Extended-spectrum β-lactamase-encoding genes in the pig production chain in Brazil

Animal husbandry is a key promoter of antibiotic resistance (AMR) and contributes to the spread of AMR genes throughout the environment and food supply. The pig industry is one of the leading sectors in animal-based food production worldwide, with Brazil ranking fourth in terms of pork production and export. The emergence of extended-spectrum β-lactamase (ESBL)-producing bacteria in this sector represents a significant public health concern. These enzymes confer resistance to a broad range of β-lactams, threatening the effectiveness of antibiotic therapy for infections in both humans and animals. A systematic review was conducted to address the current knowledge of AMR within the Brazilian pig production chain. The presence of ESBL-encoding genes in bacteria isolated from pig feces, intestine, carcass, and urine, as well as pork-based food, was investigated. TEM-type genes were detected in 11 of the 12 studies, including blaTEM-1A (n=33 strains) and blaTEM-1B (n=44 strains). Both genes were found in Salmonella isolated from all sample categories. Additionally, blaTEM-1 was detected in E. coli (n=4 strains from feces) and Salmonella spp. (n=2 from carcass; n=5 from feces). CTX-type genes were detected in Proteus mirabilis (blaCTX-M-65; n=6 from food) and Salmonella (blaCTX-M-8; n=1 from feces; n=1 from pig carcass). blaCMY-2 was detected in Salmonella from feces (n=1) and carcass (n=1), whereas blaCMY-M2 was detected in E. coli (n=5) from pig feces. blaPSE-1 and blaSHV-1 genes were investigated using PCR in E. coli strains isolated from pig feces; however, these were not detected. In conclusion, the pig industry may contribute to the spread of ESBL-encoding genes, posing a public health risk. Data reveal a significant presence of blaTEM genes across various samples, alongside other ESBL-encoding gene types in the Brazilian pig production chain. These findings highlight the need for integrated strategies to control AMR, particularly to reduce risks that may arise from animal -based food production systems.