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  • 學位論文

加氯消毒環境中抗生素抗藥性基因監測、轉移風險評估與控制

Monitoring, Assessment, and Control of Antibiotic Resistance Genes Transfer Risks in Chlorinated Water Environment

指導教授 : 童心欣
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摘要


抗生素抗藥性是二十一世紀最嚴峻的公共衛生挑戰,抗生素抗藥性基因(antibiotic resistance genes, ARGs)也因具有可複製、不易降解及可水平基因轉移等特性被視為生物型新興污染物。次氯酸是淨水程序中常用消毒劑,同時也被發現是抗生素抗藥性基因演化選擇壓力(selective pressure),因此了解次氯酸劑量與抗生素抗藥性基因消長關係是保障水質安全之重要課題。本研究分為抗生素抗藥性基因之監測、轉移風險評估與控制三大部分,於監測中,本研究對自來水與游泳池進行採樣調查,結果發現抗生素抗藥性基因(sul1、sul2及ermB)與第一類整合子(intl1)普遍存在自來水與游泳池中,模擬滯水實驗發現脫氯後抗生素抗藥性細菌再生長數量少於總體細菌,因此抗生素抗藥性基因絕對濃度上升,相對濃度下降。於轉移風險評估中,本研究以Escherichia coli DH5α和pUC19質體做為模式系統,探討次氯酸劑量對抗生素抗藥性基因藉由轉形作用(transformation)水平轉移風險之影響,結果發現次氯酸可藉由抑制E. coli DH5α活性而降低轉形效率,且不會促進自然轉形(natural transformation)發生。於控制中,本研究比較紫外光(UV, 254 nm)、次氯酸與UV/Chlorine高級氧化程序(advanced oxidation process, AOP)對於細菌16S rRNA基因與抗生素抗藥性基因之降解效能,結果發現UV對兩種基因降解效能低;次氯酸可有效降解細菌16S rRNA基因,但對抗生素抗藥性基因降解效能較差;UV/Chlorine AOP對細菌16S rRNA基因及抗生素抗藥性基因皆有最佳去除能力,且反應後尚可提供適當餘氯維持消毒效力。

並列摘要


The dissemination of antibiotics resistance (AR) poses a critical challenge for public health, and antibiotic resistance genes (ARGs) have been considered as emerging biological contaminants due to their reproducibility, persistence, and transferability through horizontal gene transfer in the environment. Chlorine works as both a disinfectant, usually used in water treatments, and an evolution pressure for promoting AR. To ensure water safety and to avoid the rapid spread of AR, it is necessary to investigate the relationship between chlorine dosage and dynamics of ARGs in chlorinated water environments. In the first part, we sampled drinking water distribution systems, point of use tap water, indoor and outdoor swimming pool. ARGs (sul1, sul2, and ermB) and class 1 integrons (intl1) were commonly detected, and they showed higher chlorine-tolerance compared to total bacteria genes. The increment of antibiotic resistance bacteria after regrowth was less than total bacteria, so the relative abundances of ARGs were diluted under water stagnant scenario. In the second part, by using a model bacterium Escherichia coli DH5α as the recipient and plasmid pUC19 carrying ampicillin resistance gene as the exogenous ARG, we found that chlorine would reduce the transformation efficiency through inactivation of E. coli DH5α. In the last part, we demonstrated the degradation kinetics of chromosomal 16S rRNA gene and plasmid-encoded ARG using UV254, chlorination, and UV/Chlorine advanced oxidation process (AOP). UV254 disinfection could effectively deactivate E. coli DH5α but could not destroy the integrity of both kinds of genes. Chlorination showed better removal performance on chromosomal DNA than plasmid DNA. UV/Chlorine AOP not only effectively diminished both chromosomal and plasmid DNA but also provided enough residual chlorine against microbial regrowth.

參考文獻


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