Department of Civil and Environmental Engineering, University of Virginia, P.O. Box 400742, Charlottesville, VA, 22904-4742, United States.
Department of Biomedical Engineering, University of Virginia, P.O. Box 800759, Charlottesville, VA, 22908-0759, United States.
Chemosphere. 2019 Dec;237:124421. doi: 10.1016/j.chemosphere.2019.124421. Epub 2019 Jul 20.
Antibiotics in the effluents of municipal wastewater treatment plants (WWTP) may create selective pressures to induce antibiotic resistance in bacteria downstream. This study evaluates ciprofloxacin (CIP) removal by a freshwater alga, Scenedesmus dimorphus, to assess the efficacy of algae-based tertiary treatment in reducing effluent-induced CIP resistance. Results show significant CIP removal in light-exposed samples without algae and experimental algae (EA) samples: 53% and 93%, respectively, over 144 h. A residual antibiotic potency assay reveals that untreated CIP is significantly more growth-inhibiting to a model bacterium (Escherichia coli) than the algae-treated and light-exposed samples during short exposures (6 h). Adaptive laboratory evolution (ALE), again using E. coli, reveals that treated samples exhibit reduced capacity to elicit CIP resistance during sustained exposures compared to untreated CIP. Finally, observed CIP resistance in the CIP-exposed ALE lineages is corroborated via genotype characterization, which reveals the presence of resistance-associated mutations in gyrase subunit A (gyrA) that are not present in ALE lineages exposed to algae treated or light-exposed samples. As such, algae-mediated tertiary treatment could be effective in suppressing CIP resistance in bacterial communities downstream from WWTP. In addition, ALE is useful for assessing the potential of wastewater-relevant samples to elicit antibiotic resistance downstream.
污水处理厂（WWTP）废水中的抗生素可能会对下游细菌产生抗生素耐药性的选择压力。本研究评估了淡水藻类 Scenedesmus dimorphus 对环丙沙星（CIP）的去除效果，以评估基于藻类的三级处理在减少废水诱导的 CIP 耐药性方面的效果。结果表明，在暴露于光的无藻和实验藻（EA）样品中，CIP 的去除率分别为 53%和 93%，在 144 小时内。残留抗生素活性测定表明，未经处理的 CIP 在短时间暴露（6 小时）时对模式细菌（大肠杆菌）的生长抑制作用明显大于藻类处理和暴露于光的样品。同样使用大肠杆菌的适应性实验室进化（ALE）表明，与未经处理的 CIP 相比，处理过的样品在持续暴露期间诱导 CIP 耐药的能力降低。最后，通过基因型特征证实了在 CIP 暴露的 ALE 谱系中观察到的 CIP 耐药性，这表明在未暴露于藻类处理或暴露于光的样品的 ALE 谱系中存在与耐药相关的突变。因此，藻类介导的三级处理可以有效抑制 WWTP 下游细菌群落中的 CIP 耐药性。此外，ALE 可用于评估废水相关样品在下游引发抗生素耐药性的潜力。
