How Does The NaCl IN MSA Kill Organisms?

What did you use to establish what constitutes good growth?

What did you use to establish what constituted “good growth?” The nutrient agar plate inoculated with the same organisms provided examples of what “good growth” for each organism looks like on a nonselective media..

Would removal of sodium chloride from MSA?

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

What ingredient makes MSA differential?

sugar mannitolThe 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.

How is S aureus differentiated from other staphylococci on MSA?

Staphylococcus aureus produce yellow colonies with yellow zones, whereas other Staphylococci produce small pink or red colonies with no colour change to the medium.

What would be the likely consequences of omitting the NaCl?

What would be the likely consequences of omitting the NaCl in Mannitol Salt Agar? Why? Non-staphylococcus bacteria would be able to grow on the media. This may lead to false positives for Non-staphylococcus that can ferment mannitol.

What can grow on a blood agar plate?

Blood Agar is used to grow a wide range of pathogens particularly those that are more difficult to grow such as Haemophilus influenzae, Streptococcus pneumoniae and Neisseria species. It is also required to detect and differentiate haemolytic bacteria, especially Streptococcus species.

What ingredient makes EMB selective?

Eosin methylene blue (EMB, also known as “Levine’s formulation”) is a selective stain for Gram-negative bacteria. EMB contains dyes that are toxic to Gram-positive bacteria. EMB is the selective and differential medium for coliforms. It is a blend of two stains, eosin and methylene blue in the ratio of 6:1.

What is the role of sodium chloride in MSA?

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

What is the function of the 7.5% NaCl in mannitol salt agar?

Mannitol salt agar is selective in allowing bacteria capable of growth in 7.5% NaCl while preventing the growth of salt sensitive microbes. Additionally, mannitol salt agar contains the sugar mannitol.

What organisms are inhibited from growing on MSA?

It contains a high concentration (about 7.5–10%) of salt (NaCl), making it selective for most Gram-negative and some Gram-positive bacteria (Staphylococcus, Enterococcus and Micrococcaceae) since this level of salt is inhibitory to most other bacteria.

Can 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.

Why is MSA selective and differential?

MSA is a Selective Medium because of its high (7.5%) sodium chloride concentration that inhibits the growth of most organisms. MSA is a Differential Medium because of the presence of the sugar mannitol and the pH indicator Phenol Red.

Does Streptococcus grow on MSA?

MSA contains a high concentration of salt (NaCl), and therefore, selects for the growth of microbes that can tolerate high salt concentrations. Staphylococcus species are halotolerant, whereas Streptococcus species and many other organisms are inhibited by high concentrations of NaCl.

Does Micrococcus luteus grow on MSA?

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. … They can ferment mannitol and produce lactic acid, producing yellow colored colonies on MSA.

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 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 Bacteria grows on MSA?

Welcome to Microbugz – Mannitol Salt Agar. 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 MSA 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.