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    MICROBIOLOGY

Pathogenic Gram-Positive
    Bacilli (Bacillus)
Bacillus
 Gram-positive bacilli, that occur singly, in pairs, or in
 chains
  It is an aerobe and facultative anaerobe
  They are non-motile and capsulated inside the body
  Forms endospores outside the body
  Spores are central and oval
 Anthracoides or non-pathogenic members include
 Bacillus subtilis, Bacillus mycoides & Bacillus
 mesentericus
  Bacillus stearothermophilus is thermophilic
 Bacillus anthracis is a strict pathogen of animals and
 humans
Bacillus anthracis
 Anthrax is primarily a disease of herbivores, but
 humans can contract the disease from infected animals
      Humans contract the bacteria via one of three routes
     • Inhalation of spores
     • Inoculation of spores into the body through a break
       in the skin
     • Ingestion of spores
Pathogenicity and Diseases
 Pathogenicity
       Anthrax toxin (oedema factor, protective antigen,
    lethal factor)
       Capsule made of D-glutamic acid
 Diseases
       Anthrax is the only disease caused by Bacillus
    anthracis
       Anthrax can have three clinical manifestations
     • Gastrointestinal anthrax
        • Rare in humans
        • Intestinal hemorrhaging and eventually death
Pathogenicity and Diseases
     • Cutaneous anthrax (hide porter’s disease)
        • Produces a painless ulcer called an eschar
          (malignant pustule) and toxemia (20% fatal)
     • Inhalation anthrax (wool sorter’s disease)
        • Spores germinate in the lungs and secrete toxins
          that are absorbed into the bloodstream
        • High mortality rate (100% down to 50%)
Epidemiology
 Primarily a disease of herbivores (zoonotic)
 Endospores contaminate the soil and remain viable for
 many years
 Humans get infected through damaged skin (cuts and
 scratches) in contact with infected carcasses, bones,
 hides, hairs and skins of animals
 Or infection through inhalation of spores (rare)
 Biological warfare
Diagnosis and Treatment
 Diagnosis
       Presence of large, nonmotile, Gram-positive
    capsulated bacilli in clinical samples of the lungs or
    skin




 Treatment
       Penicillin, Ciproflaxacin and many other
    antimicrobials are effective against B.anthracis


       It can be deadly even after treatment
Prevention
      Control the disease in animals (vaccination, burning
   or deep burying in lime pits)




     An anthrax vaccine is available but requires
   multiple doses and boosters




      Destroy spores on animal hairs
Bacillus cereus
 An aerobic, spore forming Gram positive rod
 Found in soil and on raw and dried foods
 Causes food borne intoxication and opportunistic
 infections
 Spores are not killed during cooking and they
 germinate in the unrefrigerated food
 There is an emetic type of food poisoning caused by a
 heat stable enterotoxin associated with rice dishes (1-6
 hrs)
 And a diarrheal type caused by heat labile enterotoxin
 associated with meat dishes (8-16 hrs)
 Can also cause endophthalmitis

				
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