Impacts of solids retention time on trace organic compound attenuation and bacterial resistance to trimethoprim and sulfamethoxazole

Majid Neyestani, Eric Dickenson, Jean E T Mclain, Eduardo Robleto, Channah M Rock, Daniel Gerrity

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Bacteria can grow in the presence of trimethoprim and sulfamethoxazole by expressing antibiotic resistance genes or by acquiring thymine or thymidine from environmental reservoirs to facilitate DNA synthesis. The purpose of this study was to evaluate whether activated sludge serves as a reservoir for thymine or thymidine, potentially impacting the quantification of antibiotic resistant bacteria. This study also assessed the impacts of varying solids retention time (SRT) on trimethoprim and sulfamethoxazole removal during wastewater treatment and single and multi-drug resistance. When assayed in the presence of the antibiotics at standard clinical concentrations, up to 40% increases in the relative prevalence of resistant bacteria were observed with (1) samples manually augmented with reagent-grade thymidine, (2) samples manually augmented with sonicated biomass (i.e., cell lysate), (3) samples manually augmented with activated sludge filtrate, and (4) activated sludge samples collected from reactors with longer SRTs. These observations suggest that longer SRTs may select for antibiotic resistant bacteria and/or result in false positives for antibiotic resistance due to higher concentrations of free thymine, thymidine, or other extracellular constituents.

Original languageEnglish (US)
Pages (from-to)149-158
Number of pages10
JournalChemosphere
Volume182
DOIs
StatePublished - Sep 1 2017

Keywords

  • Antibiotic resistance
  • Solids retention time (SRT)
  • Sulfamethoxazole
  • Trimethoprim
  • Wastewater

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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