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The Gram’s positive spore former aerobic bacilli The genus Bacillus

The Gram’s positive spore former aerobic bacilli The genus Bacillus. Microscopic characteristics: Gram-positive spore-forming, non-motile, aerobic large bacilli, 5-8 µm x 1.5 µm, arranged in chains. In Smears from specimens, bacilli are capsulated.

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The Gram’s positive spore former aerobic bacilli The genus Bacillus

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  1. The Gram’s positive spore former aerobic bacilliThe genus Bacillus Microscopic characteristics: Gram-positive spore-forming, non-motile, aerobic large bacilli, 5-8 µm x 1.5 µm, arranged in chains. In Smears from specimens, bacilli are capsulated. When stained with Loeffler’s polychrome methylene blue (McFadyean’s reaction), the capsular material appear as fragmented pink rim round blue bacillus.

  2. Bacillus anthracis. Gram stain. 1500X a

  3. Malachite green stain show the microbe with its endospores: a

  4. Electron microscopy demonstrating some motile flagellated Bacillus species. a

  5. Cultural characteristics: The organism grows on nutrient agar or blood agar giving large 2-5 mm grey white irregular colonies. On blood agar the colonies are non-haemolytic bacterium. The colonies should be differentiated from those of bacillus cereus which are beta haemolytic bacterium.

  6. Bacillus anthracis colonies are non-hemolytic on blood agar, while beta hemolytic activity is presented by Bacillus cereus growth. a

  7. Pathogenesis of Bacillus anthracis: AnthraxAnthrax is primarily a disease of herbivorous animals, such as cattle, sheep, horses, mules, and goats. The most common form of the disease in humans is cutaneous anthrax, which is usually acquired via injured skin or mucous membranes. The spores germinate, vegetative cells multiply, and a characteristic gelatinous edema will be established.

  8. a Edema will be converted into papule within 12-36 hours after infection. The papule changes rapidly to a vesicle, then a pustule (malignant pustule), and finally into a necrotic ulcer from which infection may disseminate, giving rise to septicemia. Lymphatic swelling also occurs within seven days.

  9. a Another form of the disease, inhalation anthrax (woolsorters' disease), results most commonly from inhalation of spore-containing dust where animal hair or meat are being handled. Gastrointestinal anthraxis analogous to cutaneous anthrax but occurs on the intestinal mucosa. The bacteria spread from the mucosal lesionto the lymphatic system. Intestinal anthrax results from the ingestion of poorly cookedmeatfrom infected animals.

  10. Bacillus cereusfood poisoning: Bacillus cereuscauses two types of food-borneintoxications. One type is characterized by nauseaand vomitingand abdominalcrampsand has an incubation period of 1 to 6 hours. This is the "short-incubation" or emeticformof the disease. The second type is manifested primarily by abdominal cramps and diarrhea with an incubation period of 8 to 16 hours. Diarrhea may be a small volume or profuse and watery. This type is referred to as the "long-incubation" or diarrhealformof the disease.

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