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Principle
- A Mannitol mobility test medium is used to detect the mannitol fermenters and the mobility of microorganisms. The media is composed of a peptic digest of animal tissue, mannitol, potassium nitrate, phenol red and agar.
- Peptic digestion of animal tissue promotes the luxuriant growth of highly fastidious microorganisms and provides nitrogen and other necessary growth factors. Mannitol is a carbon source.
- Potassium nitrate stimulates the motility of microorganisms. Phenol red is a pH indicator. Less concentration of agar, which makes it very soft and allows the mobile bacteria to migrate.
- The inoculum is stabbed into the center of a semisolid agar deep using a sterile inoculating needle. The mannitol fermenters produce acid and the media color changes from red to yellow.
- If the mannitol fermenting bacteria are motile the color of the media changes throughout the medium and if non-motile the color of the media changes towards the stab line and the surrounding media remains pink to red in color.
- While the non-mannitol fermenters diffuse into the media and growth extending out from the line of inoculation without changing the color of the media.
- The dynamic motile organisms grow throughout the entire medium, whereas sluggish organisms show small areas or nodules that grow out from the line of inoculation. The non-motile bacteria only grow and show growth on the stab line where they are inoculated.
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