Question
The following culture appearance on solid medium is seen in growth of which organism:
A. Bacillus Anthracis
B. Staphylococcus Aureus
C. Clostridium tetani
D. Corynebacterium Diphtheria
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Correct Answer » A Explanation |
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Ans:A. Bacillus Anthracis.
Medussa Head Colony appearance is Seen in the image,characteristic of Bacillus Anthracis.
B Anthracis.
Historical impotance
- First pathogenic bacteria to be seen under microscope
- First demonstration of blood borne transmission
- The first bacterium shown to be the cause of a disease- Koch’s Postulate
- First effective vaccine (Pasteur 1881).
Microbiology
- Gram positive rods
- 3-10 micron by 1-1.6 micron
- Aerobic bacilli forming heat-resistant spores
- Non acid fast, Non-motile
- Capsule (poly d-glutamate-protein).
Identification
Staining:
- Gram stain:Gram positive bacilli forming chains. The cells have characteristic squared ends. The endospores are ellipsoidal shaped and located centrally in the sporangium. The spores are highly refractile to light and resistant to staining.
- Mac Faydean Reaction:Polychrome Methylene Blue for demonstrating the capsule
Cultural characteristics
- Solid medium : Medusa head colony
Edge of a colony is composed of long,interlacing chains of bacilli resembling ,locks of matted hair
- Polymyxin lysozyme EDTA thallous acetate (PLET agar).
- Gelatin stab culture:Inverted Fir tree Appearance.
- String of pearl appearance of Culture medim with Penicillin
VIRULENCE FACTORS
- Anthrax Toxin – Complex of proteins ( all the components thermolabile)
- Edema factor (Factor I)
- Protective factor (Factor II)
- Lethal Factor (Factor III)
- Protein capsule – Poly D Glutamic acid capsule- Inhibits phagocytosis
Killing of Spores:
- DUCKERING: 2% Formaldehyde kills spores at 30-40˚C for 20 mins for disinfection of wool and as 0.25% at 60˚C for 6 hrs for animal hair and bristles