Occurrence and temporal variation of antibiotic resistance genes (ARGs) in shrimp aquaculture: ARGs dissemination from farming source to reared organisms.

Considerable attention has been paid to the occurrence and abundance of antibiotic resistance genes (ARGs) in aquatic environments. However, the temporal variation and dissemination of ARGs in aquaculture environments and reared organisms need further study. This study investigated the abundance and diversity of ARGs and bacterial community in water source, shrimp pond water, sediment, and shrimps during the rearing period in Pearl River Delta region, South China. The results showed that sul1, qnrD, cmlA, and floR were the predominant ARGs in the aquaculture samples. A trend of decreasing abundance of ARGs was observed for pond water samples during the rearing period, whereas an increasing trend was observed in the sediment and shrimp samples. The total concentration of ARGs in water source was significantly higher than that in shrimp pond water (p<0.05). A significant negative correlation was found between the total concentrations of ARGs in pond waters and sediments (p<0.01). The total abundances of ARGs in intestinal tract of adult shrimps were 4.48-19.0 times higher than those in juvenile shrimps. Similar to water source and pond water, cmlA and sul1 were the predominant ARGs in shrimp intestinal tract. The bacterial community in the shrimp intestinal tract changed greatly from juvenile to adult. The results of the present study indicated that the abundances of ARGs in aquaculture varied temporally during the rearing period. Water source was an important medium disseminating ARGs to the aquaculture environments and reared organisms. Sul1 could be used as a potential indicator for ARGs in both water and sediment in aquaculture in the estuary of the Pearl River Delta, South China. This study represents a case study for the temporal variation of abundance and dissemination of ARGs in aquaculture and is a reference for potential risks to food safety and human health.