Wastewater Treatment Works: A Last Line of Defense for Preventing Antibiotic Resistance Entry Into the Environment

Keira Tucker, Wendy Stone, Marelize Botes, Edward J. Feil, Gideon M. Wolfaardt

Research output: Contribution to journalArticlepeer-review

3 Citations (SciVal)


With their large, diverse microbial communities chronically exposed to sub-inhibitory antibiotic concentrations, wastewater treatment works (WWTW) have been deemed hotspots for the emergence and dissemination of antimicrobial resistance, with growing concern about the transmission of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) into receiving surface waters. This study explored (1) the prevalence of ARG and ARB in local WWTW, (2) the effect of sub-inhibitory antimicrobial exposure on ARG copy numbers in pure cultures from WWTW, and (3) two WWTW with different treatment configurations. For each WWTW, qPCR determined the prevalence of mcr3, sul1, sul2, and blaKPC during the treatment process, and culture methods were used to enumerate and identify ARB. Bacterial colonies isolated from effluent samples were identified by 16S rDNA sequencing and their respective minimum inhibitory concentrations (MIC) were determined. These were compared to the MICs of whole community samples from the influent, return activated sludge, and effluent of each WWTW. Resistance genes were quantified in 11 isolated cultures before and after exposure to sub-MIC concentrations of target antibiotics. The numbers of ARG and ARB in both WWTW effluents were notably reduced compared to the influent. Sul1 and sul2 gene copies increased in cultures enriched in sub-MIC concentrations of sulfamethoxazole, while blaKPC decreased after exposure to amoxicillin. It was concluded, within the parameters of this study, that WWTW assist in reducing ARG and ARB, but that sub-inhibitory exposure to antimicrobials has a varied effect on ARG copy number in pure cultures.

Original languageEnglish
Article number883282
JournalFrontiers in Water
Publication statusPublished - 16 May 2022

Bibliographical note

Funding Information:
KT was supported in part by the National Research Foundation of South Africa (Grant numbers: 118159 and 130527) and the Water Research Commission (Project No. K5/2733). WS was supported by Biogeochemistry Research Infrastructure Platform (BIOGRIP), funded by the Department of Science and Innovation of South Africa.

Funding Information:
The authors wish to thank Edward Archer, Mercia Volschenk, and the City of Cape Town for assisting with and permitting sampling of WWTW, the Central Analytical Facility at Stellenbosch University for DNA sequencing support, and the financial assistance from the NRF, WRC, and BIOGRIP.


  • antibiotic resistance genes
  • colistin
  • sub-inhibitory antibiotic concentrations
  • sulfamethoxazole
  • wastewater effluent
  • β-lactamases

ASJC Scopus subject areas

  • Water Science and Technology


Dive into the research topics of 'Wastewater Treatment Works: A Last Line of Defense for Preventing Antibiotic Resistance Entry Into the Environment'. Together they form a unique fingerprint.

Cite this