The consensus up until recently was that the antibiotics could kill bacteria off completely; however, this had changed. The scientists have revealed that they found out some bacteria can come back as cells resistant to antibiotics.
Bacteria Becoming Resistant to Antibiotics
Escherichia Coli, a bacteria that can often cause urinary tract infections, has a protein that can pump harmful chemicals out of it. The scientists called this protein the “AcrAB-TolC multidrug efflux pump,” and it is not quite powerful to defeat the antibiotics by itself. However, it does have enough strength to push most of the antibiotics molecules out of the bacteria. Doing so, it buys its bacteria host enough time to produce actual antibiotics-resistant proteins. The researchers published this discovery in the Science magazine on May 24.
The science was already familiar with the fact that bacteria can often transfer genes that are resistant to antibiotics from one to another. These immune genes are located in the small circles of the bacteria DNA called plasmids. When two bacteria meet, they exchange these plasmids from resistant cells to the sensitive ones. What scientists first thought though, was that this happened only in the absence of antibiotics that would kill the non-resistant cells.
This is precisely the way the antibiotics should work; their duty is to stop bacteria from exchanging antibiotic-proof genes. Kim Lewis, a microbiologist at Northeast University in Boston, says that this was the acknowledged theory, at least up until recently. He stated that he would need to change and re-examine his views after reading today’s paper.
Christian Lesterlin, a bacterial geneticist at the Lyon University in France, wanted to examine the way bacteria exchange these genes. He and his team decided to genetically engineer a special kind of E.Coli that have fluorescent proteins. This helped his team observe the way bacteria swap plasmids under the microscope. Most importantly, they were able to watch how bacteria produce antibiotic-resistant proteins in real time.
They found out that the transfer happens very quickly. In only three hours, 70% of sensitive genes have become antibiotic-resistant. When tetracycline, the antibiotic that they used for the experiment, was added, nearly a third of sensitive genes became resistant as well. Lesterlin says that this discovery was quite surprising at the least.
However, even once bacteria receive this antibiotic-resistant DNA, they still need to produce TetA protein. TetA pumps tetracycline out of bacteria. The good thing about tetracycline is that it stops the bacteria from producing resistant proteins. So if a specific bacteria still hasn’t produced TetA, it means that it won’t get to because this antibiotic will kill it before it does.
The surprising thing is that even once Tetracycline kills the bacteria, they are still somewhat alive. This is because the protein pump still remains, and sometimes it can push out more TetA proteins. They could eventually return microbes to life, Lesterlin’s team discovered.
In the case of bacteria that remained alive, the protein pump even helped them develop resistance to other antibiotics. The good thing is that if one removes this pump from the bacteria, it is completely exposed to antibiotics. There are drugs that disable these pumps, which makes bacteria unavailable to swap resistant DNA. Now, the bad thing is that this type of drug has not been tested on people yet, as they are still quite unsafe.
Christian says that their research didn’t bring any good news for the humans, but that it is good to know the enemy and the way it functions.