Lesson 5b: Bacillus species

Question 1

Bacillus Species

Answer 1

• Large, gram-positive rods (but few non-pathogenic species are gram-negative)
• endospores produced
• majority are non-pathogenic environmental organisms
• Bacillus anthracis causes anthrax
• Bacillus licheniforms is implicated in sporadic abortions in cattle and sheep
• environment

Question 2

5mm diameter, flat, dry, greyish and with a ‘ground glass’ appearance after incubation for 48 hrs, curled outgrowths from the edge of the colony impart a characteristic ‘medusa head’ appearance

Answer 2

B. anthracis

Question 3

same with B. anthracis but are larger and with greenish tinge. Majority of strains produce with zone of complete haemolysis around the colonies. Sheep Blood

Answer 3

B. cereus

Question 4

colonies are dull, rough, wrinkled and strongly adherent to the agar that becomes brown with age. Characteristic hair-like outgrowths are produced from streaks of the organism on agar media

Answer 4

B. licheniformis

Question 5

cause of abortion in cattle and sheep associated with the feeding of contaminated silage of mouldy hay and diagnosed by isolation in heavy, pure culture from foetal abomasal contents

Answer 5

Infections with B. licheniformis

Question 6

Ruminants are highly susceptible, pigs and horses are moderately susceptible to infection. while carnivores are comparatively resistant. Birds are almost totally resistant to infection, due to their relatively high body temperatures

Answer 6

Anthrax

Question 7

encodes for exotoxin (protective antigen, oedema factor anf lethal factor)

Answer 7

PXO1

Question 8

encodes for capsule (inhibit phagocytosis)

Answer 8

PXO2

Question 9

both encoded by plasmid and important in a disease production

Answer 9

capsule and toxin

Question 10

Diagnoses: Carcasses of animals that have died from anthrax;

Answer 10

bloated, putrefy rapidly, do not exhibit rigor mortis