Abstract:Litopenaeus vannamei culturing industry is an important part of the rural economy in coastal areas. With the development of the shrimp farming industry, diseases breakout frequently. Antibiotic overuse can lead to bacterial antibiotic resistance and antibiotic resistance genes (ARGs). These then threatens human health and safety. Therefore, the evaluation of bacterial antibiotic resistance phenotypes and antibiotic ARG abundance can help to understand antibiotic pollution in specific areas. According to our preliminary investigation, more probiotics were used during L. vannamei culturing in Jiangsu Province. In order to avoid damaging the microbial community structure in ponds, less antibiotics were used during shrimp farming. To understand the relationship between bacterial resistance in L. vannamei intestinal culturable bacteria and different growth stages, four main culture models of L. vannamei in Jiangsu Province were selected as research objects. This study investigated the bacterial resistance to 12 antibiotics (tetracycline, doxycycline, fluorobenicol, chloramphenicol, sulfamethoxazole, cotrimoxazole, neomycin, gentamicin, ciprofloxacin, norfloxacin, ceftriaxone, and cefotaxime) and the abundance of nine ARGs (tetA, tetG, qnrA, qnrS, cmle3, floR, aadA, sul1, and sul2) of the intestinal culturable bacteria in samples using the K-B disc diffusion method and qRT-PCR technology. The results showed that Vibrio was the dominant bacterial genus among the shrimp intestinal culturable bacteria in different aquaculture models. The species and quantity of culturable bacteria in adult shrimp intestines increased significantly compared to those in post-larvae intestines (P<0.05). The proportion of antibiotic resistant bacteria decreased. The abundance of ARGs declined significantly (P<0.05). No obvious regularity was observed among the different aquaculture models. The antimicrobial resistance and abundance of ARGs in the intestinal bacteria of adult shrimp were lower than those in juvenile shrimp under different aquaculture patterns, indicating that reducing the use of antibiotics by administering probiotics may reduce the resistance of culturable bacteria in the intestinal tract of L. vannamei. In future research, the differences in the bacterial antibiotic resistance and ARG abundance in the intestinal tract of L. vannamei under different aquaculture models can be further explored by combining the methods of metagenomics.
