Bacillus anthracis


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Bacillus anthracis

  1. 1. BACILLUS ANTHRACIS G.HARIPRASAD M.Sc.,(Med micro), M.phil., Lecturer in Microbiology Department of Microbiology Thoothukudi Govt. Medical College Thoothukudi
  2. 2. <ul><li>Aerobic, </li></ul><ul><li>Gram positive </li></ul><ul><li>sporulating </li></ul><ul><li>capsulated </li></ul><ul><li>non-motile bacilli. </li></ul>Cause of anthrax BACILLUS ANTHRACIS (GRAM STAIN)
  3. 3. Resistance <ul><li>Vegetative forms are destroyed – 600C in 30min. </li></ul><ul><li>Spore form – viable for years in soil </li></ul><ul><li>Autoclaving – kills anthrax spores </li></ul><ul><li>4% KmNo4 in 15 mts - kills anthrax spores </li></ul><ul><li>Susceptible to many antibiotics like pencillin etc., </li></ul>
  4. 4. ANTIGENS <ul><li>Important antigen: </li></ul><ul><li>Capsular antigen </li></ul>Other antigens: Cell wall polysaccharide antigens Somatic protein antigens
  5. 5. 1. Polypeptide capsule – antiphagocytic 2. Anthrax toxin Multicomponent anthrax toxin Factor I – Edema factor Factor II – Protective factor Factor III – Lethal factor Toxin binds with susceptible cells through factor II Factor I & III enters the cell Factor I – causes edema by rising cAMP levels. Factor III – Kills the cell finally.
  6. 6. <ul><li>Pathogenesis </li></ul><ul><li>Animals get infection rarely by contact with infected animals </li></ul><ul><li>Ingestion of spores – very common. </li></ul><ul><li>Infected animals – discharge more anthrax bacilli from mouth, nose & rectum – sporulation in soil – survive for years – source for other animal </li></ul>
  7. 7. HUMAN ANTHRAX <ul><li>Accidental infection </li></ul><ul><li>Secondarily infected from diseased animal </li></ul><ul><li>Three clinical types </li></ul><ul><li>- Cutaneous anthrax – most common </li></ul><ul><li>- Pulmonary anthrax – less common </li></ul><ul><li>- Intestinal anthrax – very rare </li></ul>
  8. 8. CUTANEOUS ANTHRAX <ul><li>Spores enter thro’ abraded skin </li></ul><ul><li>Germinate & Multiply at the site of entry. </li></ul><ul><li>Localised lesions - Face, neck & hand. </li></ul><ul><li>Papule – vesicle – pustular – centrally necrosed – black coloration. </li></ul>
  9. 10. PULMONARY ANTHRAX <ul><li>Inhalation of the dust or filaments of wool from infected animals, particularly in wool factories ( wool sorter’s disease) </li></ul><ul><li>Haemotogenous spread – 50% meningitis </li></ul>
  10. 11. INTESTINAL ANTHRAX <ul><li>Consumption of improperly cooked infected meat. </li></ul><ul><li>Causes violent enteritis with bloody diarrhoea </li></ul>All clinical conditions lead to septicaemic anthrax if not treated early – Highly fatal!!!
  11. 12. Laboratory diagnosis <ul><li>Pus from pustules – cutaneous anthrax </li></ul><ul><li>Sputum – pulmonary anthrax </li></ul><ul><li>Stool / suspected food – intestinal anthrax </li></ul><ul><li>Blood – septicaemic anthrax </li></ul>
  12. 13. <ul><li>Microscopy </li></ul><ul><li>Gram stain – for bacilli demonstration </li></ul><ul><li>McFadyean’s reaction – for capsule demonstration. </li></ul><ul><li>Spore staining – for spore demonstration. </li></ul>Gram stain McFadyaen’s reaction Spore stain
  14. 15. Culture <ul><li>Other non-selective media </li></ul><ul><li>Nutrient agar – colonies – medusa head appearance on low power microscopy </li></ul><ul><li>Blood agar – usually non-haemolytic </li></ul>
  15. 16. Gelatin liquefaction Maximum liquefaction on the surface than at the bottom INVERTED FIR TREE APPEARANCE
  16. 17. Nitrate reduction test Nitrate negative Nitrate positive
  17. 18. <ul><li>ANIMAL INOCULATION </li></ul><ul><li>Mouse/ guinea pigs are injected with specimens. </li></ul><ul><li>Animal dies in 48 hrs </li></ul><ul><li>Examine bacilli in blood of dead animal. </li></ul>
  18. 19. TREATMENT <ul><li>Pencillin </li></ul><ul><li>Erythromycin </li></ul><ul><li>Antitoxins – in emergency cases </li></ul>ANIMAL VACCINE – Sterne vaccine HUMAN VACCINE – Alum Precipitated Toxoid – 3 doses intramuscularly at intervals of 6 weeks and 6 months Booster dose after one year.