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Mechanics of solid tissue invasion by the mammalian pathogen Pythium insidiosum

J P Ravishankar1, C M Davis, D J Davis

  • 1Department of Botany, Miami University, Oxford, Ohio 45056, USA.

Fungal Genetics and Biology : FG & B
|December 1, 2001
PubMed

Insights

Pythium insidiosum cannot mechanically penetrate intact mammalian tissues. This oomycete requires secreted proteinases to degrade tissue, highlighting the importance of enzymatic action in fungal invasion.

Area of Science:

  • Mycology and Pathogenesis
  • Oomycete Biology
  • Infectious Diseases

Background:

  • Solid tissue invasion by fungal pathogens is crucial for disease development.
  • The relative roles of mechanical force and enzymatic degradation in tissue penetration remain unclear for most fungal diseases.
  • Pythium insidiosum, an oomycete, causes severe infections in mammals.

Purpose of the Study:

  • To determine the physical forces exerted by Pythium insidiosum hyphae.
  • To compare the pathogen's mechanical pressure with the strength of mammalian tissues.
  • To elucidate the mechanism of tissue invasion by Pythium insidiosum.

Main Methods:

  • Utilized miniature strain gauges to measure the force exerted by single hyphal tips of P. insidiosum.
  • Quantified the mechanical strength of human cutaneous and subcutaneous tissues via puncture resistance.
  • Assessed the pressure required to penetrate equine skin strips.

Main Results:

  • P. insidiosum hyphal apices generate pressures up to 0.3 microN/µm².
  • Human dermal and subcutaneous tissues exhibit mean strengths of 24 microN/µm².
  • Equine skin requires a mean pressure of 30 microN/µm² for penetration.

Conclusions:

  • P. insidiosum lacks the mechanical force to breach intact skin or underlying tissues.
  • The pathogen must rely on secreting proteinases to weaken tissue barriers.
  • Enzymatic degradation is essential for P. insidiosum to initiate solid tissue invasion.

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