Bacteria Invasion Process

Study Notes

Bacteria invasion is the entry and possible multiplication of pathogenic microbes in an individual or population/community through a particular route, resulting in an infection or disease when vital functions or systems are damaged.
There are four major steps involved in bacteria invasion: Introduction, Establishment, Growth and Spread, and Impact.

The human body has three primary lines of defense against foreign invaders: physical and chemical barriers, non-specific innate responses, and specific adaptive responses.
Physical and Chemical Barriers:
- Destroy pathogens on the outer body surface and inner body linings.
- Examples include sweat, mucus, tears, and saliva containing enzymes that kill pathogens; urine with acidic properties that kill pathogens; and semen containing zinc that most pathogens cannot tolerate.
Body Natural Defense Mechanisms:
- Skin, mucous membranes, tears, earwax, mucus, and stomach acid act as natural barriers.
- Normal flow of urine washes out microorganisms that enter the urinary tract.

Non-Specific Immune Responses (Innate Immunity):
- Defense system with which one is born.
- Protects against all antigens.
- Involves barriers that keep harmful materials from entering the body.
Specific Immune Response:
- Refers to an immune response against a specific antigen.
- Activated due to the failure of the innate immune system to fight against pathogens.
- Major elements include lymphocytes and antibodies.
- Lymphocytes possess surface receptors and secrete proteins (antibodies) that bind specifically to antigens, which may destroy pathogens.

Virulence: the ability of a bacterium to infect the host and cause a disease.
Virulence factors: molecules that assist the bacterium in colonizing the host at the cellular level.
Examples of virulence factors:
- Motility: contacting host cells and disseminating within a host.
- Adherence: ability to stick to host cells.
- Resisting physical removal due to appropriate attachment structures.
- Ability to invade host cells.
- Ability to compete for iron and other nutrients.

Contagion: the concept of a disease being spread from person to person.
Contagious disease: a disease that can be spread through direct contact, indirect contact, or droplets.
Examples of contagious diseases: leprosy.