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Yersinia pesti is a gram-negative bacterium belonging to the genus of Enterobacteriaceae, which was first isolated and identified by Alexander Yersin during the pestis in Hong Kong in 1894. The bacterium is transmitted through rat flea bites or aerosols, causing glandular pestis, pulmonary pestis and septicemia pestis. The mortality rate before treatment is 75% -100%. It carries pathogenic components such as capsule FI antigen, virulence V/W antigen, and mouse toxin, and can survive for several months in cold environments, with strong infectivity. In history, the bacterium caused three world pandemics: the Justinian plague in the 6th century, the Black Death in Europe in the 14th century, and the Oriental pestis at the end of the 19th century. In 2014, scholars extracted DNA from medieval remains and confirmed that it is the common ancestor of modern strains. The prevention and control measures include rodent and flea control, vaccination, and the use of antibiotics such as streptomycin.
Figure 1. Yersinia Pestis. (Easterday W R, et al, 2012)
Yersinia Pestis is a short gram-negative coccobacterium. The newly isolated strains are stained with methylene blue or Giemsa, showing strong staining at both ends and capsule (or envelope). In the lesion specimen and primary culture, it appears oval shaped. Growing in short chain arrangement in liquid culture medium. Aerobic and facultative anaerobic bacteria are best isolated at a temperature of 27-28 ℃. For initial isolation, animal blood, sodium sulfite, and other substances should be added to the culture medium to promote growth. After 48 hours of cultivation at 28 ℃ on a blood plate, the bacteria will grow into opaque, central raised, non hemolytic, and border like colonies, which are characteristic of this bacterium. After 24 hours of incubation in liquid medium, a flocculent precipitate gradually forms. Within 48 hours, a thin bacterial film is formed on the surface of the liquid, and vertical hyphae grow from the film to the bottom of the tube in the form of stalactites.
Figure 2. Structure of Yersinia Pestis. (Sebbane F, et al, 2020)
After contact with host cells, pestis pestis will deploy its T3SS, which is a molecular syringe that can directly inject Yersinia exoproteins (Yops) into the cytoplasm of immune cells, mainly macrophages, neutrophils and dendritic cells. These effectors coordinate to release key host defense pathways by targeting specific signaling molecules and cytoskeletal components:
| Inspection Method | Details |
| Phagocytosis and Destruction of Innate Immunity | YopH is a potent protein tyrosine phosphatase. It dephosphorylates key adhesive spot proteins, including p130Cas, focal adhesion kinase (FAK), and Pyk2. This effect disrupts the necessary cytoskeleton structure for phagocytosis, effectively paralyzing the phagocytic mechanism of macrophages and neutrophils. Meanwhile, YopE acts as a GTPase activator protein (GAP) for Rho family GTPases (RhoA, Rac1, Cdc42). By inactivating these molecular switches, YopE induces the breakdown of the actin cytoskeleton, further blocking phagocytic uptake and cell migration. |
| Inhibition of Proinflammatory Signals | YopJ (also called YopP in other species of pestis pestis) acetylated MAP kinases (MAP2Ks, such as MKK1, MKK3, MKK4, MKK6) and key serine and threonine residues in the IKK β activation ring of inhibitory kinase. This double acetylation irreversibly blocks the MAPK (ERK, JNK, p38) and NF - κ B signaling pathways. Therefore, infected macrophages are prevented from producing pro-inflammatory cytokines such as TNF - α and IL-1 β, and from undergoing apoptosis. This creates a 'silent' infection, where bacteria replicate uncontrollably when the host's alarm system is disabled. |
The inspection of Yersinia Pestis must strictly follow the management rules of virulent bacteria, and pay attention to prevent aerosol infection or flea bites. Animal experiments should have protective equipment, and the culture and equipment used in the experiment should be disinfected in a timely manner. Take the smear of the test material, fix it with methanol or alcohol ether mixture for 5-10 minutes, then carry out Gram or methylene blue staining, and observe the morphological characteristics of Yersinia Pestis under microscope. Inoculate the test material onto regular agar plates, gentian purple blood agar plates, and Hottinger agar plates. After incubating at 28 ℃ for 48 hours, observe the characteristics of the colonies, select suspicious colonies, smear, stain, and examine under a microscope. If necessary, inoculate the thick golden agar slope and broth for further identification through bacteriophage lysis, agglutination, or precipitation tests. When the first confirmed case of pestis is reported, guinea pig subcutaneous or skin rub inoculation test shall be conducted.
