrated the benefits of early exposure to a wide variety of environmental bacteria.

Scientists from The Ohio State University found that bacteria and other microbes from rural Amish babies was far more diverse – in a beneficial way – than what was found in urban babies’ intestines. And, in a first-of-its-kind experiment, they found evidence of how a healthier gut microbiome might lead to more robust development of the respiratory immune system.

Good hygiene is important, but from the perspective of our immune systems, a sanitized environment robs our immune systems of the opportunity to be educated by microbes. Too clean is not necessarily a good thing.

The research team collected fecal samples from 10 Ohio babies who were around 6 months to a year old. The five Amish babies all lived in rural homes with farm animals. The other five babies lived in or near Wooster, a midsize Ohio city, and had no known contact with livestock.

The samples revealed important differences – particularly a wide variation in microbes and an abundance of beneficial bacteria in the Amish babies’ guts that wasn’t found in their city-dwelling counterparts. The researchers expected this, based on the infants’ exposure to the livestock and the fact that the Amish tend to live a relatively less-sanitized lifestyle than most other Americans.

What they really wanted to know was how these differences might affect development of the immune system, setting the groundwork for a body’s ability to identify and attack diseases and its resistance to allergies and other immune-system problems.

This connection has led to a theory called the “hygiene hypothesis,” which is built on the idea that hyper-clean modern life – think antibacterial soap, ubiquitous hand sanitizer and scrubbed-clean homes and workplaces – has led to an increase in autoimmune and allergic diseases.

Given that the trillions of microbes in the human gut are known to play an important role in health and disease progression, the Ohio State researchers wanted to explore how different gut microbiomes might contribute to immune system development. To do this, they used fecal transplants from the babies in the study to colonize the guts of newborn pigs.

“We wanted to see what happens in early immune system development when newborn pigs with ‘germ-free’ guts are given the gut microbes from human babies raised in different environments,” Renukaradhya Gourapura, co-lead author of the study and Ohio State professor, said. “From the day of their birth, these Amish babies were exposed to various microbial species inside and outside of their homes.”

The researchers saw a connection between the diverse Amish gut microbes and a more-robust development of immune cells, particularly lymphoid and myeloid cells in the intestines.

Though the primary difference between the babies in the study was their exposure to a farming environment, the researchers also noted that two of the non-Amish babies were only formula-fed, while all of the Amish babies in this study were breast-fed. Another important difference that could contribute to gut microbiome differences between the groups is that the Amish families grew and routinely ate their own produce.

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