Mannitol Salt Agar, MSA, is used for growing Staphylococcus. The high salt concentration in the medium inhibits the growth of mostother genera. This medium is also useful because the pathogen, Staph. aureus, ferments mannitol and changes agar from redto yellow, while the normal flora, Staph. epidermis, doesnot change the color of medium. Is MSA a differential medium or aselective medium or both or neither? Explain.