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Research opportunities for antimicrobial resistance control in China's factory farming.

A resistance (AMR) is well recognized as a major threat to public health worldwide. Infections caused by antimicrobial-resistant bacteria are more difficult and take longer time to cure, and result in higher rates of disability and death. Various public health authorities, including the World Health Organization and U.S. Centers for Disease Control and Prevention, have advocated for reducing antimicrobial use to prevent the emergence and spread of AMR. After imposing the most stringent decree against the overuse and misuse of antimicrobials in human health care in 2012, China banned the nontherapeutic use of 227 drugs, including 150 antimicrobials, in food animal production recently. The ban opens new research opportunities for studying the development and spread of antimicrobial-resistant bacteria in animal husbandry and controlling AMR to protect public health. We believe scientists and researchers can significantly accelerate the AMR control in China by developing alternatives to antimicrobials for disease prevention and growth promotion, surveillance programs to assess the contribution of antimicrobial use in livestock production to AMR development, and animal waste processing technologies to prevent environmental spread of resistant bacteria, as well as by outreaching to animal producers. Besides human misuse and overuse, the ubiquitous use of antimicrobials in food animal production, particularly the nontherapeutic use, also contributes to the selection and propagation of resistant bacteria. As illustrated in Figure 1, AMR developed in animal populations can spread easily to humans through direct contact with these animals and animal products, as well as through food chain, air, water, and manurefertilized soils. As the world’s largest livestock meat producer (over 80 million tonnes in 2013), China has experienced a major shift toward factory farming operations over the past decade. Animal agriculture is estimated to consume about 97 000 tonnes of antimicrobials annually, and overuse and abuse of veterinary drugs have resulted in many food safety scandals in China. Meanwhile, the emergence of AMR as a “hidden” side-effect from the extensive use of antimicrobials in factory farming has not caught much public attention. A total of 70 types of antimicrobial resistance genes (ARGs) have been found in the gut microbiota from over half of the samples of Chinese individuals, compared to 49 and 45 types in Spanish and Danish individuals, respectively. Significant increases in the abundance of ARGs for antimicrobials used in food-producing animals and for those with a longer history of use were observed in human gut microbiome, indicating antimicrobials used in animal husbandry contributed to AMR development in human commensal bacteria. A recent survey detected a total of 149 ARGs in the manures of swine farms across China, which use all major classes of antimicrobials except vancomycins, with the top 63 ARGs being enriched 192 (median) up to 28 000 (maximum) folds compared to the antimicrobial-free manures and soils. The experience from the European countries (e.g., Sweden and Denmark) and a large and growing body of scientific evidence support that the environmental load of ARGs can be diminished by stopping the nontherapeutic use of antimicrobials in food animal production. A total of 150 medically important antimicrobials have become available only by prescription for the control and treatment of animal diseases in China since March 1, 2014. While the regulatory ban presents animal producers with emerging challenges, scientific research community can contribute significantly to controlling antimicrobial abuse, and development and spread of AMR in China’s factory farming, as discussed below: Antimicrobials are used in livestock production for multiple purposes, including treatment or prophylaxis of infections, growth promotion, and feed efficiency improvement. Collaborative research with pharmaceutical industry should be conducted to develop new antimicrobials, vaccines, and alternatives to antimicrobials for growth promotion and disease prevention in animal husbandry. In particular, significant effort should be made toward the development of vaccines against common infectious diseases of farmed animals.