Distribution and influencing factors of antibiotic resistance genes of crayfish intestine

Crayfish (Procambarus clarkii) is the most productive freshwater crayfish in crayfish culture in China, and it is valuable to investigate the gut microbes of Crayfish as well as antibiotic resistance genes (ARGs). However, there are poorly comprehensive studies on the major crayfish farms in China, especially on the distribution and characteristics of high-risk ARGs in the crayfish gut. Here, we employed 16S rRNA gene sequencing and high-throughput quantitative PCR techniques to study crayfish intestine collected from a total of 40 farms in seven major crayfish farming provinces. The results showed that the highest abundance of ARGs was detected in Hubei Province. Beta-lactamase resistance genes had the highest mean abundance, superior to tetracycline resistance genes. High-risk ARGs: ermB had the highest abundance and the widest distribution. The highest mean abundance of high-risk ARGs was found in the crayfish gut from Jiangsu Province, which is situated in the downstream Yangtze River basin. There was a significant correlation between several ARGs and TOC in the aquatic environment. The probiotic Enterococcus occupied an important position in the crayfish gut microbial community. Nevertheless, there was a significant positive correlation between probiotics and several MGEs, implying that these probiotics may be closely associated with the spread of ARGs.