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Table of Contents:
Taxonomy Information
  1. Species:
    1. Brucella melitensis (Morenoa et al., 2002):
      1. GenBank Taxonomy No.: 29459
      2. Variant(s):
        • Brucella melitensis biovar 1 strain 16M (Morenoa et al., 2002, Gandara et al., 2001):
          • Common Name: Brucella melitensis strain 16M
          • GenBank Taxonomy No.: 224914
          • Parents: Brucella melitensis
          • Description: Strain 16M, corresponding to ATCC 23456, is the type strain for this biovar. Strain 16M primarily affects goats and sheep, and is the most virulent of the Brucellae in humans.
        • Brucella melitensis biovar 1 (Gandara et al., 2001):
          • Parents: Brucella melitensis
          • Description: Brucella melitensis biovar 1 strain 16M, corresponding to ATCC 23456, is the type strain for this biovar. Strain REV-1 is the rough attenuated vaccine strain of this biovar. Brucella melitensis biovar 1 isolates 78, 87, 91, 113, 219, 256, 261, 376, 391, 392, 393, 400, 401, 402, 415, 450, 456, 457, 458, 461, 462, 485, LAR, and P217 were obtained from human blood and bone marrow samples. Brucella melitensis isolates 279, 280, and 371 were obtained from goat milk samples.
        • Brucella melitensis biovar 2 (Gandara et al., 2001):
          • Parents: Brucella melitensis
          • Description: Strain 63/9, corresponding to ATCC 23457, is the type strain for this biovar. Brucella melitensis isolate 84 was obtained from human blood and bone marrow samples.
        • Brucela melitensis biovar 3 (Gandara et al., 2001):
          • Parents: Brucella melitensis
          • Description: Ether strain, corresponding to ATCC 23458, is the type strain for this biovar. Brucella melitensis biovar 3 isolates 254, 255, 257, 258, 259 and 306 were obtained from human blood and bone marrow samples. Brucella isolates G914, G1024 and T64/40 also belong to B. melitensis biovar 3.
    2. Brucella abortus :
      1. GenBank Taxonomy No.: 235
      2. Variant(s):
        • Brucella abortus biovar 1 (Gandara et al., 2001):
          • Parents: Brucella melitensis biovar Abortus
          • Description: Strain 544, corresponding with ATCC 23448, is the type strain for this biovar. Strain S19 is a smooth attenuated vaccine strain of this biovar. Strain RB51 is a rough attenuated vaccine strain of this biovar. Strain ENCB was obtained from human blood and bone marrow samples. Brucella abortus biovar 1 isolates 223, 240, 264, 265, 266, 267, 268, 269, 270, 271, 272, 275, 307, 308, 309, 311, 312, 313, and 314 were obtained from cow milk and cheese samples.
        • Brucella abortus biovar 2 (Gandara et al., 2001):
        • Brucella abortus biovar 3 (Gandara et al., 2001):
        • Brucella abortus biovar 4 (Gandara et al., 2001):
        • Brucella abortus biovar 5 (Gandara et al., 2001):
          • Parents: Brucella melitensis biovar Abortus
          • Description: Brucella abortus biovar 5 strain B3196, corresponding to ATCC 23452, is the type strain for this biovar. Isolates 273 and 274 were obtained from cow milk and cheese samples. Strain 49/8 also belongs to Brucella abortus biovar 5.
        • Brucella abortus biovar 6 (Gandara et al., 2001):
        • Brucella abortus biovar 7 (Gandara et al., 2001):
        • Brucella abortus biovar 9 (Gandara et al., 2001):
    3. Brucella suis :
      1. GenBank Taxonomy No.: 29461
      2. Variant(s):
Lifecycle Information
    1. Stage Information:
      1. Vegetative cell(Ministry of Agriculture and Fisheries, 1977):
        • Size: Brucella species range in size from 0.6 - 1.5 microns by 0.5 - 0.7 microns.
        • Shape: Brucella species are classified as gram-negative coccobacilli.
        • Picture(s):
          • B. abortus SEM Image (Website 16)



            Description: Scanning Electron Micrograph of Brucella abortus - Gram-negative, coccobacillus prokaryote; causes bovine spontaneous abortion due to its rapid growth in the presence of erythritol (produced in the placenta).This is an example of tissue specificity. This zoonotic microorganism can pass from cattle to humans in contaminated dairy products. Magnification: x3,900.
