Genetics and toxins Flashcards
exotoxin coded where
plasmids and bacteriophages
endotoxin coded where
bacterial chromosome
antigenicity of exo and endo toxins
exotoxins very antigenic
endotoxins not antigenic
heat stability of exo and endo toxins
exotoxins: stable up to 60 degrees Celsius except for staph enterotoxin
endotoxin: stable for 1 hr in 100 degrees
examples of exotoxins
tetanus
botulism
diphtheria
examples of endotoxin
meningococcemia
GN sepsis
what are some things exotoxin can do (6)
- inhibit protein synthesis
- increase fluid secretion
- inhibit phagocytic activity
- inhibit release of NT
- lyse cell MB
- superantigens causing shock
what organisms’ exotoxins inhibit protein synthesis? (4)
- Corynebacterium diphtheriae
- Pseudomonas aeruginosa
- Shigella spp
- EHEC 0157:H7
Diphtheria toxin
- who secretes it
- action
- clinical manifestation
- corynebacterium diphtheriae.
- inactivates elongation factor (EF2) to inhibit protein synthesis
- pharyngitis w/pseudomembranes in th roat and severe LAD (bull neck)
exotoxin A
- who secretes it
- action
- clinical manifestation
- pseudomonas
- inactivates elongation factor (EF2) to inhibit protein synthesis
- host cell death
shiga toxin (ST)
- who secretes it
- action
- clinical manifestation
- Shigella spp
- inactivates 60S subunit by removing adenine from rRNA
- GI mucosal damage –> dysentry … potential HUS 2/2 cytokines
shiga-like toxin (SLT)
- who secretes it
- action
- clinical manifestation
- EHEC
- inactivates 60S subunit by removing adenine from rRNA
- enhances cytokine release –> HUS … cannot invade host cells
what organisms have exotoxins that can increase fluid secretion (3)
- ETEC
- vibrio cholera
- bacillus anthracis
heat-labile toxin (LT)
- who secretes it
- action
- clinical manifestation
- ETEC
- increase cAMP –> increase Cl and H2O secretion in GI
- watery diarrhea
heat-stable toxin (ST)
- who secretes it
- action
- clinical manifestation
- ETEC
- increase cGMP –> decrease resorption of NaCl and water in gut
- watery diarrhea
cholera toxin
- who secretes it
- action
- clinical manifestation
- vibrio cholerae
- increases cAMP by permanent activation of Gs –> increase Cl and water excretion in GI
- voluminous “rice-water” diarrhea
edema factor
- who secretes it
- action
- clinical manifestation
- bacillus anthracis
- mimics AC –> increases cAMP
- edmatous borders of black eschar in cutaneous anthrax
what organism has exotoxin that inhibits phagocytic ability (1)
- bordetella pertussis
pertussis toxin
- who secretes it
- action
- clinical manifestation
- bordetella pertussis
- increase cAMP by disabiling Gi –> impairs phagocytosis
- Whooping cough
what organisms have exotoxins that inhibit release of NT (2)
- clostridium tetani
2. clostridium botulinum
tetanospasmin
- who secretes it
- action
- clinical manifestation
- clostridium tetani
- protease that cleaves SNAREs that release GABA
- spasticity and lockjaw 2/2 inability relax
botulinum toxin
- who secretes it
- action
- clinical manifestation
- clostridium botulinum
- protease that cleaves SNAREs that release Ach
- flaccid paralysis
what organisms have exotoxins that lyse cell MBs? (2)
- clostridium perfringens
2. strep pyogenes
alpha toxin
- who secretes it
- action
- clinical manifestation
- clostridium perfringens
- phospholipase (lecithinase) that degrades tissue and cell MB
- PL degradation –> myonecrosis (gas gangrene) and hemolysis (“double zone” of hemolysis on blood agar)
streptolysin O
- who secretes it
- action
- clinical manifestation
- strep pyogenes
- protein that degrades cell MB
- lyses RBCs –> beta-hemolysis
ASO titers used to dx rheumatic fever
what organisms have exotoxins that cause shock (2)
- staph aureus
2. strep pyogenes
toxic shock syndrome toxin (TSST-1)
- who secretes it
- action
- clinical manifestation
- staph aureus
- recruits MHC-II and TCR to cause overwhelming release of IFN-gamma and IL-2 –> shock
- fever, rash, shock
exotoxin A
- who secretes it
- action
- clinical manifestation
- strep pyogenes
- recruits MHC-II and TCR to cause overwhelming release of IGN-gamma and IL-2 –> shock
- fever, rash, shock
some consequences of endotoxin (9)
ENDOTOXIN
Edema Nitric oxide DIC / Death On outer MB TNF-alpha O-antigen Xtremely heat stable IL-1 Neutrophil chemotaxis
what three things does lipid A of endotoxin activate?
- activates macrophages
- activates copmlement
- activates TF
consequences of LPS activating macrophages? (3)
- IL-1 –> fever
- TNF –> fever and hypotension
- NO –> hypotension
consequences of LPS activating TF? (1)
- coagulation cascade –> DIC
consequences of LPS activating complement? (2)
- C3a –> hypotension and edema
2. C5a –> neutrophil chemotaxis
what is bacterial transformation?
taking up naked DNA from environment after cell lysis
which organisms are better known for ability for transformation (3)
SHiN
strep pneumo
h flu
neisseira
conjugation partners
F+ : has plasmid for genes of pilus and conjugation
F- the receiver
what’s trasnferred in conjugation
just plasmid DNA, not actual bacterial chromosomal genes
what’s transposition
where transposon (DNA segment) can jump from one location to another (b/w plasmid and genome etc)
what are the two types of transductions?
- generalized
2. specialized
what’s generalized transduction
“packaging event”
lytic phage infects bacterium, cleaves bacterial DNA and parts of bacterial DNA packaged in viral capsid
phage will then infect next cell and transfer genes
what’s specialized transudction
“excision event”
lysogenic phage infects bacterium
viral DNA goes into bacterial DNA and excises out the flanking bacterial genes
genes for which toxins are coded on lysogenic phages? (5)
- ShigA-like toxin
- Botulinum toxin
- Cholera toxin
- Diphtheria toxin
- Erythrogenic toxin of strep pyogenes
