Antimicrobial resistance continues to spread

Antibiotic resistance appears to be spreading more rapidly than expected among human and animal pathogenic bacteria. Significant genetic transfer between bacteria in our ecosystems is believed to be a contributing factor, but certain factors—such as consideration of animal welfare in livestock farming—must not be overlooked.     According to the World Health Organization, antibiotic resistance is one of the greatest threats to global health, food safety, and development. Antimicrobial resistance is already estimated to cause more than 33,000 deaths per year in Europe alone, and this figure could rise in the coming years. Resistance spreads fairly easily from one bacterium to another via plasmids carrying resistance genes. This process, called conjugation, allows a bacterium to acquire new characteristics found in other bacteria, including antibiotic resistance. It is therefore important to implement measures that can curb this transfer, such as limiting the overuse of antimicrobials. Despite these efforts, researchers have observed that in recent years, resistance genes have been spreading to human pathogens at a much higher rate than expected. In particular, many genes appear to originate from a wide range of bacterial species and environments, such as soil, water, and plants. This is quite surprising. Although conjugation is a common phenomenon, researchers believed it was limited to distinct bacterial types. Indeed, plasmids belong to different mobility groups (or MOB groups) that cannot be transferred between just any bacterial species. But new data analysis methods—which made it possible to study the genetic sequences of more than 4,600 natural plasmids from different types of bacteria—appear to confirm the existence of genetic transfer on a much larger scale than previously anticipated. In fact, not only did the number of mobile plasmids turn out to be twice as high, but the number of bacterial species possessing mobile plasmids nearly doubled. Furthermore, the genetic sequences that enable conjugation appear to be much more numerous. Consequently, genetic transfers are far less restricted than previously thought and can occur between many quite distinct bacteria. Exchanges between bacteria found in humans, animals, plants, soil, aquatic environments, and industry would therefore not only be possible but also quite frequent. Resistance genes could therefore originate from a natural genetic reservoir much larger than previously envisaged. This assessment is cause for concern. The threat of our only weapon against bacteria becoming ineffective is very real. If multidrug-resistant bacteria continue to grow and spread, it will become increasingly difficult to control infections that, today, can be treated in a matter of days. The consequences will be severe, and overall health and well-being will be compromised for both humans and animals. To prevent this from happening, global health policies aim to reduce infections, maintain the effectiveness of medications, combat the misuse of antibiotics, and develop alternative solutions, with a particular focus on the agricultural sector. In fact, overall, more antibiotics are consumed by farm animals than by humans. They are therefore a major part of the equation and the delicate balance at stake. But the risk varies depending on the specific farm. The breed of the animal being raised is a key factor, but not the only one. Antibiotic use can also be influenced by factors specific to the farm, such as animal welfare and biosecurity procedures or the farmer-veterinarian relationship. Furthermore, high standards of internal and external biosecurity, along with preventive practices implemented on the farm, can lead to improved animal health and productivity, which in turn results in reduced antibiotic use. However, the practices and views of some livestock producers regarding the use of antibiotics can hinder the changes needed to prevent the emergence of antibiotic resistance. In particular, some are reluctant to eliminate or modify the use of these drugs, despite the now-established correlation between biosecurity, animal welfare and health standards, animal performance, and responsible use of antibiotics. It is therefore important to continue engaging with antibiotic users in the field so that comprehensive policies are implemented and understood, for the benefit of both animals and humans. Looking ahead, to combat antimicrobial resistance, researchers recommend, in particular, focusing on strategies to improve both external and internal biosecurity, as well as on targeted animal welfare programs to meet the specific needs of each farm.