Bacillus

Question 1

What is Bacillus?

Answer 1

• Gram positive rods
• Spore-forming
• Several species
• Most are nonpathogenic (saprophytic)

Question 2

What is Bacillus anthracis?

Answer 2

• Gram Positive Rods
  
  • long chains in culture
  • Short chains in tissue
• Central Spores
• Capsule
• First bacterium shon to cause disease
• Rober Koch in 1877
  
  • Koch’s postulates

Question 3

What are the Bacillus anthracis spores?

Answer 3

• Formed when cells are exposed to air
• Rarely in blood and tissues
• High CO₂ inhibits sporulation
• Spores are highly resistant
  
  • Can remain dormant for decades

Question 4

What are B. cereus and B. licheniformis?

Answer 4

• No invasive ability but grow in tissues weakened by injury
• Mastitis in cows and abscesses in animals
• B. cereus - food borne intoxication

Question 5

What is B. cereus?

Answer 5

• Normal soil bacterium
  
  • also in grains and spices
• Food borne intoxications
• Emetic Form:
  
  • Incubation period of 1 - 6 h
  • Nausea, vomiting, and abdominal cramps
  • Heat stable enterotoxin (5 KDa)
• Diarrheal Form:
  
  • Incubation period of 8 - 16 h
  • Abdominal cramps and diarrhea
  • Heat labile enterotoxin (50 KDa)

Question 6

What is the colony morphology of Bacillus anthracis?

Answer 6

• Nonhemolytic
• Ground Glass appearance
• Medusa Head

Question 7

What are the Types of Bacillus anthracis?

Answer 7

• Types A - Worldwide
  
  • Strains:
    
    • Sterne - Avirulent, used for vaccine
    • Vollum - virulent
    • Ames - virulent
• Type B - Southern Africa

Question 8

What are the Virulence Factors of Bacillus anthracis?

Answer 8

• Capsule
• Exotoxins
  
  • pXO2
    
    • Codes for capsule
    • Prevents phagocytosis
  • pXO1
    
    • Codes for:
      
      • Protective antigen (PA)
      • Edema Factor (EF)
      • Lethal Factor (LF)
    • Cytotoxicity and cell death

Question 9

What are the Tripartite toxins of Bacillus anthracis?

Answer 9

• EdTx: Edema factor and Protectie antigen
  
  • Adenylate cyclase enzyme
  • Increases cAMP → edema
• LeTx: Lethal factor and protective antigen
  
  • Zn metalloprotease
• Protective antigen facilitates entry of edem and lethal factor into the target cells

Question 10

What is the Capsule of Bacillus anthracis?

Answer 10

• Encoded by pXO2
• Poly D-glutamic acid
• The negative charge on the capsule inhibits phagocytosis of the vegetative cells
• Sterne strain is noncapsulated

Question 11

What is the mode of infection of Bacillus anthracis?

Answer 11

• Ingestion or Inhalation of spores
• Contaminated feed (Bone meal) and water
• Skin infection

Question 12

What is the pathogenesis of Bacillus anthracis

Answer 12

• Massive bacteremia
• Systemic signs of anthrax
• Death
• 80% of the organisms in blood and 20% in spleen

Question 13

What is Anthrax in Animals?

Answer 13

• Cattle, sheep, and goats are most susceptible
• Horses intermediat susceptibility
• Pig and dogs are generally resistant
• Wild ruminants are susceptible
• Lab animals - Guinea pigs

Question 14

What is anthrax in Ruminants?

Answer 14

• Usually acute
• High fever with death in 1 - 2 days
• Dead animals will have blood exuding from orifices
• Necropsy is not recommened
• Spleen is enlarged, dark, and exudes thick, black colored blood when cut
• Enlarged lymph nodes

Question 15

What is Anthrax in horses?

Answer 15

• Generally acute
• Death in 1 - 3 days

Question 16

What is anthrax in pigs?

Answer 16

• Rare
• Edematous swelling of the head and neck

Question 17

What is cutaneous anthrax?

Answer 17

• Skin infection
• Not common in animals

Question 18

How is Bacillus anthracis Diagnosed?

Answer 18

• Suspected based on clinical signs, pathological findings, and epidemiological data
• Occurs in an area in systemic cyclicity
• Only in a few animals, generally in summer following wet spring
• Suspected cases reported immediately to state public health officials
• Premise should be quarantined
• Blood sample (ear vein) or swabs of exuding blood or edematous lesions for microscopic examination
  
  • String of Pearls
• Fluorescent antibody technique to demonstrate capsule
• PCR for virulence genes

Question 19

How is Bacillus anthracis treated and prevented?

Answer 19

• Acute cases will NOT recover
• Early stages:
  
  • Penicillin, Ciproflaxin, amoxicillin, erythromycin, etc
• Penicilin and Oxy are very effective
• Vaccination in endemic areas
  
  • Sterne vaccine - live spore vaccine with no plasmid for capsule
  • Immunity because of antibodies against PA (Factor 2)

Question 20

What are the control measures for Bacillus anthracis?

Answer 20

• Rapid diagnosis, quarantine, vaccination, and surveillance
• Carcasses of dead animals should be burned or buried deep
• Opening of the carcasses should be avoided

Question 21

What is Anthrax in Humans?

Answer 21

• Occupational, accidental or terroristic
• 3 Forms:
  
  • Cutaneous anthrax
  • Gastrointestinal anthrax
  • Inhalation anthrax
  • Injection anthrax

Question 22

What is cutaneous anthrax?

Answer 22

• Most common
• Head, neck, hands, legs
• Skin break
  
  • spores enter and germinate
• Skin lesion: itchy redness to dark blister to black eshcar

Question 23

What is Gastrointestinal Anthrax?

Answer 23

• Eating meat contaminated with spores
• Highly fatal
• Not reported in the US

Question 24

What is inhalation Anthrax?

Answer 24

• Most serious form
• Inhalation of spores
• Signs:
  
  • Cough with/without blood
  • Fever
  • muscle pain
  • malaise
• Death in 1 - 7 days
• Only 18 cases in US in 20th century
  
  • between 10/4/01 and 11/20/01 - 11 cases, 5 deaths

Question 25

What is Woolsorter’s Disease?

Answer 25

• Occupational disease
• Hide and wool handlers
• Inhalation of spores
• Respiratory distress and death in 24 h

Question 26

How is Bacillus anthracis a Agent of Biological Warfare?

Answer 26

• Easy to acquire
• Can be stored in dry form for decades
• Easy to disseminate
• US military developed a strain of anthrax so lethal
  
  • just 8 gallons could kill everyone on earth