| Inspection Method | Details |
| Specimen | Since pestis is highly infectious, aseptic operation must be strictly carried out when collecting samples. According to the type of disease, lymph node puncture fluid, swelling tissue fluid, pus, blood, and sputum are used. Human and animal corpses can be obtained from liver, spleen, lungs, diseased lymph nodes, and heart blood. Extract bone marrow from an old corpse. Send the collected specimens to a specialized laboratory with strict protective measures for inspection, and prohibit operations in general laboratories. |
| Testing Nucleic Acid | Detection of Yersinia pestis nucleic acid by DNA probe hybridization or PCR technology is helpful to the diagnosis of pestis. PCR is extremely sensitive, and 10 Yersinia pestis infections in fleas can be detected by PCR technology. |
| Serological Test | It can be used to check Yersinia pestis antigen or specific antibody. Sensitive and specific testing methods include ELISA, solid-phase radioimmunoassay, SPA co agglutination test, etc. |
| Separate Cultivation and Identification | Blood samples need to be placed in broth for bacterial culture first. Generally, blood agar plates are used for isolation and cultivation. After 24 hours at 28 ℃, small droplet like colonies can be seen. Continuing cultivation will increase the colony size to 1mm~2mm, with a thick and dense center and gradually thinner periphery. Take suspicious bacterial colonies for smear staining microscopy, bacteriophage lysis test, serum agglutination test, specific fluorescent antibody staining, and other identification methods. |
| Direct Smear Microscopy Examination | Except for blood samples, smears or prints are generally required, which are fixed with methanol after drying, stained with Gram or Lysimachia blue, and examined under a microscope. In different materials, there are significant differences in the size and morphology of bacterial cells. In addition to the typical morphology, it is often observed that bacterial cells have multiple morphologies, which should be taken into account. |
Yersinia pestis is still a huge threat, because it has good adaptability as the pathogen transmitted by fleas, and has a strong pool of immunosuppressive virulence factors. Its molecular strategy centers on the delivery of T3SS mediated effector proteins such as YopH, YopE, and YopJ, disrupting host signaling nodes (p130Cas/FAK, Rho GTPase, MAPK/NF - κ B pathway) to enable rapid systemic disease. Although modern antibiotics can effectively treat epidemics if used early, the continued presence of zoonotic hosts, the risk of antibiotic resistance, and their potential as biological weapons require continued vigilance. Continuous research on its pathogenesis and immunology is crucial for developing the next generation of vaccines and treatments to alleviate the persistent threat of this ancient scourge.
References
| Target | Cat. No. | Product Name | Host | Isotype | Application | |
| Y. pestis V Antigen | DMABT-51632MY | Anti-Yersinia Pestis V antigen monoclonal antibody, clone Wb24 | Mouse | IgG1 | IHC, ELISA, FC, FuncS, IF, IP, WB | Inquiry |
| Yersinia Pestis V antigen | DMABT-51634MY | Anti-Yersinia Pestis V antigen monoclonal antibody, clone Wb59 | Mouse | IgG1 | IHC, ELISA, FC, FuncS, IF, IP, WB | Inquiry |
| Target | Cat. No. | Product Name | Host | |
| Y. pestis | DAGA-974 | Recombinant yersinia pestis F1 capsule antigen(aa 22-170,>90%) [His] | Yeast | Inquiry |
| DAGA-972 | Recombinant yersinia pestis cpn60 protein in E. coli (aa 1-548) [His] | E. coli | Inquiry | |
| DAG-WT644 | Recombinant Yersinia pestis F1 protein | E. coli | Inquiry | |
| DAGA-971 | Recombinant yersinia pestis cpn60 protein (a.a. 1-548) [His] | Yeast | Inquiry |
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