Comparison of Antibiotic Resistance Distribution According to Difference of Disinfection in Wastewater Treatment Plant

Abstract

Since the development of antibiotics, the use of antibiotics has soared, and the spread of antibiotic resistance (AR) has become a global problem. Wastewater treatment plants (WWTPs) collect wastewater from a various source including hospital, livestock, household and research industry. WWTPs utilize various microorganisms in the biological treatment process. It has been suggested that the possibilities of gene exchange through the horizontal gene transfer (HGT) between antibiotic resistance bacteria (ARB) and the bacteria of the WWTPs during the treatment process. For that reasons the WWTPs is suspected to be the main cause of AR transmission to the environment. In this study, six WWTPs were surveyed to investigate the role of WWTPs in the dissemination of AR. WWTPs were using different disinfection method including chlorination, ozonation, and UV radiation. A total of 4,080 bacteria were isolated from the influent, effluent, and upstream water of WWTPs. 2,097 strains were identified at the genus level using 16S rRNA sequencing. Multi-drug resistance (MDR) test against 18 antibiotics of 1,696 strains were investigated using disc diffusion method. In addition, SmartChip real-time PCR was performed to detect 343 antibiotic resistance genes (ARGs) and 36 mobile genetic elements (MGEs). Acinetobacter, Aeromonas, and Pseudomonas known as ubiquitous bacteria in the aquatic environment were identified at all sites. Most of the sites showed low resistance rates in meropenem, ciprofloxacin, whereas showed high resistance rates in amoxicillin, cephalexin. The proportion of MDR strains increased in effluent of WWTPs located in the Yeongsan River basin. In addition, MDR and aminoglycoside related ARGs and Insertion sequence (IS) related MGEs were dominantly detected in all sites. Furthermore, aminoglycoside (aad, aac and str) and beta-lactam (blaGES, fox5, blaOXA) genes were dominantly detected in all ARGs with inactivation mechanisms at all WWTPs. This result shows that it is difficult to completely remove ARB and ARG through the wastewater treatment process. The effluent containing ARB and ARGs is released to the river and spreads to the environment. For public health, methods for removing ARB and ARGs should be developed quickly.