Mannitol Salt Agar (MSA) is used to determine if the bacteria is halophilic (salt loving) and if the bacteria can ferment mannitol. If the bacteria is able to grow then it is a halophilic bacteria, due to it’s ability to grow in a high salt environment.

What does a positive mannitol test mean?

A positive test consists of a color change from red to yellow, indicating a pH change to acidic.

Which bacteria is known to give a positive MSA?

For this reason, we say that Mannitol salt agar (MSA) is selective for the Gram-positive bacteria Staphylococcus spp. since most other bacteria are unable to grow.