Swine waste, environmental contamination, and antimicrobial resistance under the One Health approach

ABSTRACT Swine farming is a key driver of global agribusiness and food security, but it generates millions of tons of liquid waste each year. This effluent is rich in organic matter, microorganisms, and antimicrobial residues, and when improperly managed, it becomes a major source of environmental pollution affecting soil, water, air, plants, animals, and humans. Anaerobic biodigestion is an effective and widely adopted process for managing this waste, producing both biofertilizers and biogas. However, biofertilizers may act as reservoirs of antimicrobial-resistant and multidrug-resistant bacteria, arising either from direct exposure to antimicrobial residues widely used in swine farming or through horizontal gene transfer among bacteria during digestion. The use of untreated biofertilizers can therefore disseminate resistance determinants into agricultural soils and beyond. In this context, understanding the microbiota of biofertilizers is essential to assess risks, improve waste management practices, and develop mitigation strategies. This narrative review synthesizes data on swine farming, waste generation, biodigestion processes, and antimicrobial-resistant microorganisms, with emphasis on their implications for the One Health approach. It also discusses emerging alternatives, such as probiotics, that may contribute to breaking the cycle of resistance dissemination and ensuring sustainable livestock production.