This document provides information on Bacillus anthracis, which causes anthrax. It describes the morphology, staining properties, culture characteristics, virulence factors, pathogenesis, clinical signs, diagnosis and treatment of anthrax. B. anthracis is a gram-positive, spore-forming bacterium that forms an anti-phagocytic capsule. It produces two virulence factors, including a lethal factor and edema factor, which are encoded on plasmids. Anthrax most commonly affects herbivores and can be transmitted to humans by contact with infected animals or their products.

1. By
Assiut University
New-Valley branch
Department of Microbiology & Immunity

2. Morphology :-
Gram +ve bacteria
Large (3-8 x 1-2 µm) , Encapsulated Bacilli (Polypeptide capsule)
Spore forming
Non- Motile
Facultative anaerobic
May be Single , paired or long chain
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3. The poly peptide capsule consist of D-glutamic acid
* Anti-Phagocytic & Plasmid encoded
* Not good Immunogen ( Resisted to Antibodies)
Morphology :-
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5. With spore stain spore appear pink & bacilli appear blue .
With Gram stain (or Methylene blue) B. anthracis is violet or blue &
surrounded by Hallo zone .
With Polychrome Methylene Blue (Mc Fadyean’s reaction) B. anthracis appear
blue bacilli surrounded by purplish bink capsule ( diagnostic for B. anthracis ) .
With fluorescent-labeled antibody B. anthracis become fluorescent .
Staining :-
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6. Nutrient broth >>> produce floccular turbidity >>> appear as cotton
wool in the tube.
Nutrient agar >>> gray white , irregular colonies >>> “Medusa head “
appearance.
Blood agar >>> produce Non-hemolyic gray-white colonies , with
irregular margins (curled hair).
Gelatin stap >>> slow lequification >>> inverted fir tree appearance.
Culture :-
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7. (blue)
(red)
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8. B. anthracis on Blood Agar
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9. B. anthracis is catalase , nitrate reduction , starch hydrolysis , gelatin
lequification tests >>> +ve .
On litmus milk>>> soft card is formed and digested quickly.
MR. & V.P. tests are variable , H2S production is -ve .
Biochemical characteristic :-
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10.  Starch Hydrolysis (Amylase Activity) :-
* Principle :
Starch + Iodine >>>>> Blue color
Glucose + Iodine >>>>> No reaction
* Procedure :
* Result :
Biochemical characteristic :-
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11. B. anthracis contain 2 plasmid encoded virulence factors :
1) Capsule >>> linear γ-D-glutamic acid polymer.
2) Exotoxin (Trimer) consist of :
A- Protective Antigen (PA) :
It form Membrane channel that allow Edema Factor (EF) and Lethal Factor
(LF) to enter the mammalian cell via endocytosis.
B- Lethal Factor (LF) :
Both PA and LF are required for lethal activity.
C- Edema Factor (EF) :
Both PA and EF are required for edema to occur.
Virulence factors :-
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12. Pathogenesis :-
Synonyms : Splenic fever
Characters :
- Zoonotic , highly infectious disease
- primarily affecting herbivores animals such as cattle , sheep , horses , mules
and goats & secondary affecting man .
Etiology :
-B. anthracis which belong to family Bacillaceae
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13. Anthrax (cont.)
Susceptibility :
- herbivores animals such as cattle , sheep , horses , mules , goats , pigs , dogs .
- human is accidental host while birds are resistant.
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15. Anthrax (cont.)
Mode of transmission & source of Infection :-
- Herbivores animals infection by >>>> ingestion or inhalation of spores in the soil.
- Carnivores become infected through consumption of infected animals that have died
from anthrax.
- Human infected through :
1) broken skin (injuries).
2) Inhalation anthrax spores from contaminated animal products as flesh , bones ,
hides , hair & wool.
3) Ingestion of infected animal meat.
** N.B : Accidentally via biting flies ( Minor route ) during sever outbreaks.
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16. Anthrax (cont.)
Clinical signs :-
1- Peracute course of illness:
* Mainly in cattle & sheep. * Lasts approximately for 1-2 hours.
* Characterized by : Sudden death of the animal ( 1st indication for anthrax ).
2- Acute course of illness:
* Mainly in equines. * Lasts approximately 96 hours.
* Characterized by : Fever, enteritis, septicemia >>>> death.
3- Subacute / chronic course of illness:
* Mainly in swine, dogs and cats.
* Characterized by : Dysphagia, dyspnea, sever enteritis.
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17. Anthrax (cont.)
Post mortem lesions :-
- Bloody discharge from natural openings e.g.: nose, mouth, anus, etc.
- Rabid bloating , failure of blood to clot.
In MAN anthrax has 3 forms :-
- Cutaneous form (malignant pastule).
- pulmonary form (wool sorter’s disease).
- Gastrointestinal form.
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18. Bloody dischargeBloating
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19. Anthrax (cont.)
Diagnosis :-
1) Sampling :
- Blood sample >>> only taken from ear , tail
vein or natural openings of the dead animals
*** Blood smear stained by :
- With Gram stain (or Methylene blue)
- With Polychrome Methylene Blue
(Mc Fadyean’s reaction)
2) Isolation & Identification :
Don’t Open
the carcass
of the dead
animal
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20. Anthrax (cont.)
Diagnosis :-
3) Laboratory animal inoculation :
4) serological test :
- ELISA for PA , LF and EF
*** Ascoli test :
1- Procedure :-
2- Result :-
+ve reaction >>>> formation of a ring of precipitate at the junction of the
2 fluids in the capillary tube.
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21. Anthrax (cont.)
Diagnosis :-
5) Fluorescent labeled antibody staining :
6) PCR :
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22. Anthrax (cont.)
Treatment :-
1- Large doses of antibiotics with immune serum .
2- Penicillin & tetracycline are the most active .
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23. Anthrax (cont.)
Prevention and control :-
1- Notification of the authorities .
2- Quarantine the area .
3- Don’t open the carcass or examine postmortem & minimize the contact .
4- Passive immunization .
*** Vaccination :-
1) Animal Vaccine 2) Human Vaccine
- Pasteur Vaccine - Spore Vaccine
- Sterne attenuated spore vaccine - UK Vaccine - US Vaccine
*** Simultaneous Method : The best method is to inject 10-20 c.c. of hyper immune serum in one
shoulder & at the same time a dose of used vaccine is injected into the other shoulder .
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