Antibiotic resistance genes and antibiotic resistant bacteria as emerging contaminants in wastewater: fate and persistence in engineered and natural environments
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PhD Dissertation_David Mantilla.pdf
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PhD Dissertation_David Mantilla
Type
DissertationAuthors
Mantilla Calderon, David
Advisors
Hong, Pei-Ying
Committee members
Plewa, Michael J.Daffonchio, Daniele

Saikaly, Pascal

Program
BioscienceDate
2018-12Embargo End Date
2020-03-25Permanent link to this record
http://hdl.handle.net/10754/631716
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At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2020-03-25.Abstract
The emergence and rapid spread of antimicrobial resistance (AMR) is a phenomenon that extends beyond clinical settings. AMR has been detected in multiple environmental compartments, including agricultural soils and water bodies impacted by wastewater discharges. The purpose of this research project was to evaluate what factors could influence the environmental persistence of antibiotic resistance genes (ARGs), as well as to identify potential strategies employed by human pathogens to survive in secondary environment outside the host. The first part of this dissertation describes the incidence of the New Delhi metallobeta lactamase gene (blaNDM-1) – an ARG conferring resistance to last resort antibiotics – in the influent of a wastewater treatment facility processing municipal wastewater from Jeddah, Saudi Arabia. Detection of blaNDM-1 was followed by the isolation of a multi-drug resistant strain of E. coli (denoted as strain PI7) at a frequency of ca. 3 x 104 CFU/m3 in the untreated municipal wastewater. Subsequently, we described the decay kinetics of E. coli PI7 in microcosm experiments simulating biological treatment units of wastewater treatment plants. We identified that transition to dormancy is the main strategy prolonging the persistence of E. coli PI7 in the microcosm experiments. Additionally, we observed slower decay of E. coli PI7 and prolonged stability of extracellular DNA in anoxic/anaerobic conditions. In the last chapter of this thesis, the fate of extracellular DNA is further explored. Using as a model Acinetobacter baylyi ADP1, we describe the stimulation of natural transformation frequencies in the presence of chlorination disinfection byproducts (DBPs). Moreover, we demonstrate the ability of BAA to stimulate transformation is associated with its capacity to cause DNA damage via oxidative stress. Overall, this dissertation addresses important knowledge gaps in our current understanding of ARB and extracellular ARG persistence in the environment. The results from this project highlight the importance of retrofitting the existing water treatment process with advance membrane filtration units, and the need to relook into the current disinfection strategies. Wastewater treatment technologies should be assessed for their efficacies in not only inactivating ARB and ARGs, but also whether unintended consequences such as stimulated horizontal gene transfer would occur.Citation
Mantilla Calderon, D. (2018). Antibiotic resistance genes and antibiotic resistant bacteria as emerging contaminants in wastewater: fate and persistence in engineered and natural environments. KAUST Research Repository. https://doi.org/10.25781/KAUST-I9I1Xae974a485f413a2113503eed53cd6c53
10.25781/KAUST-I9I1X