Bacillus anthracis 2016 2017 original

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

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
Prof / Mohamed A. Madany
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The poly peptide capsule consist of D-glutamic acid
* Anti-Phagocytic & Plasmid encoded
* Not good Immunogen ( Resisted to Antibodies)
Morphology :-
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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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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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(blue)
(red)
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B. anthracis on Blood Agar
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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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 Starch Hydrolysis (Amylase Activity) :-
* Principle :
Starch + Iodine >>>>> Blue color
Glucose + Iodine >>>>> No reaction
* Procedure :
* Result :
Biochemical characteristic :-
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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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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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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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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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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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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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Bloody dischargeBloating
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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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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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Anthrax (cont.)
Diagnosis :-
5) Fluorescent labeled antibody staining :
6) PCR :
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Anthrax (cont.)
Treatment :-
1- Large doses of antibiotics with immune serum .
2- Penicillin & tetracycline are the most active .
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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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Bacillus anthracis 2016 2017 original

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