Effect of pH on the mitigation of extracellular/intracellular antibiotic resistance genes and antibiotic resistance pathogenic bacteria during anaerobic fermentation of swine manure

Effects of various initial pH values (i.e., 3, 5, 7, 11) during anaerobic fermentation of swine manure on intra-cellular and extracellular antibiotic resistance genes (iARGs and eARGs) and ARG-carrying potential microbial hosts were investigated. The abundance of almost all iARGs and eARGs decreased by 0.1-1.7 logs at pH 3 and pH 5. The abundance of only three iARGs and eARGs decreased by 0.1-0.9 logs at pH 7 and pH 11. Under acidic initial fermentation conditions (pH 3 and pH 5), the ARG removal effect was more pronounced. Acidic conditions (pH 3 and pH 5) significantly reduced the diversity and abundance of the microbial community, thereby elim-inating many potential ARG hosts and antibiotic-resistant pathogenic bacteria (ARPB). Therefore, the study results contribute to the investigation of the effects of swine manure anaerobic fermentation on the removal and risk of contamination of ARGs and ARPB.

Automated summary

This study investigated the effects of different initial pH values (i.e., 3, 5, 7, 11) during anaerobic fermentation of swine manure on intra-cellular and extracellular antibiotic resistance genes (iARGs and eARGs) and ARG-carrying potential microbial hosts. The abundance of most iARGs and eARGs decreased at pH 3 and 5, while only three iARGs and eARGs decreased at pH 7 and 11. Acidic conditions (pH 3 and 5) resulted in a more pronounced removal effect of ARGs and reduced diversity and abundance of microbial community, eliminating potential ARG hosts and antibiotic-resistant pathogenic bacteria. The study findings contribute to understanding the impact of swine manure anaerobic fermentation on ARGs and ARPB removal and contamination risk.