Antibiotics have been one of the greatest scientific discoveries for humanity. Their great success has been hindered by the increasing of antibiotic resistance events.
Conventional wisdom considers antibiotic resistance as a strictly clinical issue. In reality, more and more studies have proven that non-clinical environments, especially aquatic environments, are critical factors for the spread of antibiotic resistance. Antibiotic resistance genes (ARGs) are usually located on mobile genetic elements, which can disseminate among taxonomically unconnected species. Therefore, environmental bacteria can serve as hotspots for the development and dissemination of antibiotic resistance.
The aim of this thesis is to determine how human originated pollution affects the antibiotic resistance abundance in the surrounding water environments. The case studies were three example environments, wastewater treatment plants (WWTPs), receiving river bodies and combined sewer overflows (CSOs).
Molecular microbiology methods have been applied to analyse the resistance levels of bacterial communities from WWTP, CSOs and wastewater affected environments at different European geographical locations. Additionally, a novel approach consisting in an amplicon sequencing is described, in order to be able to investigate and asses the composition of a significant amount of integron gene cassettes.
Findings consistently indicate that effluents originated from WWTPs and CSOs have a significant impact on the levels of ARGs of the receiving water bodies. Moreover, this thesis suggests that gene blaOXA-58, could be utilized as a proxy to investigate the spread of ARGs. Its occurrence has been reported to show, consistently throughout the chapters, lower concentrations upstream, but at higher concentrations in the WWTP effluent, CSOs and downstream of the effluent.
In conclusion, although antibiotic resistance genes and integrons are part of the environmental resistome, water environments that are affected by anthropogenic wastewater display high levels of the above-mentioned genetic elements.
These findings clearly suggest the need to limit pollution levels, as well as the need to establish a more responsible policy in antibiotic prescriptions.
This must take place in order to be able to perform efficient risk assessments and to establish acceptable levels of antibiotic and ARGs pollution.:List of Figures VII
List of Tables IX
List of Abbreviations X
1. Introduction 11
1.1 Antibiotic resistance: an increasing problem 11
1.2 Intrinsic antibiotic resistance and horizontal gene transfer 13
1.2.1 Transformation 13
1.2.2 Transduction 13
1.2.3 Conjugation 14
1.3 Gene transfer elements 14
1.4 Antibiotic resistance and anthropogenic impact on surrounding environments 16
1.5 Study goals 17
2. Genetic variations of the resistome of wastewater treatment plants driven by the seasonality of antibiotic prescription 18
2.1 Introduction 18
2.2 Materials and methods 19
2.3 Results and discussion 20
3. Assessment of inter-laboratory variations of quantitative analyses of antibiotic resistance genes 27
3.1 Introduction 27
3.2 Materials and methods 27
3.3 Results and discussion 30
3.4 Conclusions 36
4. Antibiotic resistance genes in treated wastewater and in the receiving water bodies: A pan-European survey of urban settings 37
4.1 Introduction 37
4.2 Materials and methods 38
4.3 Results 44
4.4 Discussion 49
4.5 Conclusions 53
5. Analysis of integron gene cassettes composition in treated wastewater 55
5.1 Introduction 55
5.2 Materials and methods 55
VI
5.3 Results 56
5.4 Discussion 57
6. Role of combined sewer overflows in the dissemination of antibiotic resistance in surrounding environments 59
6.1 Introduction 59
6.2 Materials and methods 60
6.3 Results 61
6.4 Discussion 66
7. Closing Conclusions 68
References 70
List of publications 88
Note on the commencement of the doctoral procedure 89
Acknowledgments 90
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:73719 |
| Date | 02 February 2021 |
| Creators | Cacace, Damiano |
| Contributors | Berendonk, Thomas U., Weitere, Markus, Merlin, Christophe, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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