Distribution and influencing factors of antibiotic resistance genes of crayfish intestine. 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.

克氏原螯虾（Procambarus clarkii）是我国淡水小龙虾养殖中产量最高的品种，对其开展肠道微生物与抗生素抗性基因（antibiotic resistance genes, ARGs）的研究具有重要价值。然而，目前针对我国主要小龙虾养殖产区的相关研究尚不够全面，尤其是关于小龙虾肠道内高风险抗生素抗性基因的分布与特征的研究仍存在不足。本研究采用16S rRNA基因测序与高通量定量PCR技术，对采自7个主要小龙虾养殖省份共计40个养殖场的小龙虾肠道样本展开分析。研究结果显示，湖北省的抗生素抗性基因丰度最高。β-内酰胺酶类抗性基因的平均丰度最高，高于四环素类抗性基因。在高风险抗生素抗性基因中，ermB的丰度最高且分布范围最广。位于长江流域下游的江苏省，其小龙虾肠道内的高风险抗生素抗性基因平均丰度最高。水环境中部分抗生素抗性基因与总有机碳（total organic carbon, TOC）存在显著相关性。益生菌肠球菌（Enterococcus）在小龙虾肠道微生物群落中占据重要地位。然而，益生菌与多种可移动遗传元件（mobile genetic elements, MGEs）存在显著正相关，提示这些益生菌可能与抗生素抗性基因的传播过程密切相关。