Cienciaes.com: Resistance to antibiotics.

2021-01-14 22:39:47

The discovery of penicillin by Fleming is considered the most important therapeutic advance in Medicine. The existence of an antibiotic substance opened the door to the discovery of others, until reaching the panoply of different natural or synthetic antibiotics that we have today. However, since antibiotics began to be widely used in the 1940s, bacteria began a war of resistance and learned to fight and win against them.

Surely you have taken antibiotics on more than one occasion, and probably stopped as soon as you felt better. This behaviour, which is very logical (why take a medicine that I don’t need?), favors, however, that the next time we take the antibiotic it will be less effective against the infection. And it is that the resistance of bacteria to antibiotics is a fragment of the evolution of the species functioning before our very eyes. The adverse environment to which bacteria are subjected in the presence of antibiotics is lethal for those most susceptible to their activity. But a bacterial population, or any other type, possesses genetic diversity. Not all bacteria are equally sensitive to the antibiotic. The most sensitive die before and the most resistant do not if it is not with higher doses of the substance. By not finishing taking our antibiotic prescription, we have ended the life of easy-to-eliminate bacteria, but the resistant ones have not been completely eliminated. Our immune system is able to control the situation, but some bacteria escape into our body waiting for the opportunity to enter another organism. Those bacteria will no longer be killed as easily by treatment with the same antibiotic. When this cycle is repeated many times, it is possible to select a completely resistant population of bacteria. Today bacteria have been detected that are resistant to eighteen or more different antibiotics. Faced with them, only our immune system can save us; And you can’t always do it.

But how have bacteria learned to resist antibiotics? Today it is known that when bacteria are in hostile environments they start hypermutation processes, the mechanism of which is not fully understood, which produce their genetic change. Many of the mutated bacteria die, but others, by chance, have produced mutations in one or several genes that allow them to survive in this hostile environment. These genes, once produced, can be transmitted from bacterium to bacterium, that is, if only one bacterium finds the solution that allows it to survive, it is enough, because, in addition to reproducing, it can transmit it to the rest of its companions, even if they do not they are of their own kind. In this way resistance spreads through bacterial populations.

Two new antibacterial control strategies are being developed at Wayne State University in Detroit, USA. These strategies are derived from a better understanding of the resistance phenomenon. One of the tricks most used by bacteria to resist our antibiotics is to modify their molecular structure, adding or removing a group of atoms. Wayne researchers have come up with an antibiotic that fools the bacteria. The antibiotic allows its structure to be modified, but this new antibiotic has a kind of “molecular elasticity” and, once modified, it spontaneously returns to its original structure, recovering its antibacterial activity.

Another of the strategies developed by the same researchers is based on the fact that many of the antibiotics we use are resistant to degradation in the external environment. In other words, the massive use of antibiotics, which we eliminate from our bodies mainly through urine, has produced an ecological environment for bacteria that contains much higher concentrations of antibiotics than a few years ago. The selection process for resistant bacteria does not only take place inside our bodies, but also in the external environment. To prevent this from happening, researchers have modified the structure of an antibiotic to make it light-sensitive while making it effective. This means that, when leaving our bodies to the outside environment and receiving light radiation, the antibiotic loses its activity. In this way we do not increase the concentration of antibiotics in our rivers, lakes and seas, where bacteria live, and we do not favor the selection of the most resistant ones.

It is too early to say whether these strategies will have any effect on the fight against bacteria. If so, especially in the case of the last strategy, our responsibility to finish taking the antibiotic prescription, even if we feel better, will increase. And we must keep in mind that antibiotics are not medicines like the others. They do not try to cure the cells or organs of our body, but to poison their invaders.

Works by Jorge Laborda.

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