ABSTRACT: Luminescent Vibrio harveyi is common in sea and estuarine waters. It produces several virulence factors and negatively affects larval penaeid shrimp in hatcheries, resulting in severe economic losses to shrimp aquaculture. Although V. harveyi is an important pathogen of shrimp, its pathogenicity mechanisms have yet to be completely elucidated. In the present study, isolates of V. harveyi were isolated and characterized from diseased Penaeus monodon postlarvae from hatcheries in Kerala, India, from September to December 2016. All 23 tested isolates were positive for lipase, phospholipase, caseinase, gelatinase and chitinase activity, and 3 of the isolates (MFB32, MFB71 and MFB68) showed potential for significant biofilm formation. Based on the presence of virulence genes, the isolates of V. harveyi were grouped into 6 genotypes, predominated by vhpA⁺ flaB⁺ ser⁺ vhh1^- luxR⁺ vopD^- vcrD⁺ vscN^-. One isolate from each genotype was randomly selected for in vivo virulence experiments, and the LD₅₀ ranged from 1.7 ± 0.5 × 10³ to 4.1 ± 0.1 × 10⁵ CFU ml^-1. The expression of genes during the infection in postlarvae was high in 2 of the isolates (MFB12 and MFB32), consistent with the result of the challenge test. However, in MFB19, even though all genes tested were present, their expression level was very low and likely contributed to its lack of virulence. Because of the significant variation in gene expression, the presence of virulence genes alone cannot be used as a marker for pathogenicity of V. harveyi.

中文翻译：

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黑虎虾对虾斑节对虾哈维弧菌毒力基因表达的体内和体外表达。

摘要：发光哈氏弧菌在海水和河口水域很常见。它会产生多种毒力因子，会对孵化场中的对虾幼体虾产生负面影响，给虾类养殖造成严重的经济损失。尽管哈维氏弧菌是虾的重要病原体，但其致病机理尚未完全阐明。在本研究中，从患病对虾斑节对虾分离并鉴定了哈维氏弧菌。2016年9月至2016年12月，来自印度喀拉拉邦孵化场的后幼虫。所有23种分离株的脂肪酶，磷脂酶，酪蛋白酶，明胶酶和几丁质酶活性均为阳性，其中3种分离株（MFB32，MFB71和MFB68）具有形成生物膜的潜力。 。基于毒力基因的存在，的菌株哈氏弧菌被分为6种基因型，由占优势VHP甲⁺ FLA乙⁺ SER ⁺ VHH 1 ^- 勒克司- [R ⁺ VOP d ^- VCR d ⁺ VSC ñ ^- 。从每种基因型中随机选择一个分离株用于体内毒力实验，LD ₅₀为1.7±0.5×10 ³至4.1±0.1×10 ⁵ CFU ml ^-1。两种分离株（MFB12和MFB32）在幼虫感染期间的基因表达较高，这与攻毒试验的结果一致。但是，在MFB19中，即使存在所有测试的基因，它们的表达水平仍然很低，并且可能导致其缺乏毒力。由于基因表达的显着变化，不能单独使用毒力基因作为哈维弧菌致病性的标志。