Non-Fermentative Gram Negative Bacilli

Question 1

Define the term “non-fermentative organism”

Answer 1

Aerobic, non-spore forming bacilli that does not ferment glucose

Question 2

List the 3 primary criteria used to identify the non-fermentative gram-negative bacilli.

Answer 2

1. Gram Stain Morphology
2. Oxidase Test
3. MAC Agar

Question 3

Recognize the key biochemical difference between a non-fermenter and fermenter (enteric)

Answer 3

Lack of glucose fermentation
KIA Slant/Butt: Alkaline/Alkaline (K/K)
Decarboxylase Base: No change

Question 4

Identify (in order) the three most common non-fermenters found in the clinical laboratory.

Answer 4

1. Pseudomonas aeruginosa
2. Acinetobacter species
3. Stenotrophomonas maltophilia

Question 5

Recognize the name and color of pigments produced by some non-fermenters.

Answer 5

Pyoverdin: green/yellow; fluorescent under UV light
Pyocyanin: blue pigment
Pyorubin: red pigment
Melanin: brown pigment
Carotenoids: orange pigment
Violacein: purple pigment

Question 6

Differentiate the more common non-fermenters based on their Gram stain morphology and staining reactions.

Answer 6

ALL are straight GNR with the exception of Acinetobacter spp. – they are GNC/B