Brucella

Clinical Background

Brucellosis is a major bacterial zoonoses that involves many mammals including cows (B. abortus), pigs (B. suis), goats and sheep (B. melitensis), dogs (B. canis), and wild animals such as deer, elk and moose.

Epidemiology

Incidence - 1/100,000 in U.S.
Transmission
- A common route of Brucella infection is from eating or drinking infected, unpasteurized dairy products
- Infection can be via skin wounds
- Inhalation (majority are occupational exposure for this route)
- Vertical transmission via breast feeding

Organism

Brucella (gram-negative coccobacillus)
Facultative intracellular pathogen
Human infections are caused most frequently by B. melitensis, B. suis and B. abortus; rare infections are caused by B. canis

Risk Factors

Occupational or vocational exposure to animals
- Over 70% of reported cases occur in the meat-processing and livestock industries
- Brucella are able to penetrate intact skin so infections can result from simply handling infected animals

Clinical Presentation

Brucellosis in humans has a variable incubation time, an insidious or abrupt onset and no pathognomonic symptoms or signs
- Also called undulant fever
Following an incubation of 1-3 weeks, during which the organism resides in the lymph nodes, flu-like symptoms appear
- Constitutional - fever, chills, headache, weakness
- Osteoarticular - sacroiliitis, spondylitis, osteomyelitis
- Gastrointestinal - hepatomegaly (granulomatous hepatitis), splenomegaly
- Genitourinary - orchiepididymitis, glomerulonephritis, renal abscesses
- Neurologic - peripheral neuropathies, chorea, meningoencephalitis
- Mucocutaneous - purpura, maculopapular lesions, Stevens Johnson syndrome
- Pulmonary - pneumonia, pleural effusions
- Cardiovascular - endocarditis (aortic valve most common)
Chronic symptoms (recurrent fever, arthritis and fatigue) may also occur up to 1 year from illness onset

Treatment

Treatment is required and may be prolonged, and typically requires multiple antimicrobial agents
Relapse rate around 30%, even in compliant patients

Prevention

Control of disease in domestic livestock
Avoid unpasteurized milk and soft cheese produced from unpasteurized milk; especially goat cheese

See Also

Bartonella Species

Francisella tularensis

Tests

Tests generally appear in the order most useful for common clinical situations

Test name: Brucella Antibodies, IgG & IgM

ARUP #: 0050333

Methodology: Enzyme-Linked Immunosorbent Assay

Use:

Detect presence of Brucella antibodies in serum samples from patients with congruent clinical history

Limitations:

May not detect antibodies to B. canis

Cross-reactions may occur between Brucella and F. tularensis antigens and antisera; parallel tests should be run with these antigens

Follow-up:

Test name: Brucella Culture

ARUP #: 0060159

Methodology: Standard reference procedures for Brucella culture and identification

Use:

Gold standard for detection of Brucella in blood (optimum), CSF, body fluids and abscesses

Limitations:

Serologic tests are generally used for the diagnosis of brucellosis because isolation of organism is difficult

Follow-up:

Test name: Febrile Antibodies Panel

ARUP #: 0051638

Methodology: Direct Agglutination/Enzyme-Linked Immunosorbent Assay/Immunofluorescence Assay

Use:

Use to confirm presence of disease; not recommended for initial testing

Panel includes IgM Rickettsia rickettsii antibody by ELISA testing; as well as testing for antibodies to Brucella, Rickettsia typhi, Salmonella O and H

Limitations:

Initial testing may not be helpful; base treatment decision on clinical and other laboratory assessments

Additional Tests Available

Test name: Brucella Antibody, IgG

ARUP #: 0050334

Methodology: Enzyme-Linked Immunosorbent Assay

Comments:

Test name: Brucella Antibody, IgM

ARUP #: 0050336

Methodology: Enzyme-Linked Immunosorbent Assay

Comments:

Test name: Brucella Antibody

ARUP #: 0050135

Methodology: Bacterial Agglutination

Comments:

Test name: Organism Identification by 16S rDNA Sequencing

ARUP #: 0060720

Methodology: 16S rDNA Sequencing

Comments:

Test name: Aerobic Organism Identification

ARUP #: 0060115

Methodology: Standard reference procedures for aerobic bacterial identification and/or 16s rDNA sequencing for select bacterial isolates.

Comments:

Test name: Aerobic Organism Identification with Reflex to Susceptibility

ARUP #: 0065070

Methodology: Standard reference procedures for aerobic bacterial identification and/or 16s rDNA sequencing for select bacterial isolates and susceptibility tests.

Comments: