25 - Pseudomonas aeruginosa

Question 1

Pseudomonas aeruginosa

Answer 1

• Gram negative, aerobic, non spore forming rod
• Adaptable to anaerobic environments
• Metabolic diversity
• Large repertoire of transporters, transcriptional regulators, and two-
  component regulatory systems which allows adaptation

Question 2

Large genome of Pseudomonas aeruginosa

Answer 2

• Conserved core genome of low sequence diversity
• Highly variable accessory genome that communicates with other
  pseudomonads and genera via horizontal gene transfer

Question 3

Ecology

Answer 3

• Widely distributed in soil, water, plants guts of humans
• Human and animal faeces important reservoirs
• Reservoirs in urban communities (e.g. hot tubs, pools)
• Reservoirs in hospitals

Question 4

Clinical manifestations in healthy patients

Answer 4

• Puncture wounds in foot
• Swimmers ear
• Hot tub folliculitis

Question 5

Clinical manifestions in immunocompromised

Answer 5

• Chronic lung infection
• Pneumonia
• UTI
• Bacteraemia

Question 6

Virulence determinants

Answer 6

• Exopolysaccharides (alginate, Psl and Pse)
• T3SS
• Exotoxin A
• Enzymes that break down host tissue
• Siderophores
• Antioxidant enzymes
• Regulation of virulence factors via quorum sensing

Question 7

Motility

Answer 7

• Single polar flagellum
• Type IV pili (crucial for twitching motility and attachment to host cells)
• Both are also virulence determinants

Question 8

Exopolysaccharides (alginate, Psl and Pse)

Answer 8

• Contribute to the biofilm matrix
• Impair bacterial clearance
• Promote the establishment of chronic infection

Question 9

Four cytotoxic effectors injected via T3SS

Answer 9

ExoU, ExoT, ExoS, ExoY

Question 10

Exotoxin A

Answer 10

Inhibits host protein synthesis due to its ADP-ribosylating activity

Question 11

Enzymes that break down host
tissue

Answer 11

• Proteolytic elastases
• Alkaline protease
• Phospholipase C

Question 12

Antioxidants

Answer 12

Help overcome oxidative stress (e.g. KatA, KatB and KatE)

Question 13

Adaption in CF airways

Answer 13

Selective pressure foster loss of flagella, adaptation of metabolism, antibiotic resistance

Question 14

Tolerance

Answer 14

Favoured when high antibiotic concentrations are applied in growth restricting conditions.

Question 15

Mechanisms of antibiotic tolerance in biofilms

Answer 15

• Upregulation of expression of drug
  efflux pumps
• Decreased pH, accumulation of waste products may antagonize actions of antibiotics
• Persister cells

Question 16

Resistance

Answer 16

• Favoured when the nutrient concentration is sufficiently high to allow growth, while the antibiotic concentration is low enough to be overcome by resistance mutations
• Arises through mutation or horizontal gene transfer

Question 17

Mechanisms of resistance

Answer 17

• Antimicrobial inactivation
• Bacterial target site modification
• Persistence
• Reduced antibiotic accumulation