Clostridium tetani

C. tetani produces an exotoxin called tetanospasmin, which targets inhibitory neurons (Renshaw cells) in the spinal cord. When tetanospasmin enters a neuron at the neuromuscular junction, it travels in a retrograde direction via the motor protein dynein to reach the central nervous system.

Once in the central nervous system, tetanospasmin cleaves a SNARE protein (soluble NSF attachment), synaptobrevin 2, thus preventing the fusion of the membrane vesicles and inhibiting the release of GABA and glycine from the inhibitory cells. Therefore, the excitatory neurons are not countered by the inhibitory neurons resulting in a hyperactivity of the muscles when stimulated and leading to tetanic spasms.

Clostridium botulinum

C. botulinum toxin inhibits (stimulatory) acetylcholine release at the neuromuscular junction leading to flaccid paralysis.

Clostridium perfringens

associated with motorcycle accidents; military combat wounds

spore-forming

anaerobe

clostridio myonecrosis = gas gangrene

Alpha toxin = lecithinase (break down cell membrane)

lecithinase can cause red cell hemolysis

forms double zone of hemolysis on blood agar

Nagler Reaction

Food poisoning -> slow-onset watery diarrhea

Tx

IV Penicillin

Clostridium difficile

Exotoxin A - causes watery diarrhea

Exotoxin B - depolymerization of actin filaments;