摘要

       污水处理厂出水的消毒可能是限制抗生素抗性细菌 (ARB) 和抗生素抗性基因 (ARG) 传播的重要障碍。虽然理想情况下消毒应该破坏 ARGs，以防止基因水平转移到下游细菌，但对传统水消毒技术对 ARGs 的影响知之甚少。本研究检查了紫外线消毒对细胞外形式和宿主 ARB 中存在的四种 ARG（mec(A)、van(A)、tet(A) 和 amp(C)：耐甲氧西林金黄色葡萄球菌）的破坏潜力(MRSA)、耐万古霉素屎肠球菌 (VRE)、大肠杆菌 SMS-3-5 和铜绿假单胞菌 01。开发了一种扩展的扩增子长度定量聚合酶链反应测定，以增强对 ARG 损伤事件的捕获，并标准化为等效长度的目标 DNA（~1000 bp）以进行比较。发现两种革兰氏阳性 ARB（MRSA 和 VRE）比两种革兰氏阴性 ARB（大肠杆菌和铜绿假单胞菌）更能抵抗紫外线消毒。这两种革兰氏阳性生物体的总基因组大小也较小，这也可能降低了它们对紫外线的敏感性，因为潜在的嘧啶二聚体靶标较少。细胞类型对 ARG 损伤的影响仅在 VRE 和铜绿假单胞菌中观察到，后者可能是因为细胞外聚合物。一般来说，ARG 的损伤需要比 ARB 灭活（10-20 mJ/cm2 减少 4 到 5 个对数）更大的紫外线剂量（200-400 mJ/cm2 减少 3 到 4 个对数）。紫外线处理后可放大 ARG 的比例与相邻胸腺嘧啶的数量呈强烈负相关（Pearson r < -0.9；p < 0.0001）。紫外线处理后存活的 ARB 与总基因组大小（Pearson r < -0.9；p < 0.0001）和相邻胞嘧啶（Pearson r < -0.88；p < 0.0001）呈负相关，但与相邻胸腺嘧啶正相关（Pearson r > 0.85；p < 0.0001）。这表明胸腺嘧啶二聚体的形成并不是 ARB 失活的唯一机制。总体而言，结果表明紫外线对 ARG 的破坏潜力有限，应探索其他消毒技术。

       Disinfection of wastewater treatment plant effluent may be an important barrier for limiting the spread of antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs). While ideally disinfection should destroy ARGs, to prevent horizontal gene transfer to downstream bacteria, little is known about the effect of conventional water disinfection technologies on ARGs. This study examined the potential of UV disinfection to damage four ARGs, mec(A), van(A), tet(A), and amp(C), both in extracellular form and present within a host ARBs: methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), Escherichia coli SMS-3-5, and Pseudomonas aeruginosa 01, respectively. An extended amplicon-length quantitative polymerase chain reaction assay was developed to enhance capture of ARG damage events and also to normalize to an equivalent length of target DNA (∼1000 bp) for comparison. It was found that the two Gram-positive ARBs (MRSA and VRE) were more resistant to UV disinfection than the two Gram-negative ARBs (E. coli and P. aeruginosa). The two Gram-positive organisms also possessed smaller total genome sizes, which could also have reduced their susceptibility to UV because of fewer potential pyrimidine dimer targets. An effect of cell type on damage to ARGs was only observed in VRE and P. aeruginosa, the latter potentially because of extracellular polymeric substances. In general, damage of ARGs required much greater UV doses (200–400 mJ/cm2 for 3- to 4-log reduction) than ARB inactivation (10–20 mJ/cm2 for 4- to 5-log reduction). The proportion of amplifiable ARGs following UV treatment exhibited a strong negative correlation with the number of adjacent thymines (Pearson r < −0.9; p < 0.0001). ARBs surviving UV treatment were negatively correlated with total genome size (Pearson r < −0.9; p < 0.0001) and adjacent cytosines (Pearson r < −0.88; p < 0.0001) but positively correlated with adjacent thymines (Pearson r > 0.85; p < 0.0001). This suggests that formation of thymine dimers is not the sole mechanism of ARB inactivation. Overall, the results indicate that UV is limited in its potential to damage ARGs and other disinfection technologies should be explored.

https://pubs.acs.org/doi/abs/10.1021/es303652q