Graduate Thesis Or Dissertation
 

Prevalence and Fate of Antibiotic-resistant E. coli in Municipal Wastewater Treatment Plants across Oregon

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  • Wastewater treatment plants are considered one of the main sources and reservoirs of antimicrobial resistance (AMR). This study investigated the prevalence of 8 different phenotypes of AMR, multi-drug resistant (MDR), and extended-spectrum beta-lactamases (ESBL) producing E. coli in 17 wastewater treatment plants across Oregon in winter and summer of 2019 and 2020. Overall, 1187 E. coli colonies were isolated from influent, secondary effluent, final effluent, and biosolids. 31.8% of all collected isolates exhibited resistance to at least one antibiotic, and 8.7% carried MDR phenotypes, of which 16.2% harbored resistance to more than five classes of antibiotics. From a total 246 sampling incidences, 23 demonstrated multiple antibiotic resistance (MAR) index above 0.2, suggesting high risk of antibiotic contamination. Significantly higher MAR index and prevalence of ciprofloxacin-resistant E. coli was observed in biosolids. Highest AMR rates amongst collected E. coli isolates were observed for ampicillin (18.4%) followed by streptomycin (13.8%) and tetracycline (13.6%). Additionally, resistance to trimethoprim- sulfamethoxazole showed significant associated with the occurrence of ampicillin, tetracycline, and streptomycin phenotypes (p ˂ 0.01). Results revealed that in different flows (influent, secondary effluent, effluent, and biosolids), the AMR rate was higher in winter compared to summer with the highest AMR rate observed in the final effluent (42.6%) and biosolids (46.5%) in winter. Similarly, the MAR index and AMR frequency of samples were higher in winter than summer. When comparing different phenotypes of AMR between winter and summer in the influent, significantly higher prevalence of ciprofloxacin-resistant E. coli was observed in summer (p ˂ 0.01), suggesting the seasonality of different phenotypes. Findings suggest that the removal efficiency of AMR E. coli in wastewater treatment plants is likely influenced by seasonal variations. Of great importance was the presence of ESBL-producing phenotypes observed in 14 E. coli isolates which further complicates treatment options for infections by these superbugs. This state-wide study confirms the widespread proliferation of this global threat and further identifies wastewater surveillance as an epidemiological screening and identification tool.
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  • This work is supported by the USDA National Institute of Food and Agriculture, Agriculture and Food Research Initiative Competitive Program, Agriculture Economics and Rural Communities, grant number: 2018-67017-2763
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  • Pending Publication
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  • 2021-03-03 to 2022-04-04

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file details KhorshidiZadehMarjan2021.pdf 2021-03-03 公开 下载