15 - Pathogenicity Flashcards
What are some ways microbes enter the body?
- mucous membranes
- skin
What is the most common way microbes enter the body?
respiratory tract
What is the second most common way microbes enter the body?
gastrointestinal tract
What is the ID50?
dose of microbe that is infectious for 50% of the population
What are four ways that microbes evade the host immune response?
- capsules (resist immune defense)
- cell wall (certain proteins/lipids resist immune response)
- enzymes
- antigenic variation
Antigenic variation
surface antigens become unaffected by antibodies
How can bacteria damage host cells?
use of host’s nutrients and direct damage (cell lysis/nutrient use/produce waste)
Endotoxin
- toxins composed of lips that are part of the cell membrane
- outer portion of cell wall in Gram - LPS (lipid A is endotoxin) released when gram - bacteria die (cell walls lysed)
- all endotoxins produce same symptoms
- cause macrophages to release high level of cytokines
Exotoxin
- toxic substances released outside the cell
- mostly gram +
- destroy host cell or inhibit metabolic functions
- disease is generally caused by exotoxin and not bacteria
- 3 different types
What are the 3 types of exotoxins?
- A-B toxins
- Membrane-disrupting toxins
- Superantigens
What do A-B toxins do?
most common exotoxins - A-enzyme component, B-binding component
A-B toxin examples
- diphtheria toxin
- botulinum toxin
- tetanus toxin
- vibrio enterotoxin
Membrane-disrupting toxin function
form protein channels, and disrupt phospholipid portion/lyse host cells
Example of membrane-disrupting toxin
gas gangrene toxin
Superantigens function
bacteria proteins, provoke intense immune response
Superantigens example
- Streptococcus pyogenes
- Staphylococcal enterotoxin
What are some examples of endotoxins?
- Salmonella typhi
- Neisseria meningitis
What can happen when you take antibiotics for a gram-negative infection, why?
The cell death from the antibiotics releases endotoxin and worsens the symptoms until the toxin is degraded.
What 7 ways can viruses damage host cells?
- stop host cell macromolecule synthesis
- destruction of intracellular contents
- inclusion bodies (granules contain viral parts)
- fuse adjacent cells
- changes in function, reduce cytokine production
- changes in surface antigens of host, target for destruction
- cancer
How do microbes exit the body (4)?
- mucous membranes
- skin or wounds
- generally the same as endry
Endotoxic chock
macrophages release TNF, increase blood capillary permeability, lose fluid, drop in blood pressure
