Air-drying beds reduce the quantities of antibiotic resistance genes and class 1 integrons in residual municipal wastewater solids

Environ Sci Technol. 2013 Sep 3;47(17):9965-71. doi: 10.1021/es4024749. Epub 2013 Aug 16.

Abstract

This study investigated whether air-drying beds reduce antibiotic resistance gene (ARG) concentrations in residual municipal wastewater solids. Three laboratory-scale drying beds were operated for a period of nearly 100 days. Real-time PCR was used to quantify 16S rRNA genes, 16S rRNA genes specific to fecal bacteria (AllBac) and human fecal bacteria (HF183), the integrase gene of class 1 integrons (intI1), and five ARGs representing a cross-section of antibiotic classes and resistance mechanisms (erm(B), sul1, tet(A), tet(W), and tet(X)). Air-drying beds were capable of reducing all gene target concentrations by 1 to 5 orders of magnitude, and the nature of this reduction was consistent with both a net decrease in the number of bacterial cells and a lack of selection within the microbial community. Half-lives varied between 1.5 d (HF183) and 5.4 d (tet(X)) during the first 20 d of treatment. After the first 20 d of treatment, however, half-lives varied between 8.6 d (tet(X)) and 19.3 d (AllBac), and 16S rRNA gene, intI1, and sul1 concentrations did not change (P > 0.05). These results demonstrate that air-drying beds can reduce ARG and intI1 concentrations in residual municipal wastewater solids within timeframes typical of operating practices.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / analysis
  • Anti-Bacterial Agents / pharmacology
  • Bacteria / genetics
  • Bacteria / isolation & purification*
  • Bacteria / metabolism
  • Bacterial Proteins / analysis*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Drug Resistance, Microbial
  • Integrons
  • RNA, Ribosomal, 16S / genetics
  • RNA, Ribosomal, 16S / isolation & purification
  • RNA, Ribosomal, 16S / metabolism
  • Real-Time Polymerase Chain Reaction
  • Waste Disposal, Fluid / methods*
  • Wastewater / analysis*
  • Wastewater / microbiology
  • Water Pollutants, Chemical / analysis
  • Water Pollutants, Chemical / pharmacology
  • Water Pollution, Chemical / prevention & control*

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • RNA, Ribosomal, 16S
  • Waste Water
  • Water Pollutants, Chemical