Commensals And Pathogenic Microorganism

Commensal Microorganism

• Commensal microorganism are those that live harmony with their host without causing harm.

• They are often part of normal flora of the body present in area as skin, mouth, respiratory tract and guts.

Characteristics

• They do not cause any disease under normal condition.

• Play vital role in host health

• They are part of normal flora present in the body

• Live in harmony with the host often providing mutal benifits.

Function

• Important role in breaking down food and absorbing nutrients.

• Produce essential vitamins such as vitamin B and vitamin K

• Regulate immune system

  • Example

    • Lactobacillus

    • Escherichia coli

    • Staphylococcus epidermidis

    • Streptococcus salivarius

Pathogenic Microbes

• Pathogenic microbes are those that can cause disease in their host.

• Pathogenic microbes can be bacteria, virus, fungi or parasites

• Pathogens have mechanism that allow then to invade the host evade the immune system and cause damage.

Characteristics

• Capable of causing illness and disease in the host

• utilize strategies to avoid detection and destruction by the host immune system.

• Penetrate and spread within host tissue often causing inflammation and tissue damage.

Types of pathogenic microbes

1. Bacteria:

   • Single celled organism that can cause wide range of disease.

   • They can be classified based on their shape gram staining and oxygen requirement.

2. Virus:

   • Viruses are acellular microorganism that consist either DNA or RNA, not both.

3. Fungi

   • Eukaryotic organism that include yeast and mushrooms.

4. Parasites

   • Parasite that live inside the host

   • parasite can be protozoa, helminths, or ectoparasites.

Mechanism of pathogenesis

• Adherence: Pathogens often have specialized structures ( pilli, fimbria, adhesion, molecules that allow them to attach to host cell and tissue.

• Invasion: Pathogen can invade host tissue by producing enzymes ( hyaluronidase, collagenase) that break down extracellular matrix or by using mechanism to penetrate host cell.

• Toxin: Many bacteria produce toxin that can damage host tissue. Toxin can be classified as exotoxin and endotoxin.

• Immune evasion: Pathogen have evolved various strategies to evade the host immune system, including

  • Antigenic variation

  • capsule formation

  • Intracellular survival

• Example:

  • Staphylococcus aureus

  • mycobacterium tuberculosis

  • E.coli