🦠

Understanding Pathogenicity: Entry and Exit Points

May 12, 2025

Mechanisms of Pathogenicity: Portals of Entry and Exit

Introduction

  • Discussion on the mechanism of pathogenicity focusing on the portals of entry and exit.
  • Relationship between portals of entry and exit.

Portals of Entry

  • Definition: The ways in which pathogens enter a host.
  • Preferred Portals: Pathogens prefer portals closest to the target cell types or tissues.
  • Common Portals:
    1. Mucous Membranes
      • Respiratory System: Entry through inhalation of droplets or airborne organisms.
      • Digestive System: Entry via consumption of contaminated food or drink.
      • Genitourinary System
    2. Skin: Generally needs to be broken to allow pathogen entry.
    3. Parenteral Route: Bypasses skin or mucous membranes via:
      • Needle stick injuries
      • Insect bites
      • Broken skin
    4. Other Sites:
      • Nose and mouth
      • Eyes (conjunctiva)
      • Ears
      • Urethra
      • Anus
      • Vagina

Special Cases

  • Placenta: Generally acts as a barrier but some pathogens (e.g., Listeria) can cross it.
  • TORCH Infections: A specific group of infections that can cross the placenta (not detailed in this lecture).

Portals of Exit

  • Definition: The routes through which pathogens leave the host to infect others.
  • Commonality with Entry Points: Portals of exit are often the same as entry portals.
    • Example: Gastrointestinal pathogens enter and exit via the GI tract.

Examples of Portals of Exit

  • Respiratory Secretions
  • Gastrointestinal Secretions (Feces)
  • Tears and Breast Milk: Less obvious but potential routes.
  • Skin and Broken Skin: Pathogens can spread through blood from broken skin or bites.
  • Ear Wax: Can carry infectious agents.

Importance of Portals of Exit

  • Essential for the spread of pathogens to new hosts.
  • Prevents the host from being a dead end for the pathogen.

Conclusion

  • Understanding portals of entry and exit is crucial in controlling the spread of infectious diseases.
  • Note: A future video will cover organisms that can cross the placenta and cause infection during pregnancy (TORCH infections).

Full transcript