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Mannitol Salt Agar is selective for staphylococci as the high salt (sodium chloride) levels prohibit most other bacteria from surviving and it is differential as Staphylococci ferment mannitol, producing acid, lowering the pH and turning the media yellow. The development of yellow media presumes the bacteria to be pathogenic Staphylococcus (usually S. aureus). From A Photographic Atlas for the Microbiology Laboratory by Leboffe and Pierce.
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What culture media is specific for Staphylococcus aureus?
Mannitol Salt Agar (MSA) is a selective and differential medium that is specific for Staphylococcus aureus. Staphylococcus aureus can ferment mannitol, leading to acid production that changes the pH indicator in the medium, causing yellow colonies to form. Additionally, the high salt concentration in MSA inhibits the growth of other bacteria, allowing for selective isolation of Staphylococcus aureus.
Do Gram negative organisms grow on MSA plates?
No, Gram-negative organisms do not grow on Mannitol Salt Agar (MSA) plates because MSA contains high salt concentration and phenol red, which create a selective and differential medium that inhibits the growth of most Gram-negative bacteria while allowing for the growth of certain Gram-positive bacteria.
Can enterobacter aerogenes grow on mannitol salt agar?
Enterobacter aerogenes is not typically a salt-tolerant organism and would not be expected to grow well on Mannitol Salt Agar, which contains a high concentration of salt. This medium is more selective for salt-tolerant organisms like Staphylococcus species.
What does msa plates test for?
MSA plates test for the presence of Staphylococcus aureus bacteria. These plates are selective media used to isolate and differentiate this specific pathogenic bacterium from other microorganisms present in a sample.
Can proteus vulgaris grow on msa?
Proteus vulgaris typically does not grow well on Mannitol Salt Agar (MSA) because it is a non-fermenter of mannitol and cannot utilize this substrate. MSA is selective for salt-tolerant organisms like Staphylococcus species, which can ferment mannitol, resulting in a pH decrease and color change. Proteus vulgaris is more commonly found on media like MacConkey agar.
Does s. epidermidis grow on msa?
Streptococcus cannot grow on MSA plates because MSA is a selective and differential media. It is selective because only certain microorganisms can grow on it due to its high NaCl content, in which this concentration - near 10% in MSA - has an inhibitory effect on most bacteria, such as Streptococci.
Does E. faecalis test positive for MSA agar test?
E. faecalis typically does not ferment mannitol, so it does not grow well on mannitol salt agar (MSA) and would not test positive on this medium. MSA is selective for organisms that can ferment mannitol, such as Staphylococcus species.
What culture media is specific for Staphylococcus aureus?
Mannitol Salt Agar (MSA) is a selective and differential medium that is specific for Staphylococcus aureus. Staphylococcus aureus can ferment mannitol, leading to acid production that changes the pH indicator in the medium, causing yellow colonies to form. Additionally, the high salt concentration in MSA inhibits the growth of other bacteria, allowing for selective isolation of Staphylococcus aureus.
What is MSA agar?
Mannitol salt agar or MSA is a commonly used growth medium in microbiology. It contains a high concentration (~7.5%-10%) of salt (NaCl), making it selective for Staphylococci (and Micrococcaceae) since this level of NaCl is inhibitory to most other bacteria.
Can B subtilis grow on MSA?
No, Bacillus subtilis cannot grow on Mannitol Salt Agar (MSA) as it cannot ferment mannitol and does not tolerate the high salt concentration in MSA. MSA is selective for Staphylococcus species that can ferment mannitol.
Do Gram negative organisms grow on MSA plates?
No, Gram-negative organisms do not grow on Mannitol Salt Agar (MSA) plates because MSA contains high salt concentration and phenol red, which create a selective and differential medium that inhibits the growth of most Gram-negative bacteria while allowing for the growth of certain Gram-positive bacteria.
Is msa a defined or undefined medium?
MSA, or Mannitol Salt Agar, is considered a defined medium because it contains specific, known quantities of its ingredients, such as mannitol, sodium chloride, and phenol red. These components provide a selective environment for the growth of certain bacteria, particularly staphylococci, while inhibiting others. The precise formulation allows for reproducibility in experiments and clear interpretation of results.
Which Media for the isolation and identification of staph aureus?
For the isolation and identification of Staphylococcus aureus, Mannitol Salt Agar (MSA) is commonly used. MSA is selective due to its high salt concentration, which inhibits most other bacteria, while S. aureus can tolerate it and ferments mannitol, leading to a color change in the medium. Additionally, Baird-Parker Agar is another selective medium that helps in the identification of S. aureus, as it contains egg yolk and tellurite, allowing for the visualization of characteristic colonies.
When a substance is added to solid medium which inhibits growth of unwanted bacteria but permits the growth of wanted bacteria the medium is known as?
selective medium
Can enterobacter aerogenes grow on mannitol salt agar?
Enterobacter aerogenes is not typically a salt-tolerant organism and would not be expected to grow well on Mannitol Salt Agar, which contains a high concentration of salt. This medium is more selective for salt-tolerant organisms like Staphylococcus species.
What is the role of sodium chloride in MSA and how does it work?
In Mannitol Salt Agar (MSA), sodium chloride serves as a selective agent that inhibits the growth of most bacteria except for staphylococci, which are tolerant to high salt concentrations. The high salt concentration creates an osmotic environment that most other bacteria cannot survive. Additionally, MSA contains mannitol as a fermentable carbohydrate, allowing for the differentiation of staphylococci based on their ability to ferment mannitol, which produces acid and changes the pH indicator in the medium, resulting in a color change.
What does msa plates test for?
MSA plates test for the presence of Staphylococcus aureus bacteria. These plates are selective media used to isolate and differentiate this specific pathogenic bacterium from other microorganisms present in a sample.
