Vibrio parahaemolyticus, a halophilic bacterium often found in the marine or estuarine environment is a well-known enteropathogen responsible for foodborne outbreaks associated with seafood. The pathogenic strains of V. parahaemolyticus are marked by the presence of thermostable direct hemoylsin (tdh) and/or TDH related hemolysin (trh) genes. This study aimed to investigate the prevalence and characteristics of potentially pathogenic V. parahaemolyticus in selected retail markets of Cochin, Kerala, along the south-western coast of the Indian subcontinent. One hundred samples collected from 10 retail markets were analyzed for the presence of pathogenic isolates of V. parahaemolyticus. Out of the 721 presumptive isolates, 648 were confirmed to be V. parahaemolyticus by toxR gene amplification, among which 29 were Kanagawa phenomenon (KP) positive. Among these potentially pathogenic isolates, 17 possessed the tdh gene whereas none of them had the trh gene. The faint amplification bands produced during the amplification of tdh gene from two isolates was confirmed by sequencing. Multiplex O serotyping identified O1 serotype as the most prevalent serotype among the 29 potentially pathogenic isolates. Further, studies on the pandemic nature of these isolates revealed that 14 of the 29 were positive for the PGS-PCR, whereas all the isolates were negative for GS-PCR and HU-α PCR. The antibiogram of the isolates revealed that three isolates had significant Multiple Antibiotic Resistance (MAR) index of 0.2 or above. Pathogenic isolates resistant to second, third and fourth generation Cephalosporins were found to be present in the seafood studied. The molecular fingerprinting studies using ERIC-PCR, and PFGE revealed that three of these isolates shared close genetic similarities with the clinical strains. The environmental and seafood isolates that produced faint amplification bands during the amplification of tdh gene suggests that the tdh gene often goes undetected in environmental isolates. The conventional methods used to identify the pathogenic V. parahaemolyticus would be good for clinical isolates, but a more elaborate method is recommended for the detection of tdh gene in environmental isolates. This is the first comprehensive study on pathogenic V. parahaemolyticus in Kerala, India and demonstrates for the first time, the isolation of potentially pathogenic V. parahaemolyticus, carrying tdh gene from seafood collected from retail markets in Kerala.

中文翻译：

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印度喀拉拉邦零售海鲜中副溶血性弧菌分离株的流行，毒力特征，AMR模式和遗传相关性。

副溶血性弧菌是一种常在海洋或河口环境中发现的嗜盐细菌，是引起与海鲜有关的食源性暴发的众所周知的肠病原体。副溶血性弧菌的致病性菌株的特征是存在热稳定的直接溶血素（tdh）和/或TDH相关溶血素（trh）基因。这项研究旨在调查印度次大陆西南沿海喀拉拉邦科钦的部分零售市场中潜在致病性副溶血性弧菌的流行情况和特征。分析了从10个零售市场收集的100个样品中副溶血性弧菌的病原菌。在721个推定分离株中，通过toxR基因扩增证实648个为副溶血性弧菌，其中29个为神奈川现象（KP）阳性。在这些潜在病原体中，有17个具有tdh基因，而没有一个具有trh基因。通过测序证实了从两个分离株扩增tdh基因期间产生的微弱扩增条带。多重O型血清分型将O1型血清型确定为29种潜在病原菌中最普遍的血清型。此外，对这些分离株的大流行性质的研究表明，在29株中有14株对PGS-PCR呈阳性，而所有分离株对GS-PCR和HU-αPCR均为阴性。分离株的抗菌谱显示，三个分离株的显着多重抗药性（MAR）指数为0.2或更高。研究海鲜中发现了对第二，第三和第四代头孢菌素具有抗性的病原菌。使用ERIC-PCR进行分子指纹研究 PFGE和PFGE揭示，其中三株与临床菌株具有相似的遗传相似性。在tdh基因扩增过程中产生微弱扩增条带的环境和海鲜分离株表明，在环境分离株中tdh基因经常未被发现。用于鉴定致病性副溶血性弧菌的常规方法对于临床分离株将是有益的，但是建议使用更复杂的方法检测环境分离株中的tdh基因。这是印度喀拉拉邦对致病性副溶血弧菌的首次全面研究，并首次证明了从喀拉拉邦零售市场采集的海鲜中携带tdh基因的潜在致病性副溶血性弧菌的分离。