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It is a fact. More and more bacteria are resistant to antibiotics. The public is aware, through information campaigns, that the main explanation comes from a high "selection pressure" on bacteria, due to the massive and inappropriate use of antibiotics, in human health but also in animal health.

But this is not the only explanation. A group of mechanisms present in bacteria is also implicated: the "horizontal transfer of genes". Bacteria are capable of exchanging fragments of DNA amongst themselves. Certain fragments of exchanged DNA provide nothing whereas others could provide material conferring resistance to antibiotics. If scientists know what mechanisms transmit messages for gene resistance, they could find ways to help fight against bacterial resistance.

Bacteria exchange fragments of DNA?

These fragments of DNA could be liberated into the environment (they then are available to all other bacteria that can incorporate them), or transmitted via "reproduction" between bacteria, called conjugation. A third pathway is the transmission of genes used by bacteriophages, these small viruses of bacteria that are capable of transmitting their DNA from one bacteria to another.

Bacteriophages, resistance vectors?

For over 10 years, a subject has divided the scientific community: are bacteriophages, notably those used in phagotherapy, capable of transmitting genes for antibiotic resistance to bacteria? A scientific article*, published in Nature in 2013, answered this question positively, but this answer has never been unanimous.

Scientists from INRAE, interested by this controversy, decided to challenge it. They carried out metagenomic studies (analysis of all genes) on bacteriophages from 14 different pig farms. Thanks to in-depth computer analysis, they finely dissected the DNA from all these bacteriophages and their conclusion is clear: the bacteriophages studied do not possess a single gene for antibiotic resistance. They cannot provide gene resistance to bacteria.

These studies provide information on antibioresistance, which is a key challenge to public health. Bacteriophages conserve their status of allies against bacterial resistance to antibiotics, via phagotherapy. This technicque, little used for the moment, could be used on patients infected by bacteria resistant to all antibiotics. The bacteriophages attack and destroy these bacteria, without the possibility of transmitting resistant genes to other bacteria. A hope, amongst others, in the fight against this growing phenomena of antibioresistance.

* Modi et al. Antibiotic treatment expands the resistance reservoir and ecological network of the phage metagenome Nature. 2013, 499(7457):219-22

Reference

Billaud, M., Lamy-Besnier, Q., Lossouarn, J. et al. Analysis of viromes and microbiomes from pig fecal samples reveals that phages and prophages rarely carry antibiotic resistance genes. ISME COMMUN. 1, 55 (2021). https://www.nature.com/articles/s43705-021-00054-8