中国北方典型流域水体中致病性弧菌的溯源与传播机制研究

The dissemination of pathogenic Vibrio spp. in a river often leads to communitive diarrhea events. In a typical river system of North China, the water flow is small and seawater backfilling is much severe. Therefore, pathogenic Vibrio spp. might transmit from upstream to downstream or disseminate from estuary to inland by seawater backfilling. To validate above hypothesis, we chose Hun-Tai River in Liaoning Province as a typical river system. Our previous study identified V. parahaemolyticus, V. mimicus and non-O1/O139 group Vibrio cholerae in several water sources along the Hun-Tai River. In this study, we will select 12 water sources along the Hun-Tai River and isolated pathogenic Vibrio spp. systematically. First of all, we will adopt MLST typing to identify the distribution of different STs along the Hun-Tai River. Afterward, we will select representative strains in different areas for whole-genome sequencing and tracking the sources of pathogens. Core genomic typing technique will be used to subtype pathogenic Vibrio spp. isolated from the river and identify their sources. At last, the genomic characteristics will be analyzed to reveal the spatiotemporal variations of the pathogenic Vibrio spp. genomes, which would unravel the distribution and transmission mechanism of different genotypes in the river based on the hydrographic features of Hun-Tai River. Combined with phenotypic tests regarding toxin genes and antibiotic resistance, our results will reveal their virulence features and evaluate their potential risk for public health. This study would provide valuable information for understanding the transmission mechanism of the pathogenic Vibrio spp. in a typical river system of North China and preventing their future epidemics.

致病性弧菌在特定流域的传播易引发群体性腹泻。中国北方流域具有水域流量小，海水倒灌严重等特点。因此，致病性弧菌在中国北方流域内除了自上游向下游的传播模式外，还可能沿河口向内陆逆向传播。为验证上述科学假设，前期工作以辽宁省浑太河流域为研究对象，在其多个水源中发现了副溶血性弧菌等三种致病性弧菌。本研究拟选择该流域上中下游12个地区的水源点监测致病性弧菌，首先采用MLST分型法对流域内致病性弧菌不同基因型的地理分布进行研究。随后采用核心基因组分型法，研究致病性弧菌的基因组进化关系，对流域内致病性弧菌进行基因组流行病学溯源，确定致病性弧菌的来源。最后通过时空进化关系分析，确定致病性弧菌不同克隆群在不同河流段中的分化时间；结合流域水文特征，推断副溶血性弧菌、拟态弧菌和非O1/O139群霍乱弧菌的传播机制；结合表型特征综合分析其毒力和耐药特征。本研究将揭示中国北方流域内致病性弧菌的传播机制并评估其危害。

致病性弧菌在特定地区水源中传入和扩散是其造成水产动物与人类感染的重要流行形式之一。本项目旨在阐明北方典型流域致病性弧菌的基因组流行病学特征，探明区域内致病性弧菌种群变化与播散特征。本项目先后对辽宁省浑太河流域、鸭绿江流域和天津河口地区的致病性弧菌进行了系统性环境监测，结果表明浑太河流域和鸭绿江流域均存在不同程度的海水倒灌问题，并造成了霍乱弧菌和副溶血弧菌由河口向内陆传播。采用多位点序列分型 (MLST)的方法，发现浑太河流域分离的副溶血性弧菌和霍乱弧菌分别可分为16个和4个ST (sequence type)型，而鸭绿江流域发现了副溶血性弧菌的5个ST型和霍乱弧菌的2个ST型。对2013年-2018年从天津河口地区分离的76株副溶血弧菌进行分型，共分为12个ST型，其中以ST1797、ST424、ST1、ST917a和ST122为主。选择代表性菌株进行全基因组测序，结果表明所有分离的副溶血弧菌均呈tlh阳性，tdh阴性，部分菌株trh阳性。另外，vvhA、pilA、viuB和rtxA均在3株创伤弧菌中检测到。对于霍乱弧菌，hlyA、rtxA和rtxC均呈阳性。除1株霍乱弧菌tcpA为阳性外，其余菌株均为阴性。随后的比较基因组学发现了在河口开放环境下，不同弧菌之间基因交换非常频繁，并发现了5类基因具有水平转移能力包括耐药基因、毒力基因、VI型或IV型分泌系统基因、生物膜形成相关基因和代谢相关基因。本项目对阐明北方典型流域致病性弧菌的种群演替、水平基因转移和毒力进化，具有重要意义。在本项目的资助下，项目完成人在国际学术期刊mSystems、Clinical Infectious Diseases、Water Research、Science of the Total Environment和Aquaculture等杂志上发表SCI论文13篇,中文核心期刊发表论文2篇，取得了预期成果，为进一步开展相关研究打下了基础。

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