66.Genus Brucella (taxonomy, habitat, morphology, staining). Characterisation of R-type Brucella species.

Question 1

BRUCELLA Taxonomy:

Answer 1

Taxonomy:

• monospecies system:
• B. melitensis, within the species biovars
• B. melitensis biovar abortus 1, 2, 3, ….
• high level of genetic relationship
• multispecies system:
• B. abortus 1, 2, 3, ….
• both systems are in use

Question 2

Brucella Habitat

Answer 2

Habitat:

• infected host
• mucous membrane of the genitals
• lymph nodes
• udder
• joint, tendon sheaths, bursae

Question 3

Brucella Morphology

Answer 3

Morphology:

• 0.6-1.5 µm coccoid rods
• lipids and proteins in the cell wall

Question 4

Brucella Staining

Answer 4

• Gram-negative

• Köster-staining
• 3% safranin 3-5 minutes, steam once
• 0.5% H2SO4
• washing
• methylene blue 2 min
• modified Ziehl-Neelsen (Stamp) staining

Question 5

R colonies?

Answer 5

• R colonies: B. canis, B. ovis

Question 6

Biochemistry?

Answer 6

Biochemistry: • catalase +, • oxidase +, • urease +

Question 7

Culture?

Answer 7

Culture: • obligate aerobic, • fastidious • blood agar, serum agar • vitamin (B vitamins), yeast extract • CO2 , (some B. abortus biotypes and B. ovis) • S-R colonies (at the isolation) • S colonies: B. melitensis, B. abortus, B. suis • R colonies: B. canis, B. ovis • selective culture: • polymyxin, bacitracin, cycloheximide, etc. • (laboratory animals)