Long Term Monitoring for Fluctuation of Antibiotic Resistance Genes and Bacteria in Rivers and Wastewater Treatment Plants, South Korea

Abstract

Antibiotic resistance has been considered as global concerns due to the continuous emergence of antibiotic resistant bacteria in various environmental settings. Wastewater treatment plant (WWTP) is thought to be a sink and a source of antibiotic resistance, reflecting the anthropogenic activity. WWTPs discharge the effluent into the aquatic environment, disseminating the antibiotic resistance genes and antibiotic resistant bacteria. Then, in the aquatic environment, antibiotic resistance could be transferred between bacterial strains, with evolution of environmental bacteria into multidrug resistant bacteria. Thus, antibiotic resistance has been largely investigated in WWTP and the adjacent river basins. Culture dependent and independent methods have been applied to investigate the antibiotic resistance in WWTPs and the aquatic environments. This study is focused on investigating the diversity, distribution profile of antibiotic resistance in nine WWTPs and adjacent river basins of South Korea for four years. The followings are the routes of research. 1. High-throughput quantitative analysis of antibiotic resistance genes was conducted using SmartChip and metagenomic analysis. 2. Antibiotic resistance in influent and effluent was compared in a WWTP for evaluation of treatment effectiveness against reduction of antibiotic resistance. 3. For four years, nine WWTPs and adjacent river basins were investigated for impact of WWTPs on the dissemination of antibiotic resistance in the aquatic environments. 4. From a WWTP, carbapenemase producing Enterobacteriaceae was screened from the WWTP. Pathogenic NDM-5 producing E. coli strain was isolated from the influent of a WWTP, and genomic characterization showed various antibiotic resistance genes, including blaNDM-5, were clustered in mobile genetic elements such as insertional sequences and plasmids. In summary, our finding suggested there have been extensive circulation of antibiotic resistance between various environmental settings. Thus, antibiotic resistance has already been largely disseminated in the aquatic environment. Statistical analysis showed that no significant difference in the abundance of about 343 antibiotic resistance genes was observed. However, linear discriminant analysis reveals that the abundance of core ARGs was significantly different between WWTPs and the aquatic environments. Decision-making tree model supported that the core ARGs could play a key role in classification of the groups of WWTPs and the aquatic environments.