Melioidosis

Burkholderia pseudomallei
Phylum	Proteobacteria
Class	Beta Proteobacteria
Order	Burkholderiales
Family	Burkholderiaceae
Genus	Burkholderia
Species	B.pseudomallei

Also known as: Pseudoglanders

Caused by: Burkholderia pseudomallei also known as Pseudomonas pseudomallei — Malleomyces pseudomallei

Burkholderia pseudomallei colonies on a Blood agar plate.( Marco Tolo 2007, Wikimedia commons)

Overview

Burkholderia pseudomallei is a species of the Burkholderia genus. B.pseudomallei causes melioidosis, an opportunistic infection which is endemic in Asia and Australia. It primarily infects rodents.

Pathogenesis

Infection occurs via ingestion, inhalation or via skin wounds from the environment. The bacteria contains an exotoxin, dermonecrotic protease and lecithinase which is implicated in pathogenicity. Strain virulence and host immunosuppression is important. Burkholderia pseudomallei is also motile, by polar flagellae.

Diagnosis

Diagnosis of the B.pseudomallei bacteria can be made via specimens, including; pus from abscesses, affected tissues and blood. The fluorescent antibody technique can be done on tissue smears. B.pseudomallei grows on blood agar and MacConkey agar plates, incubated aerobically. The colonies have a musty smell and you see lactose fermentation on MacConkey. Slide agglutination, ELISA, complement fixation and indirect haemagglutination tests for serum antibodies are also all diagnostic of B.pseudomallei.

Melioidosis Learning Resources
Literature Search Search for recent publications via CAB Abstract (CABI log in required)	Burkholderia pseudomallei publications

Melioidosis

• 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