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Under pressure: How to explain the emergence of antibiotic resistance?
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Under pressure: How to explain the emergence of antibiotic resistance?

In this video Professor Fernanda Petersen discusses the development of antibiotic resistance as an evolutionary response of microbes to antibiotics.
Antibiotics were the miracle drugs of the 20th century. Today, they not only remain a major tool in the fight against infections, but they are a mainstay of modern medicine. The problem is that antibiotics are stopping working. To dig into the reasons on why this is happening, we need to understand the resistance, where is it found, when did it first emerge. A common misconception is that only diseased patients carry antibiotic resistance. But here’s the fact– we all care millions of bacteria, and among these, you always find antibiotic resistance. Actually, antibiotic resistance are found almost everywhere where there are bacteria– in soil, wastewater, animals and more.
And as we’ll discuss later in this course, this information is important for how to control the spread of antibiotic resistance. Many think that antibiotic resistance first emerged with the discovery of antibiotics and their use in human medicine. That is another misconception. If that’s true, what about groups that have never been exposed to our antibiotics? This question was addressed by a group led by Gautam Dantas in the USA, who studied antibiotic resistance in isolated Indigenous people living in the Amazon. What they found was an amazing variety of antibiotic resistance genes in their samples, even though they had never been exposed to our antibiotics.
In another beautiful study led by a Canadian group, the researchers went to Alaska to interrogate pieces of our past locked in ice. They found antibiotic resistance genes in permafrost sediments that dated back 30,000 years. So the work revealed to the world that antibiotic resistance predates our own human existence. What would have been the selective force driving the emergence of antibiotic resistance thousands of years ago, before the discovery of antibiotics? The answer is in nature. It turns out that most of the antibiotics we use have their origin in bacteria and fungi. So these bacteria have needed to find ways to resist their own antibiotics. And so did other bacteria in their surroundings.
This means that the selective pressure by antibiotics has been there well before human discovery of antibiotics. In this figure, you see normal colonies of the bacteria Staphylococcus and an area of inhibition created by a compound produced by a fungus on the top of the image. This compound turned out to be penicillin, the first antibiotic to be discovered. If antibiotics and antibiotic resistance have existed before the discovery and the use of antibiotics by humans, what has happened that many infections now no longer respond to antibiotics? It turns out that the amount of antibiotics produced in nature cannot be compared to the massive amounts of antibiotics that have been introduced by humans.
Bacteria can divide so fast that, in the presence of antibiotics, selection of a single resistant bacteria can lead to millions of resistant bacteria in a fraction of a day. The problem is quickly amplified. The correlation between antibiotic use and the development of antibiotic resistance is evident, and has been demonstrated in several independent studies. Here is an example by Stephan Harbarth and colleagues, showing a clear relationship between total antibiotic consumption and Streptococcus pneumoniae resistance to penicillin in 20 industrialised countries. The lower the antibiotic consumption, the lower is antibiotic resistance.
For now, I hope that having learned that antibiotic resistance genes are found almost everywhere and that it predates human existence, that this knowledge will help you to reflect upon the magnitude of the problem and the importance of understanding resistance in a broad context.

In this video Professor Fernanda Petersen discusses the development of antibiotic resistance as a natural evolutionary response of microbes to antibiotic exposure.

The landscape of antibiotic and other antimicrobial resistance genes in microbial communities is known as resistomes. These are found in virtually all environments where there are microbial communities, and have been present in bacteria far before the discovery and clinical use of antibiotics. Actually, phylogenetic studies indicate that antibiotic resistance genes pre-date our own human existence. However, with the selective pressure created by the introduction of antibiotics in the market, resistance has reached critical levels. Understanding the evolutionary context behind the development of antibiotic resistance in microbial communities is key to comprehend how antibiotic resistance develops and spreads.

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Exploring the Landscape of Antibiotic Resistance in Microbiomes

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