Lecture 10 pt. 2 Flashcards
What is pathogenicity
ability of microbe to cause disease
-all or nothing, it either causes or it does not
What is Virulence?
Degree or extent of a disease; has different levels
What are Virulence factors?
items microbes use to defeat our defenses
-toxicity, aggressiveness, transmission
What is attenuated virulence?
still infectious, but weakened and destroyed easily; basis for vaccines
What is the difference between ID50 and LD50
ID50– how many cells needed to establish infection 50% of the time
LD50– amount of cells needed to kill 50% of nontreated hosts
What are/is:
- Toxins
- Toxigenic
- Toxemia
Toxins= molecules that generate a range of damage to the host Toxigenic= microbes that can make toxins Toxemia= when toxins reach the bloodstream
What are the characteristics of endotoxins and where do they come from?
Released from gram negative cells (attached to LPS) when they lyse
- causes fever, chills, body aches, etc.
- causes septic shock
What are the characteristics of exotoxins and where do they come from?
They come from both gram negative and gram positive cells
- Present from growing bacteria
- Some have vaccines
- More dangerous than endotoxin (has a lower LD50)
What is the difference between type I, type II, and type III exotoxin types?
Type I-membrane acting; bind host receptor without entering cell and causes signal that alters cell
Type II- membrane damaging; forms pores, removes phosphate head and cell lysis
Type 3- Same as type I
Endotoxins vs Exotoxins
- What type of bacteria are they found in?
- When are they made present?
- Is there a cure?
- Does the host show signs?
Is a lipid / Is a protein
Gram (-) only / Gram (-) and (+)
From dead bacteria / From growing bacteria
No vaccine available / Vaccine available
Host always has a fever / Sometimes host has fever
What is the portal of entry? (1st step to infection)
where the pathogen enters host -largest area is skin, eye, and ears -Respiratory- most common portal GI-fecal/oral Urogenital/placental- STDs, UTI
What is adhesion? (2nd step to infection)
Adhere to host tissue Adhesins(1000s of them)
- nonspecific(hydrophobic) then specific interactions
- Pathogen mimics something the host cell naturally binds
What are the 4 different means of adhesion?
- Fimbriae and pili- bind host cell carbohydrates
- Sialic acid factor- bind host cell sugar molecule
- Heparan binding factor- binds host cell sugar molecule
- Fibronectin binding factor- binds host cell protein molecule
What do cells do during the process of invasion (3rd step of infection)?
Will either: A) Stay at surface B)Stay in cell C)Invade deeper tissue D)Pass between cells to deeper tissue -Will obtain nutrients to grow
What are the things that aid in Invasion of the cell?
Flagella- used to spread around
Lipases- break down lipids
Proteases- Break down proteins
Siderophores- steal iron from host
