Pseudomonas aeruginosa and Other Non-Fermenting Bacilli

Question 1

What are some possible characteristics of Glucose NON-fermenting G(-) Bacilli?

Answer 1

• G(-), NONspore-forming bacteria may be rods or coccobacilli
• obligate aerobes
• good growth usually seen in 24hrs
• glucose not fermented
• Natural habitat: water, soil, plants

Question 2

What are Pseudomonas aeruginosa?

Answer 2

• aerobic G (-) rod
• motile with polar flagella
• mucoid polysccharide slime layer
• pili in cell surface assist with attachment
• harder to treat because survive living in environment

Question 3

What is the epidemiology of P. aeruginosa?

Answer 3

-environmental organism
-grows in unsterile water, medications, disinfectants
-hospital environment
-moist areas
»sinks
»toilets
»cut flowers
»floor mops
»equipment

Question 4

Why is P. aeruginosa an opportunistic pathogen?

Answer 4

Factors predisposing to serious infection:

• burn patients
• CF patients
• pts with hematologic malignancies
• immunocompromised pts
• can be part of the microbial flora in hospitalized patients and ambulatory, immunocompromised hosts

Question 5

What are three exmaples of opportunities for pseudomonas skin infections?

Answer 5

1. burn wounds
2. folliculitis-hots tubs, whirlpools, pools, water slides
3. nail infections

Question 6

What are the characteristics of pseudomonas pulmonary infections?

Answer 6

• starts with asymptomatic colonization
• CF, chronic lung dz
• severe necrotizing bronchopneumonia
• most common cause of ventilator associated pneumonia (VAP)

Question 7

What are other pseudomonas infections?

Answer 7

1. UTI
2. ear infections
   »swimmers ear
   »malignant external otitis
   »chronic otitis media
3. eye infections (*eye cosmetics)
4. Bacteremia-ecthyma gangrenosum
   -uncommon cutaneous infection but well-recognized
   -in pts that are critically ill and immunocompromised, almost always a sign of pseudomonal SEPSIS
   -characteristic lesions are hemorrhagic postules or infarcted-appearing areas with surrounding erythema that evolves into necrotic ulcers surrounded by erythema
   -the transformation of an early lesion –> necrotic ulcer in

Question 8

What are the virulence factors of Pseudomonas aeruginosa?

Answer 8

A. Structural
-capsule, pili, LPS, and pyocyanin (agar turns blue) + pyoverdin (ylw pigment)=green
B. Toxins and Enzymes
-Exotoxin A
-Exoenzyme S
-Elastase

Question 9

Virulence Factor-Exotoxin A of P. aeruginosa

Answer 9

• blocks protein synthesis (like diphtheria toxin)

- most likely contributes to dermatonecrosis in wounds and tissue damage in lungs

Question 10

Virulence Factor-Exoenzyme S of P. Aeruginosa

Answer 10

• ADP ribosylating toxin

- epithelial cell damage facilitates bacterial spread, tissue invasion, and necrosis

Question 11

Virulence Factor-Elastase of P. aeruginosa

Answer 11

• results in tissue destruction and hemorrhagic lesions (ecthyma gangrenosum)
• 2 enzymes: Las A and Las B act synergistically to degrade elastin
• degrades compliment components and inhibits neutrophil chemotaxis and function

Question 12

How is P. aeruginosa diagnosed?

Answer 12

-Culture
»grows on blood and MacConkey agar, spready colonies with metallic sheen, alligator skin
-Identification
»beta hemolytic
-glucose NON-fermenter
-oxidase POSITIVE
-grape-like odor
**-produces pyocyanin (ONLY one in da world)
**-Grows at 42 C
-forms mucoid, gets worse and worse with CF pt, eventually will need a lung transplant

Question 13

What is the best treatment for pseudomonas infections?

Answer 13

• resistant to many of the common antibiotics used for G(-) infections
• resistance due to changes in porins
• combination therapy of cell wall active agent + aminoglycoside for serious systemic infections

Question 14

General info about Burkholderia pseudomallei

Answer 14

• originally pseudomonas

- B. mallei and B. pseudomallei