Brucella

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Brucella
Scientific classification
Kingdom: Bacteria Phylum: Proteobacteria Class: Alpha Proteobacteria Order: Rhizobiales Family: Brucellaceae Genus: Brucella
Species
B. abortus B. canis B. melitensis B. neotomae B. ovis B. suis

This page is about microbiologic aspects of the organism(s).  For clinical aspects of the disease, see brucellosis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Danitza Lukac, Vishal Devarkonda, M.B.B.S[2]

Overview

Human brucellosis is caused by four Brucellae species: B. abortus, B. canis, B. melitensis, and B. suis.

Causes

• Brucella is a genus of Gram-negative bacteria. They are small (0.5 to 0.7 by 0.6 to 1.5 µm), non-motile, encapsulated coccobacilli.
• Brucella is the cause of brucellosis, a true zoonotic disease (i.e. human-to-human transmission has not been identified).
• It is transmitted by ingesting infected food, direct contact with an infected animal, or inhalation of aerosols.
• Minimum infectious exposure is between 10 - 100 organisms.
• Brucellosis primarily occurs through occupational exposure (e.g. exposure to cattle, sheep, pigs), but also by consumption of unpasteurised milk products.
• Four species infect humans: B. abortus, B. canis, B. melitensis, and B. suis.
  • B. abortus, is less virulent than B. melitensis and is primarily a disease of cattle.
  • B. canis affects dogs.
  • B. melitensis is the most virulent and invasive species; it usually infects goats and occasionally sheep.
  • B. suis is of intermediate virulence and chiefly infects pigs.

Brucella species have been found primarily in mammals:

Brucellae Species, Host and Human Virulente

Species	Host	Human Virulence
B. melitensis	Goats, sheep	++++
B. abortus	Cattle	++/+++
B. canis	Dogs	+
B. suis	Pigs	+
B. ovis	Sheep	-
B. neotomae	Desert woodrat	-
B. pinnipedialis	Seal	+
B. ceti	Dolphin, porpoise, whale	+
B. microti	Common vole	N/A
B. inopinata	Unknown	N/A
Brucella sp. NVSL 07-0026	Baboon	N/A

Oxidase and catalase tests are positive for most members of the genus Brucella:

Brucellae Species and Host

Test	B. melitensis	B. abortus	B. suis	B. neotomae	B. ovis	B. canis
Need to CO2	-	+	-	-	+	-
Production of H2S	-	+	+	+	-	-
Growth on basic fushin 0.002%	+	+	-	-	+	-
Growth on thionin 0.004%	-	-	+	-	+	+
Growth on thionin 0.002%	+	-	+	+	+	+
Destroy with Tb phage	-	+	-	-	-	-