Quick Answer: What Is The Role Of Mannitol And Phenol Red In MSA?

What does a red color symbolize in a MSA plate?

Bacteria growing on mannitol salt agar are positive for mannitol fermentation if the culture medium under their colonies is changed from its normal red color to yellow, indicating acidic growth products.

Bacteria unable to use mannitol usually change the medium to a magenta color in the vicinity of growth..

What Bacteria grows on MSA?

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.

Does E coli grow on MSA?

(A) Staphylococcus aureus, (B) Staphylococcus epidermidis, and (C) Escherichia coli streaked on a mannitol salt agar plate. … The growth of E. coli was inhibited by the high salt concentration.

What is the application of MSA?

Mannitol Salt Agar (MSA) is used as a selective and differential medium for the isolation and identification of Staphylococcus aureus from clinical and non-clinical specimens. It encourages the growth of a group of certain bacteria while inhibiting the growth of others.

What does an MSA plate test for?

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.

Can gram negative bacteria grow on MSA?

The MSA agar will retain its initial red color and will not change to yellow. Gram-negative bacteria like E. coli and P. aeriginosa are not tolerant to salt (not halophilic) and will not grow colonies on MSA (see quadrants II and IV).

What is the role of phenol red in MSA?

If an organism can ferment mannitol, an acidic byproduct is formed that causes the phenol red in the agar to turn yellow. It is used for the selective isolation of presumptive pathogenic (pp) Staphylococcus species.

What ingredient makes MSA selective?

Mannitol salt agar is selective due to the presence of 7.5% sodium chloride (NaCl).

Would removal of sodium chloride from MSA?

Answer and Explanation: Yes, the removal of sodium chloride from MSA will alter the medium’s sensitivity or specificity to a great extent.

How does the NaCl IN MSA kill organisms?

Provides the substrate for fermentation and makes the medium differential. What does the NaCl contained in MSA do? Makes the medium selective because its concentration is high enough to dehydrate and kill most bacteria. … Indicates whether fermentation has taken place by changing color as the pH changes.

What will turn MSA yellow?

The differential ingredient in MSA is the sugar mannitol. Organisms capable of using mannitol as a food source will produce acidic byproducts of fermentation that will lower the pH of the media. The acidity of the media will cause the pH indicator, phenol red, to turn yellow.

What is the role of sodium chloride in MSA and how does it work?

Answer and Explanation: Sodium chloride is used in MSA to provide the essential fermentation substrate. It limits the growth of most organisms apart from bacteria in mixed…