Melioidosis

(Pseudoglanders)

• Caused by Pseudomonas (Malleomyces) pseudomallei, Closely related to P. mallei in horses
• Causes disease in sheep, goats and pigs, occasionally other species
• Starts as a pyemia and localises in varius tissues, including the lung as abscessation
  • Encapsulated abscesses contain yellow, caseous or creamy pus

• Pathogenesis:
  • Infection via ingestion, inhalation or skin wounds from environment
  • Exotoxin, dermonecrotic protease and lecithinase implicated in pathogenicity
  • Strain virulence and host immunosuppression important
• Clinical infections:
  • Opportunistic infection with stress and immunosuppression predisposing to disease
  • Abscesses develop in many organs including lungs, spleen, liver, joints, CNS, upper respiratory tract
  • Chronic, debilitating, progressive disease with long incubation period
  • Many animal species susceptible
  • Referred to as pseudoglanders in horses
• Diagnosis:
  • Specimens: pus from abscesses, affected tissues, blood
  • Fluorescent antibody technique on tissue smears
  • Blood agar and MacConkey agar plates, incubated aerobically
  • Colonies have musty smell
  • Lactose fermentation on MacConkey
  • Slide agglutination
  • ELISA, complement fixation and indirect haemagglutination tests for serum antibodies
• Treatment/control: slaughter of infected animals where exotic
• Pneumonia and arthritis are the most common presentation