Abstract：
Antibiotic resistance genes (ARGs) are abundantly shed in feces. Thus, it is crucial to identify their host sources so that ARG pollution can be effectively mitigated and aquatic ecosystems can be properly conserved. Here, spatiotemporal variations and sources of ARGs in the Longjiang watershed of South China were investigated by linking them with microbial source tracker (MST) indicators. The most frequently detected ARGs (>90%) were sulI, sulII, blaTEM, tetW, ermF, and the mobile element intI1. Spatial distribution analyses showed that tributaries contributed significantly more sulI, sulII, and ermF contamination to the Longjiang watershed than the main channel. MST indicator analysis revealed that the Longjiang watershed was contaminated mainly by human fecal pollution. Livestock- and poultry-associated fecal pollution significantly declined after the swine fever outbreak. The occurrence of most ARGs is largely explained by human fecal pollution. In contrast, pig fecal pollution might account for the prevalence of tetO. Moreover, combined human-pig fecal pollution contributed to the observed blaNDM-1 distribution in the Longjiang watershed. Subsequent analysis of the characteristics of MST markers disclosed that the relatively lower specificities of BacHum and Rum-2-Bac may lead to inaccurate results of tracking ARG pollution source. The present study determined spatiotemporal variations and ARG origins in the Longjiang watershed by combining MST markers. It also underscored the necessity of using multiple MST markers simultaneously to identify and characterize ARG pollution sources accurately.
摘要：
抗生素抗性基因(ARGs)在粪便中大量脱落。因此，确定其宿主来源至关重要，以便有效减轻ARG污染并适当保护水生生态系统。这里,通过将其与微生物源跟踪器（MST）指标联系起来，研究了华南龙江流域ARG的时空变化和来源。最常见的ARGs(>90%)是sulI，sulII,blaTEM,tetW,ermF,和移动元件intI1。空间分布分析表明，支流贡献了更多的sulI，sulII,和ermF污染对龙江流域的影响比主要河道大。MST指标分析表明，龙江流域主要受到人类粪便污染。猪瘟爆发后，与家禽和家禽相关的粪便污染显着下降。大多数ARGs的发生主要是由于人类粪便污染。相比之下,猪粪便污染可能是tetO流行的原因。此外，在龙江流域观察到的blaNDM-1分布是人猪粪便污染的原因。随后对MST标记特征的分析表明，BacHum和Rum-2-Bac的特异性相对较低，可能导致跟踪ARG污染源的结果不准确。本研究通过结合MST标记确定了龙江流域的时空变化和ARG起源。它还强调了同时使用多个MST标记以准确识别和表征ARG污染源的必要性。
