Clostridium species is a topic covered in the Johns Hopkins ABX Guide.

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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 the 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 components of mixed infections or bacteremia; pathogenic role often unclear.
Clostridia + Clostridial toxins*




Gastrointestinal tract

  • C. perfringens 


Food intoxication, diarrhea, sudden infant death

Beta toxin

Necrotic enteritis

  • C. difficile 

Ted A + Ted B

Antibiotic-associated diarrhea + colitis

  • C. septicum 


Intestinal myonecrosis

  • C. botulinum

BoNT/A, B, E

Human botulism

Wound-related diseases

  • C. perfringens 

alfa toxin

Gangrene, Puerperal sepsis

  • C. sordellii 

Tcsl, Tcstl


  • C. tetani 



  • C. novyi 



  • C. botulinum

BoNT/A + B

Wound botulism

* Adapted from Popoff MR, Bouvel P; Future Microbio 2009; 4: 1021[9]

TeNT - Tetanus toxin; BoNT - Botulinum neurotoxin; TcsH - C. sordellii hemorrhagic toxic; TcsL - C. sordellii lethal toxin; TcdA, alpha-toxin; TedB - Beta toxin

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Last updated: November 7, 2019