Bacillus

• Bacillus

  • Large rod-shaped
  • Aerobic or facultatively anaerobic
  • Gram positive
  • Catalase positive
  • Sporulating bacteria that occur in chains
• Classification of Bacillus

  • Bacillus anthracis (Pathogenic)
  • Other Bacillus species (Non pathogenic)
• Bacillus anthracis


  • Possession of capsule
  • Produces anthrax toxin and requires thiamin as a growth factor
  • Non motile and Non haemolytic
• Other Bacillus species


  • No capsule present
  • Produces emetic toxin and does not require thiamin for growth
  • Motile and haemolytic
• Anthrax is the only disease associated with Bacillus anthracis
• Anthrax is a zoonosis
• Types of human anthrax


  • Occupational disease of Vets
  • Farmers
  • Woolsorters
• Cutaneous Anthrax

  Incubation period ranges from 1-19 days, usually 2-7 days<|>Begins with Pruritic papule<|>Papule enlarges with ring of vesicles seen within 2-4 days<|>Erythema and edema develops<|>No pus and lesion is painless unless there is a secondary infection
• Pathogenicity of Bacillus anthracis

  • Depends on the capsule (poly-D-glutamic acid: inhibit phagocytosis)
  • Toxin has 3 components: Protective antigen (PA)
  • Edema factor (EF)
  • Lethal factor (LF)
• Toxin production

  1. Spore develops into vegetative organism

  2. Organism enters blood

  3. Resists phagocytosis and multiplies

  4. Toxin is produced leading to symptoms
• Laboratory diagnosis of anthrax

  • Specimen: pus
  • Blood
  • Sputum
  • Faeces
  • Food
• Laboratory diagnosis steps

  1. Culture on blood or selective agar plates with incubation in 5% CO2

  2. Gram stain to observe rods in chains

  3. Detection of capsule
• Growth on blood agar

  • Nonhaemolytic gray to white colonies
  • Rough texture and ground-glass appearance
  • Comma-shaped outgrowths (medusa head) may project from the colony
• Phage typing

  • Lysis by a specific anthrax gamma bacteriophage is helpful in the identification of the organism
• Immunofluorescence staining

  • B. anthracis can be identified in dry smears by immunofluorescence staining technique
• Treatment of anthrax

  • Penicillin
  • Ciprofloxacin
  • Erythromycin
  • Doxycycline
• Control of anthrax

  • Infected dead animals should be deeply buried with lime or the carcass burnt
  • Quarantine of healthy animals during outbreaks
  • Animal products should be autoclaved
  • Use of protective clothing and gloves for handling infected animals
  • Vaccination of animals and humans
• Other Bacillus species

  • Motile
  • Haemolytic
  • Non-pathogenic
  • May occasionally cause opportunistic infections especially Bacillus cereus
  • Bacillus cereus may produce an enterotoxin causing food poisoning
• Food poisoning types

  • Emetic type
  • Diarrheal type
• Emetic type food poisoning

  Heat stable toxin<|>Occurs 1-5 hours after ingestion of rice<|>Nausea, vomiting, abdominal cramps, and occasionally diarrhea<|>Self-limiting and recovery occurs within 24 hours
• Diarrheal type food poisoning

  Heat labile toxin<|>Incubation period of 8-16 hours<|>Profuse diarrhea, abdominal pain, and cramps<|>Enterotoxin may be preformed in the food or produced in the intestine
• B. subtilis are lab contaminants and now cause disease in immunocompromised patients