Update: Mar 4, 2023
Studies show that even a single dose of antibiotics changes the gut microbiota of healthy volunteers. Antibiotics play a fundamental role in medicine, but they also have a dark side. An increasing number of studies show that even a short course of antibiotics can alter the composition of bacterial species in the gut. These changes in the microbiota can be so profound that the microbiota after taking antibiotics taxonomically resembles that of critically ill patients in intensive care (!). And the microorganisms that survive the treatment have resistance genes that they tend to share with pathogens, allowing them to acquire this resistance, so that they can evade the action of the antibiotics themselves.
Researchers recruited 20 healthy volunteers, dividing them into four groups, each of which received a different antibiotic or a combination of antibiotics for five days. Stool samples were collected and analyzed before, during, and after antibiotic treatment, with the last sample taken six months after treatment. In this way, it was possible to thoroughly study how the taxonomic diversity of gut bacteria changed.
Immediately after taking antibiotics, the total richness of intestinal bacterial species decreased. In most volunteers, these readings returned to baseline after two months, but the species present continued to change. In three of the healthy volunteers assigned to different treatment groups, the gut microbiota was particularly disturbed. In these, the diversity of the microbiome continued to decrease even after six months had passed. The gut microbiota was more similar to that of an intensive care patient than to that of a healthy person.
Antibiotics change the gut microbiome
Antibiotics not only lead to changes in the composition of the microbiota, but also seem to increase the prevalence of resistance genes. In the study by Anthony and colleagues, it was found that three out of four antibiotics increased the relative number of antibiotic resistance genes in samples taken six months after treatment, a change the authors call "antibiotic scars." This means that when antibiotics are taken, some bacteria disappear, while others grow excessively, so that the balance changes. In this new balance, we get bacteria that are more resistant to antibiotics. In a recent study, it was even observed that antibiotic-resistant gut bacteria are able to break down the concentration of antibiotics in the gut, protecting pathogens from the effects of the drugs.
Why does the microbiome of some people react differently to antibiotics?
It is still unclear why the microbiota of some people seems to be particularly disturbed by antibiotics. The state of the microbiome before treatment certainly plays a key role. On this point, we await the results of future research. What we have certainly learned so far about the effects of antibiotics on the gut microbiota is that it is always advisable to restore the balance of the gut microbiota after taking antibiotics (and not only!), even if it does not seem that the individual has any particular effects from the use of the drug.
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Prevention is your conscious behavior!!!
