This is not the first time that antibiotic resistance has been singled out as a major public health problem, an issue that is expected to become increasingly threatening in the decades to come. But this time, very old bacteria are the cause. Discovered in a 5,000-year-old layer of ice, these bacteria showed how climate change could lead to an increase in antibiotic resistance.
The bacteria in question, named Psychrobacter SC65A.3, was isolated from a 25-meter ice core extracted from the Scărișoara ice cave in Romania, reports IFL Science. The researchers sequenced its genome and tested it against 28 antibiotics. They then discovered that it was resistant to 10 of them.
“The 10 antibiotics to which we found resistance are widely used in oral and injectable treatments to treat a range of serious bacterial infections.says Dr Cristina Purcarea, from the Bucharest Institute of Biology of the Romanian Academy. Studying microbes such as Psychrobacter SC65A.3 reveals how antibiotic resistance developed naturally in the environment – long before modern antibiotics were used.»
At first glance, this may seem strange. How could an ancient bacterial strain have learned to resist the antibiotics we use today, when they didn’t exist thousands of years ago? Yet the truth is that this battle has been going on for millions, if not billions, of years. In fact, most of our antimicrobial weapons come from the molecules that microbes use to fend off other microbes.
New antimicrobial capabilities
This proves that there is a common misconception about how bacteria and other microbes develop drug resistance: it is not new genes that appear in response to treatment. They already exist in the microbial ecosystem, the drugs simply create an environment in which resistant microbes reproduce more easily than their unprotected cousins.
Thus, when antimicrobial drugs are widely used, antimicrobial resistance genes that were essentially dormant become more prevalent within a species. They can even be transmitted between species.
Although researchers have known these last points for a long time, it now appears clear that this type of organism, pushed to the limit of survival by the hostile environments in which they live, have a particular propensity to develop genes with new antimicrobial capacities.
“Microbes from extreme environments like ice caves are often resistant to antimicrobials because they have evolved over millennia, even millions of years, to survive stressful conditions and compete with other microbescomments Dr Cristina Purcarea. Their biomolecules responsible for natural (resistance) may also offer protection against modern antibiotics, making these microbes a valuable reservoir of resistance genes.»
