What is MSA agar used for?
Mannitol Salt Agar is used as a selective media for the isolation of pathogenic Staphylococci. It is recommended for the detection and enumeration of coagulase-positive Staphylococci in milk, food and other specimens. It is recommended in U.S.P. for use in the performance of microbial limit tests.
What is MSA in microbiology?
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 does an MSA plate selective for quizlet?
MSA contains a high salt concentration and only organisms that can grow in a high salinity environment can grow in this media. Most selective for Staphylococci.
What is the indicator for fermentation in MSA quizlet?
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. Most pathogenic staphylococci, such as Staphylococcus aureus, will ferment mannitol.
What are the components of MSA?
MSA typically contains:
- 5.0 g/L enzymatic digest of casein.
- 5.0 g/L enzymatic digest of animal tissue.
- 1.0 g/L beef extract.
- 10.0 g/L D-mannitol.
- 75.0 g/L sodium chloride.
- 0.025 g/L phenol red.
- 15.0 g/L agar.
- pH 7.4 ± 0.2 at 25 °C.
Is MSA a defined or undefined Agar?
Is MSA a defined or undefined medium? MSA is an undefined medium because the exact composition of beef extract and peptone are unknown. The goal of this medium is to isolate desired organisms, and once the undesired organisms have been inhibited, you want the desired ones to grow well.
Is MSA a defined or undefined agar?
Is MSA agar selective or differential?
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).
Is an MSA plate selective or differential?
This type of medium is both selective and differential. This is in contrast to Streptococcus species, whose growth is selected against by this high salt agar (plate on the right in the picture below). The differential ingredient in MSA is the sugar mannitol.
Which main ingredients are present in MSA?
As its name suggests mannitol salt agar (MSA) contains 1% mannitol (sugar), 7.5% salt, and agar as a solidifying agent.
What does the change in color of the MSA medium indicate?
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. This color change indicates medium ingredients other than mannitol supported growth.
Is MSA selective or differential?
