Ecological niche adaptation of a bacterial pathogen associated with reduced zoonotic potential-猫眼课题宝

DOI：

10.1101/2020.09.09.288845

发表时间：

2020-09

期刊：

bioRxiv

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

Mark Kirkwood;P. Vohra;Matt Bawn;Gatan Thilliez;Hannah V. Pye;Jennifer Tanner;Cosmin Chintoan-Uta;Priscilla Branchu;L. Petrovska;Tim J Dallman;Neil Hall;Mark P. Stevens;Robert A. Kingsley

新细菌病原体的出现是对农业和食品安全的持续挑战。鼠伤寒沙门氏菌（S. Typhimurium）是全世界食源性疾病的主要原因，而猪是主要的人畜共患病宿主。鼠伤寒沙门氏菌噬菌体 U288 型和单相鼠伤寒沙门氏菌 (S. 4,[5],12:i:-) ST34 两种变体出现，在过去二十年中占英国猪分离株的大部分，但它们具有不同的宿主范围和食品安全风险。 ST34 占人类所有鼠伤寒沙门氏菌感染的 50% 以上，而 U288 占不到 2%。 U288 和 ST34 在鼠伤寒沙门氏菌中形成不同的系统发育簇，由其 5 Mbp 基因组内大约 600 个 SNP 定义。 U288 进化枝从 LT2 样祖先进化而来的特点是 AMR 基因的获得、毒力质粒 pU288-1 中的插入和删除以及多态性的积累，其中一些导致编码序列的截短。与 ST34 分离株相比，U288 分离株在干燥后表现出较低的生长率和活力，这些特征可能会影响通过食物链的传播。 U288 和 ST34 分离株在小鼠结肠炎模型中表现出不同的感染结果，并以影响疾病症状和器官分布的方式定植猪。 U288感染更多地在淋巴结中传播，而ST34在肠内容物中回收的数量更多。这些数据与鼠伤寒沙门氏菌 U288 对猪的适应进化一致，这可能决定了其人畜共患潜力的降低。重要性细菌病原体不断进化，以利用由于人类活动（包括农业、医疗或社会实践）而出现的新生态位。新病原体出现的后果可能会影响感染的结果以及对人类或动物健康的风险。基因组序列可以解析种群结构，识别进入新生态位时正在进化的变异，并查明潜在的功能分歧。我们报告了一种鼠伤寒沙门氏菌变种，它适应了一个独特的生态位，与同一猪群中流行的第二种鼠伤寒沙门氏菌变种所占据的生态位不同。适应伴随着表型和基因型的变化，这与流行病学记录中观察到的更具侵入性的生活方式和人畜共患病可能性的降低相一致。我们的研究结果表明，病原体基因型变异可能有助于估计人畜共患病的潜力和对牲畜福利的威胁。

The emergence of new bacterial pathogens is a continuing challenge for agriculture and food safety. Salmonella enterica serovar Typhimurium (S. Typhimurium) is a major cause of foodborne illness worldwide, with pigs a major zoonotic reservoir. Two variants, S. Typhimurium phage type U288 and monophasic S. Typhimurium (S. 4,[5],12:i:-) ST34 emerged and have accounted for the majority of isolates from pigs in the UK in the past two decades, but have distinct host range and risk to food safety. ST34 accounts for over 50% of all S. Typhimurium infections in people while U288 less than 2%. U288 and ST34 form distinct phylogenetic clusters within S. Typhimurium, defined by approximately 600 SNPs within their 5 Mbp genomes. Evolution of the U288 clade from an LT2-like ancestor was characterised by the acquisition of AMR genes, insertions and deletions in the virulence plasmid pU288-1, and the accumulation of polymorphisms, some of which resulted in truncation of coding sequences. U288 isolates exhibited lower growth rate and viability following desiccation compared to ST34 isolates, characteristics that could affect transmission through the food chain. U288 and ST34 isolates exhibited distinct outcomes of infection in the murine model of colitis, and colonised pigs in a manner that affected the disease symptoms and distribution in organs. U288 infection was more disseminated in the lymph nodes while ST34 were recovered in greater numbers in the intestinal contents. These data are consistent with the evolution of S. Typhimurium U288 adaptation to pigs that may determine their reduced zoonotic potential. Importance Bacterial pathogens continually evolve to exploit new ecological niches as they emerge due to human activity including agricultural, medical or societal practice. The consequences of the emergence of new pathogens may affect outcome of infection and risk to human or animal health. Genome sequence can resolve the population structure, identify variants that are evolving as they enter a new niche, and pinpoint potential functional divergence. We report a variant S. Typhimurium that adapted to a unique niche distinct to that occupied by a second S. Typhimurium variant circulating in the same pig populations. Adaptation was accompanied by phenotypic and genotypic changes consistent with a more invasive lifestyle and a decreased zoonotic potential observed in the epidemiological record. Our findings suggest that pathogen genotypic variation may be useful in estimating zoonotic potential and threat to livestock welfare.

Ecological niche adaptation of a bacterial pathogen associated with reduced zoonotic potential

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