Anthrax Flashcards
1) classification
Family: bacillaceae
Genus: Bacillus
Species: b.anthracis
Saprophyticus organism
Lives on or get it’s nourishment from dead organisms or decay organic materials
2) morphology
- Large gram positive rods
- have square ends
- arranged in long chains
- capsulated
- non motile
- two forms:
Vegetative
Endospores:
Spores are located in the center
3) growth characteristics
- aerobic or facultative anaerobic
- non fastidious
- utilize simple sources of nitrogen and carbon for energy and growth
- spores are resistant to environmental changes
withstand dry heat and certain chemical disinfectants for moderate periods
persist for years in dry earth
4) antigenic structure
- capsular antigen
- cell wall polysaccharide antigens
- somatic antigens
5) virulence factors
- anthrax toxin
This is made up of three proteins:
- protective antigen (PA)
- edema factor (EF)
- lethal factor (LF)
EF is an adenyly cyclase; with PA it forms edema toxin
LF plus PA form lethal toxin- major virulence factor and cause of death in infected animals
Toxins are responsible for tissue damage and edema
6) diseases
Cutaneous anthrax - malignant pustule (typical local lesion)
Pulmonary anthrax
Intestinal anthrax
Anthrax sepsis
7) microbiological diagnosis
> DME
Gram-staining:
Large, gram positive rods in chain
IFA
> Culture
Nutrient agar:
Large, spreading, grey-white colonies with irregular margins (so called Medusa head appearance)
Blood agar plate:
Nonhemolytic, gray colonies with typical microscopical morphology
> specific tests
Gelatin:
- inverted pine tree growth; slow liquefaction
- specific identification may be made by use of a gamma bacteriophage
- in vivo test for virulence- anthrax bacilli kill mice or guinea pigs upon intraperitoneal injection
8) treatment and prevention
- penicillin is the drug of choice
- tetracyclines, erythromycin or clindamycin may be effective
CET
Prevention:
Person with high occupational risk should be immunized with vaccine, containing purified protective antigen
