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Comparison of Yersinia pestis from rat buboes and laboratory cultures

ABSTRACT: Yersinia pestis causes bubonic plague in humans and rats. The disease is characterized by an enlarged, painful lymph node, termed a bubo, that develops following bacterial dissemination from an intradermal flea bite injection site. In susceptible animals, the bacteria quickly overcome host innate immune defenses in the lymph node, spread systemically through the blood, and produce fatal sepsis 1,2. At the terminal stage of disease, the bubo contains massive numbers of extracellular bacteria, necrotic lymphoid tissue, hemorrhage, and fibrin 2. The extreme virulence of Y. pestis has been largely ascribed to its ability to avoid innate immunity by preventing phagocytosis, selectively killing immune cells, and down regulating the proinflammatory response 3. Here we report that two innate immune effector mechanisms are generated during bubonic plague in the rat: iron limitation and nitrosative stress. The expression of nitric oxide synthase (iNOS) by rat polymorphonuclear neutrophils (PMNs) was induced in the bubo, and mutation of the Y. pestis hmp gene, which encodes a flavohemoglobin important for resistance to nitric oxide (NO), attenuated virulence. Thus, although Y. pestis avoids uptake and intracellular killing by phagocytes, it still encounters innate immune effector molecules, particularly phagocyte-derived reactive nitrogen species, in the extracellular environment of the bubo. Keywords: repeat

ORGANISM(S): Coxiella burnetii Yersinia pestis Streptococcus pyogenes Staphylococcus aureus Chlamydia trachomatis Borreliella burgdorferi

PROVIDER: GSE3793 | GEO | 2006/07/28

SECONDARY ACCESSION(S): PRJNA93993

REPOSITORIES: GEO

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Project description:Yunnan Province, China is thought to be the original source of biovar Orientalis of Yersinia pestis, the causative agent of the third plague pandemic that has spread globally since the end of the 19th century. Although encompassing a large area of natural plague foci, Y. pestis strains have rarely been found in live rodents during surveillance in Yunnan, and most isolates are from rodent corpses and their fleas. In 2017, 10 Y. pestis strains were isolated from seven live rodents and three fleas in Heqing County (HQ) of Yunnan. These strains were supposed to have low virulence to local rodents Eothenomys miletus and Apodemus chevrieri because the rodents were healthy and no dead animals were found in surrounding areas, as had occurred in previous epizootic disease. We performed microscopic and biochemical examinations of the isolates,and compared their whole-genome sequences and transcriptome with those of 10 high virulence Y. pestis strains that were isolated from the adjacent city (Lijiang). We analyzed the phenotypic, genomic, and transcriptomic characteristics of live rodent isolates. The isolates formed a previously undefined monophyletic branch of Y. pestis that was named 1.IN5. Six SNPs, two indels, and one copy number variation were detected between live rodent isolates and the high virulence neighbors. No obvious functional consequence of these variations was found according to the known annotation information. Among the genes that were differentially expressed between the live rodent isolates and their high virulence neighbors, we detected five iron transfer-related genes that were significantly up-regulated in live rodent isolates compared with high virulence isolates (|log2 (FC) | >1, p.adjust <0.05), indicating these genes may be related to the low-virulence phenotype. The novel genotype of Y. pestis reported here provides further insights into the evolution and spread of plague as well as clues that may help to decipher the virulence mechanism of this notorious pathogen.

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Comparison of Yersinia pestis from rat buboes and laboratory cultures

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