Environmental reservoirs and transmission pathways of antimicrobial resistance across the pork production continuum
Sun Ae Kim
Department of Food Science and Biotechnology
Antimicrobial resistance (AMR), often called a "silent pandemic," occurs when bacteria are no longer killed by the drugs designed to treat them. Since 1990, more than one million people have died each year as a direct result of drug-resistant infections. If current trends continue, annual deaths directly caused by AMR are projected to reach 1.91 million by 2050. Including deaths in which AMR plays a role, the number could reach 8.22 million per year. Because AMR links people, animals, and the environment, it requires a One Health approach.
Antibiotic use in livestock farming can promote the selection and spread of resistant bacteria and antimicrobial resistance genes (ARGs) in animals and farm environments. However, most previous studies have only measured resistance on farms or in final meat products. It remains largely unknown where resistance enters and how it spreads as animals move through slaughter, processing, and distribution.
A research team led by Professor Sun Ae Kim of the Department of Food Science and Biotechnology at Ewha Womans University tracked AMR across the entire pork production chain, from the farm to the slaughterhouse, processing plant, and retail store. Using shotgun metagenomic sequencing, a method that reads all the DNA in a sample, the team identified which bacteria were present, which ARGs they carried, and whether these genes could move between bacteria.
ARG levels were high at the farm, slaughterhouse, and processing stages and decreased toward retail. However, clinically important resistance genes remained throughout processing. Notably, about 93% of the ARGs found on pig carcasses at the slaughterhouse were traced to the surrounding environment and handling practices.
Hardy environmental bacteria, such as Acinetobacter and Pseudomonas, were the main carriers of ARGs in slaughterhouses and processing plants. Many ARGs were found next to mobile genetic elements, DNA segments that can move between bacteria, suggesting that resistance could spread from one bacterium to another. Bacteria from slaughterhouse and processing environments also shared similar resistance and virulence (disease-causing) traits, suggesting that they may persist and adapt within these facilities.
The study shows that AMR in the pork supply chain is shaped by the environment at each stage, not only by antibiotic use on farms. Slaughterhouses and processing plants are important reservoirs of AMR and practical points for intervention. The findings provide a scientific basis for expanding AMR control beyond farms to include environmental monitoring and hygiene management in food production facilities.
The study, titled "Environmental reservoirs and transmission pathways of antimicrobial resistance across the pork production continuum," was published in Microbiome (IF 14.9).