Pseudomonas (G-)

Question 1

describe the shape, location, mobility, and need or O2 of Pseudomonas aeruginosa.

Answer 1

• G- bacilli (rods)
• ubiquitous (found everywhere): soil & water
• motile: one/several polar flagella, polar pili (twitching)
• aerobic (this species): some strains anaerobically grow with nitrate

Question 2

what do the pseudomonas aeruginosa colonies produce?

Answer 2

• water soluble pigments that function as antibacterials
  
  • pyocyanin (blue-green)
  • pyoverdin (green)
  • fluorescein (yellow fluorescence)
• fruity or grape like odor to colonies (or near wounds)

Question 3

pseudomonas aeruginosa grows rapidly and is very robust… does it have nutritional requirements?

Answer 3

• minimal nutritional requirement
  
  • do not ferment (oxidize sugars): indophenol oxidase (like Neisseria sp.)
  • need only acetate and ammonia as carbon and nitrogen sources (most organic compounds can provide this including petroleum and toxic wastes
• can survive in hand creams, soaps, and dilute antiseptics

Question 4

name the persistence virulence factors of pseudomonas.

Answer 4

• mucoid polysaccharide capsule (alginate) shields from immune system
• siderophores
• elastase
• exotoxin A
• phopholipase C

Question 5

name the dissemination virulence factors of pseudomonas.

Answer 5

• toxin A
• collagenase
• elastase
• exoenzymes
• flagella
• heat stable hemolysin
• tissue damage by proteases and toxins

Question 6

which 3 of the dissemination factors are considered spreading factors?

Answer 6

1. collagenase
2. elastase
3. exoenzymes

Question 7

which 2 virulence factors are nutritional aids? describe them

Answer 7

1. siderophores (iron binding compounds): complete with transferrin for iron, iron limitation causes increase production of elastase and exotoxin A
   * damages tissue/creates conditions that make iron more accessible
2. phospholipase C: hydrolyzes phospholipids (lecithin) in the eukaryotic membrane, releasing usable phosphate

Question 8

where and how do we encounter pseudomonas?

Answer 8

• where = soil and water
• how:
  
  • adheres to vegetables and plant matter
  • in water taps, drains, wet surfaces: otis externa (swimmer’s ear)
  • hot tubs! (folliculitis, dermatitis): hot tub rash

Question 9

pseudomonas is an OPPORTUNISTIC pathogen… how does it enter into a host cell?

Answer 9

• local or systemic breach of immune system
• immunocompromised patients
• *org does not adhere well to healthy epithelium:
  
  • can enter thru abrasions, cuts, etc.
  • usually they don’t get far unless in large #s

Question 10

**after entry of pseudomonas the ability of it to spread and multiply depends on what two things?

Answer 10

1. avoiding phagocytosis

2. successful adherence to a surface

Question 11

**adherence of pseudomonas to epithelia is mediated by what 2 things?

Answer 11

1. flagella
2. pili
   * interactions with glycolipid (cleaves sialic acid to create asialo GM1; receptor for Type 4 pili) on host cells and toll like receptors (TLR5)

Question 12

what kind of phenotype is the pseudomonas polysaccharide capsule (alginate)?

Answer 12

mucoid phenotype

Question 13

what components of the pseudomonas polysaccharide capsule (alginate) helps with its spread and multiplication?

Answer 13

• major adhesin and component of biofilm in cystic fibrosis patients
• production is highly regulated

Question 14

what are the two key factors in pseudomonas spread and multiplication?

Answer 14

1. polysaccharide capsule (alginate)

2. numerous cytolytic exotoxins

Question 15

how do pseudomonas spp cause damage?

Answer 15

• LPS
• exotoxins (cause local inflammation)
• multifunctional enzymes (proteases)
• type III secretion system

Question 16

how does LPS cause damage?

Answer 16

• adhesin
• lipid A = endotoxin; which interacts with host TLR4 to initiate inflammatory response
  * fever, hypotension, G- sepsis
  * less inflamm than e. coli or s. typhimurium
• core oligosaccharide interacts with CFTR (an ATP-binding cassette transporter; cystic fibrosis transmembrane conductance regulator)
  * bacterial internalization, initiation of immune resistance
• Long O-antigen side chains
  * responsible for resistance to human serum, antibiotics, detergents

Question 17

how do endotoxins cause damage?

Answer 17

• they cause local inflammation
• some kill host tissue (exotoxin A): ADP-ribosylation of EF-2 (similar to diptheria toxin)
• all are tightly regulated

Question 18

how do multifunctional enzymes (proteases) cause damage?

Answer 18

• elastase:
  
  • cleaves elastin & colllagen: direct tissue damage
  • cleaves proteinase inhibitors
  • cleaves immune system components: complements Ig’s
• LasA:
  
  • serine protease that works with elastase to degrade elastin

Question 19

how does the type III secretion system cause damage?

Answer 19

• delivers virulence factors directly into host cells
  
  • transfer from bacterial cytosol to host cytoplams
• similar to flagella
• targets specific proteins on host cells
• induced by host cell contact or low calcium levels

-secretion effectors include ExoS, ExoT, ExoU, and ExoY which are transcriptionally controlled by ExsA

Question 20

what type of epithelium does P. aeruginosa adhere to best?

Answer 20

• does not adhere well to normal intact epithelium

- piliated strains adhere better than non-pilated strains

Question 21

why do cystic fibrosis respiratory cells bind more P. aeruginosa than those of normal cells?

Answer 21

• cystic fibrosis transmembrane conductance regulator (CFTR)
• dysfunctional in CF patients:
  
  • loss of Cl- transport
  • hereditary
• can be rescued with normal copy of gene

Question 22

what can CFTR cause?

Answer 22

-decreased sialylation of surface glycolipids: p. aeruginosa binds to these asialo-glycolipids

Question 23

what happens to mucous production in cystic fibrosis and p. aeruginosa?

Answer 23

• thick mucous produced which impairs mucociliary system

- dehydration of respiratory secretions

Question 24

how is p. aeruginosa shielded from the immune system?

Answer 24

• mucoid exopolysaccharide (alginate) shields organism from immune system
• however these alginate strains produce less protease and toxins

Question 25

what component of pseudomonas causes sepsis and describe how it happens?

Answer 25

• LPS (endotoxin) mediated:
  
  • specific lipid A moiety
  • triggers production of tumor necrosis factor (TNF)
  • TNF stimulates macrophages to produce IL-1

Question 26

what is sepsis?

Answer 26

severe systemic illness marked by hemodynamic derangements and organ malfunction brought about by the interaction of certain microbial products with host reticulendothelial cells

Question 27

what is MODS (multi-organ dysfunction syndrome)?

Answer 27

• high cardiac output, lowered blood pressure

- distributive shock (lack of perfusion of selected vascular beds)

Question 28

sepsis has 3 requirements, what are they?

Answer 28

1. large population of infecting/colonizing organisms
2. presence of bacterial products that stimulate release of host cytokines
3. widespread dissemination of microbial products to host’s reticuloendothelial system

Question 29

mortality can occur with pseudomonas spp., what does it depend on?

Answer 29

• nature and severity of infection
• host defense state
• promptness and efficacy of treatment

Question 30

how is infection with pseudomonas diagnosed?

Answer 30

easily cultured and ID’ed

Question 31

how is infection with pseudomonas treated?

Answer 31

• antibiotic treatment depends on the geographic locale:
  
  • in some hospitals certain antibiotic-resistant strains predominate
  • resistance is due to limited permeability of outer membrane, efflux pumps, and antibiotic resistance genes
• frequently requires antibiotic synergism to treat