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Butyrate Disk Test Principle and Procedure

In this butyrate disk test principle and procedure post we have briefly explained butyrate disk test principle, objectives, requirements, Butyrate disk test procedure, uses and limitations of Butyrate disk test.

Butyrate Disk Test Principle and Procedure

Butyrate disk test shows how bromo-chloro-indolyl butyrate is hydrolyzed by enzymes, resulting in a blue colour response. This substrate is not hydrolyzed by Neisseria spp., hence it will remain colourless. Moraxella (Branhamella) catarrhalis, formerly assumed to be a non-pathogenic microbe, is now thought to be a probable respiratory infection agent.

Because M.catarrhalis can be found in the same places as pathogenic Neisseria spp. and has certain physiological and biochemical similarities, it’s critical to have a screening test for Moraxella catarrhalis differentiation. The bulk of clinical disorders involving M.catarrhalis as an etiologic agent are caused by infections of the respiratory tract.

Otitis media, sinusitis, bronchitis, and pneumonia are examples of these illnesses. Although this bacterium can cause otitis media at any age, most studies demonstrate that infections are most common among children.

Objectives

For the presumptive diagnosis of Moraxella (Branhamella) catarrhalis, the Butyrate disk test is performed to identify the presence of butyrate esterase in bacterial colonies isolated on culture media.

Principle

Butyrate disk test is used to determine the presence of butyrate esterase in bacterial colonies isolated on culture media for the presumptive diagnosis of Moraxella (Branhamella) catarrhalis.

Requirements

1. Colonies

2. Pipets

3. Forceps

4. Microscopic slide

5. Distilled water (pH: 6.5 -7.5)

6. Butyrate disks

Procedure

1. Place the butyrate disk on a clean glass slide after removing it from the vial. To moisten the disc, add 1 drop of distilled water.

2. Using a sterilised wooden applicator stick or loop, extract a heavy, visible inoculum from a 24 to 72 hour culture and spread it over the disk.

3. Incubate for up to 5 minutes at room temperature. Incubation for longer periods of time may result in false-positive results. After 5 minutes, stop reading.

Result

Butyrate esterase test positive:  Development of a blue to violet color, Butyrate esterase test Negative: No color change

Quality Control

Moraxella catarrhalis, Moraxella catarrhalis: Positive, Neisseria gonorrhoeae, Neisseria meningitidis: Negative

Applications

1. Moraxella (Branhamella) catarrhalis identification assistance. Helps distinguish between Neisseria gonorrhoeae (negative) and Moraxella catarrhalis (positive), both Gram negative diplococci with Oxidase.

Limitations

1. Butyrate disk test is part of a larger system for identifying gram-negative diplococci that are oxidase-positive. For a definite diagnosis, additional biochemical and serological tests may be required. Consult the right sources.

2. Some Moraxella spp. bacillary strains can produce a strong or weak positive reaction. Unrelated species like staphylococci and pseudomonads can also cause a positive reaction. If insufficient inoculum is utilised, false-negative results may arise.

Further Readings

Reference