Antimicrobial Resistance Awareness Week 2024 / VI – Stools

The livestock sector is very important in our country, as well as in other European Union countries. To combat animal diseases caused by bacteria, drugs called antibiotics are used; however, their excessive use can lead to, in addition to the contamination of various environments —soil or water—, the so-called problems of antibiotic resistance. On the other hand, animal manure can be used to fertilize fields, as has always been done; however, it would be beneficial to ensure that these fertilizer products are free from antibiotics and agents that cause bacteria to develop resistance to these antimicrobial products.
It has been shown that during the transformation (and stabilization) process of pig manure to create organic fertilizer, a significant proportion of antibiotics present in livestock waste can be eliminated. It has also been demonstrated that the so-called “bacterial antibiotic resistance genes” are largely removed.
This is relevant because the direct application to soil (without transformation) of manure from animals that have been treated with antibiotics (and which remain present in the manure) would lead to an increase in these substances in the soil where they are applied as fertilizers (and therefore, soil and groundwater contamination). Additionally, the direct application of animal manure, without the removal of antibiotic-resistant agents, would increase the load of antibiotic-resistant microbes, thereby increasing the likelihood of transferring resistant bacteria from the soil to crops, and ultimately, to the consumers of these plants, whether animals or humans.
Thus, studies conducted by IRTA and CSIC show that if manure is first transformed through a process called composting, the harmful effects of directly applying manure can be avoided. One of these studies has already been published in a scientific journal: Evolution of microbiome composition, antibiotic resistance gene loads, and nitrification during the on-farm composting of the solid fraction of pig slurry using two bulking agents – PubMed.
Rafaela Caceres