Genomic comparison in Vibrio parahaemolyticus strains by comparative genomic hybridization.. Vibrio parahaemolyticus

Vibrio parahaemolyticus is a Gram-negative marine bacterium. A limited population of the organisms causes acute gastroenteritis in humans. Almost all of the clinical V. parahaemolyticus isolates exhibit a beta-type hemolysis on Wagatsuma agar, known as the Kanagawa phenomenon (KP). KP is induced by the thermostable direct hemolysin (TDH) produced by the organism, and has been considered a crucial marker to distinguish pathogenic strains from non-pathogenic ones. Since 1996, so-called “pandemic clones”, the majority of which belong to serotype O3:K6, have caused worldwide outbreaks of gastroenteritis. In this study, we used a DNA microarray constructed based on the genome sequence of a pandemic V. parahaemolyticus strain RIMD2210633 to examin the genomic composition of 22 strains of V. parahaemolyticus, including both pathogenic (pandemic as well as non-pandemic) and non-pathogenic strains. Over 85% of the RIMD2210633 genes were conserved in all the strains tested. Many of variably present genes formed gene clusters on the genome of RIMD2210633 and were probably acquired through lateral gene transfer. At least 70 genes over 10 loci were specifically present in the pandemic strains when compared with any of the non-pandemic strains, suggesting that the difference between pandemic and non-pandemic strains is not due to a simple genetic event. Only the genes in the 80-kb pathogenicity island (Vp-PAI) on chromosome II, including two tdh genes and a set of genes for the Type III secretion system, were detected only in the KP-positive pathogenic strains. These results strongly suggest that acquisition of this Vp-PAI was crucial for the emergence of V. parahaemolyticus strains that are pathogenic for humans. Keywords: comparative genomic hybridization, CGH Overall design: Total 66 test samples were analyzed. Genomic DNA from each test strain and a reference strain (RIMD2210633) were labeled with Cy3 and Cy5, respectively, and were cohybridized on a single array. Labeling and hybridization were performed three times independently.

副溶血性弧菌（Vibrio parahaemolyticus）是一种革兰氏阴性海洋细菌。该菌的有限种群可引发人类急性胃肠炎。几乎所有临床分离的副溶血性弧菌菌株在和泉氏琼脂（Wagatsuma agar）上均表现出β型溶血现象，即所谓的神奈川现象（Kanagawa phenomenon，KP）。KP由该菌产生的耐热直接溶血素（thermostable direct hemolysin，TDH）诱导，一直被视为区分致病性与非致病性菌株的关键标志。自1996年以来，以血清型O3:K6为主体的所谓“流行克隆”已引发全球范围内的胃肠炎暴发。本研究基于流行性副溶血性弧菌菌株RIMD2210633的基因组序列构建DNA微阵列（DNA microarray），对22株副溶血性弧菌的基因组组成进行分析，涵盖致病性（包括流行株与非流行株）与非致病性菌株。在所有检测菌株中，RIMD2210633超过85%的基因均保守存在。大量可变存在的基因在RIMD2210633的基因组上形成基因簇，推测通过水平基因转移（lateral gene transfer）获得。与所有非流行株相比，流行株至少在10个基因位点上特异性携带至少70个基因，这表明流行株与非流行株之间的差异并非由单一简单遗传事件导致。仅在染色体II上的80kb致病岛（Vp-PAI）中的基因，包括2个tdh基因以及一套III型分泌系统相关基因，仅在KP阳性致病性菌株中被检测到。上述结果强烈提示，该Vp-PAI的获得是引发人类致病的副溶血性弧菌菌株出现的关键因素。关键词：比较基因组杂交（comparative genomic hybridization，CGH）
整体实验设计：共分析66份检测样本。将各待测菌株与参考菌株（RIMD2210633）的基因组DNA分别以Cy3与Cy5标记，随后共同杂交至单张微阵列芯片上。标记与杂交实验独立重复三次。