Paracoccidioides

Shmuel Shoham , M.D.
Paracoccidioides is a topic covered in the Johns Hopkins ABX Guide.

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MICROBIOLOGY

  • Paracoccidioides species
    • P. brasiliensis species complex:
      • P. brasiliensis (also known as S1a and S1b)
      • P. americana (PS2)
      • P. restrepiensis (PS3)
      • P. venezuelensis (PS4)
    • P. lutzii
  • Geographic distribution:
    • Most cases occur in Brazil, but the range is as far north as Mexico.
      • P. brasiliensis, P. americana (PS2) and P. lutzi: found across South America.
      • P. restrepiensis and P. venezuelensis: found in Colombia and Venezuela respectively.
      • Significant differences in annual incidence rates reported among Brazilian states (range 0.7 to 40 cases per 100,000 inhabitants)[2].
  • Ecological associations: Mostly in rural and peri-urban environments.
    • Humid, rainy, forested areas near rivers
    • Agricultural (especially coffee and tobacco crops)
    • Armadillo hunting
    • Large-scale construction projects (e.g., hydroelectric dams) that disturb soil.
  • Morphology (dimorphic nature)
    • Mycelium phase (mold): this is the form found in the environment and when samples are cultured at 25C. Hyphae and conidia.
    • Yeast phase: This is the form found in tissues and body fluids and when samples are cultured at 37C
      • Microscopic appearance is of a large parent cell with multiple budding yeasts [Fig 1] emerging from it to create the characteristic ship’s wheel appearance [Fig 2].
  • Pathogenesis:
    • Infectious propagules (conidia) produced by the environmental mycelium phase are inhaled by accidental hosts (humans and armadillos are the main ones).
    • The transition from conidia to yeast phase occurs in the lungs.
      • Most infected individuals will control infection with T cell-driven granuloma formation and will not develop clinical disease.
      • Acute/subacute (“juvenile”) form: This occurs in children and young adults whose T cells responses are unable to control the infection.
        • Occurs weeks to months after initial exposure.
      • Chronic (“adult”) form: >80% of cases
        • Quiescent fungus in granuloma that had previously been controlled becomes active long after the initial infection.
      • Predisposing factors:
        • Gender: The male to female ratio is ~22:1. One reason is that circulating estrogens inhibit the transformation of the aspirated conidia into yeast cells.
        • Genetic variables: the presence of certain MHC antigens (HLA-A9, HLA-B13 and C4B*-Q0) and the IL12RB1 641AA genotype are associated with risk for developing the disease.

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MICROBIOLOGY

  • Paracoccidioides species
    • P. brasiliensis species complex:
      • P. brasiliensis (also known as S1a and S1b)
      • P. americana (PS2)
      • P. restrepiensis (PS3)
      • P. venezuelensis (PS4)
    • P. lutzii
  • Geographic distribution:
    • Most cases occur in Brazil, but the range is as far north as Mexico.
      • P. brasiliensis, P. americana (PS2) and P. lutzi: found across South America.
      • P. restrepiensis and P. venezuelensis: found in Colombia and Venezuela respectively.
      • Significant differences in annual incidence rates reported among Brazilian states (range 0.7 to 40 cases per 100,000 inhabitants)[2].
  • Ecological associations: Mostly in rural and peri-urban environments.
    • Humid, rainy, forested areas near rivers
    • Agricultural (especially coffee and tobacco crops)
    • Armadillo hunting
    • Large-scale construction projects (e.g., hydroelectric dams) that disturb soil.
  • Morphology (dimorphic nature)
    • Mycelium phase (mold): this is the form found in the environment and when samples are cultured at 25C. Hyphae and conidia.
    • Yeast phase: This is the form found in tissues and body fluids and when samples are cultured at 37C
      • Microscopic appearance is of a large parent cell with multiple budding yeasts [Fig 1] emerging from it to create the characteristic ship’s wheel appearance [Fig 2].
  • Pathogenesis:
    • Infectious propagules (conidia) produced by the environmental mycelium phase are inhaled by accidental hosts (humans and armadillos are the main ones).
    • The transition from conidia to yeast phase occurs in the lungs.
      • Most infected individuals will control infection with T cell-driven granuloma formation and will not develop clinical disease.
      • Acute/subacute (“juvenile”) form: This occurs in children and young adults whose T cells responses are unable to control the infection.
        • Occurs weeks to months after initial exposure.
      • Chronic (“adult”) form: >80% of cases
        • Quiescent fungus in granuloma that had previously been controlled becomes active long after the initial infection.
      • Predisposing factors:
        • Gender: The male to female ratio is ~22:1. One reason is that circulating estrogens inhibit the transformation of the aspirated conidia into yeast cells.
        • Genetic variables: the presence of certain MHC antigens (HLA-A9, HLA-B13 and C4B*-Q0) and the IL12RB1 641AA genotype are associated with risk for developing the disease.

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Last updated: July 4, 2021