Bacteria are winning the war against antibiotics… How can we destroy them?
We know that antibiotics, whose discovery revolutionized the treatment of infectious diseases in the 20th century, kill bacteria. We also know that the effectiveness of antibiotics has declined as certain types of bacteria have become resistant and adaptable, having evolved genetically. Antibiotics have become ineffective against some of these bacteria and the diseases they cause. But we may not know that some microbes are not only immune to antibiotics, but can also consume these drugs and use them as food for growth and reproduction, rather than as weapons to kill or eradicate them. Scientists have proven that many bacteria living in the soil have become resistant to antibiotics and can even feed on them. This is bad news for treating infectious diseases, but it's not all bad. Researchers at Gautam Dantas's lab, including Trink Croft of the University of Washington, have discovered how this could also be beneficial for humans. They discovered that we might be able to harness these antibiotic-resistant microbes to clean up the land and water contaminated with these drugs. This drug contamination is a major cause of bacterial evolution, leading to antibiotic resistance and disease.
But how do bacteria eat the antibiotics they're supposed to kill?
It might seem hard to imagine microbes eating the drugs humans use to kill them. But from a bacterial perspective, antibiotics may be nothing more than a source of the essential elements for life: carbon, hydrogen, oxygen, and nitrogen. Moreover, most of the antibiotics your doctor prescribes are made from, or derived from, fungi and bacteria that live in the soil. So it makes sense that these benign soil microorganisms feed on the carbon compounds produced by soil microbes, according to a report by Trinkcroft, a researcher at the University of Washington.
For the past decade, scientists at Dantas Lab have been investigating how bacteria do this, and we now believe we've solved the mystery by identifying a set of genes that code for the enzymes microbes need to consume penicillin (discovered in its natural form by Alexander Fleming in 1928). The scientists discovered that ingesting the drug is a two-step process. First, the bacteria remove the first part of the antibiotic by breaking off a piece called the β-lactam warhead. Without this, the remaining penicillin is harmless and can be used as food, allowing the microbes to thrive at high concentrations of the drug. Second, the bacteria break down another part of the drug, using a specialized set of enzymes to further break it down before ingesting it. Now that scientists understand the enzymes bacteria use to deactivate the antibiotic, they can develop defensive and resistance strategies. This is crucial because antibiotic-resistant bacteria cause severe illness in more than two million people in a country like the United States, resulting in more than 20,000 deaths annually. These infections are more difficult and costly to treat because they require extended hospital stays. This results in direct losses to the US economy each year due to treatment costs ($20 billion) and indirect losses due to lost productivity ($35 billion).
Resistance against resistance: Why might bacteria be a powerful weapon against their own kind?
The research team hoped to use their findings to address one of the main causes of antibiotic resistance: soil and water pollution. These natural resources are contaminated by wastewater from farms where animals are fed antibiotics to fatten them, and by the illegal dumping of pharmaceutical waste or untreated sewage, particularly from mass-producing companies in China and India. The team believes that these drugs can be removed through bioremediation, which uses living organisms to clean up the mess created by humans. While the bacteria they focused on grew slowly when fed a penicillin diet, "we may be able to engineer new strains that remove antibiotics more efficiently by speeding up drug absorption," the study authors say. As a proof of concept, scientists cut and pasted genes from microorganisms in our soil, along with a previously discovered gene they believed would have a similar function, into benign laboratory strains of E. coli bacteria, transforming them into microbes that actually feed on antibiotics, according to a report published on an Australian science website. The intriguing discovery was that penicillin requires two separate sets of genes to work together, starting with an antibiotic resistance gene to break down the β-lactam warhead of the toxic antibiotic. Without this critical enzyme, the bacteria cannot disarm the antibiotic, and without the enzyme responsible for removing the ring from penicillin, there is nothing for the bacteria to eat. This suggests that we might be able to create new strains of benign bacteria to remove antibiotics from the environment. However, this doesn't mean people can freely use antibiotics, but it could provide a safe way to curb the spread of antibiotic resistance in the future.