Elsevier

Environmental Pollution

Volume 242, Part A, November 2018, Pages 164-170
Environmental Pollution

Hot spots of antibiotic tolerant and resistant bacterial subpopulations in natural freshwater biofilm communities due to inevitable urban drainage system overflows

https://doi.org/10.1016/j.envpol.2018.06.081Get rights and content

Highlights

  • 3 antibiotics were determined in sewage and in brook water.

  • A significant inhibition started at 1.0 mg L−1 with single dosed antibiotics.

  • Mixtures with 0.1 mg L−1 are as effective as single agents with 10.0 mg L−1.

  • Increased antibiotic tolerance and resistance determined downstream of CSO.

Abstract

Antibiotic resistant bacteria are a threat to human life. Recently, sewers have been identified as potential reservoirs. The intermittent injection of sewage into adjacent surface waters is inevitable, due to capacity limitations of the urban drainage system. Information regarding the effect to natural freshwater biofilms (NFB) due to the intermittent contaminations are scarce. Therefore, a fundamental screening is necessary. In April, we placed NFB-attachment constructions in a brook upstream and downstream from urban drainage overflow constructions. In meanwhile two sampling campaigns were conducted. The sewage and the brook water were collected to gather information about antibiotic background exposure of ciprofloxacin (CIP), clarithromycin (CLA) and doxycycline (DOX). Six months later we experimentally determined the oxygen uptake rate (OUR) of the NFB-communities after a 24 h lasting exposure with additionally dosed antibiotics. Concentrations of 0.1, 1.0 and 10.0 mg L−1 were selected. CIP, CLA and DOX were individually dosed, and also in mixtures. The mean antibiotic background concentration in sewage was in a range of 575.5–1289.1 ng L−1, which mainly exceeded the concentrations published in literature. The determined mean concentration in the brook was in a range of 4.6–539.0 ng L−1. The first significant inhibition of the OUR with individually dosed antibiotics started mainly at a concentration of 1.0 mg L−1. Antibiotics in a mixture with concentrations of 0.1 and 1.0 mg L−1 were as effective as single dosed antibiotics with a concentration of 10.0 mg L−1. The increased antibiotic tolerance and resistance of NFB-communities downstream of the combined sewer overflow (CSO) structure was a consequence of a severe impact due to urban drainage overflows. Hence, NFB-communities downstream of CSO-constructions are hot spots of antibiotic tolerant and resistant subpopulations and access restrictions should be announced, if an infection risk is present.

Introduction

The majority of urban surface waters are continuously impacted by wastewater treatment plant effluents and intermittently by combined sewer overflow discharges – a composite of sewage and storm water – due to capacity limitations of urban drainage systems. In particular, urban wastewater contains not only a large repertoire of antibiotic residues, but also antibiotic resistant bacteria and antibiotic resistance genes. The identification of antibiotic resistance genes (ARG) in wastewater treatment plant effluents had been focused (Czekalski et al., 2014; Novo et al., 2013; Rizzo et al., 2013). Investigations, which assess the impact of ARG to surface water biofilms, followed (Aubertheau et al., 2017; Guo et al., 2018; Lehmann et al., 2016; Marti et al., 2013; Proia et al., 2016). Consequently, biofilms may represent an ideal setting for the promotion and spreading of antibiotic resistance. However, studies identifying tolerant and resistant bacterial subpopulations in natural freshwater biofilm (NFB) communities due to intermittent and untreated sewage are rare. Marathe et al. (2017) investigated the impact of uncontrolled discharge of inadequately treated and untreated urban effluents; Subirats et al. (2017) even measured a more pronounced effect of raw wastewater than treated sewage.

Identifying environments where ARGs are enriched is important for the design of mitigation strategies to control antibiotic resistance (Berendonk et al., 2015). The identification of hot spots is challenging. Currently, there are two major ways of evaluation present, either the response-assessment due to toxicity tests or the determination of specific genes. The evaluation of effects due to antibiotic mixtures is another challenge: pharmaceutical cocktails shape the microbial community (Menz et al., 2017) and the three-dimensional matrix of the biofilm (Bruchmann et al., 2013). This short communication focuses the identification of hot spots of tolerant and resistant bacterial subpopulations in NFB-communities due to intermittent urban drainage overflows. The inhibition of activity due to antibiotic exposure – individually dosed and in mixture – is measured as oxygen uptake rate. This approach is appropriate to characterize effects (Friedrich et al., 2015, 2016, Kaeseberg et al., 2015, Lee et al., 2006, Spanjers and Vanrolleghem, 1995). To the best of the authors' knowledge, this is the first look at NFB-communities for a stormwater pollution aspect. The following investigations were conducted to (i) quantify the antibiotic concentrations in sewage and adjacent surface water; (ii) growth of NFB-communities attached to self-designed biofilm attachment constructions, which were placed upstream and downstream of a rainwater overflow structure respectively upstream and downstream of a combined sewer overflow structure; (iii) quantify activity inhibition of those NFB-communities due to individually dosed antibiotics and antibiotic mixtures; and (iv) identify hot spots of increased antibiotic tolerance and resistance.

