Mannitol Salt Broth is supplied by HiMedia. It is a sterile ready prepared media containing red coloured solution in bottles. Mannitol Salt Broth is generally used for the selective isolation of presumptive pathogenic Staphylococci. It is advisable to store this ready prepared media between 2-8C. Composition (in gm/L) is as follows:

Proteose peptone (10.00)

Beef extract (1.00)

Sodium chloride (75.00)

D-Mannitol (10.00)

Phenol red (0.025)

Mannitol Salt Broth is formulated by Chapman and is used for the selective isolation of pathogenic Staphylococci. This medium is highly recommended for the detection and enumeration of coagulase-positive Staphylococci in milk. Beef extract and proteose peptone in the medium, make it very nutritious since they provide essential growth factors and trace nutrients. Most of bacteria except Staphylococci are inhibited by 7.5% sodium chloride. Mannitol is the fermentable carbohydrate source. The differential action of the medium is attributed to D-Mannitol. Staphylococcus aureus ferments mannitol to produce yellow coloured medium. Most coagulase-negative species of Staphylococci and Micrococci do not ferment mannitol and therefore the medium remains red in colour. The colour of the medium can be attributed to the reactivity of phenol red to the pH of the medium; phenol red is red at pH 8.4 and yellow at 6.8. Presumptive Staphylococcus showing yellow coloured medium should be further tested for production of coagulase.