VetBact logo


Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
Veterinary bacteriology

Species/Subspecies: Clostridium botulinum, group I
Categories: Causes hemolysis; spore forming; motile; notifiable diseases and bacteria
Etymology: Genus name: a small spindle.
Species epithet: refers to sausage.
Significance:  [Very important]   
Type Strain: Typ A: ATCC 25763. Referensstammar: Proteolytisk typ B: ATCC 7949. Proteolytisk typ F: ATCC 25764.
Macromorphology (smell): Large greyish white colonies (5 mm in diameter) with very irregular edges, which usually produce β-hemolysis on blood agar.
Micromorphology: Large spore forming rods (0.6-1.4 x 3.0-20.2 µm). Most of the strains are motile. Gives hemolysis on bloodagar.
Gram +/Gram -:G+ (kan vara svår att gram-färga).
Metabolism: Anaerobic
Other Enzymes: Esculinase +, lecithinase -, tryptophanase -.
Biochemical Tests: Hydrogen sulphide (H2S) +.
Fermentation of carbohydrates:
Other carbohydrates: Fructose (-), galactoes -, mannose -, ribose -, xylose -.
Spec. Char.: Proteolytic bacteria produce phenols, indols and ammonia from the digestion of proteins.
Special Media:
Reservoir: Soil, carcasses, meat, fish, canned products.
Disease:Botulism or botulinus intoxication is a serious and potentially fatal disease in humans and animals. Botulism is usually an intoxication caused by intake of preformed toxin. It may also happen that spores of C. botulinum germinate in the intestine or in a deep wound and the bacteria may then start to produce toxin. This condition is termed a toxicoinfection.
HostsDiseaseClinical picture
Humans (type A, B, E, F)Classic botulism, food poisoning
Wound botulism
Infant botulism
Nausea, vomiting, diarrhea (sometimes constipation), general malaise, dizziness, fatigue, dry mouth, eye muscle paralysis (possible visual impairment, double vision), speech difficulties and possible respiratory paralysis
Horse (type B)BotulismMuscle tremor, stumbling, knuckling and ataxia with inability to lift the head. Dropping eyelids, large pupils, paralysed tongue with drooling saliva and inability to chew. Death of respiratory failure.
Poultry (type C/D)Botulism (Limberneck)Paralysis of neck, wings and legs. Death of respiratory paralysis
Mink (type C)BotulismPhotophobia, hind end paresis, paralysis, recumbency, and dyspnea. Sudden death due to respiratory paralysis.
Cattle (type C)BotulismPartial or complete function of tongue, sudden death due to respiratory paralysis.
Virulence Factors: C. botulinum strains within group I produce botulinum toxin type A, B or F

The different toxin types have the same basic structure and mechanism of action, but are serologically distinct. Botulinum toxin is a neurotoxin, which is similar to tetanospasmin in structure and mode of action, but they act on different parts of the nervous system. Botulinum toxin is (like tetanospasmin) composed of two protein subunits and one is a protease that destroys the fusion protein to which vesicles containing acetylcholine should bind. Thereby inhibiting the signal transduction between the efferent (= motoric) nerve and muscle cells by preventing vesicles from anchoring to the membrane to release acetylcholine.

This results in a flaccid paralysis. C.f. Clostridium tetani.

Botulinum toxin is very potent, and the lethal dose for humans is approximately 1 ng/kg body weight.

Genome Sequence:
Acc-noStrainSize (bp)Genome
NC_009697 ATCC 19397 (toxin type A) 3 863 450 1c + 0 

16S rRNA Seq.:
Acc-noStrainNumber of NTOperon
L37585 ATCC 25763T 1 453 

, group I - Fig. 202:1. Phylogenetic tree, which illustrates the relations between members of the genus Clostridium (C.). Names of taxa in blue are included in VetBact and taxa in bold are included in this bacterial page. Note that the species C. botulinum is distributed into four different phylogenetic groups. C. botulinum of toxin types B and F can also be found in group II. The tree was generated on line by using the computer program "Tree Builder" at the website of RDP. Bacillus cereus was chosen as outgroup. (T) means type strain and A-G refer to toxin type. Date: 2015-11-18.">Clostridium botulinum</i>, group I<i>  
About 180 differens species have been descibed within genus Clostridium. C. botulinum can be classified into four different phenotypic groups: I-IV. C. botulinum-strains within group I are most closely related to Clostridium sporogenes and Clostridium putrificum and not to any of the other three phenotypic groups of C. botulinum.
Legislation: In Sweden, botulism in animals and humans is notifiable to the Swedish Board of Agriculture and the Public Health Agency of Sweden, respectively. Clostridium botulinum belongs to category A as a potential bioterrorism agent according to NIAID.
Comment:Clostridium botulinum actually represents four different species (phenotypic groups), all of which have at least one of the botulinum toxin genes. The type strain is of toxin type A. In the case of C. botulinum, you can really say that taxonomy is not consistent with phylogeny.
Reference(s): No. 4, 33
Link: Botulinum + Tetanus Toxin Mechanism

Recently Updated

Recent blog posts

Most recent comment

Swedish University of Agricultural Sciences