Question: Would Mannitol Salt Agar Still Be Selective For Species Of Staphylococcus If It Did Not Have Salt In It Why Or Why Not?

Does Staphylococcus epidermidis grow on blood agar?


epidermidis is a very hardy microorganism, consisting of nonmotile, Gram-positive cocci, arranged in grape-like clusters.

It forms white, raised, cohesive colonies about 1–2 mm in diameter after overnight incubation, and is not hemolytic on blood agar..

Can gram negative bacteria grow on mannitol salt agar?

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.

What is the purpose of adding salt to mannitol salt agar?

What is the purpose of adding salt to mannitol salt agar? High concentrations of salt inhibit the growth of non-halophilic organisms but allow for the growth of bacteria from the genus Staphylococci.

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.

Would this medium still work if it did not have salt in it?

Would this medium still work if it did not have salt in it? Why or why not? No the high concentration of sodium makes the medium selective by inhibiting the growth of most bacteria and allowing staphylococcus aureus to grow.

What bacteria can grow on mannitol salt agar?

Most pathogenic staphylococci, such as Staphylococcus aureus, will 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.

Is mannitol salt agar selective is it differential explain?

Mannitol Salt Agar (MSA) This is a medium that is both selective and differential. The high salt concentration (7.5%) is the selective ingredient. Staphylococcus species, which commonly inhabit human skin, can grow on this high salt concentration (left plate in picture below).

How would Staphylococcus epidermidis appear on mannitol salt agar?

Mannitol fermentors such as S. aureus appear as yellow colonies with yellow zones in the media. Non-mannitol fermentors such as S. epidermidis, if present, will have clear pink to red colonies with no yellow color change in the medium.

Why doesn’t e coli grow on mannitol salt agar?

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). … Staphylococcus aureus is also able to ferment mannitol, because this bacterial species has the enzyme coagulase required for the process.