Updated: 11/27/2018

Brucella

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Snapshot
  • A farmer from Argentina presents to a local clinic with daily fevers and fatigue. He supports his family by supplying wool and providing unpasteurized milk for drinking and making cheese. For the past month, he has had general malaise, daily fevers, and some nausea and vomiting. On physical exam, he has a low-grade fever but otherwise a normal physical exam. Based on his occupational exposures, he is tested for zoonotic bacterial infections and started on empiric antibiotics.
Introduction
  • Classification
    • Brucella genus
      • most often Brucella melitensis
        • B. abortus and B. suis can also infect humans
      • facultative intracellular gram-negative zoonotic coccobacilli
      • transmission via ingestion of contaminated foods
      • causes an undulant fever
  • Epidemiology
    • incidence
      • endemic in Mediterranean countries and South America
      • the most common bacterial zoonosis
    • demographics
      • adults > children
    • risk factors
      • ingestion of unpasteurized dairy products
      • occupational exposure to animals
  • Pathogenesis
    • requires a very low dose
    • the bacteria enter through the intestinal mucosa, into the lymphatics, and into the blood
    • the bacteria are taken into macrophages and modify the intracellular environment to survive
  • Prognosis
    • often recurs
    • if untreated, the illness may progress to chronic disease that lasts for years
Presentation
  • Symptoms
    • undulant fever and chills (most common)
    • malaise
    • headaches
    • nausea and vomiting
    • arthritis
  • Physical exam
    • may have lymphadenopathy
    • may have hepatosplenomegaly
    • rarely may present with encephalopathy
Imaging
  • Magnetic resonance imaging (MRI)
    • indication
      • suspected neurologic involvement
    • findings
      • abnormal enhancement in the meninges
Studies
  • Labs
    • culture of bacteria from blood or bone marrow
    • detection of immunoglobulin G (IgG) and IgM on serology
  • Making the diagnosis
    • based on clinical presentation and confirmed with laboratory studies
Differential
  • Q fever
    • distinguishing factor
      • also zoonotic and causes fevers but presents as pneumonia
Treatment
  • Medical
    • doxycycline
      • indication
        • all patients
    • aminoglycosides
      • indication
        • relapse of disease
Complications
  • Heart failure
  • Spontaneous abortion
 

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