          • B. melitensis SEM Image (Website 16)



            Description: Scanning Electron Micrograph of Brucella melitensis - Gram-negative, aerobic, coccobacillus prokaryote; causes brucellosis fever (also known as undulant or Malta fever). This zoonotic microorganism passes from goats and sheep to humans in contaminated dairy products. Magnification: x3,600.
Genome Summary
  1. Genome of Brucella melitensis biovar 1 strain 16M(Website 12, Website 13)
    1. Description: Brucella melitensis contains two circular chromosomes, and is not known to contain any naturally occurring plasmids(Website 12, Website 13).
    2. chromosome(Website 12)
      1. GenBank Accession Number: AE008917
      2. Size: Brucella melitensis chromosome I is 2117144 base pairs long.
      3. Gene Count: Brucella melitensis chromosome I contains 2059 protein encoding genes.
      4. Description: Chromosome I is circular.
    3. chromosome(Website 13)
      1. GenBank Accession Number: AE008918
      2. Size: Brucella melitensis chromosome II is 1177787 base pairs long.
      3. Gene Count: Brucella melitensis chromosome II contains 1139 protein encoding genes.
      4. Description: Chromosome II is circular.
  2. Genome of Brucella suis biovar 1 strain 1330(Paulsen, 2002)
    1. Description: Brucella suis contains two circular chromosomes, and is not known to contain any naturally occurring plasmids.
    2. chromosome(Website 12)
      1. GenBank Accession Number: NC_004310
      2. Size: Brucella suis 1330 chromosome I is 2107792 base pairs long.
      3. Gene Count: Brucella suis 1330 chromosome I contains 2185 protein encoding genes.
      4. Description: Chromosome I is circular.
    3. chromosome(Website 13)
      1. GenBank Accession Number: NC_004311
      2. Size: Brucella suis 1330 chromosome II is 1207381 base pairs long.
      3. Gene Count: Brucella suis 1330 chromosome II contains 1203 protein encoding genes.
      4. Description: Chromosome II is circular.
Biosafety Information
  1. General biosafety information
    1. Level: Biosafety level three (3) procedures should be followed in all laboratory culture of all virulent Brucellae.
    2. Precautions: Brucellosis is the most commonly reported laboratory acquired infection. Brucella organisms may be misidentified. Brucella organisms can become airborne during standard laboratory procedures.
    3. Disposal: Upon termination of use of the agent, all cultures and stocks of it will be a) securely stored in accordance with prudent laboratory practices b) transferred to another registered facility in accordance with CDC regulations, or c) destroyed on site by autoclaving, incineration, or another recognized sterilization or neutralization process. When an agent, previously transferred to a facility in accordance with government regulations, is consumed or destroyed, the responsible facility official must formally notify the registering entity. Formal notification must be noted on CDC Form EA-101 and a copy kept on record by the responsible facility official for a period of five (5) years.
Culturing Information
  1. General Culturing Information (Alton et al., 1988):
    1. Description: From humans the organism is most commonly isolated from blood or bone marrow, but may be isolated from the liver, the spleen, cerebrospinal fluid or focal abscess. From sheep, goats, and cattle, the organism is most commonly cultured from the reproductive tract or reproductive fluids, including semen, uterine fluids and tissues, and milk.
    2. Medium: Standard blood media may be used for blood or bone marrow specimens, other specimens may use Trypticase soy agar with 5% sheep blood agar, MacConkey agar, or Martin Lewis agar (BD Bioscience or Remel, Inc., or equivalent).
    3. Optimal Temperature: 35-37 degrees Celsius.
    4. Note: Plate cultures should be incubated in 5% carbon dioxide. It takes 3-7 days to form colonies on plates.
Epidemiology Information:
  1. Outbreak Locations:
    1. . Brucellosis is pandemic (except UK and Australia); prevalence is higher in countries not requiring pasteurization of dairy products, especially Mediterranean Europe, the Middle East, and parts of South America(Boschiroli et al., 2001).
  2. Transmission Information:
    1. From: Bos taurus , To: Bos taurus (Boschiroli et al., 2001)
      Mechanism: Brucella abortus may be transmitted vertically (transmammary or transplacental), venereally, orally, through the conjunctiva, or by inhalation of aerosolized organisms.
    2. From: Bos taurus , To: Homo sapiens (Boschiroli et al., 2001)
      Mechanism: Brucella abortus, Brucella suis, or Brucella melitensis may be transmitted by ingestion of unpasteurized dairy products, direct contact of infected tissues to mucous membranes or wounds, inhalation of aerosolized organisms.
