Corpse Degradation of Farmed Fish Increases the Abundance of Antibiotic Resistance Genes but Exhibits the Temporal Stability

Abstract

Serious concerns have been raised regarding resistomes causing by corpse decomposition in the aquatic environment, which pose threats to the water environment and human health. However, antibiotic resistance genes (ARGs) in large-volume tap water and their temporal stability during corpse decay are poorly explored. Here, high-throughput quantitative polymerase chain reaction (HT-qPCR) and amplicon sequencing were applied to profile ARGs and bacterial communities in experimental and control groups containing 50 L of tap water at 7th, 15th and 100th day during corpse decomposition. We found that most of the ARGs in experimental groups had higher abundance compared with the control groups independent of time. And the absolute abundance of some ARGs in the carcass groups was even enriched by 259 to 413,640-folds. The tetracycline and beta-lactamase resistance genes of the experimental groups were obviously enriched compared with control groups, and the ARG profiles were convergent during different decay stages, which indicated the long-term persistence of ARGs. Treatment, dissolved oxygen (DO) and pH were three important factors determining ARG profiles during corpse decomposition. Twelve opportunistic pathogens, especially Burkholderia, Legionella and Halomonas, remarkably increased as decomposition proceeded. Network analysis showed that opportunistic pathogens were significantly associated with ARGs. Our results emphasize that corpse decay increases the abundance and diversity of ARGs in large-volume drinking water independent of time while exhibits temporal persistence of ARGs, thereby uncovering the harmful effects of animal cadavers. It also provides valuable suggestions for the risk assessment and management of source water caused by corpse decay.