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- Clostridia produce the largest number of toxins of any bacterial class.
- The common source of entry in humans is the gastrointestinal tract or trauma.
- Obligate anaerobic bacteria with unusual features: spore formation, toxin production and normally reside in the environment or the gastrointestinal tract of humans and animals. Dominant form in human intestinal flora.
- Belongs to phylum Firmicutes which is the dominant component of the fecal microbiome. Clostridia spp. account for 50% or about 1013/gm stool.
- Species specific toxin expression:
- Non toxigenic strains are often often component of mixed infections or bacteremia; pathogenic role often unclear.
Food intoxication, diarrhea, sudden infant death
Ted A + Ted B
Antibiotic-associated diarrhea + colitis
BoNT/A, B, E
Gangrene, Puerperal sepsis
BoNT/A + B
* Adapted from Popoff MR, Bouvel P; Future Microbio 2009; 4: 1021 
TeNT - Tetanus toxin; BoNT - Botulinium neurotoxin; TcsH - C. sordellii hemorrhagic toxic; TcsL - C. sordellii lethal toxin; TcdA, alpha toxin; TedB - Beta toxin