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Updated: May 15 2021

Yersinia pestis


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  • Snapshot
    • A 53-year-old man presents to occupational health for suspected exposure to the plague. He works in a research laboratory that conducts research on infectious diseases and accidentally poked himself with a needle he used on an infected animal. He has had headaches, fatigue, and enlarged and painful "bug bite-like lesion" on his right groin. On physical exam, he has inguinal lymphadenopathy and a large and tender buboe in the right inguinal area. He is started on the appropriate antibiotics, and the incident is reported to the Centers for Disease Control and Prevention.
  • Introduction
    • Classification
      • Yersinia pestis
        • a nonmotile, gram-negative, facultative intracellular bacillus
          • non-lactose fermenting, oxidase negative, and does not produce H2S
        • reservoirs are rats and prairie dogs
        • transmitted via fleas
        • causes the bubonic plague (most common) and pneumonic plague
    • Epidemiology
      • incidence
        • rare but outbreaks occur in the Southwest in the US
      • demographics
        • occurs in young people
      • risk factors
        • exposure with infected patients or small rodents, alive or dead
        • flea bites
        • occupational exposure
    • Pathogenesis
      • produces endotoxin, coagulase, and fibrinolysin
      • bacteria migrate to regional lymph nodes and survive intracellularly within macrophages
        • F1 capsular antigen is antiphagocytic
    • Prevention
      • plague vaccine
        • field workers in endemic areas
        • laboratory personnel who work with Yersinia pestis
    • Prognosis
      • if untreated, the disease will lead to death
      • if untreated, mortality rates range from 10-50%
      • pneumonic plague has the highest mortality
  • Presentation
    • Symptoms
      • sudden onset high fever and chills
      • headache
      • myalgias
      • fatigue
    • Physical exam
      • bubonic plague
        • unilateral swollen and tender lymph nodes (buboes)
        • often in the groin (Greek bubon = groin) and axilla
        • can grow up to 10 cm in size
        • may have eschar and vesicles
        • buboes may rupture and have malodorous pus discharge
      • pneumonic plague
        • cough
        • chest pain
        • hemoptysis
        • dyspnea
  • Imaging
    • Chest radiography
      • indication
        • suspected lung involvement
      • findings
        • diffuse patchy infiltrates or consolidations
  • Studies
    • Peripheral blood smear
      • toxic granulations and Dohle bodies
      • Wright-Giemsa stain with rods
      • Wayson stain reveals “safety pin” appearance of bacteria with bipolar staining
    • Labs
      • positive blood cultures are diagnostic but can be hazardous
      • rapid F1 antigen detection via immunofluorescence
    • Lymph node aspirate
      • Yersinia pestis on microscopy or culture
    • Making the diagnosis
      • based on clinical presentation and laboratory studies
  • Differential
    • Anthrax
      • distinguishing factor
        • presents with a necrotic ulcer rather than buboes
  • Treatment
    • Management approach
      • mainstay of treatment is supportive care and antibiotics
    • Conservative
      • supportive care
        • indication
          • all patients
        • modalities
          • aggressive hydration
          • respiratory support
          • hemodynamic support
    • Medical
      • aminoglycosides
        • indication
          • all patients
      • doxycycline
        • indication
          • treatment
      • fluoroquinolones
        • indication
          • treatment
          • post-exposure prophylaxis
    • Operative
      • incision and drainage
        • indication
          • enlarging buboes
  • Complications
    • Acute respiratory distress syndrome
    • Disseminated intravascular coagulopathy
    • Septic shock
    • Lymphatic scarring and chronic lymphedema
    • Superinfection of buboes with other bacteria
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