NEED help with unknown!!

[samantha0509]

I have a coccus, gram pos., oxidase pos. microbe that will not grow on Mannitol. I have five possible unknowns, Micrococcus roseus, Micrococcus leuteus, Sarcina aurantiaca, Staphylococcus aureus, ad Staphylococcus epidermidis. By the looks of the colony morphology, I suspected it to be S. aureus, but when I checked my MSA plate, no colony growth what so ever, only a light (and i mean very light) offset of color from the MSA's plate color,like a cream color. This is so perplexing and it doesn't help that there aren't very many sites containing info for S. aurantiaca, which I believe may be my unknown. If anyone knows of any available sites or tests to rule out S.aurantica it would be much appreciated!