Antimicrobial resistance genes in livestock production systems: concepts and consequences

摘要

Much of the scientific data suggests there is a clear association between antimicrobial usage at sub-therapeutic levels and an increase in antimicrobial resistance (AR). Antimicrobial use in livestock production, especially at sub-therapeutic levels for prophylaxis and growth-promotion, is therefore widely believed to have promoted AR in both pathogenic and commensal bacteria. The magnitude of risk from AR in livestock environments to public health is still difficult to quantify accurately - but it does exist - and there has been a range of responses to the agricultural use of antimicrobials as growth promotants and (or) prophylactics as a result. Although the prevalence of AR appears to decrease when antimicrobial use is reduced in livestock environments, none of the measures taken has yet to eliminate AR. As such, there are still conflicting opinions about the use of antimicrobials for non-therapeutic purposes in livestock production: whether or not the magnitude of risk has been positively impacted, or even whether there is a risk to public health at all. Part of this conflict arises from those who apply the precautionary principle compared to risk-benefit assessments, when deciding to make change. Irrespective of one's opinion, the long term efficacy of antimicrobials for medical and veterinary purposes is contingent on their prudent use, and their administration by licensed professionals seems an appropriate step to ensuring prudent use. Research that reduces the size of the AR reservoir in animal waste streams, and minimizes the dissemination of this AR into the environment or via the food chain is also warranted. Antibiotic resistance genes are also present in some varieties of first-generation genetically modified (GM) plants, and concerns have also been raised about the risk to public health from these transgenes, and their respective products. Even though fragments of these recombinant genes can occasionally be encountered in processed feeds, the animal digestive tract, and some animal products, there appears to be no evidence suggesting any impact on human (or animal) health and nutrition from the consumption of the GM plants currently in commercial use. While this does not preclude the need for monitoring and assessment of gene flow and health assessments with future varieties; it does seem more likely that the prudent use of antimicrobials and technologies that minimize the dissemination and persistence of AR in livestock (and medical) environments offers agriculture and the general public with the greatest opportunities to prolong their effective use.