A new report from the United Nations Food and Agricultural Organization (FAO) notes that while agricultural use of antibiotics likely contributes to antimicrobial resistance (AMR) in human diseases, significant knowledge gaps remain regarding the biological pathways through which pathogens acquire resistance and the actual risks associated with specific uses of antimicrobials.
The report, titled Drivers, Dynamics and Epidemiology of Antimicrobial Resistance in Animal Production, was published on Nov. 16 by the FAO.
The report notes that AMR occurs naturally in the environment, and that all uses of antimicrobials including those for therapeutic purposes in humans and animals can contribute to the emergence of AMR.
The authors write that “if the selection pressure resulting from antimicrobial usage (AMU) in animals and humans were to be removed, this would still not completely halt the emergence and global spread of AMR due to the ability of AMR genes to move between bacteria, hosts and environments, and the occurrence of spontaneous mutations.”
However, the authors go on to say that overuse of antimicrobials and improper use in many parts of the world are recognized as key drivers of the emergence and spread of AMR. They point specifically to the role of performance or growth-promotion uses, along with prophylaxis and metaphylaxis uses in livestock, as likely contributors to AMR in pathogens affecting animals and humans. The report notes that while producers in developed countries are scaling back these types of uses and increasingly limiting antibiotic use to disease treatment, the practices remain common in some countries and global growth in livestock production suggests that agriculture will account for two-thirds of the future growth in antimicrobial usage.
The report also acknowledges that the evolution of AMR within microbial population is complex and can involve a variety of biological pathways. “Dissemination of resistance genes can occur clonally, through vertical spread, and also via horizontal transfer through transposons and integrons (intracellular gene mobilization) and through integrative and conjugative elements (ICEs, such as conjugative transposons) and plasmids, among others,” the authors note. The report describes these pathways in considerable detail.
Finally, the FAO authors present a set of recommendations intended to address the knowledge gaps regarding AMR. These include:
· Investigate the extent of transfer of resistance genes between bacteria in the gut environment of humans and animals to quantify the impact of AMU on bacterial populations.
· Use molecular techniques such as metagenomics together with epidemiological data in an integrated analysis, improved databases of molecular sequences and bioinformatics techniques to gain better understanding of interactions of genes and microbes within microbiota, microbiomes and different scales of microbial ecosystems and transfer of resistance.
· Use molecular sequencing and epidemiological studies of resistant bacteria and resistance determinants to support risk assessment and simulation (modelling) studies, to better understand horizontal transfer of resistance genes and emergence of resistant bacterial clones.
· Standardize and share databases of resistance genes and mobile elements encoding resistance traits.
· Execute pharmacodynamic and pharmacokinetics studies to assess how antimicrobials interact with microbial populations, particularly in the context of treatment of infections, in order to improve the efficacy of therapy and minimize the risk of AMR emergence.
· Use metagenomic and analytical chemistry approaches, in combination with bioinformatics, to study changes in the human intestinal microbiome as a result of ingestion of low levels of antimicrobial residues in food.
· Enhance data collection to assess the association between AMU on farms and AMR among food-borne bacteria, as well as the relationship between AMR in livestock and the incidence of resistant infections in humans.
· Use epigenetics techniques in surveillance for AMR to allow tracing the origin of emergence
· Assess AMR in the context of all antimicrobial usage practices, including usage that is compliant with legislation and recommendations.
· Monitor antimicrobial residues in the environment in the same way as other hazardous substances.
· Include water treatment as a control point for reducing AMR risk.
· Prioritize development of highly biodegradable antimicrobials.
· Assess the impact of biocides and heavy metals on AMR emergence in bacteria.
· Adapt intensive livestock production methods to minimizing environmental contamination with antimicrobial residues and resistant pathogens.
· Employ effective on-farm hygiene practices to reduce human exposure to resistant pathogens.
· Adopt a “One Health” approach, integrating animal and human health systems and institutions, to improve the efficiency of AMR research, surveillance, prevention and control systems.
Read the full report from the UN Food and Agricultural Organization.