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In honor of Earth Day, I am diverging from my normal post on viruses to discuss the connection between microbial diversity, antibiotics and industrialization.
This particular tribe is called the Yanomami and is located in the secluded jungles of southern Venezuela. To clarify, the Yanomami are actually a group of 30,000 plus people living in the Amazon. However, this study focuses on one particular, remote village which is thought to have existed in complete isolation from the developed world until 2009 when a medical expedition made contact with it. The tribespeople are among a unique group of people who have never been exposed to modern antibiotics or modern, industrialized food. Dr. Maria Dominguez-Bello, a microbiologist from the NYU School of Medicine and one of the authors of the study, explains that "we need to get a better understanding of the microbiota in this community of hunter-gatherers before they are lost."
Healthcare workers from the medical expedition that first made contact with the Yanomami Tribe collected skin, oral and fecal samples from the villagers. These samples, which contained bacterial DNA, were then sequenced by Dr. Dominguez-Bello and her lab and compared to samples from Americans, Amazonian Guahibo Amerindians in Venezuela and rural Malawian populations. The results showed that the Yanomami people have "significantly" greater microbial diversity than other populations and harbour several different types of bacteria that are missing or reduced in industrialized populations. Dr. Dominguez-Bello remarks that their results "bolster a growing body of data suggesting a link between, on the 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." Dr. Dominguez-Bello further believes that some environmental factor in the last thirty years is to blame for the increase in diseases and that the "microbiome" (a collective term for the trillions of microbes living on/in the human body) is potentially involved.
Researchers also found an direct relationship between a decrease in microbial diversity and exposure to processed foods and antibiotics. Microbes are increasingly being found to be an important aspect of overall human health. Decreases in microbial diversity mean that beneficial bacteria are possibly being eliminated.
In addition to microbial diversity, Gautam Dantas of Washington University in St. Louis discovered that Yanomami villagers host antibiotic resistant bacteria. These bacteria are not only resistant to naturally occurring antibiotics in soil, but also to man made antibiotics. Dantas's team found almost sixty different bacterial genes that could rebuff antibiotics, including six that could fight off synthetic antibiotics. Researchers were surprised by these results since they weren't expecting bacteria to be resistant to synthetic antibiotics that the people themselves had not been exposed to. One of the plagues of modern medicine is antibiotic-resistant bacteria due in large part to overuse of antibiotics. When antibiotics are taken by humans, they kill some but not all the bacteria in the body. Surviving bacteria are less susceptible to the antibiotics and then are able to reproduce and spread antibiotic resistance traits to the next generation of bacteria. The fact that people carry antibiotic resistant bacteria without having ever been exposed to antibiotics is unsettling yet intriguing. The problem of resistant bacteria is on a whole other level now that we know the issue is not just overuse of antibiotics in patients and farm animals.
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