Category:Pseudomonas and Burkholderia species

Overview

• Organisms found in soil and water worldwide
• Burkholderia mallei causes glanders; rodents act as reservoir of infection
• Burkholderia pseudomallei causes meliodosis
• Pseudomonas aeruginosa, found on skin, mucous membranes and in faeces, causes opportunistic infections

Characteristics

• Gram-negative rods
• Obligate aerobes
• Oxidase and catalase positive
• Pseudomonas species and Burkholderia pseudomallei motile by polar flagellae
• Burkholderia mallei non-motile

Pseudomonas aeruginosa

Burkholderia mallei

• Causes glanders, a contagious disease of Equidae
• Nodules and ulcers in respiratory tract and on skin
• Largely eradicated but sporadic cases in Middle East, India, China
• Pathogenesis:
  • Transmited by ingestion of food/water contaminated by nasal discharge of infected Equidae; occasionally via inhalation or skin wounds
  • Organism invades nasopharyngeal mucosa and spreads to other tissues via lymphatics
  • Presence of B. mallei in host causes hypersensitivity reaction
• Clinical infections:
  • Acute septicaemic form with fever, mucopurulent nasal discharge and respiratory signs; death within weeks
  • Chronic disease more common:
    • Nasal form: rhinitis; ulcerative nodules develop on mucosa of nasal septum and lower part of turbinates; purulent blood-stained nasal discharge; regional lymphadenitis
    • Respiratory form: respiratory distress; granulomatous lesions throughout lungs
    • Cutaneous form (farcy): lymphangitis; nodules along lymphatic vesselsof limbs; ulcers develop and discharge pus
    • May die after several months or recover and shed organisms from respiratory tract or skin
  • Carnivores may contract disease by eating infected carcasses
• Diagnosis:
  • Specimens include discharges from lesions and blood for serology
  • Grows on media containing 1% glycerol; most strains are non-lactose fermenters on MacConkey agar
  • Complement fixation and agglutination
  • Serology
  • Mallein test: mallein injected intradermally below lower eyelid; local swelling and discharge indicates positive reation
• Treatment/control:
  • Test and slaughter policy where disease exotic
  • Disinfection of contaminated areas using formalin or an iodophor

Burkholderia pseudomallei

• Causes melioidosis - endemic in Asia and Australia
• Primarily infects rodents
• 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