What does mannitol do in agar?

Mannitol salt agar or MSA is a commonly used selective and differential growth medium in microbiology. It encourages the growth of a group of certain bacteria while inhibiting the growth of others.

What is the indicator for fermentation in MSA?

phenol red indicator
Principle of Mannitol Salt Agar Mannitol is the fermentable carbohydrate, fermentation of which leads to acid production, detected by phenol red indicator, aids in the differentiation of staphylococcal species.

What is mannitol fermentation?

Mannitol is the fermentable carbohydrate source, fermentation of which leads to acid production. Staphylococcus aureus grows on this medium and ferments mannitol to produce yellow colonies. Most coagulase negative species of Staphylococci and Micrococci do not ferment mannitol and grow as small red colonies.

What type of media is mannitol salt agar?

MSA also contains the sugar mannitol and the pH indicator phenol red. If an organism can ferment mannitol, an acidic byproduct is formed that will cause the phenol red in the agar to turn yellow.

How is mannitol fermented?

If an organism can ferment mannitol, an acidic byproduct is formed that will cause the phenol red in the agar to turn yellow. Most pathogenic staphylococci, such as Staphylococcus aureus, will ferment mannitol. The Staphylococcus aureus ferments mannitol and turns the medium yellow.

Why is mannitol salt agar selective?

Mannitol Salt Agar (MSA) is a selective and differential medium. The high concentration of salt (7.5%) selects for members of the genus Staphylococcus, since they can tolerate high saline levels. Organisms from other genera may grow, but they typically grow very weakly.

What bacteria grows on mannitol salt agar?

Staphylococcus aureus and Staphylococcus epidermidis on mannitol salt agar. Mannitol salt agar is a commonly used growth medium in microbiology. It encourages the growth of a group of certain bacteria while inhibiting the growth of others.

Is mannitol agar selective?

This type of medium is both selective and differential. The MSA will select for organisms such as Staphylococcus species which can live in areas of high salt concentration (plate on the left in the picture below).

What is mannitol salt agar plate?

Mannitol Salt Agar (MSA) Plate. II. III. IV. Mannitol Salt Agar (MSA) is used to determine if the bacteria is halophilic (salt loving) and if the bacteria can ferment mannitol. If the bacteria is able to grow then it is a halophilic bacteria, due to it’s ability to grow in a high salt environment.

Does Staphylococcus aureus ferment mannitol?

Most non-pathogenic staphylococci will not ferment mannitol. The Staphylococcus aureus ferments mannitol and turns the medium yellow. The Serratia marcescens does not grow because of the high salt content.

What is the role of mannitol in the fermentation process?

Mannitol is a fermentable carbohydrate. The process of fermentation produces acid which is detected by a phenol red indicator. The acid helps in the fermentation of Staphylococcal species. (1, 6, and 10) Why Mannitol is used in mannitol salt agar?

Does Micrococcus produce pink colonies on mannitol salt agar?

When grown on mannitol salt agar some species of Micrococcus ( Micrococcus is a normal flora of human skin, mucosa, and oropharynx), such as M. luteus (yellow) can produce yellow colonies. M. roseus (red) produces pink colonies on MSA.