    3. From: Goats and Sheep , To: Goats and Sheep (Boschiroli et al., 2001)
      Mechanism: Brucella melitensis may be transmitted vertically (transmammary or transplacental), venereally, orally, through the conjunctiva, or by inhalation of aerosolized organisms.
    4. From: Goats and Sheep , To: Homo sapiens (Boschiroli et al., 2001)
      Mechanism: Brucella melitensis may be transmitted by ingestion of unpasteurized dairy products, direct contact of infected tissues to mucous membranes or wounds, inhalation of aerosolized organisms.
    5. From: Goats and Sheep , To: Bos taurus (Boschiroli et al., 2001)
      Mechanism: Brucella melitensis may be transmitted from sheep or goats to cattle by feedstuff contaminated with infected feces, urine, or uterine or placental fluids as well as by intraspecies transmission mechanisms.
    6. From: Wild animals , To: Homo sapiens (Boschiroli et al., 2001)
      Mechanism: Brucella species may be transmitted in laboratory situations by direct contact of agent to mucous membranes or wounds, inhalation of aerosol organisms, accidental inoculation with infective vaccine strains, or misidentification and subsequent negligence of safety procedures.
  3. Environmental Reservoir:
    1. Wild animals(Bercovich, 2000, Website 15):
      1. Description: Wild mammals such as elk, bison, and wild boar serve as reservoirs for Brucella organisms.
      2. Survival: Brucella organisms can survive in tap water for several months. Brucella can survive in feces, slurry, or liquid manure 30-210 days. They can survive freezing temperatures and high environmental temperatures. Dessication greatly reduces survival of brucellae(Bercovich, 2000, Nicoletti, 1980, Alton et al., 1988).
    2. Wild animals(Bercovich, 2000, Website 15):
      1. Description: Laboratoty environment includes bacterial cultures and contaminations.
  4. Intentional Releases:
    1. Intentional Release Information(Website 3):
      1. Description: Brucella organisms could be released in aerosol form, by accidental spills of culture suspensions or live vaccines, or in liquids such as dairy products or water. Brucellosis has fairly low fatality rate, but could be used as an incapacitating agent, as the disease tends to be chronic, requiring prolonged treatment(Website 3).
      2. Emergency Contact: Local health departments and local law enforcement agencies should be contacted in the event of accidental or intentional release of Brucella species(Website 3).
      3. Delivery Mechanism: Brucella organisms could be aerosolized and released at infectious doses. 10-500 organisms in aerosol form constitute an infectious dose.
      4. Containment: Most commercial disinfectants are effective at killing or neutralizing Brucella organisms.
Diagnostic Tests Information
  1. Organism Detection Test:
    1. Microscopy (Bannatyne et al., 1997, Rich et al., 2000):
      1. Description: The BACTEC 9240 continuous monitoring system uses broth to culture bacteria from human blood samples; after culturing the samples are stained with Gram's stain and observed using light microscopy; suspicious cultures are tested with further biochemical tests.
      2. False Positive: Visual detection is subjective, and non-Brucella samples may be identified as suspicious for Brucella.
      3. False Negative: Brucella are fastidious and slow growing organisms which may fail to grow in synthetic media, resulting in a false negative culture.
    2. Direct Urease Test (Rich et al., 2000):
      1. Description: Detection of urease activity in bacteria grown in blood culture broth can support suspicions of Brucella.
      2. False Positive: Many bacteria are urease positive.
      3. False Negative: Not all Brucella species are urease positive.
  2. Immunoassay Test:
    1. Coombs Test (Orduna et al., 2000, Bercovich, 1998):
      1. Description: The Coombs Test is a diagonostic test using manufactured antigen and antiglobulins to detect the presence of specific antibodies. It is used very commonly in the detection of human brucellosis, but due to expense and time factors is used less often to detect animal brucellosis.
      2. False Positive: specificity of the Coombs test is reportedly ranges from 96.2 % to 99.8%.
      3. False Negative: Sensitivity of the Coombs test is reported to be 91.5%.
    2. The complement fixation test (Bercovich, 1998):
      1. Description: The complement fixation test (CFT), used to diagnose brucellosis in cattle, detects specific IgM and IgG1 antibodies.
