title: Air-drying beds reduce the quantities of antibiotic resistance genes and class 1 integrons in residual municipal wastewater solids.
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.
authors.affiliation: Department of Civil Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Tucker R
authors.initials: TR
authors.lastname: Burch
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sadowsky
authors.forename: Timothy M
authors.initials: TM
authors.lastname: LaPara
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000494:pharmacology; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001426:Bacterial Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D004352:Drug Resistance, Microbial; D032023:Integrons; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000032:analysis* / Q000382:microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000494:pharmacology; D014877:Water Pollution, Chemical / Q000517:prevention & control*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D062065:Wastewater; D014874:Water Pollutants, Chemical