Gram Negative: Hospital-Acquired Infections (mainly Pseudomonas Aeruginosa)

Question 1

What are the four major procedures that compromise normal defenses in some hospitalized patients? What are some others?

Answer 1

• IV catheters (“wires”)
• foley catheters (“water”)
• endo-tracheal tubes (“wind”)
• surgical incisions (“wounds”)
• others: antibiotics (opportunistic infections) and health care workers

Question 2

What are the four major diseases associated with hospital-acquired infections?

Answer 2

• pneumonia (intubation, mechanical ventilation)
• UTIs (foley catheter)
• wound infections (surgery, implants)
• bloodstream infections (IVs)

Question 3

Which family of bacteria is the major cause of HAIs? What are some others?

Answer 3

• major cause: family Enterobacteriacae (E. coli, Klebsiella, Enterobacter)
• others on the rise: Pseudomonads and Acinetobacter
• (the Pseudomonads: Pseudomonas aeruginosa, Burkholderia cepacia, and Stenotrophomonas maltophilia)

Question 4

Why does Pseudomonas aeruginosa only really affect hospitalized patients? What makes an infection with this organism so difficult to deal with?

Answer 4

• this organism has very weak invasive capacity on its own (hospital devices and procedures allow it to invade)
• once it manages to invade, it secretes a lot of exotoxins
• it is hard to eradicate because it is resistant to virtually every antibiotic

Question 5

What are the major characteristics of Pseudomonas aeruginosa?

Answer 5

• Gram negative bacillus
• oxidase positive
• obligate aerobe
• produces a green (pyoverdin) and blue (pyocyanin) pigment, which gives colonies and infected wounds/dressings a greenish-blue coloration
• produces a noticeable sweet grape-like scent

Question 6

Which diseases does Pseudomonas aeruginosa cause?

Answer 6

• “BE PSEUDo” for Pseudomonas
• Burn-wound infections
• Endocarditis (in IV drug users, like S. aureus)
• Pneumonia (seen in most CF patients)
• Sepsis (P. aeruginosa sepsis has a very high mortality rate)
• External malignant otitis media (seen in elderly diabetics)
• Urinary tract inefctions
• Diabetic Osteomyeltis (also in IV drug users and puncture wounds)
• (also corneal infections in contact lens wearers)

Question 7

Where are the Pseudomonads and Acinetobacter found (ie, what are the reservoirs for these organisms)?

Answer 7

• all are found in soil and water
• all Pseudomonads are also found in plants and animals
• P. aeruginosa is also found on skin and in normal gut flora
• Burkholderia cepacia is also found in the lungs of CF patients
• Stenotrophomonas maltophilia is also found in normal respiratory flora