Butyrate Disk

Question 1

Purpose of butyrate disk :

Answer 1

This is a rapid test to detect the enzyme butyr ate esterase, to aid identification of Moraxella (Branhamella) catarrhalis

Question 2

Principle of butyrate disk:

Answer 2

Organisms capable of producing butyrate ester ase hydrolyze bromochlorindolyl butyrate. Hydrolysis of the substrate in the presence of butyrate esterase releases indoxyl, which in the presence of oxygen spontaneously forms indigo, a blue to blue-violet color.

Question 3

Method of butyrate disk :

Answer 3

1. Remove a disk from the vial and place on a glass microscope slide.
2. Add 1 drop of reagent-grade water. This should leave a slight excess of water on the disk 3. Using a wooden applicator stick, rub a small amount of several colonies from an 18- to 24-hour pure culture onto the disk.
3. Incubate at room temperature for up to 5 minutes.

Question 4

Expected results of butyrate disk :

Answer 4

Positive: Development of a blue color during the 5-minute incubation period

Negative: No color change

Question 5

Limitation of butyrate disk :

Answer 5

Incubation longer than 5 minutes may result in a false positive reaction.
False-negative reactions may occur if the inoculum is too small. If the organism is negative, repeat with a larger inoculum and follow-up with additional methods

Question 6

Quality control of butyrate disk :

Answer 6

Positive: Moraxella catarrhalis (ATCC25240)- formation of blue color

Negative: Neisseria gonorrhoeae (ATCC43069) no color change