Mannitol motility medium

Mannitol motility medium is a bacterial growth medium used to detect the ability of bacteria to ferment mannite and produce nitrogen gas; and to indicate the motility of the organism.

Composition

The typical medium is composed of:

Agar – 3.0 g/L
Peptone – 20.0 g/L
Mannitol – 2.0 g/L
Potassium nitrate – 1.0 g/L
1% Phenol red solution 4 ml/L
pH: 7.6

Indications

When inoculated with a sample organism and allowed to incubate, the medium will change color from red to yellow to indicate that the mannite has been fermented. The presence of bubbles in the medium indicates the presence of gaseous nitrogen, produced by the organism. The pattern of color change indicates the motility of the organism.

Quality control

The following known results can be used to validate the proper composition of the medium:Escherichia coli – ferments mannite, motileKlebsiella sp. – ferments mannite, non-motilePseudomonas aeruginosa – does not ferment mannite, motile