10.2. PATHOGENICITY

2. Give examples of strict pathogens and opportunistic pathogens.

Strict Pathogens+ Opportunistic Pathogens 

Strict Pathogens (or Obligate Pathogens): These pathogens always cause disease when they infect a host, regardless of the host's immune status.

Examples:

  • Mycobacterium tuberculosis: The causative agent of tuberculosis.

  • Neisseria gonorrhoeae: Causes gonorrhea.

  • Yersinia pestis: The bacterium responsible for the plague.

  • Plasmodium: A genus of parasitic protozoa that causes malaria in humans.

  • Rabies virus: A deadly virus that causes rabies, primarily transmitted through the bite of infected animals.

  • Influenza virus: Causes the flu, a contagious respiratory illness.

Opportunistic Pathogens:These pathogens can cause disease when the host's defenses are compromised, but typically do not cause disease in healthy individuals.

Examples:

  • Candida albicans: A yeast that is part of the normal flora of the skin, mouth, and intestines but can cause infections, especially in immunocompromised individuals.

  • Aspergillus sp.: A mold found in the environment that can cause infections in people with weakened immune systems or lung diseases.

  • Escherichia coli (E. coli): While many strains are harmless and reside in the intestines, certain strains can cause infections, especially if they gain access to parts of the body where they don't belong.

  • Staphylococcus aureus: Normally found on the skin and in the nasal passages of healthy people, but can cause infections if it enters the bloodstream, joints, bones, lungs, or heart. Some strains, like MRSA (Methicillin-resistant Staphylococcus aureus), are resistant to many antibiotics.


Note: Some of these opportunistic pathogens, like Staphylococcus aureus, can also cause disease in healthy individuals under certain conditions, making them both opportunistic and potential strict pathogens depending on the situation.

Mind Map: Strict Pathogens and Opportunistic Pathogens

Central Idea: Pathogens that cause disease in different host conditions

Main Branches:

  1. Strict Pathogens (Obligate Pathogens)

  2. Opportunistic Pathogens

Sub-branches:

Strict Pathogens:

These pathogens always cause disease when they infect a host, regardless of the host's immune status.

Examples:

  • Mycobacterium tuberculosis

    • Causes tuberculosis

  • Neisseria gonorrhoeae

    • Causes gonorrhea

  • Yersinia pestis

    • Causes the plague

  • Plasmodium

    • Causes malaria in humans

  • Rabies virus

    • Causes rabies

  • Influenza virus

    • Causes the flu

Opportunistic Pathogens:

These pathogens can cause disease when the host's defenses are compromised, but typically do not cause disease in healthy individuals.

  • Candida albicans

    • Can cause infections in immunocompromised individuals

  • Aspergillus sp.

    • Can cause infections in people with weakened immune systems or lung diseases

  • Escherichia coli (E. coli)

    • Can cause infections if it gains access to parts of the body where it doesn't belong

  • Staphylococcus aureus

    • Can cause infections in certain conditions, including in healthy individuals

    • Some strains, like MRSA, are resistant to many antibiotics

Note: Some opportunistic pathogens, like Staphylococcus aureus, can also cause disease in healthy individuals under certain conditions, making them both opportunistic and potential strict pathogens depending on the situation.