Brucella genus and brucellosis.

Question 1

General features and habitat of Brucella genus

Answer 1

Gram – Coccobacillus

Habitat- zoonosis (domestic, farm animals)

Question 2

Biochemical Properties of Brucella genus

Answer 2

Can survive cold environments

Grows extremely slow

Question 3

Pathogenesis of Brucella genus

Answer 3

Facultative intracellular- can replicate in multiplying cells like macrophages, thus prevents phagolysosome fusion

Direct infection through direct contact with different animals: (butcher, veterinary…)
B. Suis in Pigs = Swine brucellosis 

B. Melitensis in Goats and Sheep = Malta fever 

B. Abortus in Cattle= Bang disease
B. Canis in Dogs (rarely causing infection)
*All of the above names are the same, known disease- Brucellosis

Indirect infection- by ingestion of unpasteurized milk or exudate of animal

Question 4

Clinical Features (Brucellosis) of Brucella genus

Answer 4

Undulant fever- fever rise and fall
Symptoms include anorexia, sweating (fever)


Since Brucella invades macrophages, it can enter the reticuloendothelial organs such as liver, spleen, lymph nodes. It causes macrophage lysis in these organs and thus can lead to enlargement of the reticuloendothelial organs- hepatosplenomegaly

Osteomyelitis- in chronic brucellosis infection

Question 5

Diagnosis of Brucella genus

Answer 5

Cultivation is not safe (biological weapon category B)

Brucellin skin test- injection of Ag intra-dermally, seen as wheal if positive (DTH)

Serology:
ELISA
IgM chromatography (IC)
Wright reaction (tube agglutination)- test specific antibodies in patient’s
sera and establish their titer by serial dilutions of the antigen

Question 6

Treatment of Brucella genus

Answer 6

Doxycycline (Tetracycline)
Rifampin
Aminoglycoside