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Systematic Bacteriology
Lec.(3)
Genus: Bacillus
The anthrax bacillus, Bacillus anthracis, was the first bacterium shown
to be cause of a disease. In 1877, Robert Koch grew the organism in pure
culture, demonstrated its ability to form endospores, and produced
experimental anthrax by injecting it into animals.
General characteristic:1- Gram positive rods in old culture appear as gram negative, arranged in
chain.
2- Motile by peritirchous flagella except B.anthracis (non motile).
3- Spore former bacteria.
4- B.anthracis capsulated (polypeptide) when isolated from tissue
(specimen) appear irregular & fragmented when stained by polychrome methylene blue (Mac fadyean reaction).
5- Aerobic, catalase positive & have ability to liquefied gelatin.
6- They form pellicles in liquid media.
7- They can persist for years in dry earth and may remain viable for
month in animal hides.
8- The virulence factors of B.anthracis are its capsule and threecomponent toxin, both encoded on plasmids.
Normal habitat:
- Found in infected animal.
- Spores are found in soil, vegetable, water ….. etc.
Dr. Yagoub Hamadt allah
1
albah university
Page 2 of 4
Systematic Bacteriology
Lec.(3)
Medical important species:
 B. anthracis.
 B. cereus.
 B. subtilis.
 B. mycoides.
 B. mesentericus.
Pathogenicity:
(B. anthracis):
Anthrax is caused by Bacillus anthracis. Humans acquire the
disease directly from contact with infected herbivores or indirectly via
their products (zoonotic disease). The clinical forms include
(Depending on the source and the site of infection)
1- Cutaneous anthrax (enter
through damaged skin producing
malignant pustule which usually ulcerates and surrounded by edema.
(fatal septicemia & toxaemia )
2- Pulmonary anthrax:
Caused when inhalation large number of B. anthracis spores (wool
sorter's disease).
3- Enteric anthrax:
Sever from of gastroenteritis with fever, abdominal pain and bloody
diarrhea due to ingestion infected meat.
Dr. Yagoub Hamadt allah
2
albah university
Page 3 of 4
Systematic Bacteriology
Lec.(3)
* B. cereus:
- Cause food poisoning. The toxin is produced when bacilli sporulate,
usually in rice that have been cooked and then stored in warm
temperatures.
- May cause opportunistic infection in immuno-compromised persons eg
pneumonia, bacteraemia & wound infections, (haemolysis on B. A) .
* Diagnosis:
1- Specimens)
- Fluid aspirated from cutaneous lesions.
- Sputum.
- Stool, Blood for culture.
2- stain:
Form infected tissue.
- G+ve rod, large.
- Short chains.
- Motile except B. anthracis.
- Mc fadyean reaction.
- Fixation using potassium permanganate
3- Culture:
On Blood agr:
Produce large 2 – 5 mm in diameter, produce grey- white colonies, the
colonies are non haemolytic.
- Slowly liquefies the gelatin.
- B. cereus N. L.F. rapidly liquefies gelatin.
- Mannitol egg- yolk phenol – Red polymyxin agar (selective media).
Dr. Yagoub Hamadt allah
3
albah university
Page 4 of 4
Systematic Bacteriology
Lec.(3)
- B.anthracis ( Medusa head like)
Control:Anthrax: Control in animals is essential for control in humans. In endemic
areas, animals that die suddenly should be handled cautiously and livestock
should be vaccinated annually. A human vaccine is available for individuals
in high-risk occupations. Anthrax is readily treated with antibiotics (e.g.,
penicillin, tetracycline, chloramphenicol, gentamicin, or erythromycin).
Other Bacillus Infections: Control is by good hygiene. Treatment is with
non-ß-lactam antibiotics for Gram-positive bacteria. Food poisoning is
controlled by adequate cooking, avoidance of recontamination of cooked
food, and proper storage (efficient refrigeration).
Dr. Yagoub Hamadt allah
4
albah university