CH 15 Microbial Mechanisms of Pathogenicity

What is the term for the ability to cause diseases by overcoming a host’s defenses?

Pathogenicity

What is the degree of pathogenicity?

It is called Virulence.

How do pathogens enter the human body? Which tracts and what membrane?

But what is the most frequent portal of entry?

Through the portal of entry, which includes the mucous membranes of the respiratory tract, gastrointestinal tract, and the genitourinary tract. 

The most frequent portal of entry is respiratory tract.

How can microbes gain entry to the gastrointestinal tract? 

In the gastrointestinal tract, they gain access via food, water, and contaminated fingers. 

How will microbes be destroyed in the gastrointestinal tract?

Most will be destroyed from the acids of the gut. It can also shed with feces, but the virus in feces can be transmitted to another host if not disposed correctly. 

How can the skin be a portal of entry for microbes?

They can gain entry via conjunctiva, hair follicles and sweat glands. Or by boring through intact skin. 

What can influence the intensity of duration of an infection?

The number of invading pathogens

When microbes invade the body, they are most likely to be stopped by what?

The host’s immune system.

Large numbers gaining entry are mostly likely to cause what?

Mostly likely to cause a disease.

What are siderophores?

Siderophores are molecules that bacteria use to leech iron from the host.

How can bacteria cause direct damage?

They destroy the host cells when the pathogen metabolizes and multiplies inside the host cells.

What can bacteria produce? Starts with a T.

They can produce toxins which are poisonous substances that can be transported by the blood or lymph fluid.

Some toxins can produce fevers, inhibit protein synthesis, destroy blood cells and blood vessels.

What are the 2 general types of toxins.

Exotoxins & Antitoxins

What is an Exotoxin?

They are a major group of toxins that are produced inside some bacteria, typically GRAM POSITIVE. They diffuse into the blood and destroys part of the host’s cells or inhibit metabolic functions.

What does the body do in response to the exotoxins.

The body responds by producing antitoxins.

What are the types of Exotoxins?

• Genotoxins 

• Membrane-Disrupting Toxins 

• Hemolysins

What are Genotoxins?

It damages DNA and causes mutations, disrupt cell division and may lead to cancer.

What are Membrane-Disrupting Toxins?

Causes lysis of host cells, like in Staphylococcus aureus, and some disrupt the phospholipid bilayer portion of the membrane, which is Clostridium Perfringens.

We also leukocidins are membrane-disrupting toxins that kill phagocytic leukocytes. Mostly produced by staphylococci and streptococci.

What are Hemolysins?

Destroys red blood cells, common in streptococci

What are endotoxins?

They are the outer portion of the cell wall of gram-negative bacteria. If a bacteria produces endotoxins they are going to work in the outer part of the cell wall.

These toxins are the lipid portion of the LPS

They can induce miscarriages in pregnant individuals.

What is the meaning of Adherence?

(Attachment) This is necessary for a microbe to cause an infection. They have adhesins on their microbial cell which binds to a specific receptor on a host’s cell.

Where can adhesins (ligands) be found?

They can be found on a microbe’s glycocalyx, pili, fimbriae or flagella. They vary in structure.

How can the pathogen enter the cell? How does this happen?

It can enter the cell if the ligand (adhesins) and receptor matches.

This happens because pathogen cells will make ligands that mimic……