General Micro Flashcards
What is an exotoxin?
- GN, GP or both?
- Where are genes that code for exotoxins?
- Effects // our response
GP + GN substance that is SECRETED from cells
- Genes are located on plasmids or bacteriophage
- SUPER toxic -> cause recognizable diseases
- We make Abs against exotoxins = basis of vaccine
What is an endotoxin?
- GN, GP, or both?
- Where are the genes that code for endotoxins?
- Effects
LPS on GN cell membrane = normal part of the cell that fragments off
- Genes in bacterial chromosome
- Causes fever, hypotension = shock, DIC
ENDOTOXIN mnemonic for the mechanism of endotoxin
Edema (from C3a) NO (from macrophages -> hypotension) DIC/death (due to tissue factor) Outer membrane (found here on GN) TNFa (causes fever + hypotension) O-antigen Xtremely heat stable IL 1 (causes fever) Neutrophil chemotaxis (b/c C5a)
Diptheria toxin mechanism + presentation
X elongation factor
Pharyngitis:
- Pseudomembranes = white plaques
- Severe lymphadenoapthy
Pseudomonas: toxin + mechanism + presentation
Exotoxin A
X elongation factor
Causes host cell death
Shigella toxin: mechanism + presentation
X 60s ribosome subunit
- Inflamed intestines -> bloody diarrhea
- HUS
EHEC: toxin + mechanism + presentation
Shiga-like toxin -> difference is that EHEC does not invade host cells
X 60s ribosome subunit
HUS
B.anthracis: toxin + mechanism + presentation
Edema toxin
More cAMP
Causes the red area around the black eschar in cutaneous anthrax
Cholera toxin: mechanism + presentation
More cAMP -> more Cl- secreted into the gut (water follows)
Rice water diarrhea
ETEC: 2 toxins + mechanism + presentation
- Heat labile toxin = more cAMP = Cl secretion @ gut, water follows
- Heat stable toxin = more cGMP = less NaCl reabsorbed = water follows
“Labile in the Air (adenylate cyclase) stable on the Ground (guanylate)
WATERY DIARRHEA
Most exotoxins are A-B toxins. What does that mean?
B = binding, binds to host cell receptor -> endocytosis
A = active, attaches ADP-ribosyl to disrupt host cell proteins
Often increase cAMP
Pertussis toxin: mechanism + presentation
No Gi -> more cAMP
Whooping cough
Clostridium tetani: toxin + mechanism + presentation
Tetanospasmin Cleave SNARE - no vesicle fusion X GABA or glycine release = inhibitory @ Renshaw cells in spinal cord 1. Spasm 2. Risus sardonicus 3. Lockjaw
Botulinum toxin: mechanism + presentation
X SNARE -> no vesicle release
X ACh @ NMJ
= Flaccid paralysis
Floppy baby
Clostridium perfringens: toxin + mechanism + presentation
Alpha toxin = lecithinase = enzyme that causes tissue necrosis
- Gas gangrene
- Double zone hemolysis on blood agar
Strep pyogenes: toxin + mechanism + presentation
Streptolysin O
RBC lysis = why S.py is B hemolytic
Abs made against this toxin = ASO Abs
- Dx for rheumatic fever
S.aureus: toxin + mechanism + presentation
Toxic shock syndrome toxin IL1, IL2, IFNg, TNFa 1. Toxic shock syndrome 2. Scalded skin syndrome 3. Food poisoning
What is the other toxin S.pyogenes (besides streptolysin O) can release to cause toxic shock syndrome?
Exotoxin A
Do GN or GP have T3 secretion system?
GN
What is unique to GN cell walls
Capsule (GN + GP) **Outer membrane made of LPS/endotoxin (GN only) **Space w/ peptidoglycan + B lactamases (GN only) Cytoplasmic membrane (GN + GP)
Mnemonic for bugs that don’t gram stain well:
“These Microbes May Lack Real Color”
Treponema Mycob - use carbolfuschin Mycoplasma Legionella - use silver stain Rickettsia Chlamydia
What 2 bugs get cultured on Thayer-Martin agar? Mnemonic for what is in the medium: “Very Typically Cultures Neisseria”
N. gonorrhoeae + meningitidis Vanco Trimethoprim Colistin Nystatin
Where does TB reactivate if pt is put on immune suppression? Why does this make sense?
@ apices of lung
= Highest PO2
Myco TB is aerobic bug
What antibiotic class doesn’t work against anaerobes?
Aminoglycosides
Require O2 to enter bacterial cell wall
