Lecture 9 - Pathogenicity and Virulence Flashcards
(23 cards)
what is virulence?
a measure of pathogenicity in Mo
what is virulence determined by?
ability to invade and multiply within the host
what are the 3 major portals of entry?
- mucous membranes
- skin
- parenteral route
what is pathogenicity?
ability of MO to overcome hosts defences and cause disease.
what is a mucous membrane?
A mucous membrane is an epithelial layer for protection that lines parts of nose, throat, and body systems such as digestive and respiratory.
how are most MO’s acquired? and an example of a common MO
breathing through the respiratory system.
ex. Influenza, Bordetella pertussis (whooping cough)
what 3 areas in the body have mucous membranes which are portals of entry?
- Respiratory
- Gastrointestinal
- Genitourinary tract
What are MO’s that can enter gastrointestinal?
- Shigella Spp - causes Shigella
- Salmonella enterica/Salmonella typhi - typhoid fever
what are MO’s that can enter through mucous membranes in the genitourinary tract?
- STI’s
- Neiserria gonorrheae (Gonorrhea)
- Chlamydia trachoma’s (Chlamydia)
explain the following portal of entry: skin
- Usually impermeable to MO’s (hair follicles and sweat glands)
- some MOs can penetrate such as Dermatophytic fungi, hookworm
explain the following portal of entry: parental route
- MO bypasses skin through an open wound.
what kind of MOs can cause disease through one portal?
- salmonella type (swallow)
- Streptococci spp. (inhalation)
what MOs can go through different portals of entry and cause disease?
- Yersinia pestis (plague)
- Bacillus anthraces (anthrax)
How is virulence measured?
As an ID50 value
what is an ID50 value?
- Infectious Dose 50 (sufficient to infect half of tested population)
- it is evaluated experimentally thus it can change
how is toxicity measured?
- LD50
what is LD50?
- Lethal dose 50 (sufficient to kill half of tested population)
what are the 3 major effects of pathogens damaging host cells?
- Use of host cell nutrients
- Direct damage
- Toxins
what is the “use of host cell’s nutrients”?
- MO uses metabolites before the host cell can
what is “direct damage”?
- MOs grow so large that host cell bursts or ruptures
what are toxins and the 2 types?
- toxins are poisonous substances produced by bacteria
1. exotoxins
2. endotoxins
what are exotoxins?
- toxins produced by Gram-positive cells
- synthesized during bacterial metabolism
- secreted during growth or cell lysis
- highly toxic
- toxin causes disease, not bacterial presence
what are endotoxins?
- toxins that are part of outer membrane of gram-negative cells
- Released when bacteria die
- can be triggered by antibiotics
