引言：目前，关于废水处理厂（WWTP）向河流系统排放抗生素的规定很少，这使得地表水成为抗生素和抗生素抗性基因（ARGs）的潜在蓄水池。为了更好地了解影响ARGs在环境中命运的因素，并促进对抗生素耐药性在此类栖息地传播的监测，已经提出了几个指示基因，包括整合酶基因intI1和磺酰胺耐药性基因sul1和sul2。
方法：在这里，我们使用定量PCR和长读纳米孔测序来监测这些指示基因和ARGs的丰度，它们以1类整合子基因盒的形式存在于从原始水源到污水处理厂影响水的河流系统中。将ARG丰度与通过16S rRNA基因扩增子测序、常规水参数以及磺胺甲恶唑（SMX）、磺胺二甲嘧啶（SMZ）和磺胺嘧啶（SDZ）的浓度确定的微生物群落的动力学进行比较。
结果：我们的研究结果表明，污水处理厂污水是三种磺胺类药物的主要来源，SMX浓度最高（中位数为8.6 指示基因sul1、sul2和intI1的16S rRNA基因的中位相对丰度分别为0.55%、0.77%和0.65%。污水处理厂下游的水质不断改善，包括磺酰胺浓度降低，sul1和sul2丰度降低，1类整合子中ARG的数量和多样性降低。河流微生物群落在接收污水处理厂污水后部分恢复，并通过微生物组恢复模型进行巩固。令人惊讶的是，intI1的相对丰度比13增加了3倍 公里的河段，表明存在内部基因增殖。
讨论：我们没有发现任何证据表明，水生环境中少量的磺酰胺会刺激相应ARG的维持甚至传播。尽管如此，携带各种ARGs的1类整合子仍然存在13 污水处理厂下游km处。因此，限制携带ARG的微生物的释放对于限制抗微生物耐药性的环境传播可能比减少抗生素的ng/L浓度更为关键。
Introduction: Currently there are sparse regulations regarding the discharge of antibiotics from wastewater treatment plants (WWTP) into river systems, making surface waters a latent reservoir for antibiotics and antibiotic resistance genes (ARGs). To better understand factors that influence the fate of ARGs in the environment and to foster surveillance of antibiotic resistance spreading in such habitats, several indicator genes have been proposed, including the integrase gene intI1 and the sulfonamide resistance genes sul1 and sul2.

Methods: Here we used quantitative PCR and long-read nanopore sequencing to monitor the abundance of these indicator genes and ARGs present as class 1 integron gene cassettes in a river system from pristine source to WWTP-impacted water. ARG abundance was compared with the dynamics of the microbial communities determined via 16S rRNA gene amplicon sequencing, conventional water parameters and the concentration of sulfamethoxazole (SMX), sulfamethazine (SMZ) and sulfadiazine (SDZ).

Results: Our results show that WWTP effluent was the principal source of all three sulfonamides with highest concentrations for SMX (median 8.6 ng/l), and of the indicator genes sul1, sul2 and intI1 with median relative abundance to 16S rRNA gene of 0.55, 0.77 and 0.65%, respectively. Downstream from the WWTP, water quality improved constantly, including lower sulfonamide concentrations, decreasing abundances of sul1 and sul2 and lower numbers and diversity of ARGs in the class 1 integron. The riverine microbial community partially recovered after receiving WWTP effluent, which was consolidated by a microbiome recovery model. Surprisingly, the relative abundance of intI1 increased 3-fold over 13 km of the river stretch, suggesting an internal gene multiplication.

Discussion: We found no evidence that low amounts of sulfonamides in the aquatic environment stimulate the maintenance or even spread of corresponding ARGs. Nevertheless, class 1 integrons carrying various ARGs were still present 13 km downstream from the WWTP. Therefore, limiting the release of ARG-harboring microorganisms may be more crucial for restricting the environmental spread of antimicrobial resistance than attenuating ng/L concentrations of antibiotics.

https://www.frontiersin.org/articles/10.3389/fmicb.2023.1058350/full