Aerobic Spore Forming Bacilli. Genus Bacillus

Question 1

Genus bacillus

Answer 1

Family: bacillaceae

Genus:

Bacilli (obligate aerobes)

• B.anthracis : anthrax
• B.cereus: food poisoning (opportunistic infection)

Clostridia (obligate anaerobes) 
C.difficile: acute colitis 
C.perfringens: gas gangrene
C.tetani: tetanus 
C.botulinum: food poisnoning

Question 2

Bacillus cereus

Morphology

Answer 2

• gram-positive rod
• spore-forming (relatively heat resistant)
• motile

Found in soil and grains

Question 3

Growth characteristics

Answer 3

Aerobic

Non-fastidious

Question 4

Antigenic structure

Answer 4

somatic O antigen

Flagella (H) antigens

Question 5

Virulence factors

Answer 5

Enzymes:

• phospholipids C groups of enzymes
• hemolysins

Toxins:
- diarrhoea enterotoxin
Acts like cholera toxin (i.e cAMP is increased within enterocytes)

• emetic enterotoxin

Spores
Habitat is grains, such as rice
Spores survive boiling during preparation, then germinate when rice is held at warm temperature

Question 6

Disease

Answer 6

Food poisoning
- emetic type: short incubation period

• diarrhoea type: long incubation period

Eye infections

Question 7

Microbiological diagnosis

Answer 7

Not performed

Question 8

Treatment and prevention

Answer 8

Treatment- symptomatic only

Prevention- no vaccine