Brucella Antigen (Brucellosis), Diagnosis of Brucella Infection
Sample
- It is done on the serum of the patient.
- The serum is taken in the first week of illness and later on in the 3 to 4 weeks.
- Brucella can be cultured from the blood, sputum, bone marrow, CSF, tissue, lymph node, and urine.
Indication
- Patient with fever.
- Patient with a suspected history of contact with castles.
- Patient with signs and symptoms of Brucella infection.
Pathology
- Microbiology:
- Brucellosis is caused by the Brucella abortus, B.suis, B. melitensis, or B.canis.
- Brucella is aerobic gram-negative bacilli.
- Short, slender, pleomorphic, gram-negative bacilli.
- Brucella is an oxidase-positive, urease variable.
- Brucella is nonmotile.
- These are non-sporing.
- Culture media:
- Enriched medium such as glucose serum or liver infusion broth or agar.
- Small transparent colonies develop after several days, incubation at 37 °C in aerobic conditions.
- CO2 is needed for the growth of B. abortus.
- There is growth in selective buffered charcoal yeast extract and Thayer-Martin medium.
- Enriched medium such as glucose serum or liver infusion broth or agar.
Characteristic features | B. abortus | B. melitensis | B. sius |
Biotypes of Brucella | 8 | 3 | 4 |
Production of H2S | positive | negative | positive |
Growth need for CO2 | positive | negative | negative |
Growth in | |||
Basic fuchsin | positive | positive | negative |
Thionine | negative | positive | positive |
Methyl violet | positive | positive | negative |
Lysis by phage Tb | positive | negative | negative |
Antibody Titer positive | >1:320 | >1:320 | >1:320 |
- Mode of spread:
- It is by ingestion of contaminated milk products especially goat milk.
- Sheep, goats, cows, or camels when infected with these bacteria, then their milk is also contaminated.
- These names are based on infected animals.
- Brucella mostly spread by unpasteurized milk or raw dairy products.
- Direct puncture of the skin of butchers and farmers. These bacteria can enter through the skin and mucous membranes.
- Brucella can spread through inhalation.
- Brucella can penetrate the skin, conjunctiva, lungs, and GI Tract.
- Penetration is followed by the lymphatics spread.
- There is a facultative intracellular growth in the macrophages.
- It also involves the organs.
Type of Brucella:
- There are following types of Brucella:
- Brucella abortus source is from cattle and has moderate pathogenicity.
- Brucella melitensis source is sheep, and these are highly pathogenic.
- Brucella Canis source is from dogs and has moderate pathogenicity.
- Brucella Sui’s source is from pig and these are highly pathogenic.
Antigenic structure:
- Three species share two antigens A and M.
- B. melitensis contains an excess of M antigen.
- B. abortus and suis contain an excess of An antigen.
- Monospecific antisera can be prepared and are used for identification.
Sign and symptoms:
-
- This may be the acute or insidious onset of the symptoms.
- This is a multisystem disease characterized by the acute or insidious onset of signs and symptoms.
- There may be fever, chills, and night sweating.
- The fever peak is in the evening and slowly returns to normal by morning.
- Undulant fever because of a slow rise in temperature during the day, declining at night.
- There is undue fatigue.
- There is anorexia, weight loss.
- There may be a headache and arthralgia.
- There may be pain muscles, joints, or back.
- Sometimes there is lymphadenopathy.
- If not treated then these patients may have:
- Arthritis.
- Recurrent fever.
- Swelling of the scrotal area and testes.
- Depression.
- Chronic fatigue.
- May develop endocarditis.
- Splenomegaly and hepatomegaly are a common finding.
- Spondylitis is also common.
- These symptoms may last months to years but the outcome is not fatal.
Complications:
- The patient may develop endocarditis.
- There may be arthritis and osteomyelitis.
- The infection of the testes gives rise to epididymal orchitis.
- CNS involvement may lead to meningitis or encephalitis.
- Inflammation of the liver and spleen leads to splenomegaly and hepatomegaly.
Prevention of Brucellosis:
- Please avoid the following:
- Use of unpasteurized milk and dairy products (cheese, ice cream).
- When handling animals, use preventive measures like gloves, etc.
Brucella diagnosis:
- By serological test detecting the Brucella antibodies.
- By culture of:
- Blood.
- Bone marrow.
- CSF.
- Sputum.
- Food specimen.
- Biopsy and culture of affected tissue and organs.
- By immunofluorescent demonstration of the organism in the clinical specimens.
- A skin test with brucellergin is available, but a positive result only indicates exposure to the organism and does not prove active disease.
Serology Normal values
Source 1
- This is the detection of the presence of antibodies against the Brucella antigen.
- The significant level is > 1: 320
- Borderline cases 1: 160
Source 2
- A rising titer ≥ 1:160 suggests infection, either past or present.
- A single titer 1:160 or 1:320 may be suggestive if there are clinical S/S of brucellosis.
- It can prevent the prozone phenomenon by diluting the serum ≥1: 1280.
- Antibody level decreases in 3 months or with antibiotics but it will persist at a low level for years especially in chronic infection.
Treatment
- These bacteria are sensitive to tetracycline, combined with streptomycin. This combination is the choice of treatment.