Front Microbio：饮水中或存在大量多重耐药细菌的耐药基因

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大量的细菌会通过市政设施进入环境中，尤其是医院的废水。尽管废水处理厂的处理减少了总的细菌数量，但是对于多重耐药细菌并不能杀灭，近日，研究者Eawag在洛桑日内瓦湖城开展的一项研究揭示了多重耐药细菌的存在。洛桑市大约每天处理90000立方米的污水，全部排放到日内瓦湖的海湾处，排放点长700米，深30米。洛桑市所处理的废水不仅仅是来自居民的，而且来自沃州大学医院（CHUV）。先前有研究者证实了废水中抗生素耐药性的流行，因此，研究者们的目的是调查是否抗性基因也进入了环境之中，尤其是经过处理的污水中是否含有细菌的抗性耐药基因。相关成果刊登在了近日的国际杂志<em>Frontiers Microbiology</em>上。

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研究者使用传统的方法和精细的遗传分析方法，第一种样品测试程序依据瑞士标准，研究者的测定结果符合预期，在CHUV的废水中发现了高水平的耐药细菌。研究结果令人惊讶，经过废水处理厂之后，超过75%的细菌都被杀灭了，可是剩下的耐药菌株仍然可以在废水中繁殖，从而使得细菌水平升高。微生物学家Burgmann表示，经过 污水处理厂处理，细菌的抗性基因很有可能会进行转移，细菌间可以通过高水平的群体感应信号分子来转移移动的遗传元件，细菌吸纳抗性基因并不罕见，而且对细菌自身并不会产生任何危害。我们以前并不知道，湖水中的耐药基因的水平非常高，尤其是在沉积物中的耐药基因的水平和未处理过的污水中水平几乎一样。因此，耐药基因可以在致病菌之间相互转移，不光在湖水中是这样，在人体中，和抗生素耐药性相关的移动遗传元件也会通过喝水等过程进行转移。

研究者Nadine Czekalski表示，我们饮水的深井一般离污水排出点有3公里之遥，但是在水井周围的沉积物中研究者也发现了耐药基因的存在，尽管如此，我们也不必惊慌，湖中的水在进入饮水循环系统中必须经过严格的处理。但是研究者提醒大家仍需要谨慎，而且在研究者看来，政府应当介入此事，在处理污水的时候，应当加大措施，不仅仅出去微量污染物，而且也应当除去抗药性的微生物。而且对于医院的废水，必须经过分离严格处理。

<br/><strong>关于多重耐药性</strong><br/>


研究者用多重耐药菌来描述对多种抗生素均有抗性的细菌，这些细菌频繁接触多种抗生素以及重金属、消毒剂。环境性释放带来的多重耐药细菌的存在是我们必须关注的一个问题，从长远来讲，环境中这些耐药基因的流行性会增加，通过移动遗传元件转移耐药基因，这就增加了致病菌中携带耐药基因的风险，给公众的健康带来了巨大的威胁。 

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<a title="" href="http://dx.doi.org/doi:10.3389/fmicb.2012.00106" target="_blank">doi:10.3389/fmicb.2012.00106</a>
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<br/><strong>Increased levels of multiresistant bacteria and resistance genes after wastewater treatment and their dissemination into Lake Geneva, Switzerland</strong><br/>


Nadine Czekalski1*, Tom Berthold2, Serena Caucci2, Andrea Egli1 and Helmut Bürgmann1

At present, very little is known about the fate and persistence of multiresistant bacteria (MRB) and their resistance genes in natural aquatic environments. Treated, but partly also untreated sewage of the city of Lausanne, Switzerland is discharged into Vidy Bay (Lake Geneva) resulting in high levels of contamination in this part of the lake. In the present work we have studied the prevalence of MRB and resistance genes in the wastewater stream of Lausanne. Samples from hospital and municipal raw sewage, treated effluent from Lausanne’s wastewater treatment plant (WTP) as well as lake water and sediment samples obtained close to the WTP outlet pipe and a remote site close to a drinking water pump were evaluated for the prevalence of MRB. Selected isolates were identified (16S rRNA gene fragment sequencing) and characterized with regards to further resistances, resistance genes, and plasmids. Mostly, studies investigating this issue have relied on cultivation-based approaches. However, the limitations of these tools are well known, in particular for environmental microbial communities, and cultivation-independent molecular tools should be applied in parallel in order to take non-culturable organisms into account. Here we directly quantified the sulfonamide resistance genes sul1 and sul2 from environmental DNA extracts using TaqMan real-time quantitative PCR. Hospital sewage contained the highest load of MRB and antibiotic resistance genes (ARGs). Wastewater treatment reduced the total bacterial load up to 78% but evidence for selection of extremely multiresistant strains and accumulation of resistance genes was observed. Our data clearly indicated pollution of sediments with ARGs in the vicinity of the WTP outlet. The potential of lakes as reservoirs of MRB and potential risks are discussed.
<div><br/>来源：生物谷  </div>
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