Resistances are neither more nor less than one of the manifestations of the processes of adaptation that preside over the evolution of species: in a hostile environment, only the best armed genetically survive and multiply. In the world of the infinitely small, the bacterial strains never admit defeat in the war that opposes them to antibiotics.

Genetic modifications may allow certain bacterial strains to escape the action of antibiotics. A typical example is the appearance of a gene responsible for the manufacture of an enzyme, beta-lactamase, which inactivates certain antibiotics, such as penicillins. Nine out of ten golden staphylococci have acquired this defensive weapon. Fortunately, it has been possible to synthesize inhibitors of beta-lactamase, in order to thwart these resistances. However, some bacteria have again adapted and become resistant to these inhibitors. Bacteria and pharmacologists thus lead a pursuit race, of which the bacteria always seem to come out winners.

Resistance: a shared secret

The mechanisms for acquiring new genes are well known. These are either chromosomal mutations that alter already existing genes or the integration of small circular DNA strands (plasmids), which are transmitted from bacteria to bacteria. This phenomenon can be split into six steps

1-The normal (yellow) and mutant bacteria (resistant here in red) multiply at a very high rate .; 2 and 3-The administration of an antibiotic destroys most of the normal bacteria, but the mutant bacteria resist the 4-No longer competing with normal bacteria to grow, mutant bacteria proliferate 5-These resistant bacteria adapt their cell structure to become invulnerable to the attack of the same drug. "Super-bacteria" can even share the secret of their resistance with other bacteria, allowing the development of new resistant bacterial colonies.

One of these new genes can give the bacterium resistance to a family of antibiotics. Many people harbor resistant bacteria that do not grow because they are very small compared to other bacteria present, especially in the digestive tract, and which have what is called a "barrier effect" . But it is enough that these people ingest an antibiotic so that sensitive bacteria are killed, leaving the field free to resistant bacteria. The subsequent use of the same antibiotic will then be unnecessary. Moreover, the "secret of resistance" can be shared through the integration into the cytoplasm of small strands of circular DNA (plasmids), which are transmitted from bacteria to bacteria.
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Resistance to antibiotics can thus be considered as an ecological problem, linked at least in part to the unfair prescriptions of antibiotics, indispensable medicines which save many lives but are not without inconveniences.