PDF(Pubmed)
Abstract：
In this study, V. gigantis strain C24 was isolated from cases of winter mortalities of hatchery-reared European seabass (Dicentrarchus labrax) broodstock in Türkiye. The first mortalities were reported in September 2016 and occurred annually in early autumn/late winter until the end of February 2019, when 15% of accumulated mortality was recorded. Diseased moribund fish exhibited general septicemic signs, including dermal ulcerations with hemorrhagic margins, distended abdomens, and hemorrhages below the pectorals, pelvic fins, and at the operculum. Postmortem findings showed congestion in several internal organs, hemorrhagic ascitic fluid, and congested prolapsed anal openings. The representative bacterial isolate V. gigantis strain C24 was characterized as Gram-negative, motile, nitrite-producing, and as vibrio static agent O/129-sensitive. The full-length 16S rRNA sequence (Accession No. ON778781) and gyrB gene sequence (Accession No. ON792326) of the C24 strain showed high similarity to V. gigantis strains. Moreover, the whole-genome average nucleotide identity (ANI) values (ANI > 97.7%) against four V. gigantis strains above the species demarcation limit unambiguously identified the C24 isolate as a member of this species. A preliminary virulence-gene analysis showed that the V. gigantis isolate C24 encoded at least three exotoxins, including two aerolysins and a thermolabile hemolysin. The experimental infection showed that the C24 isolate exhibited low to moderate virulence in experimentally infected European seabass juveniles. Interestingly, antimicrobial susceptibility testing revealed that the C24 isolate was susceptible to nalidixic acid, ciprofloxacin, and several other antibiotics but resistant to tilmicosin, kanamycin, streptomycin, and ampicillin. To our knowledge, this study is the first to report that V. gigantis could be considered an emerging bacterial pathogen in Türkiye, and it may threaten the international European seabass production.
摘要：
在这项研究中,V.gigantis菌株C24是从Türkiye孵化场饲养的欧洲鲈鱼（Dicentrarchuslabrax）亲鱼冬季死亡病例中分离出来的。首次死亡报告于2016年9月，每年发生在初秋/晚冬，直到2019年2月底，当时记录的累计死亡率为15％。患病的垂死鱼表现出一般的败血症症状，包括皮肤溃疡与出血边缘，腹部扩张，胸骨下面的出血，骨盆鳍,在管盘上。验尸结果显示几个内脏器官充血，出血性腹水,和肛门开口充血。代表性细菌分离株巨大弧菌菌株C24的特征为革兰氏阴性，能动,亚硝酸盐产生，并作为弧菌静电剂O/129敏感。全长16SrRNA序列(登录号ON778781)和gyrB基因序列(登录号C24菌株的ON792326）显示出与巨大弧菌菌株的高度相似性。此外，针对4个高于种界界限的大弧菌菌株的全基因组平均核苷酸同一性(ANI)值(ANI>97.7%)明确地将C24分离株鉴定为该物种的成员.初步的毒力-基因分析显示，巨大弧菌分离株C24编码至少三种外毒素，包括两种气溶素和一种不耐热溶血素.实验感染表明，C24分离株在实验感染的欧洲鲈鱼幼鱼中表现出低至中等的毒力。有趣的是,抗菌药物敏感性试验显示，C24分离株对萘啶酸敏感，环丙沙星,和其他几种对替米考星有抗药性的抗生素，卡那霉素,链霉素,还有氨苄青霉素.据我们所知,这项研究首次报道了V.gigantis可以被认为是Türkiye的新兴细菌病原体，它可能会威胁到国际欧洲的鲈鱼生产。
