The bacterial flora of a remote tribe of Yanomami Amerindians discovered in 2009 after being isolated from other people for over 11,000 years have antibiotic resistant genes, according to a new study published Friday in the journal Scientific Advances.
Since members of the tribe had never been exposed to the antimicrobial treatment, the discovery suggests that bacteria in the human body possessed the ability to resist antibiotics since long before such drugs were used to treat diseases.
Resistance to antibiotics despite lack of exposure
The Yanomami Amerindian tribe was found in a remote mountainous regions located in southern Venezuela six years ago, and since they had been isolated from other civilizations for such a long period of time, they possessed one of the most diverse bacterial floras ever seen in humans.
The microbial populations found in those people were said to be far more diverse than residents of the US and Europe, a team of researchers from the New York University School of Medicine and other universities reported in the study.
“This was an ideal opportunity to study how the connections between microbes and humans evolve when free of modern society’s influences,” Dr. Gautam Dantas, one of the study’s authors and an associate professor of pathology and immunology at Washington University, explained in a statement. “Such influences include international travel and exposure to antibiotics.”
While analyzing those tribespeople, Erica Pehrsson, a graduate student in Dr. Dantas’ lab, found genes that conveyed antibiotic resistance in bacteria found on their skin, and in their mouths and intestines as well – even though they had been long isolated from other cultures.
“These people had no exposure to modern antibiotics; their only potential intake of antibiotics could be through the accidental ingestion of soil bacteria that make naturally occurring versions of these drugs,” said Pehrsson. “Yet we were able to identify several genes in bacteria from their fecal and oral samples that deactivate natural, semi-synthetic, and synthetic drugs.”
Did the microbes gain a natural resistance to antibiotics?
Dr. Dantas, Pehrsson explained that bacterial resistances to antibiotics began thousands of years before people started using the antimicrobial to combat infections. This was when soil bacteria started producing natural antibiotics to kill off competition, and targeted microbes began developing genetic defenses through a process known as horizontal gene transfer.
While the process of gaining antibiotic resistance has accelerated over the years due to the heavy, widespread prescription of the medicine, making it harder to treat, it is not a recent phenomenon. The authors also added that the microbiomes of people in industrialized countries are roughly 40 percent less diverse than those found in the Yanomami Amerindians.
“Our results bolster a growing body of data suggesting a link between, on one hand, decreased bacterial diversity, industrialized diets, and modern antibiotics, and on the other, immunological and metabolic diseases – such as obesity, asthma, allergies and diabetes, which have dramatically increased since the 1970s,” senior author Dr. Maria Dominguez-Bello explained.
“We believe there is something occurring in the environment during the past 30 years that has been driving these diseases, and we think the microbiome could be involved,” Dr. Dominguez-Bello, an associate professor of medicine at the NYU Langone Medical Center, noted. Their research suggests that there may be a link between modern antibiotics, diets in industrialized parts of the world, and a reduced diversity in the human microbiome, she added.