Quantification of antibiotic resistance in wastewater, rivers and drinking water

Abstract

The extensive and improper use of antibiotics leads to the emergence and spread of antibiotic resistant bacteria (ARBs) and antibiotic resistance genes (ARGs). Antibiotic resistance is not only associated with clinical settings but also with environmental ones, where it is underexplored. In order to address this, the present study aimed to measure the concentrations of antibiotic residues and ARGs in selected wastewater effluent, rivers and drinking water of NWE and NW-C in North West Province, South Africa. The first part of the study is a structured review. It summarises antibiotic residues and ARGs found in wastewater treatment plants (WWTPs), drinking water production facilities (DWPFs) and surface water in South Africa. This review uncovered a lacuna when it comes to studying antibiotic residues in DWPFs, quantifying ARGs in water environments and determining whether exposure risks might occur. The second part of the study determined the presence of ARGs and antibiotic residues in DWPFs. Generally, the detection of most ARGs obtained by the end-point PCR was higher in raw water. However, higher gene detection was also detected in NW-E (DHA and sul2) and NW-C (sul1) treated water. Real-time PCR analysis showed higher ARG concentrations in treated water. Chemical analysis showed higher antibiotic and fluconazole residues in raw water. However, trimethoprim concentrations were higher in NW-C treated water. The risk quotients (RQs) were deemed low to high for target compounds. In addition, the bacterial community was determined by high-throughput 16S rRNA sequencing and correlated with ARGs, antibiotic residues and physicochemical parameters. The study's third part determined antibiotic residue and ARG patterns in wastewater effluent and rivers. The end-point and realtime PCRs showed that the wastewater effluents influenced the detection and quantification of some ARGs in the downstream rivers, with a few abnormalities. The chemical analysis results indicated that, in NW-E, the wastewater effluent did not influence the presence of fluconazole in the downstream river. In NW-C, ampicillin concentration increased from the wastewater effluent to the downstream maturation pond. The RQs of target compounds in wastewater effluent and rivers were deemed to be of high and low risk. Furthermore, highthroughput 16S rRNA sequencing revealed the presence of potential pathogens. In conclusion, since these contaminants in water are a potential threat to humans, animals and plants, the study's outcomes could form part of policymaking to improve antibiotic use, water quality and the fight against antibiotic resistance.