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Minimal selective concentrations of tetracycline in complex aquatic bacterial biofilms
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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2016 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 553, p. 587-595Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

Selection pressure generated by antibiotics released into the environment could enrich for antibiotic resistance genes and antibiotic resistant bacteria, thereby increasing the risk for transmission to humans and animals. Tetracyclines comprise an antibiotic class of great importance to both human and animal health. Accordingly, residues of tetracycline are commonly detected in aquatic environments. To assess if tetracycline pollution in aquatic environments promotes development of resistance, we determined minimal selective concentrations (MSCs) in biofilms of complex aquatic bacterial communities using both phenotypic and genotypic assays. Tetracycline significantly increased the relative abundance of resistant bacteria at 10 μg/L, while specific tet genes (tetA and tetG) increased significantly at the lowest concentration tested (1 μg/L). Taxonomic composition of the biofilm communities was altered with increasing tetracycline concentrations. Metagenomic analysis revealed a concurrent increase of several tet genes and a range of other genes providing resistance to different classes of antibiotics (e.g. cmlA, floR, sul1, and mphA), indicating potential for co-selection. Consequently, MSCs for the tet genes of ≤ 1 μg/L suggests that current exposure levels in e.g. sewage treatment plants could be sufficient to promote resistance. The methodology used here to assess MSCs could be applied in risk assessment of other antibiotics as well.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 553, p. 587-595
Keywords [en]
Minimal selective concentration, Antibiotic resistance, Risk assessment, Antibiotic contaminants, Environmental emission limits
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:umu:diva-118609DOI: 10.1016/j.scitotenv.2016.02.103ISI: 000373220700059OAI: oai:DiVA.org:umu-118609DiVA, id: diva2:914435
Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2018-10-11Bibliographically approved
In thesis
1. Antimicrobials in sewage treatment plants: occurrence, fate and resistance
Open this publication in new window or tab >>Antimicrobials in sewage treatment plants: occurrence, fate and resistance
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Antimikrobiella ämnen i avloppsreningsverk : förekomst, avskiljning och resistens
Abstract [en]

The World Health Organization (WHO) has identified antibiotic resistance as a major threat to human health. The environment has been suggested to play an important role in the emergence of antibiotic resistant bacteria. The external environment can act as a source of resistance genes that could potentially be transferred into human pathogens. It is also an important route for the dissemination of antibiotic resistance genes and bacteria. Sewage treatment plants (STPs) are among the most important routes by which antibiotics and antibiotic resistance genes enter the environment. It has been suggested that STPs are hotspots for the development of antibiotic resistance because they contain relatively high concentrations of antibiotics as well as both human and environmental bacteria. Further complicating matters, there is evidence that other substances with antimicrobial properties, such as biocides and metals, can cause antibiotic resistance due to co- and cross-resistance.

This thesis contributes new knowledge on the concentrations, mass flows, and removal efficiencies of antimicrobials in STPs and their connections to the emergence of antibiotic resistance. Paper I presents data on the levels of 40 different antimicrobials in the incoming wastewater, treated effluent, and digested sludge of eleven different STPs. Although not previously detected in STPs, chlorhexidine is shown to be ubiquitous in such plants. In Paper II, mass flows and removal efficiencies are calculated for eleven antimicrobials over various treatment steps in three STPs, showing that polar antimicrobials were inefficiently removed from the wastewater. In Paper III, the minimum selective concentration (MSC) for the antibiotic tetracycline was determined in a complex bacterial aquatic biofilm using both phenotypic and genotypic endpoints. It was found that 10 µg/L selected for phenotypic resistance, and 1 µg/L selected for certain resistance genes. Paper VI used metagenomics to determine whether there is selection for antibiotic-resistant bacteria in STPs and whether the extent of this selection can be correlated to the concentrations of antimicrobial compounds. No clear evidence for selection was identified. Paper V evaluates advanced wastewater treatment techniques for removing antimicrobial compounds using ozonation and granular activated carbon (GAC). The identity of the GAC material was found to strongly affect removal efficiency, and GAC was more efficient than ozonation for most compounds at the tested concentrations.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2018. p. 77
Keywords
biocides, antibiotics, sewage treatment plants, wastewater, sludge, ozonation, activated carbon, antibiotic resistance, antimicrobials, mass flows, LC-MS/MS, environment, advanced water treatment
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-152554 (URN)978-91-7601-938-2 (ISBN)
Public defence
2018-11-07, Aula Anatomica (Bio.A.206), Biologihuset, Umeå, 13:00 (English)
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Available from: 2018-10-17 Created: 2018-10-11 Last updated: 2018-10-15Bibliographically approved

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Östman, MarcusTysklind, Mats

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