questions 4

Pseudomonas aeruginosa

Topic updated on 01/12/17 1:21pm

  • Classification
    • Bacteria
      • Gram-negative bacilli
        • aerobes
          • Pseudomonas
            • P. aeruginosa
  • Pathogenesis
    • transmission
      • nosocomial
      • water
      • raw vegetables
      • flowers
    • reservoir
      • water (ubiquitous)
    • molecular biology
      • pyocyanin and pyoverdin (blue and green pigment)
        • has a grapelike odor
      • exotoxin A
        • stops protein synthesis via inactivation of elongation factor 2 (EF-2)
          • via ADP ribosylation
        • same mechanism as diphtheria toxin
      • endotoxin
        • causes inflammation, fever, and shock
      • capsule/slime layer
        • evades phagocytosis
  • "BE PSEUDO" most commonly affects the immunocompromised
    • Burns
    • Endocarditis
      • right valve in IV drug abusers
    • Pneumonia
      • in cystic fibrosis
      • in immunocompromised
      • ICU patients on respirator
        • productive cough with green sputum
    • Sepsis
      • ecthyma gangrenosum 
        • necrotic skin lesions
        • due to perivascular invasion and release of exotoxins
      • can occur from catheter infection
    • External otitis
      • swimmer's ear
      • malignant otitis externa in diabetics
    • UTI
      • especially with Foley catheters
    • Drug use
    • Osteomyelitis 
      • trauma (e.g. puncture wounds to foot)
      • diabetics
      • drug addicts
    • hot tub folliculitis 
      • superficial infection of the hair follicle due to exposure in a pool/hot tub/spa
    • corneal infections
      • in contact lens users
  • Non-lactose fermenting
  • Oxidase positive
  • Aminoglycoside + extended-spectrum penicillin
  • Usually antibiotic resistant


Qbank (2 Questions)

(M1.MC.4723) A 37-year-old woman presents to her primary care physician after returning from her honeymoon in Cancun. A few days ago, she began to notice an eruption of small red bumps that cover her torso, back, and buttocks. The patient first thought she had acne, but became worried when the rash continued to itch. The patient denies other symptoms. Vital signs are within normal limits. Physical exam is notable for red papules and pustules scattered across the trunk, abdomen, back, and buttocks, while sparing the limbs. Closer examination indicates inflammation of the hair follicles. Culture yields motile, gram-negative rods that are non-lactose fermenting and oxidase positive. What other finding is commonly observed in the culture of the most likely organism? Topic Review Topic

1. Pink colonies
2. Blue-green pigment
3. Alpha-hemolysis
4. Yellow sulfur granules
5. Red pigment

(M1.MC.4754) A 45-year-old male presents to his primary care physician complaining of drainage from his left great toe. He has had an ulcer on his left great toe for over eight months. He noticed increasing drainage from the ulcer over the past week. His past medical history is notable for diabetes mellitus on insulin complicated by peripheral neuropathy and retinopathy. His most recent hemoglobin A1c was 9.4%. He has a 25 pack-year smoking history. He has multiple sexual partners and does not use condoms. His temperature is 100.8°F (38.2°C), blood pressure is 150/70 mmHg, pulse is 100/min, and respirations are 18/min. Physical examination reveals a 1 cm ulcer on the plantar aspect of the left great toe surrounded by an edematous and erythematous ring. Exposed bone can be palpated with a probe. There are multiple small cuts and bruises on both feet. A bone biopsy reveals abundant gram-negative rods that do not ferment lactose. The pathogen most likely responsible for this patient’s current condition is also strongly associated with which of the following conditions? Topic Review Topic

1. Otitis externa
2. Gastroenteritis
3. Waterhouse-Friedrichsen syndrome
4. Rheumatic fever
5. Toxic shock syndrome

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