A dark pigmented colony is isolated from the leg wound of a fisherman from Florida. The gram-negative rod grows on sheep blood and MacConkey agars. The organism provides the following reactions:
TSI: K/A Indole: no color change Lysine: no color change
1 NaCL: no growth Arginine: purple Ornithine: no color change
DNase: pink halo around the area of organism inoculum
The microbiologist cannot read the oxidase reaction due to the dark pigment. What can he do to help achieve a valid oxidase reaction?
A) Grow the organism under anaerobic conditions and retest
B) Grow the organism on a non-nutrient agar and retest
C) The oxidase test is not necessary for the identification of this organism
D) Perform a modified oxidase test
Question 2
A microbiologist sets up a set of decarboxylase tubes for identification of a glucose fermenting, gram-negative rod.
After 24 hours, the tubes reveal
Base control: gray
Arginine: purple
Lysine: yellow
Ornithine: purple
These tubes should be interpreted as
A) all positive. B) positive for arginine and ornithine.
C) invalid. D) positive for lysine.
