No bacteriophages (control) set. Solar irradiation without phages

In this study, a cocktail of bacteriophages active against a New Delhi metallo beta lactamase (NDM)-positive E. coli PI-7 were isolated fromm municipal wastewater and tested for their lytic effect against the bacterial host. The bacteriophages were specific against E. coli PI-7, and when applied to activated sludge, caused only a transient perturbation to the sludge microbiota between bacteriophage-spiked and control reactors for a short period. Subseqeuntly, bacteriophages were added to sensitize this pathogenic strain to solar irradiation. Solar irradiation coupled with bacteriophages successfully reduced the length of the lag-phase for E. coli PI-7 from 4.11 ± 0.78 h to 1.82 ± 0.60 h in phosphate buffer solution. The reduction of lag-phase length effect was also observed in filtered wastewater effluent and chlorinated effluent. Gene expression analysis of solar-irradiated E. coli PI-7 revealed downregulation of cell wall functions in presence of bacteriophages, making the bacteria more susceptible to damage by solar irradiation and to bacteriophage infection. Downregulation of functions implicated in scavenging and detoxifying reactive oxygen species induced by solar irradiation was also observed in bacteriophage-infected E. coli PI-7 exposed to solar irradiation. Our findings suggest that bacteriophages can be used as low-cost and environmentally safe biocontrol tool to complement solar irradiation in mitigating of the persistence of antibiotic resistant bacteria in reuse waters.

本研究从市政污水中分离得到针对携带新德里金属β-内酰胺酶（NDM）的大肠杆菌（Escherichia coli，E. coli）PI-7的噬菌体（bacteriophages）鸡尾酒，并检测其对该宿主菌的裂解效应。该噬菌体仅对大肠杆菌PI-7具有特异性，将其投加至活性污泥后，仅在投加噬菌体的反应器与对照反应器的短时间内，对污泥微生物群造成一过性扰动。随后，研究人员利用噬菌体使该致病菌株对太阳辐照更为敏感。在磷酸盐缓冲液中，太阳辐照联合噬菌体处理成功将大肠杆菌PI-7的迟滞期从4.11 ± 0.78 h缩短至1.82 ± 0.60 h。该迟滞期缩短效应在过滤后的污水出水与氯化出水中同样得以观测。对经太阳辐照的大肠杆菌PI-7进行基因表达分析后发现，在噬菌体存在的条件下，其细胞壁相关功能基因出现下调表达，使得该菌更易受到太阳辐照与噬菌体感染的损伤。此外，在经太阳辐照且被噬菌体感染的大肠杆菌PI-7中，研究人员还观测到其清除与解毒太阳辐照诱导产生的活性氧（reactive oxygen species）的相关功能基因出现下调表达。本研究结果表明，噬菌体可作为低成本且环境友好的生物防治工具，辅助太阳辐照技术，缓解再生水中抗生素耐药菌的持续留存问题。