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What are basic characteristics of Pseudomonas aeruginosa?
- Gram negative bacillus in singles
- Thick slime layer with capsules
- Oxidase positive – does not ferment but can respire anaerobically using nitrates
- Fruity odor
- Pigments common
- Single flagellum, sometimes two
- Type IV pili for adherance
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Explain the pili found in Pseudomonas aeruginosa, Gonnococcus, and Vibrio
- Type IV pili with N-methyl-phenylalanine
- Binds to asialo-GM1 and triggers IL-8 production
- (neuraminidase converts regular GM1 into asialo-GM1 for better bacterial binding)
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What do the pigments in pseudomonas aeruginosa mean?
- Green-yellow = fluorescein (chelates iron)
- Blue = pyocyanin (convert O2 to O2-)
- Red and black are also possible, but we didn’t learn what they meant
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When pseudomonas is put on TSI agar what properties are seen?
- No growth in butt (not anaerobic)
- Red slant (more basic due to use of amino acids
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Pneumococcus and Pseudomonas have a virulence factor called Neuraminidase, what does it do?
Makes more receptor sites for pili to bind to (converts GM1 to asialo-GM1)
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What is the difference in toxic exoprotein regulation between Staph aureus and pseudomonas aeruginosa?
- Staph aureus relies on the buildup of octapeptide to switch to making exoprotein
- Pseudomonas aeruginosa relies on the buildup of homoserine lactone
- Both bind early and poison late in growth
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How does exotoxin A function? (Produced by Pseudomonas aeruginosa)
- Enters cell and is activated by furin (cleaved into two pieces)
- Enzymatically ribosylates EF2 – this inhibits protein synthesis causing cell death (swaps EF2 for NAD)
- Low iron content favors toxin A production by Pseudomonas aeruginosa
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What is the difference between a strain of Pseudomonas aeruginosa producing Exo S vs Exo U?
- Exotoxin S: invasive strain – intracellular growth then apoptosis (also T and Y)
- Exotoxin U: cytotoxic strain – cell lysis (also T)
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What do the four toxins produced by pseudomonas do? (S, T, U, Y)
- S: GTPase that causes cytoskeletal disruptions (reduced phagocytosis) plus ribosylation decreasing DNA replication and apoptosis
- T: GTPase causes cytoskeletal disruptions (reduced phagocytosis) plus ribosylation causing less cell adhesion
- U: Phospholipase that quickly kills cells (found in cytotoxic strains only)
- Y: adenyl cyclase activity that disrupts actin (reduced phagocytosis) – Favors toxin production
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Explain how Pseudomonas aeruginosa regulates virulence factor production
- cAMP -> vfr -> las R -> las I -> homoserine lactone -> expression of virulence factors (also -> las R again)
- Exo Y starts process by increasing cAMP
- Low levels of Pseudomonas have low levels of exoprotein; high levels have high so it is similar to the ACR of staph
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What are furanones?
- Compounds that inhibit las R of pseudomonas
- Not yet used for drugs but possible
- Found by Australian divers
- ** cAMP -> vfr -> las R -> las I -> homoserine lactone -> expression of virulence factors
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What drugs can be used to treat pseudomonas?
- Pseudomonas is very resistant to many drugs, the following may work
- Carbenicillin
- Beta-Lactam + Aminoglycoside (eg. Ticarcillin + tobramycin)
- Fluoroquinolones (Cipro)
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What percent of pseudomonas infections that spread to blood are lethal?
35%
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What are the leading outpatient and hospitalized patient infections associate with pseudomonas?
- Outpatient:
- #1 otitis externa (swimmers ear)
- Keratitis (contact lens)
- Folliculitis (hot tub infection)
- Wound/burn/nail
- CNS
- Osteomyelitis
- Endocarditis
- Inpatient:
- #1 Burn infections
- #1 lower respiratory tract infection
- #3 UTI
- Wound infection
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What is the leading cause of burn infection?
Pseudomonas aeruginosa
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What is the leading cause of Pneumonia?
Pseudomonas aeruginosa
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Why is Pseudomonas nearly impossible to remove in cystic fibrosis patients?
- The high salt environment induces mutation that produces copious amounts of mucoid Alginate by removing the inhibition of the repression pathway that builds sugars of alginate
- This biofilm is very protective
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What are the basics of Burkholderia pseudomallei?
- Gram negative rod
- Transmitted by dust from Southeast Asia or Australia
- Skin/soft tissue abcesses
- Treat like pseudomonas (beta lactam + aminoglycoside or Cipro)
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What are the basics of Burkholderia cepacia?
- Gram negative rod
- Nosocomial in immunocompromised or CF patients
- Bacteremia/septicemia
- Treat like pseudomonas (beta lactam + aminoglycoside or Cipro)
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What are the basics of Stenotrophomonas maltophilia?
- Gram negative rod
- Protects other bacteria by secreting broad spectrum Bla
- Often on lines or catheters
- Treat with Timentin or sulfa-trimethoprim
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