Microbial defense mechanisms : antibiotic resistance, THE challenge (1)

The environmental presence of antibiotics and the genes ensuring resistance against them is a Darwinian expression of natural selection in the microbial world. The major role of antibiotic production by a microorganism in natural environments is to enable colonization of a niche or survival in a complex polymicrobial universe. Resistance can thus be seen as a selective response to this production by the producing bacteria themselves or their target bacteria. The current crisis of multi-resistant antibiotics can therefore be seen as an exacerbation of a natural phenomenon caused by the massive introduction of "exogenous" antibiotics into the environment from the middle of the ^20th century onwards. This introduction was not limited to the medical field: its excesses extended to the veterinary, agricultural and livestock sectors. Unless drastic measures are taken, the current global outbreak of multi-drug resistance could deprive us, after a miraculous century, of one of the most effective tools of medicine. The outbreak of antibiotic resistance benefits from the richness of the "resistome", i.e. the global human, animal and environmental repertoire of potential antibiotic resistance genes (20,000?), the efficient dissemination of resistance gene vectors (plasmids, transposons, integrons), and the amplification of the phenomenon by increased national and international trade. Among the most worrying mechanisms of this resistance epidemic are carbapenemases, enzymes capable of hydrolyzing the latest generation of broad-spectrum beta-lactam antibiotics, and efflux pumps capable of effectively preventing antibiotics from reaching their targets. The World Health Organization (WHO) has recently grasped the importance of the risk, but reversing the process will be long and complex, especially given the paucity of new antibiotics on offer.