Brucella

Brucella

Brucellae are obligate parasites of humans and animals and located intracellulary.They are relatively inactive metabolically. Gram negative coccobacilli; non spore forming and non motile, aerobic, but may need added 5-10% CO2.

Disease:
Brucella typically affect the reproductive organs and abortion is often the only sign of the disorder. Placentas and fetal membranes of cattle, swine, sheep, and goats contain erythritol, a growth factor for brucellae.
In humans, the disease is called brucellosis (undulant fever, malta fever) an acute bacteremic phase fallowed by a chronic stage that may extend over many years and may involve many tissues.

Specimens:
Blood for culture, biopsy material for culture (lymph nodes, bone), and serum for serologic tests.

Culture:
? Small, convex, smooth colonies appear on enriched media in 2-3 days.
? Nutritional requirement are complex (amino acid, vitamins and glucose).
? They are aerobes but some species require an atmosphere with added CO2 (5-10 percent).
? Brucella agar, trypticase- soy agar, brain heart infusion medium and chocolate agar are used for culture brucella.
? Utilize carbohydrates with out produced CO2 and acid.
? Oxidase and catalase are produced by four species that infected human.
? Brucllae are non hemolytic.
? Brucellae are sensitive to heat and acidity, killed in milk by pasteurization.
? Incubation period is (1-6) weeks.
? Three species (B. melitensis, B. abortus, B. suis) are important human pathogens, B. canis is of lesser importance.

Diagnosis:
? Blood cultures may be positive in early disease but serology is mainstay at diagnosis.
? Molecular methods have been developed to rapidly differentiate among the various biovars.

Treatment:
The treatment of choice is tetracycline plus rifampine there is no significant resistance to these drugs.

Prevention:
Prevention of brucellosis involves pasteurization of milk, immunization of animals, and slaughtering of infected animals. There is no human vaccine.



Table: Differential Characteristics of Brucella Sp.

Species Colny Morphology Serum Requirement Lysis phage oxidase urase
B. melitensis Smooth - - + +
B. abortus Smooth - + + +
B. suis Smooth + - + +
B. neotmae Smooth - - - +
B. ovis Rough - - - -
B. canis Rough - - + +