Pseudomonas aurugenosa - MegaMicro

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Pseudomonas aurugenosa

Microbiology > Bacteriology > Gram-negative bacteria > Gram-negative bacilli > Pseudomonas
1. Structure
a. Gram-positive
b. Rod-shaped

2. Pathobiology:
a. Physiology
i. Citrate positive
ii. Catalase positive
iii. Oxidase positive
iv. Obligate anaerobe
v. Non-lactose fermenter
vi. Produces pyoverdin and pyocyanin, green and blue pigments, respectively.
vii. Thrive in aquatic environments
viii. Produces fruity grape-like odor
b. virulence factors
i. Endotoxin A
1. Inactivates eukaryotic elongation factor 2 (EF-2) via ADP ribosylation in the host cell, which inhibits protein synthesis--> necrosis
ii. Exoenzyme, ExoU
1. Degrades plasma membrane of eukaryotic cells, leading to lysis
iii. Phenazines
1. Redox-active pigments
2. Involved in quorum sensing, virulence, and ion acquisition
a. Pyocyanin
iv. Endotoxin (LPS)
1. Activate factors that result in septic shoc

3. Epidemiology
a. Reservoir: found in soil, water, skin flora

4. Disease manifestations
a. Diagnostic methods
i. Culture
ii. Microscopic analysis (Gram negative rods with blue/green colonies and fruity grape-like odor)
b. Differential diagnosis (Wound, Wind, Water, Wire)

Major clinical manifestations:
i. Hot tub folliculitis (Water)
ii. Pneumonia (Wind)
1. In cystic fibrosis patients
2. In immunocompromised patients
3. Ventilator-associated pneumonias
iii. Osteomyelitis (Wound)
1. In diabetics: due to increased risk of foot ulcers. Infection can then penetrate the bone.
2. In IV drug users
3. In children: secondary to puncture wounds to the foot
iv. Burn-wound Infections (Wound)
v. Sepsis (Wire)
1. Commonly due to infected catheters (“wires”)
vi. Ecthyma gangrenosum (Wounds)
vii. UTIs, pyelonephritis (Water)
1. Hospitalized patients with Foley catheters
viii. Endocarditis
1. In IV drug users
ix. External otitis
1. Primarily in elder diabetic patients
x. Corneal infections
1. contact lens wearers

c. Therapy
i. Often two antibiotics with anti-pseudomonal activity are given until organism is identified and drug susceptibilities are available
1. Anti-pseudomonal penicillin (piperacillin, mezlocillin)
2. Fluoroquinolones
3. Aminoglyosides
4. Fourth-generation cephalosporins (Ceftazidime, Cefipime)
ii. Resistance arises quickly

Related concepts

  • Gram-negative bacteria
  • Gram-negative bacilli
  • Pseudomonas
  • P. aeruginosa

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