On-Farm Anaerobic Digestion of Dairy Manure Reduces the Abundance of Antibiotic Resistance-Associated Gene Targets and the Potential for Plasmid Transfer
Tam T. Tran, Andrew Scott, Yuan-Ching Tien, Roger Murray, Patrick Boerlin, David L. Pearl, Kira Liu, James A. Robertson, John J. Nash, Edward Topp
Abstract
Using livestock manure for fertilization can entrain antibiotic-resistant bacteria into soil. Manure on some dairy farms is anaerobically digested before being land applied. Recommending the widespread implementation of the practice should be founded on understanding the impact of this treatment on various endpoints of human health concern. Although lab-scale anaerobic treatments have shown potential for reducing the abundance of antibiotic resistance genes, there are very few data from commercial farms. Anaerobic digestion of manure on six dairy farms efficiently abated coliform bacteria, E. coli, and a majority of antibiotic resistance-associated gene targets. In addition, the conjugation potential of plasmids carrying ESBL genes into introduced E. coli strain CV601 was reduced. Overall, anaerobic digestion abated coliform bacteria, the genes that they carry, and the potential for ESBL-carrying plasmid transfer.