Wild birds-the sentinel of antibiotic resistance for urban river: Study on egrets and Jinjiang river in Chengdu, China

Antibiotic resistance has become a comprehensive and complicated environmental problem. It is of great importance to effectively determine the abundance of various antibiotic resistance genes (ARGs) in the envi-ronment. Here, we attempted to find a practical method for monitoring environmental antibiotic resistance. The results of culture-based analysis of antibiotic resistance and metagenomic sequencing indicate that egrets inhabiting along the urban river (Jinjiang River) can be used as the sentinel of environmental antibiotic resis-tance. The antibiotic resistance in the environment fluctuated with time, while that in the wild bird was rela-tively stable. The network analysis based on metagenomic sequencing data gave the co-occurrence pattern of ARGs. The overall situation of the antibiotic resistance in the river was determined by quantifying several module hub genes of the co-occurrence network in river sediments. The temporal and spatial distribution of ARGs in Jinjiang River is highly correlated with that of human gut-specific bacteriophage (crAssphage), which indicates that one main source of the antibiotic resistance in the river is likely to be municipal sewage. The mobility potential of ARGs varying among different niches suggests the transmission direction of antibiotic resistance in the environment.