A fascinating finding: The application of traditional Chinese medicine in aquaculture prevents the spread and diffusion of antibiotic resistance genes among gut microbes

Currently, the spread and proliferation of antibiotic resistance genes (ARGs) is of great concern due to the overuse of antibiotics, especially oxytetracycline (OTC), in aquaculture. Traditional Chinese medicine (TCM) has been widely used in aquaculture because of its advantages in improving the intestinal flora. However, there is a lack of direct evidence on whether TCM impacts antibiotic resistance in aquatic environments. In this article, a short-term simulated cultivation microcosm was established to investigate the ARGs distribution and microbial community composition in the gut of fish exposed to OTC and five TCMs (Emodin, Matrine, Berberin, Andrographolide and Astragalus Polysacharin) alone or in combination using 16S rRNA gene sequencing and high-throughput quantitative PCR. The results showed that TCM alone did not significantly increase the abundance of ARGs, but ARGs abundance increased when a TCM was combined with OTC, and there was no significant interaction effect between any of the TCMs and OTC (P > 0.05). Principal component analysis indicated that OTC had a stronger effect on gut resistomes than the TCMs. TCM exposure increased the ratio of beneficial intestinal bacteria (Firmicutes to Bacteroidetes), while OTC decreased this ratio. β-diversity analysis showed that TCM had a smaller effect on the intestinal microbiome than OTC. The host network of ARGs and microorganisms showed that Enterobacter, Aeromonas, and Niveibacterium may be hosts of ARGs and mobile genetic elements (MGEs). Variation partitioning analysis suggested that the effects of MGEs accounted for 17.8% and 7.1% of the variation in the ARG spectrum in the TCM and co-exposure treatment groups, respectively. Overall, this study indicates that the risk of developing and spreading ARGs in the gut environment under exposure to TCMs is lower than that under antibiotics exposure; thus, TCM may provide a solution for antibiotic-free aquaculture in the future.