22 - Pathogenic Burkholderia Species

Question 1

Burkholderia genus

Answer 1

• Gram negative, rod shaped bacillus
• Ecological niches range from soil, plants, animals and humans
• Most non pathogenic

Question 2

Three well recognised pathogenic species in humans

Answer 2

• Burkholderia cepecia complex (BCC)
• Burkholderia mallei
• Burkholderia pseudomallei

Question 3

Burkholderia thailandensis

Answer 3

• Gram negative motile bacillus
• Soil saprophyte
• Disease in immunocompromised

Question 4

Burkholderia cepecia complex

Answer 4

• Approximately 20 closely related species
• B. cepecia is best characterised
• Found in water, soil, plants, animals and humans
• Cause onion rot
• Used to degrade pollutants in agriculture to promote the growth of desirable crops, and inhibit pests

Question 5

BCC and CF

Answer 5

• Opportunistic organisms, infecting immunocompromised individuals
• Causes Cepacia syndrome (necrotizing pneumonia, worsening respiratory failure, and bacteremia)
• Naturally resistant to many antibiotics including aminoglycosides, quinolones, polymyxins, and β-lactams

Question 6

What makes BCC pathogenic

Answer 6

• Cable pilus important for invading epithelial cells
• Biofilm formation
• Exopolysaccharide
• Intrinsic resistance and efflux pumps contributes to failure of antimicrobials
• BCESM

Question 7

BCESM

Answer 7

Genetic marker located on genomic islands containing genes involved in metabolism and virulence

Question 8

Burkholderia mallei

Answer 8

• Gram-negative, aerobic, non-motile facultative intracellular pathogen
• Glanders (horses)
• Nodular lesions in lungs, fever, septiceamia, death in humans
• Bioterrorism agent
• Oldest disease known to man

Question 9

Burkholderia pseudomallei

Answer 9

• Melioidosis
• Glanders-like
• Soil saprophyte, endemic in south east asia and northern aus

Question 10

Melioidosis

Answer 10

• Infection occurs most commonly by the cutaneous route
• Infection can also be asymptomatic
• Acute septicaemia, chronic and latent infection
• Risk factors include diabetes and renal disease

Question 11

B. pseudomallei vs B. mallei

Answer 11

• Gram negative bacilli, ‘safety pin’ appearance
• Pseudo is motile, mallei is not
• Pseudo has distinct ‘wrinkled’ appearance on Ashdown agar
• Both intracellular pathogens, mallei is host restricted
• Both have large genomes consisting of two chromosomes

Question 12

Capsule

Answer 12

• CApsular polysaccharide composed of -3)-2-O-acetyl 6-deoxy-β-D-manno heptopyranose
• Essential for survival and/or replication in macrophages
• Contributes to survival in serum by reducing opsonization and phagocytosis

Question 13

Lipopolysaccharide (LPS)

Answer 13

• An unbranched heteropolymer (-3)-β-dglucopyranose-6-deoxy-α-l-talopyranose-).
• O-antigen confers resistance against macrophage killing and promotes survival in serum by preventing killing by complement

Question 14

Type 3 secretion secretion system

Answer 14

• There are 3 T3SS in B. pseudomallei, only T3SS2
  and T3SS-3 are present in B. mallei and B. thailandensis
• The T3SS-3 are similar to the T3SSs from Salmonella and Shigella
• The T3SSs modulate intracellular behaviour of these pathogens
• T3SS-3 is required for escape from the phagocytic vesicles and for full virulence