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2021—2024年北京市某区腹泻病例分离副溶血弧菌病原特征分析

Etiological characteristics of Vibrio parahaemolyticus isolated from diarrhea cases in a district of Beijing, 2021-2024

    摘要
  • 摘要:
    目的 分析2021—2024年北京市某区腹泻病原学监测和2024年副溶血弧菌（VP）导致食源性疾病暴发相关资料和菌株资源，分析该区VP流行株及血清型演变规律。
    方法 收集2021—2024年该区腹泻监测病例粪便样本开展VP分离工作；另外收集2024年该地区经确认由VP引起的食源性疾病暴发事件中的病例、环境涂抹样本及可疑污染食品开展VP菌株分离工作。对所有菌株进行O和K抗原血清分型、tdh和trh毒力基因荧光聚合酶链式反应检测及全基因组测序。基于测序数据进行多位点序列分型、毒力与耐药基因检测，并构建基于核心基因组单核苷酸多态性的系统发育树（cgSNP）。
    结果 2021年—2024年该区散发腹泻病原学监测VP检出率为3.48%（45/1 292），O10:K4血清型占比75.56%（34/45），tdh+/trh− 型占比91.11%（41/45），ST3型占比86.67%（39/45）。2024年同地区另确认的6 起VP所致食源性疾病暴发事件，从事件关联病例粪便样本（病例株）、环境涂抹样本（环境株）及可疑污染食品（食品株）中共分离到VP34 株，病例株均为O10:K4血清型（18/18），食品株均为O1:K66血清型（6/6），环境株含7种血清型；ST3型占比64.71%（22/34）。所有菌株均携带t3ss1和mam7基因，tdh+株携带t3ss2基因。所有VP菌株均含blaCARD耐药基因。2株食品株tdh−/trh−VP携带qnrA4耐药基因。cgSNP聚类树显示tdh+与tdh−株形成独立分支，tdh+菌株所在分支中不同血清型菌株独立聚集成簇，不同年份菌株、暴发和散发监测菌株呈现交错分布，tdh+的O10:K血清型菌株单核苷酸多态性差异数介于0～20。
    结论 2021—2024年，北京市某区VP流行株以O10:K4血清型为主，属于ST3型，tdh/trh基因特征为tdh+/trh−，北京市以及附近更大区域范围内VP流行株可能都是遗传特征极为接近的单一VP克隆群。

     

    Abstract:
    Objective To analyze the etiological characteristics and serotype transition of Vibrio parahaemolyticus (VP) isolated from the etiological surveillance for diarrheal diseases during 2021-2024 and VP-associated foodborne disease outbreaks in 2024 in a district of Beijing.
    Methods Stool samples collected from diarrhea cases in surveillance during 2021-2024 were used for VP isolation. Additionally, samples from confirmed VP-associated foodborne outbreaks in this district during 2024, including clinical samples, environmental swabs, and suspected contaminated food samples, were collected for the isolation of VP. All the isolates underwent O and K antigen serotyping, fluorescence polymerase chain reaction (PCR) detection of tdh and trh virulence genes and whole-genome sequencing. Based on sequencing data, multilocus sequence typing, virulence and resistance gene screening were performed and a core-genome single nucleotide polymorphism (cgSNP)-based phylogenetic tree was constructed.
    Results From 2021 to 2024, the detection rate of VP in sporadic diarrhea cases was 3.48% (45/1 292) in etiological surveillance. The strains belonging to serotype O10:K4 accounted for 75.56% (34/45), while 91.11% of the strains (41/45) carried tdh+/trh− gene, and 86.67% of the strains (39/45) belonged to sequence type 3 (ST3). In 2024, six VP-associated foodborne outbreaks occurred in this district, in which 34 VP strains were isolated, including the strains from case stool samples, environmental swabs and suspected contaminated food samples. All the strains from the cases belonged to O10:K4 (18/18), all the strains from food samples belonged to O1:K66 (6/6), and environmental strains belonged to 7 serotypes. The strains belonged to ST3 accounted for 64.71% (22/34). All the strains carried t3ss1 and mam7 genes, while tdh+ strains also carried t3ss2 gene. All the VP strains carried blaCARB resistance gene. Two tdh−/trh− food strains carried qnrA4 resistance gene. The cgSNP phylogenetic tree showed that tdh+ and tdh− strains formed separate clades. In the tdh+ strains, different serotypes clustered independently. The strains isolated from different years, including the strains from outbreaks and the strains from sporadic cases in surveillance, were intermingled. The differences in single nucleotide polymorphism among tdh+ O10:K4 strains ranged from 0 to 20.
    Conclusions During 2021 - 2024, the predominant VP strain in this district of Beijing belonged to serotype O10:K4 and ST3, and carried tdh+/trh− gens. The VP strains isolated in Beijing and surrounding areas might be a single clone group with highly similar genetic characteristics.

     

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