The commercial channel catfish (Ictalurus punctatus) industry is adversely impacted by enteric septicemia of catfish (ESC), caused by the Gram‐negative enteric rod Edwardsiella ictaluri. In efforts to develop more effective management strategies, the use of a live‐attenuated E. ictaluri isolate as an oral vaccine was investigated. The utility and broad application of a vaccine is dependent on the protection offered against multiple field isolates. Immunization trials, followed by bacterial challenge with archived virulent E. ictaluri isolates from the catfish farming region of the southeastern United States, were conducted over a 3‐year period. These isolates were archived from 1993 to 2016 and included representatives from nonvaccinated and vaccinated populations of diseased channel catfish in Mississippi, an isolate from nonvaccinated hybrid catfish raised in Mississippi, and an isolate from nonvaccinated channel catfish from Alabama. Molecular characterization of the isolates revealed a high degree of genetic similarity evidenced by repetitive sequence‐mediated polymerase chain reaction (rep‐PCR) fingerprinting and virulence gene amplification, suggesting that the population of E. ictaluri within catfish aquaculture in Mississippi and Alabama has been genetically stable over time. Plasmid profiling revealed the existence of at least four distinct plasmids among field isolates. Nevertheless, the E. ictaluri vaccine protected fish against all isolates, irrespective of heterogeneous or homogeneous plasmid profiles. In addition, plasmid profiles were supported by antimicrobial sensitivity testing, indicating that the E. ictaluri vaccine strain does not carry natural or plasmid‐mediated multidrug resistance to the three antibiotics approved for use in U.S. food fish aquaculture. Challenge data from this study argue against the need for multivalent E. ictaluri vaccines to account for presumed antigenic or genetic variation among wild‐type E. ictaluri isolates as the vaccine was effective against all archived isolates.

中文翻译：

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口服递送的减毒爱德华氏菌活疫苗可有效保护channel鱼鱼种免受多种爱德华氏菌田间分离株的侵害

商业渠道cat鱼（Ictalurus punctatus）行业受到革兰氏阴性肠棒爱德华氏菌（Edwardsiella ictaluri）引起的cat鱼肠道败血症的影响。为了制定更有效的管理策略，研究了使用减毒活的大肠杆菌分离物作为口服疫苗的情况。疫苗的实用性和广泛应用取决于针对多种野外分离株的保护作用。进行免疫试验，然后用存档的剧毒大肠杆菌（E. ictaluri）进行细菌攻击从美国东南部的fish鱼养殖区进行了3年的分离。这些分离物的存档时间为1993年至2016年，包括密西西比州未接种疫苗和未接种疫苗的患病channel鱼种群的代表，密西西比州未接种的杂交hybrid鱼的分离株以及阿拉巴马州未接种疫苗的channel鱼的分离株。分离株的分子特征揭示了高度的遗传相似性，其通过重复的序列介导的聚合酶链反应（rep-PCR）指纹图谱和毒力基因扩增证明，表明了埃卡氏菌的种群随着时间的推移，密西西比州和阿拉巴马州cat鱼水产养殖业内的遗传稳定。质粒分析揭示了田间分离物中至少存在四个不同的质粒。然而，无论是异质质粒质粒还是同质质粒质粒，大肠杆菌疫苗都能保护鱼类免受所有分离物的侵害。此外，质粒图谱得到了抗菌素敏感性测试的支持，这表明埃塔库里埃希氏菌疫苗株对美国食用鱼养殖中使用的三种抗生素不具有天然或质粒介导的多药耐药性。这项研究的挑战性数据反对使用多价大肠杆菌疫苗来说明野生型中推测的抗原或遗传变异埃卡特氏大肠杆菌分离物，因为该疫苗对所有存档的分离物均有效。