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
How do cells evade host immune system? (4th step of infection)
- intracellular pathogens- lives inside host cell
- latency- lay and wait to attack
- masking- coats itself with host molecule
- mimicry- pathogen surface resembles host surface
- Variation- alter their surface molecules
What are the steps of transmission? (5th step of infection)
The cell travels through the portal of exit and finds the reservoir (where the cell thrives best) and attaches to a fomite (inanimate object)
What are the features of Biosafety level one and BSL2
BSL1- no harm to healthy people
(S. epidermidis)
BSL2- Cause disease, but are preventable or treatable (S. aureus)
What is the difference between BSL3 and BSL4
BSL3 is serious, some treatable, many are airborne (M. tuberculosis)
BSL4- lethal to humans, not treatable, require airtight suits (ebola)
What is universal standard precaution(s)?
all patients are treated as potentially infectious
- proper handwashing
- wear gloves
- barrier clothing, mask for splash risk
- Biosharp waste disposal
- disinfect surfaces
How do the toxicity/ LD50 of endotoxins and exotoxins differ?
Endotoxins= Low toxicity/ high LD50 Exotoxins= High toxicity/ low LD50
Can endotoxins/exotoxins be treated?
Endotoxins cannot be treated.
Exotoxins can be treated
How do bacterial cells disrupt phagocytosis (disrupt immune cell activity)?
- toxins=destroy immune cell
- capsule=immune cell can’t engulf
- Block= fusion of immune cell
- Escape= break free of immune cell
How do bacterial cells suppress immune cells?
- Destroy immune cells
- Destroy antibodies
- Disrupt immune signaling
