Antimicrobial resistance (AMR) is a One-Health (human, animal, environment) challenge that requires collaborative, interdisciplinary action. Comparable surveillance data are needed to effectively inform policy interventions aimed at preventing the spread of AMR. Environmental monitoring lags behind that of other One Health sectors and is in need of agreed upon targets and standardized methods. A challenge is that there are numerous microorganisms, antibiotic resistance genes (ARGs), and mobile genetic elements and corresponding methods that have been proposed. In this dissertation, a framework for AMR monitoring of aquatic environments was developed through a combination of literature review and stakeholder input, via surveys and a workshop. Through this process, three targets were selected for standardization: the sulfonamide resistance gene (sul1), the class 1 integron integrase gene (intI1), and cefotaxime-resistant Escherichia coli. Quantitative polymerase chain reaction (qPCR)- and culture-based protocols were developed and pilot tested in two independent laboratories on a set of six water matrices: wastewater, recycled water, and surface water from six different wastewater utilities engaging in water reuse located in five states across the USA. The impact of wastewater treatment and advanced water treatment processes was examined in terms of removal of these targets. Finally, qPCR and culture methods were used to examine the relationship between sul1, intI1, E. coli, and fecal indicators in private household wells across four states in the Southern USA that were identified as susceptible to storm events. The overall findings provide a useful baseline occurrence of the proposed AMR monitoring indicators across a range of water types and protocols that are accessible to water utilities. / Doctor of Philosophy / Life-saving drugs and treatments are failing at an increasing rate because of antimicrobial resistance (AMR). Antimicrobials, such as antibiotics, are a double-edged sword, because they are an effective weapon for killing disease-causing pathogens, but the more they are used the greater the likelihood that microbes that are resistant to them will survive, reproduce, and spread. National action plans for AMR have been created by a majority of countries, emphasizing the importance of antibiotic stewardship and other mitigation strategies. However, numerous data gaps need to be addressed in order to identify strategies that are most likely to be effective and to implement them. Environmental surveillance, including wastewater influent, wastewater effluent, and surface water, could prove an informative means to track AMR trends with time and relate them to human activities and corresponding mitigation efforts. The purpose of this dissertation was to develop a framework for AMR surveillance of aquatic environments and to test it across an array of sample types. We considered an array of possible culture- and DNA-based targets from available scientific literature and engaged experts and stakeholders in narrowing down the list to options that were both informative and feasible. We developed protocols for quantifying an antibiotic resistance gene (sul1), a mobile genetic element that has been implicated in the spread of multi-antibiotic resistance (intI1), and an extended spectrum beta-lactamase (ESBL) producing form of Escherichia coli. We compared the methods between two independent laboratories on untreated wastewater, treated wastewater, recycled water, and surface water collected from six locations across five states. We additionally did a survey of private household well water that was hypothesized to be vulnerable to contamination due to storms and lack of resources for maintenance. The results of this research can help to support environmental monitoring of AMR across the US and globally.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115715 |
| Date | 10 July 2023 |
| Creators | Liguori, Krista Margaretta |
| Contributors | Civil and Environmental Engineering, Pruden, Amy, Edwards, Marc A., Garner, Emily Dawn, Krometis, Leigh Anne Henry |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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