Brucellosis

Waseem Ahmad

James W. Myers

ORGANISM

Brucellosis is a zoonotic disease, reported for the first time in 1859 by Marston, in Malta.

Brucellae are intracellular pathogens that can survive and multiply within phagocytic cells. The inhibition of tumor necrosis factor α (TNF-α) by brucella affects natural killer cells and macrophages. Brucella are taken up by local tissue lymphocytes, then travel through lymphatics to lymph nodes, and then reach the bloodstream to disseminate to all organs of the body. Caseation and granuloma formation can be seen on pathology.

Patients can be reinfected or relapse with brucellosis.

Four species of Brucella:

1. Brucella melitensis (goats, sheep, camel). Most common cause in the world

2. Brucella abortus (cattle, buffalo, yaks)

3. Brucella suis (pigs, reindeer)

4. Brucella canis (dogs, foxes)
Brucella are nonmotile, nonsporulating, noncapsulated gram-negative coccobacilli.
- Growth on culture media is increased by the adding serum or blood.
- Serum enhances growth.
- Grows slowly, up to 4 weeks
- Aerobic but may require carbon dioxide
Able to survive in unpasteurized cheese for long periods of time
Resists freezing but not pasteurization or boiling
Shed in animal urine, stool, and after birth
Remains viable in soil for over a month

EPIDEMIOLOGY

Worldwide
Highest prevalence
- Mediterranean
- India
- Mexico and Central and South America

TRANSMISSION

Gastrointestinal tract is the usual route.
- Untreated dairy, raw meat, liver
Inhalation
- Occupational hazard of herdsmen and dairy farmers
- Lab personnel
  - Brucellosis is the number one laboratory-associated bacterial infection.
  - Biosafety level 3 precautions.
  - PEP recommendations are doxycycline 100 mg orally twice a day plus rifampin 600 mg orally once a day for 21 days.
- Penetration by pieces of bone affects abattoir workers.
Accidents related to animal vaccination by veterinarians.
Transplacental transmission, transmission via breast milk feeding, and possibly even sexual transmission.
Blood transfusion or marrow or organ transplantation.

CLINICAL FEATURES

Incubation period is usually several weeks.
Nonspecific symptoms
- An undulant fever pattern (rising and falling like a wave) is sometimes observed.
- Fever is accompanied by nonspecific complaints of fatigue, back pain, weight loss, poor appetite, body aches, and depression.
- Peculiar taste sensations
- Twenty percent to thirty percent have lymphadenopathy, hepatosplenomegaly.
Organ localization
- Gastrointestinal
  - Nausea, vomiting, diarrhea, or constipation in up to 70%
  - Tonsillitis, hepatitis, ileitis, cholecystitis, and pancreatitis
  - Mild changes in liver function tests
  - No cirrhosis
  - Abscesses; granulomas occasionally
- Genitourinary
  - Fifty percent may have a positive urine culture.
  - Epididymo-orchitis in 20% of men
  - Prostatitis, cystitis
  - Cervicitis, tubo-ovarian abscesses, changes in menses
  - Found in semen
  - Interstitial nephritis, pyelonephritis, renal calcifications
  - Granulomatous lesions with abscesses in the kidneys
- Ocular
  - Endophthalmitis. Cultures may be positive.
  - Uveitis. Usually a later complication
  - Conjunctivitis
  - Keratitis
  - Retinal detachment
- Skeletal
  - Knees
  - Hips
  - Sternoclavicular joint
  - Sacroiliitis in younger patients
  - Lumbar spondylitis in older patients
  - Vertebral osteomyelitis
  - Psoas abscesses are common.
  - Lymphocytes are seen in synovial fluid.
- Pregnancy
  - Abortion
  - Premature delivery
  - Transmission via breast milk
- Cardiovascular
  - Endocarditis is rare but fatal if untreated. Overall mortality from brucellosis is low (<1%) and almost exclusively occurs from cardiac complications.
  - The median duration of symptoms prior to diagnosis is around 3 months.
  - Forty-five percent have underlying valvular damage, and in 55% of cases, it involved a normal valve.
  - Aortic involvement is found in 82% of cases.
  - Blood cultures were positive in 63% of the patients.
  - Surgical treatment was undertaken in eight patients (72%).
  - Pericarditis occasionally
- Respiratory
  - Pneumonia
  - Lung nodules
  - Abscess
  - Empyema
- Neurologic
  - Meningitis, encephalitis, brain and epidural abscesses
  - Guillain-Barré syndrome, a multiple sclerosis-like illness, paraplegia, and rhabdomyolysis
  - Acute or chronic meningitis syndromes are most common.
    - Lymphocytic pleocytosis, high protein, and normal or low glucose
    - Results of an agglutination test for Brucella in serum were positive for all patients in one review.
- Six of sixteen patients had positive blood cultures, and four of 14 had positive CSF cultures.
  - Gram stains and cultures of cerebrospinal fluid are usually negative.
  - Specific antibodies or real-time polymerase chain tests can help make the diagnosis.
- Skin
  - Purpura; maculopapular lesions
  - Stevens-Johnson syndrome
Relapses are common.
- Ten percento
- Usually occur in the first year
- Retreat with the same antibiotics
- Milder than the initial infectiono

DIAGNOSIS

CDC Classification

Probable: A clinically compatible illness with at least one of the following:

Epidemiologically linked to a confirmed human or animal brucellosis case
Presumptive laboratory evidence, but without definitive laboratory evidence, of Brucella infection

Confirmed: A clinically compatible illness with definitive laboratory evidence of Brucella infection.