Saprophytic, non-pathogenic microorganisms prevalent in soil , water, and air , such as B. Cereus , B. subtilis . The B. anthracis is the main pathogen of the genus Bacillus . Members of this genus are sporulated aerobic gram-positive rods.
Morphology
The B. anthracis is a bacillus thick and long, cut ends bracket , arranged in chains and grampositivos .
The spore is found in the center of this immobile bacillus.
Cultivation and growth
They develop in simple culture media where they form round colonies, with a ground- glass appearance, and non-hemolytic on blood agar .
They are strict aerobes, and they liquefy gelatin , where the appearance of their growth is that of an inverted pine .
Pathogeny
The B. anthracis lives in animals ( cattle sheep, bovine and equine ), which causes the disease called Anthrax .
Its pathogenicity is due to a capsule in the tissues , composed of a polypeptide formed by D-glutamic acid .
Man becomes infected when handling sick animals (veterinarians, wool carders , butchers) or working in industries that use products derived from infected animals (brushes, hides ).
The microorganism penetrates through abrasions of the skin or mucosa , producing a necrotic ulcer (malignant pustule), from which the infection can spread, giving septicemia .
Inhalation of spores into the lungs sometimes causes highly fatal pneumonia .
ID
- Pathological products : pus from the local lesion, blood and sputum .
- Microscopic examination : chains of large gram-positive bacilli can be seen in the stained smears.
- Culture : on blood agar plates it produces characteristic non-hemolytic gray colonies . In semi-solid media, the anthrax bacillus is always immobile, unlike other non-pathogenic members of the genus Bacillus that are mobile. In the gelatin medium its action and the appearance of its growth can be appreciated.
- Ascoli thermoprecipitation reaction : infected tissue extracts show a precipitate ring when deposited on serum with specific antibodies