Although our investigations are in an initial phase in terms of the announcement of necessary policy and management options, we highlight these findings due to ubiquitous urban drainage overflow constructions, which are state of the art in the urban drainage design.

Section snippets

Area under investigation

A brook in Germany with a mean flow (MQ) of 0.34 m3 s−1 was selected for the present study. The effluents of 6 wastewater treatment plants (WWTP), 11,500 population equivalents (PE), 3650 PE, 500 PE, 400 PE, 150 PE and 130 PE, discharge into the brook before it enters Dresden (540,000 inhabitants). The WWTP with the highest capacity treats the wastewater of a rehabilitation clinic (more than 1000 beds and 1800 employees). 8 combined sewer overflows (CSO) and 26 rain sewer overflows (RSO) of the

Antibiotics in sewage

Ciprofloxacin. The sampled concentration in sewage was 985.1 ± 547.6 ng L−1 (mean value and standard deviation), see Table 2. The median value was 814.5 ng L−1, which was 82.7% of mean concentration. The maximum detected concentration in 24-h composite samples was 2151.0 ng L−1.

Clarithromycin. The analyzed concentration in 24-h composite sewage samples was 575.5 ± 544.3 ng L−1 (mean value and standard deviation), see Table 2. The median value was 330.5 ng L−1, which was 57.4% of mean

Conclusion

Surface waters and NFB-communities are intermittently exposed to urban drainage overflow plumes and consequently antibiotic stress. Antibiotic tolerant subpopulations have survival benefits, and tolerance is the preliminary stage to resistance (Levin-Reisman et al., 2017). The increased residual activity at DSCSO,10 and even DSCSO,100 was a consequence of a severe impact of urban drainage overflows. CSO-constructions are state of the art in the urban drainage design. Consequently, adjacent

Acknowledgements

This paper is part of the research project “ANTI-Resist” (Untersuchung zu Einträgen von Antibiotika und der Bildung von Antibiotikaresistenzen im urbanen Abwasser sowie Entwicklung geeigneter Strategien, Monitoring-und Frühwarnsysteme am Beispiel Dresden), funded by the German Federal Ministry of Education and Research (Grant reference 02WRS1272A) within the Framework Concept “Risk Management of Emerging Compounds and Pathogens in the Water Cycle” and managed by the Project Management Agency

References (46)

  • X.-P. Guo et al.

    Biofilms as a sink for antibiotic resistance genes (ARGs) in the Yangtze Estuary

    Water Res.

    (2018)
  • M. Harnisz

    Total resistance of native bacteria as an indicator of changes in the water environment

    Environ. Pollut.

    (2013)
  • T. Kaeseberg et al.

    Abiotic, biotic and photolytic degradation affinity of 14 antibiotics and one metabolite – batch experiments and a model framework

    Environ. Pollut.

    (2018 a)
  • T. Kaeseberg et al.

    Sewer sediment-bound antibiotics as a potential environmental risk: adsorption and desorption affinity of 14 antibiotics and one metabolite

    Environ. Pollut.

    (2018 b)
  • K. Kummerer et al.

    Standardized tests fail to assess the effects of antibiotics on environmental bacteria

    Water Res.

    (2004)
  • K. Lehmann et al.

    Trace levels of sewage effluent are sufficient to increase class 1 integron prevalence in freshwater biofilms without changing the core community

    Water Res.

    (2016)
  • N.P. Marathe et al.

    Untreated urban waste contaminates Indian river sediments with resistance genes to last resort antibiotics

    Water Res.

    (2017)
  • J. Menz et al.

    Antimicrobial activity of pharmaceutical cocktails in sewage treatment plant effluent - an experimental and predictive approach to mixture risk assessment

    Environ. Pollut.

    (2017)
  • A. Novo et al.

    Antibiotic resistance, antimicrobial residues and bacterial community composition in urban wastewater

    Water Res.

    (2013)
  • P. Paíga et al.

    Presence of pharmaceuticals in the Lis river (Portugal): sources, fate and seasonal variation

    Sci. Total Environ.

    (2016)
  • L. Proia et al.

    Occurrence and persistence of antibiotic resistance genes in river biofilms after wastewater inputs in small rivers

    Environ. Pollut.

    (2016)
  • L. Rizzo et al.

    Urban wastewater treatment plants as hotspots for antibiotic resistant bacteria and genes spread into the environment: a review

    Sci. Total Environ.

    (2013)
  • J. Rossmann et al.

    Simultaneous determination of most prescribed antibiotics in multiple urban wastewater by SPE-LC–MS/MS

    J. Chromatogr. B

    (2014)
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