凡纳滨对虾不同生长阶段肠道可培养细菌耐药性研究

在凡纳滨对虾(Litopenaeus vannamei)养殖过程中多使用微生态制剂来调节水质，为避免破坏池塘菌群结构，很少使用抗生素。为了解凡纳滨对虾肠道细菌耐药性与不同生长阶段的关系，本研究选取江苏地区4种主要养殖模式凡纳滨对虾成虾和虾苗作为研究对象，利用K-B纸片法和qRT-PCR技术，研究对虾样本肠道可培养细菌对四环素等12种抗生素的耐药性和tetA等9种抗生素耐药基因(ARGs)的丰度。结果显示，不同养殖模式中的凡纳滨对虾肠道可培养细菌优势属为弧菌属(Vibrio)；成虾肠道内可培养细菌种类和数量较虾苗显著上升(P<0.05)，耐药菌(antibiotics resistant bacteria, ARB)占比降低，ARGs丰度显著下降(P<0.05)；不同养殖模式之间规律不明显。研究表明，各模式下成虾肠道细菌耐药性和ARGs丰度均低于虾苗，提示，养殖过程中通过施用微生态制剂来减少抗生素使用量的方法能降低凡纳滨对虾肠道可培养细菌的耐药性。

Study on Bacterial Resistance in Litopenaeus vannamei Intestinal Culturable Bacteria at Different Growth Stages

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.