Since 1997, cases of Vibrio parahaemolyticus-related gastroenteritis from the consumption of raw oysters harvested in Washington State have been higher than historical levels. These cases have shown little or no correlation with concentrations of potentially pathogenic V. parahaemolyticus (positive for the thermostable direct hemolysin gene, tdh) in oysters, although significant concentrations of tdh+ V. parahaemolyticus strains were isolated from shellfish-growing areas in the Pacific Northwest (PNW). We compared clinical and environmental strains isolated from the PNW to those from other geographic regions within the United States and Asia for the presence of virulence-associated genes, including the thermostable direct hemolysin (tdh), the thermostable-related hemolysin (trh), urease (ureR), the pandemic group specific markers orf8 and toxRS, and genes encoding both type 3 secretion systems (T3SS1 and T3SS2). The majority of clinical strains from the PNW were positive for tdh, trh, and ureR genes, while a significant proportion of environmental isolates were tdh+ but trh negative. Hierarchical clustering grouped the majority of these clinical isolates into a cluster distinct from that including the pandemic strain RIMD2210633, clinical isolates from other geographical regions, and tdh+, trh-negative environmental isolates from the PNW. We detected T3SS2-related genes (T3SS2β) in environmental strains that were tdh and trh negative. The presence of significant concentrations of tdh+, trh-negative environmental strains in the PNW that have not been responsible for illness and T3SS2β in tdh- and trh-negative strains emphasizes the diversity in this species and the need to identify additional virulence markers for this bacterium to improve risk assessment tools for the detection of this pathogen.
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机译:自1997年以来,消耗华盛顿州采集的生牡蛎引起的副溶血性弧菌引起的肠胃炎病例已高于历史水平。这些病例显示与牡蛎中潜在致病性副溶血弧菌(对热稳定的直接溶血素基因,tdh呈阳性)的浓度几乎没有相关性,尽管从中分离出了高浓度的tdh + sup>副溶血弧菌。西北太平洋地区的贝类生长区。我们比较了从PNW分离的临床和环境菌株与美国和亚洲其他地理区域的菌株之间是否存在毒力相关基因,包括热稳定的直接溶血素(tdh),热稳定的溶血素(trh),尿素酶(ureR),大流行人群特异性标记orf8和toxRS,以及编码两个3型分泌系统(T3SS1和T3SS2)的基因。来自PNW的大多数临床菌株对tdh,trh和ureR基因呈阳性,而很大一部分环境分离株为tdh + sup>但trh呈阴性。分层聚类将这些临床分离株中的大多数与包括大流行株RIMD2210633,其他地理区域的临床分离株以及tdh + sup>, trh em>-阴性环境的分离株不同与PNW隔离。我们在 tdh em>和 trh em>阴性的环境菌株中检测到T3SS2相关基因(T3SS2β)。 PNW中存在大量不引起疾病的 tdh em> + sup>, trh em>阴性环境菌株和中的T3SS2β > tdh em>-和 trh em>阴性菌株强调了该物种的多样性,并需要为该细菌鉴定其他毒力标记,以改进用于检测该病原体的风险评估工具。
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