The side effects of antibiotics you didn't know about

The bacteria resistant to all antibiotics

Antibiotics are those drugs that, in just 100 years, have made infections no longer the leading cause of death in the world.

Now what about the side effects of antibiotics? Yes, they save many lives each year, but their misuse and excesses have made us worry more about collateral damage than about its benefits. A clear example is the famous resistance to antibiotics (there comes a point where bacteria stop responding to antibiotics); And on the other side is the fact that some beneficial bacteria for our body die, when they shouldn’t.

For this reason, more and more doctors are taking into account the side effects of antibiotics. At least, the well-known ones, because recent studies have revealed new collateral damage to these valuable drugs. In fact, there have been two different studies that have just revealed different side effects, caused by the same: Eliminate intestinal microorganisms benefits for our body, inadvertently.

Antibiotic Side Effects: Autoimmune Diseases After Transplantation

On the one hand, one of the recent studies that we will discuss today was published in Science Translational Medicine, which suggests that some antibiotics may worsen the evolution of a patient after a transplant.


In this case, the evolution of 857 patients after receiving a hematopoietic stem cell transplant, a type of treatment used in some types of leukemia (commonly known as blood cancer), was analyzed. Frequently, together with said treatment, antibiotics are usually associated in order to prevent or treat possible infections after transplantation, since at that time the immune system of the person receiving these stem cells is weakened.

However, sometimes things don’t go well. In the case of the study, 12 commonly used antibiotics were selected after such a transplant, and they followed the evolution after their use. According to their findings, there were two combinations in particular that increased the risk of poor evolution after transplantation: Piperacillin-TazobactanandImipenem-Cilastine. Patients treated with such combinations were at increased risk of developing a complication called Graft-versus-Host Disease, where there is a great inflammation where the transplanted cells attack their receptor, and can cause its death.

These combinations of antibiotics are used for their broad spectrum, that is, functionality against many different types of bacteria. However, what the study suggests is that these antibiotics also massacred the intestinal bacteria of the patients receiving the transplant, thus altering your immune system, and increasing the risk of this post-transplant complication.

Antibiotic Side Effects: Impaired Brain Cells and Memory

On the other hand, another independent study published in Cell Reports has discovered another situation that added to the side effects of antibiotics: Long-term use of these drugs could alter memory.


In this case, for the study, the researchers treated mice with broad-spectrum antibiotics (mixed with their water) for seven weeks. Later, they studied the development of their brain cells based on the connections between intestine, immune system and brain.

According to their findings, the mice suffered a decreased production of new brain cells in the hippocampus, the brain area responsible for memory, compared to mice not treated with antibiotics. In addition, these antibiotic-treated mice also worsened their memory test scores significantly.

At the molecular level, what happened is that antibiotics produced the decrease in a type of inflammatory cell called the Ly6c hi monocytefrom the marrow, the blood and the brain. Furthermore, when mice that already had a decrease in this type of cell without prior antibiotic treatment were studied, the same decrease in brain cell production was also detected. In other words, the researchers suggest that monocytes will be keys to the proper development of the brain and memory.

Finally, it should be noted that these side effects of antibiotics on memory can recover thanks to exercise and a cocktail of bacteria, at least in mice. At the moment we do not know if the same effect will occur in humans, but it seems that intestinal bacteria have a lot to do with proper brain function.

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