Clostridium and Anthracis - The Veterinary Site

Clostridium and Anthracis



Introduction and Morphology:

·         Very much similar to bacillus; it is also G +ve, Bacilli (rod shape), spore forming; so, it’s difficult to differentiate these two
·         Differentiate on the basis of growth on agar in aerobic conditions
·         Clostridium is obligate anaerobe and bacillus is aerobe
·         They are catalase and oxidase -ve; but bacillus is +ve
·         Form endospore
·         0.4-1.2 µm in diameter, 3-8 µm in length
·         Spore forming
·         Present in soil, elementary tract of animal, decaying vegetations, carcasses, & feces of carrier animal
·         Some species also withstand digestive system
·         Majority of species are motile except Cl. Perfringens
·         Cl. Perfringens also weak in formation of spore

Growth requirement and colony characteristics:

·         Require enrich (extra nutrient) media
·         It gives first β hemolysis and then α hemolysis
·         Form irrelevant colonies on solid media
·         They require 5-10% CO2 also. For this purpose, we use anaerobic jar
·         On meat medium à these organisms have proteolytic enzyme so medium will turn dark or blackish
·         Cl. Perfringens also ferment glucose; so, in muscle they produce gas and acid à causes gas gangrene à in which muscles turn black

Morphology and introduction:

·         G +ve, cylindrical, rod shape, aerobic, spore forming and capsular bacteria
·         Usually flagellated; some are motile and some are non-motile
·         Grow in the form of chains, they make very typical type of pairs, irregular shape colonies
·         Colonies also called as Medusa head like colonies.
·         Present in soil, vegetation, decay organic substances and increase soil fertility.


·         B. anthracis    
·         B. mucoid

·         B. cereus à opportunistic pathogen
·         B. licheniformis ànon-pathogenic, opportunistic pathogen, causes food poisoning
·         B. subtilis à lab strain, non-pathogenic

B. anthracis


·         Definite pathogenic
·         Found all over the world, specially where no organized control of animal disease exists
·         Spores can live in soil for more then 50 years, very much resistant to temperature
·         Used as bioweapon
·         In inhalation and ingestion form mortality is 100%, but in cutaneous form mortality is low.

Transmission spread:

·         Spread by soil, contaminated feed, pasture, land.
·         Carnivores can get infection by feeding on dead animal carcasses.
·         Can also be transmitted from animal to animal
·         Human deals with hides and wool sorting; they can get infection; in this case this disease also called as wool sorter’s disease.
·         Most susceptible are ruminants & humans, then equines, then very less carnivores, birds are resistant but can spread disease.

Morphology and staining:

·         Rods, cylindrical
·         1-1.2µm in diameter and 3-10 µm in length
·         They form capsule but very less protein capsule
·         Protein capsule is formed by D-glutamyl polypeptide; protein capsule is virulent factor
·         Forms endospore oval in shape. This spore contains many layers with time these layers become dry.
·         Spore is 0.7-0.8 µm in diameter and 1.5-3 µm in length
·         They are G +ve in young culture. In very old culture they give G -ve and G +ve staining

Colony characteristics and growth requirements:

·         Grow on blood agar, but give variable hemolysis
·         Aerobic, optimum temperature 37oc
·         Grow well in alkaline medium; from pH 7.5-7.8
·         Colonies are opaque, grayish white, and have irregular borders which gives Medusa head like appearance

Biochemical test:

·         Gelatin liquefication test à +ve
·         Methyl red test   à +ve acid, -ve gas
·         Nitrate reduction test à +ve
·         Can ferment; glucose, sucrose, maltose, fructose, dextrin
·         don’t ferment; lactose, galactose, rabinose, mallose, raffinose, mannitol, inulin
·         also, not produce indole and H2s
·         methylene blue test +ve; this test is used to differentiate among B. cerus and B. anthracis; for B. cerus its _ve.


1.       capsule;
o   antiphagocytic
o   it they get phagocytose but phagolysosome don’t able to kill them. They release some toxin in phagolysosome; these toxin break phagolysosomes and comes into cell.
2.       Complex toxin/complex antigen:
o   Made up of three toxins
i.                     Protective antigen à lea lethal
ii.                   Edema factor à causes edema
iii.                 Lethal factor à cause necrosis
o   Separately these three are less pathogenic
o   It causes swelling and darkening of tissue due to edema and necrosis, by increasing cAMP level
o   When they come out of cell, attacked by immune cells and these immune cells release cytokines, which increase permeability, so swelling and hemorrhages
o   Also, these toxins cause depletion of clotting factors
o   In case of more release of cytokines, body cell releases IL and INF and body got in shock; septic shock

Postmortem findings;

·         Sub cut edema, massive hemorrhages in different parts
·         Swelling of spleen, blood in dark color
·         Absence of rigor mortus
·         Usually postmortem in this disease dead animal

Forms in humans:

In humans B. anthracis has three forms
i.                     Cutaneous à less pathogenic
ii.                   Pulmonary  more pathogenic
iii.                 Ingestion à more pathogenic


·         Precipitation test for serum studies
·         Capsule staining
·          In live animal by puncturing tail vein, make smear and examine by methylene blue stain


·         Penicillin G
·         In case of resistant to penicillin G; oxytetracycline and cephalosporin
·         When septicemia develop no RX is effective


·         Annual vaccination with spore stained vaccine

Clostridium and Anthracis Clostridium and Anthracis Reviewed by Maaz ahmed siddiqui on 02 June Rating: 5

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