Positive and negative selection towards tetracycline resistance genes in manure treatment lagoons
Positive and negative selection towards tetracycline resistance genes in manure treatment lagoons
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DOI：
10.1111/j.1365-2672.2012.05252.x
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发表时间：
2012-05-01
影响因子：
4
通讯作者：
Bridges, C.
中科院分区：
文献类型：
--
作者：
Barkovskii, A. L.;Manoylov, K. M.;Bridges, C.
目的：评价养猪场粪便处理泻湖对粪便和饲用四环素耐药基因(TRG)命运的影响。方法与结果：采集养猪场附近3个不同操作方式的养猪场饲料、粪便、泻湖液和泻湖沉积物样品，分析上游来源(饲料、粪便)和下游容器(泻湖液和沉积物)中16种TRG的存在和发生频率。在广泛使用抗生素的农场中观察到TRG发生率最高，而在不使用抗生素的农场中最低。研究表明，每个农场下游栖息地的TRG丰富度和多样性都有所下降。观察到的TRG分为两组，一组是上游和下游都能检测到的持久性基因，另一组是在上游栖息地检测到但在泻湖中检测不到的瞬时基因。定量聚合酶链式反应分析表明，暂时性和持续性TRG的上游浓度和丰度(以TRG/16S rRNA基因比值确定)相似；然而，前者在泻湖中被减弱到低于检测下限的水平，而后者类似于在其(主要)液相中放大100-1000倍，并在养殖场的粪便中也被检测到。结论：猪粪养殖中对粪便和饲料携带的TRG分别进行了正选择和负选择，分别导致了它们在这些环境中的增殖或衰减。本研究的意义和影响：研究揭示了猪场向环境排放抗生素耐药性基因与其在粪池中的正选择(定义为导致这些基因的增殖的影响)有关。
Aims: To evaluate the role of manure treatment lagoons of swine operations in the fate of faeces- and feed-borne tetracycline-resistant genes (TRG).Methods and Results: Samples of feed, faeces, lagoon liquid and lagoon sediment in farm's vicinity were collected at three swine operations varied on their operational practices and analysed on the presence and frequencies of incidence of sixteen TRG in upstream sources (feed, faeces) and downstream receptacles (lagoon liquid and sediments). The highest frequency of TRG incidence was observed in a farm with extensive antibiotic usage and the lowest in the antibiotic-free farm. The study revealed a decrease in TRG richness and diversity in the downstream habitats of each farm. The observed TRG diverged into two groups, the persistent genes that were detected both upstream and downstream, and the transient genes that were detected in the upstream habitats but became nondetectable in the lagoons. Quantitative PCR analysis revealed that upstream concentrations and abundances (determined as TRG/16S rRNA gene ratios) of transient and persistent TRG were similar; however, the former were attenuated in the lagoons to the levels below the detection limit, whereas the latter were similar to 100-1000 fold amplified in their (mostly) liquid phases and were also detected in farms' vicinities.Conclusion: Manure lagoons of swine operations imposed both positive and negative selection towards faeces-and feed-borne TRG that, respectively, caused either their proliferation or attenuation in those environments.Significance and Impact of the Study: The study reveals that discharge of antibiotic resistance genes from swine farms to the environment is linked to their positive selection (defined as an impact leading to proliferation of those genes) in manure lagoons.