Pseudomonas aurugenosa - MegaMicro

a. Gram-positive

b. Rod-shaped

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

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

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

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