VetBact logo


Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
Veterinary bacteriology

Species/Subspecies: Clostridium botulinum, group III
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: Reference strains: Type C: ATCC 25766. Type D: ATCC 25767.
Macromorphology (smell):
Clostridium botulinum</i>, group III<i>  Clostridium botulinum</i>, group III<i>  
Large greyish white colonies (5 mm in diameter) with very irregular edges. Gives β-hemolysis on blood agar.
Clostridium botulinum</i>, group III<i>  
Large spore forming rods (0.5-2.4 x 3.0-22.0 µm), which appear singly or in short chains. Most strains of C or D type are motile and have peritrichous flagella.
Gram +/Gram -:
Clostridium botulinum</i>, group III<i>  Clostridium botulinum</i>, group III<i>  
G+ (can be difficult to gram stain).
Metabolism: Anaerobic
Other Enzymes: Esculinase -, lecithinase (-), tryptophanase (-).
Fermentation of carbohydrates:
Other carbohydrates: Mannose v, Xylose -.
Spec. Char.: C. botulinum strains within group III are weakly proteolytic, but not saccharolytic. C.f. other C. botulinum types.
Special Media:
Reservoir: Meat, carcasses, dead invertebrates, maggots, rotting vegetation, silage of bad quality, hay or silage contaminated with dead rodents, bones.
Disease:Botulism is a serious and potentially fatal disease. C. botulinum-strains within group III is the most common cause of botulism or botulinus intoxication in 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
Poultry (type C/D)Botulism (Limberneck)Paralysis of neck, wings and legs. Death due to respiratory paralysis
Mink (type C)BotulismPhotophobia, movement disorder, 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 III produce botulinum toxin type C or D and the genes for these toxin are carried by a bacteriophage. There are in fact two toxins of type C: C1 and C2 and it is C1, that is the neurotoxin. Strains within group III are of toxin type C or D. There are also strains having a chimeric toxin gene, i.e. the gene consists of segments from both the botulinum toxin C gene and the botulinum toxin D gene. These strains will then produce a chimeric botulinum toxin type C/D.

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.

Genome Sequence:
Acc-noStrainSize (bp)GenomeRef.
CP002410 BKT015925 2 773 157 1c + 5 c Nr 115
At least 4 strains have been sequenced and 1-5 plasmids have been reported.

16S rRNA Seq.:
Acc-noStrainNumber of NTOperon
L37590 ATCC 17782 (Type C) 1453 10 

, group III - Fig. 24:6. 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: 2015-11-19.">Clostridium botulinum</i>, group III<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 III are most closely related to Clostridium novyi and Clostridium haemolyticum and not to any strain within 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. In the case of C. botulinum, you can really say that taxonomy is not consistent with phylogeny. The type strain is of toxin type A.
Reference(s): No. 4, 33, 123
Link: Botulinum + Tetanus Toxin Mechanism

Recently Updated

Recent blog posts

Most recent comment

Swedish University of Agricultural Sciences