Lecture 50 - bacterial exotoxins Flashcards
______ are denatured forms of exotoxins that no longer have toxic effects but are antigenic –> so can be used as vaccines.
Toxoids
Diphtheria toxin (DT) is an __-__ type exotoxin.
How do these types of toxins work, and what specifically does the A component of DT do?
A-B type
A-B type toxins use the B subunit to Bind and the A subunit to carry out enzymatic Activity that is toxic to the infected cell. In the case of DT, the A subunit ADP-ribosylates
elongation Factor 2 –> blocks translation.
Pertussis and Cholera also produce A-B exotoxins. The A subunits of these exotoxins stimulate ______ cyclase, thus increasing intracellular ______ levels.
Adenyly cyclase
cAMP
Some exotoxins work by disrupting the cell membrane via _______ formation that causes cell swelling and lysis. Others have _______ activity, that cleave lipid components of the membrane –> Clostridium perfringens alpha-toxin is an example.
Pore formation
Phospholipase activity
Some exotoxins act as superantigens. _____ produced by some Staph sp. is an example.
TSST
Corynebacterium diphtheriae is a Gram ___ bacillus with _____ ends (look like little basball bats). The bacilli are palisading (clump together). C. diphteriae is an aerobic bacteria that grows on selective media and forms a _______ in the back of the throat. Diphtheria toxin is _____-regulated, so it is highly expressed when levels are low. Think about what this means for _____ deficient patients.
Gram +
Clubbed ends (palisading)
Pseudomembrane
Iron-regulated
Iron-deficient –> these patients would be more susceptible to diphtheria toxin.
Treatment of C. diphtheria infection uses antitoxin and antibiotics (penicillin or _____). There is also a combination vaccine (DTaP/Tdap) against diphtheria, tetanus, and pertussis. What is the vaccine made from?
Erythromycin
Toxoids
B. pertussis is the causative agent for _____ cough. It is a “dumpy” looking ________ (morphology). Pertussis produces two toxins, both of which increase intracellular levels of _____, thereby suppressing innate immunity. One of the toxins mimics host Adenyly cyclase (AC), and the other stimulates the host’s AC. Treatment can involve antibiotics early on to prevent the spread, but patients typically need adequate ____ support.
Whooping cough
Coccobacillus
cAMP
Oxygen
Pseudomonas aeruginosa is a Gram ___ bacillus found in soil, water, and animals. Its colonies produce a characteristic ____ odor and ____-____ pigment on agar. It is an obligate _____ (cannot ferment), but has minimal nutrition requirements. Keep in mind it is an _______ pathogen, so it infects those who are immunocompromised. This bacteria forms a slime layer –> what does this help prevent, similar to capsules?
Treatment is aggressive and uses ____ (how many?) antibiotics
Gram -
Fruity odor
Blue-green pigment
Opportunistic
This helps prevent phagocytosis, so it evades immunity.
2
ALL Clostridium are Gram ___ bacilli that are obligate ______ (should make sense since C. diff is in intestines.)
Gram +
obligate Anaerobes
Clostridium tetani have a characteristic ____ stick morphology, because at the end of the bacili they have spores. Clinical appearance can include spastic ______ or local paralysis (lockjaw). Tetanus toxin is an ___-___ toxin that acts on inhibitory neurons by cleaving synaptobrevin (a SNARE protein), thus preventing the release of ______ (inhibitory neurotransmitter). Keep in mind the toxin is endocytosed at the neuromuscular junction but is retrograde transported, release in the synapse between the motor neuron and inhibitory neuron, and taken up into the inhibitory neuron where it acts.
Drum stick
Paralyisis
A-B toxin
GABA
Clostridium botulinum is a Gram + slender _____ (morphology) with endospores at the ends. It causes _____ paralysis (opposite of tetanus), and it can cause “floppy baby” syndrome in babies who consume _____. Because it has the opposite effect of tetanus toxin, and yet it acts in the same way by cleaving SNARE proteins, where might the botulinum A-B toxin act and which NT does it prevent release of?
Keep in mind infection is typically from ingestion of the _____, rather than infection with the bacteria.
Bacillus
Flaccid Paralysis
Honey
It acts in the motor neuron after being taken up at the NMJ, and it prevents the release of Ach –> hence the flaccid paralysis.
Toxin
Clostridium perfringens is also a spore forming Gram + ______ (morphology). It is a commensal bacteria found in the GI of vertebrates, so it is considered an ________ pathogen (immunocompromised and those with severe wounds are higher risk).
Its alpha toxin is the cause for gas ______ (aka myonecrosis), and its enterotoxin is the cause for about 7% of ______ poisoning cases in the US.
The alpha toxin is a _______ C that hydrolyses _______, thus dirupting cell membranes. The gas is formed from the fermentation of tissue carbs.
CPE, the enterotoxin, forms pores in target cells that allow the influx of _____, which triggers apoptosis and necrosis.
The most important treatment is surgical _______ of a wound showing signs of gas gangrene, and administration of _______ IV. Hyperbaric O2 is controversial (but makes sense since ALL Clostridium bacteria are obligate anaerobes.)
Bacillus
Opportunistic pathogen
gas Gangrene
Food poisoning
Phospholipase C
Phospholipids
influx of Ca++
Debridement
Penicillin IV
