摘要

废水排放物增加了接收河流的营养负荷，同时引入了大量的人为化学污染物，挑战了居民的水生（微）生物群。解决这两种压力源及其潜在相互作用对细菌群体中抗生素抗性基因传播的影响需要高度控制的操纵性实验。在这项工作中，我们调查了营养素（低，中，高浓度）和新出现的污染物（环丙沙星，红霉素，磺胺甲恶唑，双氯芬酸和对羟基苯甲酸甲酯）混合物对细菌组成，丰度和抗生素耐药性在人造溪流中生长的生物膜轮廓。特别是，我们调查了这种联合应激对编码对环丙沙星（qnrS），红霉素（ermB），磺胺甲恶唑（sul1和sul2）以及1类整合子 - 整合酶基因（intI1）耐药性的基因的影响。在研究期间，只有在所有处理中检测到对磺酰胺（sul1和sul2）和intI1基因具有抗性的基因。此外，暴露于新出现的污染物的细菌群落显示出比未暴露的更高的sul1和intI1基因的拷贝数，而营养物质修饰并不影响它们的丰度。然而，暴露于新出现的污染物和高营养浓度（分别为1,25和1mgL-1的磷酸盐，硝酸盐和铵）的细菌群体显示出对sul1和intI1基因丰度的最高增加，因此表明一个因子协同作用两种压力源的影响。由于没有任何处理引起细菌群落组成的显着变化，所以社区内的sul1和intI1基因的富集是由它们在营养物和新出现的污染物施加的联合压力下的传播引起的。据我们所知，这是第一项研究，证明在控制条件下营养物质对流化床生物膜中抗生素抗性基因的维持和传播的贡献。我们的结果还强调，营养物质可以增强新兴污染物对抗生素耐药性传播的影响。

Wastewater effluents increase the nutrient load of receiving streams while introducing a myriad of anthropogenic chemical pollutants that challenge the resident aquatic (micro)biota. Disentangling the effects of both kind of stressors and their potential interaction on the dissemination of antibiotic resistance genes in bacterial communities requires highly controlled manipulative experiments. In this work, we investigated the effects of a combined regime of nutrients (at low, medium and high concentrations) and a mixture of emerging contaminants (ciprofloxacin, erythromycin, sulfamethoxazole, diclofenac, and methylparaben) on the bacterial composition, abundance and antibiotic resistance profile of biofilms grown in artificial streams. In particular, we investigated the effect of this combined stress on genes encoding resistance to ciprofloxacin (qnrS), erythromycin (ermB), sulfamethoxazole (sul1 and sul2) as well as the class 1 integron-integrase gene (intI1). Only genes conferring resistanceto sulfonamides (sul1 and sul2) and intI1 gene were detected in all treatments during the study period. Besides, bacterial communities exposed to emerging contaminants showed higher copy numbers of sul1 and intI1 genes than those not exposed, whereas nutrient amendments did not affect their abundance. However, bacterial communities exposed to both emerging contaminants and a high nutrient concentration (1, 25 and 1 mg L-1 of phosphate, nitrate and ammonium, respectively) showed the highest increase on the abundance of sul1 and intI1 genes thus suggesting a factors synergistic effect of both stressors. Since none of the treatments caused a significant change on the composition of bacterial communities, the enrichment of sul1 and intI1 genes within the community was caused by their dissemination under the combined pressure exerted by nutrients and emerging contaminants. To the best of our knowledge, this is the first study demonstrating the contribution of nutrients on the maintenance and spread of antibiotic resistance genes in streambed biofilms under controlled conditions. Our results also highlight that nutrients could enhance the effect of emerging contaminants on the dissemination of antibiotic resistance.

https://www.ncbi.nlm.nih.gov/pubmed/29573631