Chapter 15 Flashcards
Pathogenicity Introduction
What is pathogenicity?
Pathogenicity is the ability to cause disease.
How Microbes Enter a Host (Portals of Entry)
What are the main portals of entry for microbes?
- Mucous membranes
- Skin
- Parenteral route (direct deposit into tissues; needle injecting through the skin)
- Preferred portal of entry
Preferred poral of entry is important because it causes infections through their specific portal of entry.
How Bacteria Penetrate Host Defenses
What are the three main mechanisms by which bacteria penetrate host defenses?
Answer:
* Capsules
* Enzymes
* Cell Wall Components
How Bacteria Damage Host Cells
What are the mechanisms by which bacteria damage host cells?
Bacteria can damage host cells by:
Using host’s nutrients
Causing direct damage in the immediate vicinity of the invasion
Producing toxins that damage sites far removed from infection
Endotoxins
What are endotoxins?
Endotoxins are toxins that are part of the bacterial cell, usually found in Gram-negative bacteria.
They are released during bacterial multiplication and cell death, causing symptoms like fever, weakness, and shock.
Endotoxin = Lipid A
What are exotoxins?
Exotoxins can be found in gram positive or gram negative.
They are proteins or enzymes that can be carried on plasmids or phages.
Exotoxins can be very harmful and destroy particular parts or inhibit metabolic functions of host cells.
Types of Exotoxins
What are the three types of exotoxins based on their effects?
Type 1. Superantigens
Type 2. Membrane-Disrupting Toxins
Type 3. A-B Toxins
Superantigens
What are superantigens, and what symptoms do they cause?
Superantigens cause an intense immune response due to the release of cytokines, leading to symptoms like fever, nausea, vomiting, diarrhea, shock, and even death.
Staphylococcal toxins are examples of superantigens.
Membrane-Disrupting Toxins
What is the main effect of membrane-disrupting toxins, and give examples of these toxins?
Membrane-disrupting toxins lyse host cells by disrupting plasma membranes. Examples include leukocidins (kill leukocytes), hemolysins (kill erythrocytes), and streptolysins (hemolysins produced by streptococci).
A-B Toxins
What are A-B toxins, and give an example?
A-B toxins contain an enzyme component (A part) and a binding component (B part). An example is the diphtheria toxin.
They release Genotoxins, these cause DNA mutations. Can cause cancer.
Fungal Toxins
What are fungal toxins, and provide an example.
Fungal toxins include ergot alkaloid toxins like lysergic acid diethylamide (LSD) and aflatoxin, which is carcinogenic and produced by Aspergillus.
Mycotoxins from mushrooms are also neurotoxic.
What does ID50 and LD50 mean?
- ID50: the amount of pathogens it takes to infect 50 percent of the population. (The lower the number, the more dangerous the pathogen)
- LD50: the amount of pathogens it takes to lethaly infect 50 percent of the population. (The lower the number, the more dangerous the pathogen)
How do capsules help bacteria evade the immune system?
Capsules make it harder for phagocytes to grab onto them. They are slippery.
What are the 5 enzymes produced by bacteria that allows them to lyse the cell wall?
- Coagulases
- Kinases
- Hyaluronidase
- Collagenase
- IgA Proteases
Pathogens have different ways to enter a host. One of those ways involves the mucous membrane. What are they different ways pathogens enter the various mucous membranes?
- Repiratory tract: Nose and mouth
- GI tract: Food, water, contaminated fingers
- Genital tract: Sex
- Conjuctiva: Eyelids and covers the white of eyeballs
