The relationship between culturable doxycycline-resistant bacterial communities and antibiotic resistance gene hosts in pig farm wastewater treatment plants

Abstract

Pig farm wastewater treatment plants (WWTPs) are an important repository for resistant bacterial communities (RBCs) and antibiotic resistance genes (ARGs). However, the relationship between RBCs and ARG hosts has not been well characterized. In this study, water samples from influent and effluent from five pig farm WWTPs were collected. Gradient concentrations of doxycycline (DOX) were used to screen the culturable RBCs. The abundance of 21 subtypes of ARGs and the bacterial community were investigated. This study detected a large number of culturable DOX-RBCs and ARGs in the influent and effluent of pig farm WWTPs. The abundances of ARGs and RBCs in all effluent samples was significantly lower than that in the influent samples (P < 0.05), which indicated that the WWTPs can effectively remove most ARGs and RBCs in pig farm wastewater. The main potential culturable RBCs in pig farm wastewater were the dominant bacteria Proteobacteria, Actinobacteria, Pseudomonas, and Rheinheimera. However, most of the ARGs were mainly present in Bacteroidetes, Actinobacteria, Corynebacteriaceae, Macellibacteroides, Acinetobacter, and Enterobacteriaceae, which are considered potential ARG hosts. The results presented here showed that there were obvious differences between the species of culturable DOX-RBCs and ARG hosts in the pig farm WWTPs, which may be due to various environmental factors. This highlights the urgent need for further research on the relationship between RBCs and ARG hosts.