Opportunistic Pathogen: Pseudomonas aeruginosa

Question 1

History of resistance
-drugs

-what type of patients it commonly affects

Answer 1

• Sulphonamide resistance 1920-1930
• Emerging resistance to antibiotics
• 1980s emergered as pathogen for Cystic fibrosis patients and burns patients

Question 2

Identification

• of bacterial colonies
• special characteristic

Answer 2

• Gram negative bacillus
• Motile via polar flagella (at one end)
• catalase, oxidase positive
• growth at 42 degrees (can resist fever)
• many have metallic sheen on blood agar
• blue/green pigment = antibiotic pyocyanin
• yellow pigment = siderophore pyoverdine

Question 3

Why does it have quite a large genome? (4 reasons)

Answer 3

• Codes for just as many proteins as an eukaryote
• it inherits resistance (antibiotics & antiseptics)
• Large array of virulence factors
• Diverse substrates (need different proteins to be able to synthesis them)

Question 4

E.g. of some methods of antibiotic resistant mechanisms (4)

• 2 general features
• 2 features to specific antibiotic classes

Answer 4

• Contains enzymes that can modify aminoglycosides (class of antibiotics)
• can neutralise cephalosporins
• Actively pumps out foreign antibodies (has active efflux systems)
• Has diminished outer membrane permeability (very specific porins that restricts what can get in)

*Inherent chromosomal resistance & horizontal transfer of resistance = need for alternative/supplementary treatments

Question 5

Conjugation

• what is it in terms of resistance
• what happens

Answer 5

• Antibiotic gene resistant cassettes that can code for more than one resistance (e.g. integron ABr gene cassette)
  
  • can be transferred w/ other species, other generations or other strains
• occurs through sex pilus
• bit problem with bacteria

Question 6

Habitat of P. aeruginosa

Answer 6

• Ubiquitous (tend to pick it up on our skin daily)
• Soil and water organism
• Ability to grow using various organic compounds & survive w/ minimal nutrition (i.e. bottled mineral water)
• habitat facilitates animal/plant contact
• Model for biofilm production

Question 7

Biofilm -> what it is

-when it occurs

Answer 7

• Biofilm = gunky layer that tends to be polymicrobial
  
  • occurs when levels of organims reach a threshold (bacteria know via quorum sensing)
    
    • bacteria then synthesise biofilm

Question 8

Disease of P. aeruginosa

-e.g. of what it can cause

Answer 8

• Opportunistic pathogen of plants, nematodes, insects, animals
• Urinary Tract infections, indwelling catheters
• can cause severe disease, esp. for immunosuppressed patients
• can also produce enzymes that are capable of liquefying eye (risk for ppl with contact lenses)

Question 9

Severe Human diseases

-situations when likely to develop (i.e. what people are more susceptible)

Answer 9

• may rely on predisposition (i.e. illness, genetic, immune suppression)
• HIV/AIDS
• Cystic fibrosis
• Dermal Injuries; burns (offer a large portal of entry)
  
  • ppl burnt by flame get a crusty surface which has to be surgically removed as it is toxic)

Question 10

Virulence factors of P. aeruginosa

• Pilus
• flagellum
• Alginate/Biofilm
• extracellular products

Answer 10

• Pilus: can use it for “twitching motility” - can shoot it and pull itself along
• flagellum: propels it along (can sense nutrient gradient and move towards it)
• Alginate/biofilm: biofilm = exoproduct -> helps it become inpenetratable to antibiotics
• Extracellular products produced;
  
  • proteaases
  • hemolysins
  • exotoxin A
  • exoenzyme S
  • pyocyanin (pigment)

Question 11

Exotoxin A effect on cell

Answer 11

• affects receptor that pump out collagen to maintain the integrity of skin
• binds to receptor and translocates to inside of cell
  
  • affects translation which means no protein synthesis & Cell death
• prolonged decrease of cells in faascia (fibroblasts and neutrophils)
• also causes loss of maintenance of extracellular matrix

Question 12

P. aeruginosa elastase

Answer 12

• degrades elastin and collagen
• also degrades human immunoglobulins and complement C3 (part of host defence)
• increases exudation (fluid)
• damages blood vessels
• degrades collagen of extracellular matrix

Question 13

Phospholipase C -> effect on cell

Answer 13

• attacks bond between glyceral and phosphate -> opens phospholipid molecule up to other destructors
  
  • is first part to membrane breakdown

Question 14

Key facts of P. aeruginosa

Answer 14

• Large genome
• Large number of VFs
• Hosts include animals, plants, insects
• Ab resistant; intrinsic and acquired
• opportunistic pathogen of susceptible hosts