      2. False Positive: specificity of this test is reported to be 98%.
      3. False Negative: Sensitivity of this test is reported to be 81%.
    3. Competitive ELISA (Lucero et al., 1999, Diaz-Aparicio et al., 1994):
      1. Description: Competitive ELISA detects serum antibody and is able to distinguish between vaccine and infection derived antibodies. ELISA is used for detection of brucellosis in humans, cattle, sheep and goats.
      2. False Positive: specificity of this test is reported to be between 60% and 96.5%.
      3. False Negative: Sensitivity of this test is reported to be between 94 % and 94.8%.
    4. A radial immunodiffusion (RID) test (Diaz-Aparicio et al., 1994):
      1. Description: A radial immunodiffusion (RID) test uses manufactured Brucella antigens in a gelling agent with wells for goat serum. Sera positive for antibodies to Brucella will diffuse into the gelling agent and cause a visible color change.
      2. False Positive: RID tests are reported to have a 95% specificity for subcutaneously vaccinated sheep and a 100% specificity 120 days after conjunctival vaccination.
      3. False Negative: RID tests are reported to have sensitivity ranging between 53.0% and 94.5%.
    5. Counter immunoelectrophoresis (Diaz-Aparicio et al., 1994):
      1. Description: Counter immunoelectrophoresis (CIEP) is used to detect brucellosis in goats. Manufactured antigen binds with antibodies present in sera and the combination is electrophoresed to analyze antibody titers.
      2. False Positive: CIEP is reported to have a specificity of 90%.
      3. False Negative: CIEP is reported to have sensitivity of 93%.
    6. Milk Ring Test (MRT) (Bercovich, 1998):
      1. Description: The milk ring test is a serological test for lacteal anti-Brucella IgM and IgA bound to milk fat globules in cow or goat milk.
      2. False Positive: False positives may occur with this test in colostrum, milk at the end of a lactation period, or cows suffering from a hormonal disorder or mastitis; however the specificity is reported to be 99%.
      3. False Negative: False negatives may occur with this test in milk with a low concentration of lacteal antibodies or lacking fat-clustering factors; the sensitivity is reported to be 56%.
    7. Brucellacapt (Orduna et al., 2000):
      1. Description: Brucellacapt is an immunocapture agglutination test for the serodiagnosis of human brucellosis.
      2. False Positive: specificity for the Brucellacapt test is reported to be between 81.5 % and 99.0%.
      3. False Negative: Sensitivity for the Brucellacapt test is reported to be 95.1%.
    8. Serum Agglutination Test (SAT) (Bercovich, 1998, Orduna et al., 2000):
      1. Description: The Serum agglutination test (SAT) is used commonly in the detection of both human and bovine Brucella specific antibodies.
      2. False Positive: The SAT is reported to have specificity between 95% and 100%.
      3. False Negative: The SAT is reported to have sensitivity between 70% and 91.5%.
    9. Rose Bengal Test (RB) (Bercovich, 1998, Diaz-Aparicio et al., 1994):
      1. Description: The RB test is a spot agglutination technique that uses dyed B. abortus antigen to detect serum antibodies of bovine brucellosis.
      2. False Positive: Specificity of the RB test is reported to be between 71% and 80%.
      3. False Negative: Sensitivity of the RB test is reported to be between 78% and 100%.
    10. 2-Mercapto-ethanol Test (2-ME) (Bercovich, 1998):
      1. Description: The 2ME test is usually used in serial testing to distinguish between vaccinated and infected cattle.
      2. False Positive: Specificity of the 2-ME test is reported to be 97%.
      3. False Negative: Sensitivity of the 2-ME test is reported to be 56%.
    11. Skin Delayed-Type Hypersensitivity Test (SDTH) (Bercovich, 2000):
      1. Description: The SDTH test uses manufactured brucellin to elicit a skin hypersensitivity in livestock infected with acute, chronic, or latent brucellosis.
      2. False Positive: Specificity of the SDTH test is reported to be 93.9%.
    12. Dipstick Assay (Smits et al., 1999):
      1. Description: A dipstick assay for rapid detection of Brucella specific immunoglobulin uses manufactured Brucella antigen on a nitrocellulose strip. When incubated for three hours with a serum sample, positive samples will form a distinct line, which can be graded from 1-4.
      2. False Positive: Specificity of the dipstick assay is reported to be 98.6%.
      3. False Negative: Sensitivity of the dipstick assay is reported to range from 89.0% at 0-2 months after the onset of the disease to 29.8% at 6 or more months after the onset of the disease.
  3. Nucleic Acid Detection Test: