What type of bacteria can grow on MSA?
Emma Johnson
Updated on March 01, 2026
Result Interpretation on Mannitol Salt Agar
| Organisms | Results |
|---|---|
| Staphylococcus aureus | Yellow colonies with yellow zones. |
| Staphylococci other than S. aureus (e.g. Staphylococcus epidermidis ) | Colorless or Red colonies with red zones. |
| Streptococci | No growth to trace growth. |
| Micrococci | Large white to orange. |
Does S aureus grow on MSA?
Mannitol Salt Agar is differential due to the presence of mannitol and the pH indicator Phenol Red. aureus grow on Mannitol Salt Agar. About 8 % to 12 % of Staph. aureus strains will not ferment mannitol.
What bacteria Cannot grow on MSA?
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). Pathogenic gram-positive Staphylococcus aureus salt-tolerant (halophilic) and will produce colonies on MSA.
What is the role of NaCl in MSA?
The sodium chloride in MSA ensures that only Staphylococci species survive due to the high salt concentration. This eliminates all other gram-positive microbes. Further, we can confidently identify Staphylococcus aureus in MSA because it is the only type of Staphylococci species that can ferment mannitol in MSA.
Does e Aerogenes grow on MSA?
This test showed the bacterium did not contain the enzyme urease. Four more tests, Casein, Starch, Simmons Citrate and a Nitrate test, were all performed to confirm the bacterium was Enterobacter aerogenes. This resulted in the growth of bacteria and the MSA test was concluded to be positive for mannitol fermenters.
Why does S aureus look different than S epidermidis on MSA?
On MSA, only pathogenic Staphylococcus aureus produces small colonies surrounded by yellow zones. The reason for this color change is that S. aureus have the ability to ferment the mannitol, producing an acid, which changes the indicator color from red to yellow.
Can Enterobacter aerogenes grow on MSA?
What is the role of sodium chloride in the MSA plate and how does it work?
Sodium chloride is used in MSA to provide the essential fermentation substrate. It limits the growth of most organisms apart from bacteria in mixed…
Does Micrococcus luteus grow on salt agar?
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. M. roseus (red) produces pink colonies on MSA.
What are Micrococcus luteus cells under the microscope?
Under the microscope they are round cells. When looking at the genetic tests, most of the identified strains in the Korona test are Micrococcus luteus. The identified reads only made up a total of twenty seven percent of the total reads, but the majority of those reads were for M. luteus.
Is Micrococcus luteus an obligate or obligate aerobe?
Wikipedia also says that Micrococcus luteus is an obligate aerobe, backing up what my results show (2019). The oxidase test results suggest that the microbe does not contain oxidase, despite what the metagenome binning test showed.
Is Micrococcus luteus motile or nonmotile?
Fact Sheet: Micrococcus luteus 1 Description: Micrococcus luteus (M. luteus) is a Gram-positive to Gram-variable, non-motile, coccus, saprotrophic bacterium. 2 Interesting Facts: M. luteus is found in soil, dust, water, and in human skin flora. 3 Infection: M. 4 In the Lab / at Wickham Laboratories Ltd.
