Unit 3: Bacterial Diseases Flashcards
Endotoxin
- part of the outer portion of the cell wall in gram negative bacteria
-liberated when the bacteria dies and cell wall breaks apart
Exotoxin
-mostly in gram positive bacteria as part of their growth and metabolism
- released into surrounding medium
What are the 3 types of exotoxins?
1) superantigens
2) toxins
3) AB toxins
Type 1: Superantigens
1) non-specifically stimulate many families of CD4+ T cells
2) lead to massive cytokine release
Examples of superantigens
-Toxic shock syndrome toxin
-streptococcal mitogenic exotoxin
- streptococcal pyrogenic toxin
Type 2: toxins
destroy host cells by distributing membranes
Examples of toxins
- streptolysion pneumolysin
-alpha toxin
-beta toxin - phospholipase C
Effects of endotoxin on host
-luekocytes release cytokines leading to fever
-some cytokines damage blood vessel walls causing a drop in BD- which leads to shock
- activate innate system comprised of complement proteins that cause inflammation- which could drop BP leading to shock
Causative agent of necrotizing fasciitis
Streptococcus Pyogenes
enters thru breaks in skin
Alpha hemolysis
-Incomplete
-oxidizes iron in hemoglobin producing a “greenish” discoloration on blood plates
Beta hemolysis
Complete destruction of red blood cells ; resulting in clearing around growth
Gamma Hemolysis
No hemolysis ; results in no change in media
What type of hemolysis does streptococcus pyogenes cause?
Beta hemolysis
What exotoxin destroys neutrophils?
Streptolysin
Bullae
Large fluid filled sac
Ecchymosis
Subcutaneous bleeding
Crepitus
Crackling sound under skin
Necrosis
Death of soft tissue
Ex: skin, subcutaneous tissue, muscles
Do clostridium tetani & clostridium botulinum require aerobic or anaerobic environment?
Anaerobic-no oxygen
What structure do c.tetani & c.botulinum capable of forming when not in the right environment?
Endospores
C. Tetani =spore terminal
C. Botulinum = spore subterminal
What type of exotoxins are botulinum toxin & tetanospasmin?
Neurotoxin
What is the mechanism of botulinum toxin
Blocks release of acetylcholine at neuromuscular junction & form preganglionic sympathetic and pre and post ganglionic parasympathetic neurons
What type of paralysis does botulinum toxin cause?
Flaccid paralysis = muscles cannot contract
Nystagmus
Rapid, involuntary movement of eyes
associated w/ botulism
What is Botox?
Botulinum toxin = ability to inhibit contraction of skeletal muscle
Cosmetic uses for BOTOX
-frown lines
-crows feet
- under eye lines
-forehead lines
Strabismus
Eyes are not aligned crossed
Blepharospasm
Sometimes chronic condition in which the eyelids uncontrollably twitch
Where are endospores of C. Botulinum found?
Soil, ponds and lake sediments
By what vehicle do the C. botulinum toxins get into humans?
Home-canned products that have been insufficiently heated
Heat-labile w/ respect to botulinum toxin
Destroyed by heat
food must be ingested uncooked or be inadequately cooked for someone to get botulinum toxin
What is the anti-toxin for botulism and how does it work?
Best way to prevent botulism?
Properly can food and eat cooked food
Mechanism of action for tetanospasim
Blocks release of inhibitory neurotransmitters (glycine & y-aminobutyric acid -these stop the action of acetylcholine) at the neuromuscular junction
What type of paralysis does tetanospasmincause?
Spastic paralysis = muscles cannot relax
Trismus
Masseter muscles - inability to open jaw (lock jaw)
associated w/ tetanus
Opisthotonos
Back muscles paralysis
associated w/ tetanus
Where are spores of clostridium tetani found?
- soil (manure-treated especially)
- intestinal tract of humans and other animals
How do the spores of clostridium tetani get into humans?
Puncture wounds
Best way to prevent tetanus
Not going outside barefoot & vaccines
What is human tetanus immune globulin and how does it work?
What is tetanus toxoid?
Inactivated toxin that retains antigenicity (what we get injected w/ as a vaccine)
What combined vaccine is the tetanus toxoid apart of?
DTaP (it is the T part)
