城市河流异养菌耐药状况及微生物群落结构特征

为深入了解城市河流中细菌的耐药状况和微生物群落结构特征,在西安市浐河和灞河河段8个采样点以及某污水处理厂二级出水排放口采集水样,利用细菌培养技术、PCR检测和DGGE(变性梯度凝胶电泳)分析技术,对河流中异养菌耐药率、四环素抗性基因以及微生物群落结构进行研究. 结果表明:浐河和灞河水样中异养菌对SMZ(磺胺甲恶唑)、TET(四环素)、CIP(环丙沙星)和CTX(头孢噻肟)的平均耐药率分别为18.3%、6.2%、2.7%和1.3%,耐药率高低顺序与污水厂排放水中的异养菌相同. 城市河流中异养菌浓度与其耐药率并不存在显著的相关性. 与上游河段相比,污水厂排放口下游河段的异养菌浓度没有明显增加,但对多种抗生素的耐药率却有所升高. 浐河和灞河中四环素抗性基因主要是tetA和tetB,检出率分别为100%和75%,这意味着城市河流中异养菌对TET的耐药性可能主要通过编码外输泵蛋白的抗性机制来实现. 污水厂排放水进入城市河流,并未显著影响河流中的微生物群落结构,但却使某些原有的敏感物种消失,而病原菌或条件致病菌在邻近污水厂排放口的下游河段则有所增加. 

Antibiotic Resistance of Heterotrophic Bacteria and Characteristics of Microbial Community Structure in Urban Rivers in China

Abstract: In order to further understand the antibiotic resistance of bacteria and microbial community structure characteristics in urban rivers, water samples were collected from eight sites located in the Chanhe River and the Bahe River reaches and one outlet of a wastewater treatment plant in Xi''an City. Using bacterial culture, PCR detection and denaturing gradient gel electrophoresis analysis technology, the resistance rates of heterotrophic bacteria, tetracycline resistance genes and microbial community structure in urban rivers were investigated. The results showed that the average resistance rate of heterotrophic bacteria in various water samples from the Chanhe River and the Bahe Rivers to sulfamethoxazole, tetracycline, ciprofloxacin and cefotaxime were 18.3%, 6.2%, 2.7% and 6.2% respectively. The order of resistance rate of heterotrophic bacteria in urban river samples to four kinds of antibiotics was the same as that in the effluent discharged from wastewater treatment plant. There was no significant correlation between heterotrophic bacteria concentrations and their resistance rate in the urban river. Compared with the upper reaches of urban rivers, the concentration of heterotrophic bacteria in the lower reaches from wastewater treatment plant outlet did not increase significantly, while their resistance rate to several antibiotics increased. The main resistance genes to tetracycline were tetA (100% detection rate) and tetB (75% detection rate), showing that the tetracycline resistance of heterotrophic bacteria in urban rivers could be realized by alternations of the efflux-pump. Effluent discharge did not significantly affect the microbial communty structure in urban rivers, but caused the disappearance of some sensitive species and the increase of pathogenic bacteria or opportunistic pathogens in the downstream reaches neighboring outlet of the wastewater treatment plant.