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G.HARIPRASAD M.Sc.,(Med micro), M.phil.,Lecturer in Microbiology Department of Microbiology Thoothukudi Govt. Medical College Thoothukudi
• Aerobic,
• Gram positive
• sporulating
• capsulated
• non-motile bacilli.
Cause of anthrax
BACILLUS ANTHRACIS
(GRAM STAIN)
Resistance
• Vegetative forms are destroyed – 600C in 30min.
• Spore form – viable for years in soil
• Autoclaving – kills anthrax spores
• 4% KmNo4 in 15 mts - kills anthrax spores
• Susceptible to many antibiotics like pencillin etc.,
ANTIGENS
Important antigen:
• Capsular antigen
Other antigens:Cell wall polysaccharide antigens Somatic protein antigens
1. Polypeptide capsule – antiphagocytic2. 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 cellFactor I – causes edema by rising cAMP levels.Factor III – Kills the cell finally.
Pathogenesis• Animals get infection
rarely by contact with infected animals
• Ingestion of spores – very common.
• Infected animals – discharge more anthrax bacilli from mouth, nose & rectum – sporulation in soil – survive for years – source for other animal
HUMAN ANTHRAX
• Accidental infection• Secondarily infected
from diseased animal• Three clinical types - Cutaneous anthrax –
most common - Pulmonary anthrax –
less common - Intestinal anthrax – very
rare
CUTANEOUS ANTHRAX• Spores enter thro’
abraded skin • Germinate & Multiply at
the site of entry.• Localised lesions - Face,
neck & hand.• Papule – vesicle –
pustular – centrally necrosed – black coloration.
PULMONARY ANTHRAX
• Inhalation of the dust or Inhalation of the dust or filaments of wool from filaments of wool from infected animals, infected animals, particularly in wool particularly in wool factories ( wool sorter’s factories ( wool sorter’s disease)disease)
• Haemotogenous spread Haemotogenous spread – 50% meningitis– 50% meningitis
INTESTINAL ANTHRAX
• Consumption of improperly cooked infected meat.
• Causes violent enteritis with bloody diarrhoea
All clinical conditions lead to septicaemic anthrax if not treated early – Highly fatal!!!
Laboratory diagnosis
• Pus from pustules – cutaneous anthrax
• Sputum – pulmonary anthrax
• Stool / suspected food – intestinal anthrax
• Blood – septicaemic anthrax
Microscopy • Gram stain – for
bacilli demonstration • McFadyean’s
reaction – for capsule demonstration.
• Spore staining – for spore demonstration.
Gram stain
McFadyaen’s reaction
Spore stain
SELECTIVE MEDIA – PLET MEDIUM –POLYMYXIN, LYSOZYME, EDTA & THALLOUS ACETATE
Culture
Culture
• Other non-selective media
• Nutrient agar – colonies – medusa head appearance on low power microscopy
• Blood agar – usually non-haemolytic
Gelatin liquefaction
Maximum liquefaction on the surface than at the bottom
INVERTED FIR TREE APPEARANCE
Nitrate reduction test
Nitrate negative Nitrate positive
ANIMAL INOCULATION
• Mouse/ guinea pigs are injected with specimens.
• Animal dies in 48 hrs
• Examine bacilli in blood of dead animal.
TREATMENT
• Pencillin
• Erythromycin
• Antitoxins – in emergency cases
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.