Co-occurrence of Tetracycline Antibiotic Resistance Genes and Microbial Communities in Plateau Wetlands Under the Influence of Human Activities

Abstract

The widespread use of antibiotics has led to a large number of antibiotics entering the environment, to which microorganisms have become resistant. In recent years, with the intensification of human activities in the plateau region, the occurrence and migration of antibiotic resistance genes (ARGs) in plateau wetlands have attracted considerable attention. Here, we selected the Caohai National Wetland Park, located in the Yunnan-Guizhou Plateau, as our study area. The contents of tetracyclines, sulfonamides, quinolones, and macrolides in sediments from the upstream (the pristine habitat near the spring eye) and downstream (the sewage discharge outlet of residents) areas of the river in the park were analyzed. Among them, the detection content of tetracycline antibiotics was 103.65-2185 μg·kg-1, which was the highest antibiotic detection content. To further investigate the occurrence characteristics and influencing factors of tetracycline resistance genes, the influence of environmental factors, bacterial community structure, and pathogenic bacteria on tetracycline ARGs under the influence of human activities were revealed via correlation analysis and network analysis. The results showed that a total of 15 tetracycline resistance genes were detected in the upstream and downstream sediments. Among them, seven resistance genes including tetPA, tetD, and tetPB were detected in the upstream, and 13 resistance genes such as tetPA, tetE, tetM, and tetX were detected in the downstream. The abundance of eight new resistance genes in the downstream accounted for 43.44% of the downstream genes. The tetracycline-like antibiotics and soil physicochemical indicators (i.e., available phosphorus, total organic carbon, nitrate nitrogen, and total phosphorus) were the main environmental factors affecting the distribution of tetracycline ARGs. Additionally, the bacteria detected in the upstream and downstream sediments belonged to 64 bacterial phyla, among which Proteobacteria, Firmicutes, and Bacteroidota were the main phyla affecting the abundance of tetracycline ARGs; meanwhile, 27 pathogenic bacteria were detected in the upstream and downstream sediments. Network analysis showed that the correlation between the eight new resistance genes and pathogens in the downstream area accounted for 70% of the network connectivity, and Listeria monocytogenes, Enterococcus faecalis, and Bacteroides vulgatus were identified as potential hosts for the transmission of tetracycline ARGs. Compared to the pristine habitat, the discharge of domestic sewage introduced large amounts of antibiotics and also changed the microenvironment and microbial community structure of the river wetland. Additionally, it increased the species of ARGs in sediments, which promoted the spread and transmission of ARGs among microorganisms and even pathogens.