Mannitol Motility Test: Medium And Result

Mannitol motility test medium is a bacterial growth medium used to detect the ability of bacteria to ferment mannite and produce nitrogen gas and indicate the organism’s motility. The mannitol motility test medium is designed to differentiate bacteria based on their motility and ability to
ferment mannitol.

Mannitol Motility Test Composition

IngredientsGms / Liter
Peptic digest of animal tissue20.00
Mannitol2.00
Potassium nitrate1.00
Phenol red0.04
Agar3.00
Mannitol Motility Test Medium Composition

Mannitol Motility Test Principle

The Mannitol Motility Test Medium is designed to differentiate bacteria based on their motility and ability to ferment mannitol. The highly nutritious peptic digest of animal tissue supports the luxuriant growth of fastidious bacteria like Staphylococci. The semi-solid nature of the medium due to 0.3% agar helps to detect motility. Motile bacteria produce diffused growth throughout the medium while non-motile bacteria grow only along the inoculation line. Fermentation of mannitol produces acidity in the medium. which detects acidity by exhibiting a visible color change from red to yellow.

Mannitol Motility Test Procedure

  • Suspend 26.04 grams of the medium in one liter of distilled water.
  • Heat to boiling to dissolve the medium completely.
  • Dispense into test tubes.
  • Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
  • Cool the tubed medium in an upright position.

Mannitol Motility Test Result

Mannitol fermentation is indicated by a change in the color of the medium from red to yellow, while no color change is observed with non-fermenters. Motile bacteria show a diffuse growth away from the stabline causing turbidity, while non-motile organisms only grow along the stab line.

S/R. No.OrganismsInoculum
(CFU)
GrowthMannitol fermentationMotility
1.Escherichia Coli50 -100Good-LuxuriantPositive Reaction,
Yellow Colour
Positive, Growth Away from
Stabline Causing Turbidity
2.Proteus Mirabilis50 -100Good-LuxuriantNegative Reaction,
No Colour Change
Or Red
Positive, Growth Away from
Stabline Causing Turbidity
3.Proteus Vulgaris50 -100Good-LuxuriantNegative Reaction,
No Colour Change
Or Red
Positive, Growth Away from
Stabline Causing Turbidity
4.Salmonella Typhi50 -100Good-LuxuriantPositive Reaction,
Yellow Colour
Positive, Growth Away from
Stabline Causing Turbidity
5.Shigella Sonnei50 -100Good-LuxuriantPositive Reaction,
Yellow Colour
Negative, Growth along the Stabline,
Surrounding Medium remains
Clear
6.Staphylococcus Aureus50 -100Good-LuxuriantShigella sonneiNegative, Growth along the Stabline,
Surrounding Medium remains
Clear
7.Staphylococcus Epidermidis50 -100Good-LuxuriantNegative Reaction,
No Colour Change
Or Red
Negative, Growth along the Stabline,
Surrounding Medium remains
Clear
The organisms listed are the minimum that should be used for quality control testing.

Mannitol Motility Test Quality Control

1. Control of general characteristics, labels, and print.

MicroorganismsGrowthMotility
Escherichia coliGood+
Enterobacter aerogenesGood+
Klebsiella pneumoniaeGood
Salmonella typhimuriumGood+

Mannitol Motility Test Sample Collection

Ensure that all samples are properly labeled. Follow appropriate techniques for handling samples as per established guidelines. Some samples may require special handling, such as immediate refrigeration protection from light, following the standard procedure. The samples must be stored and tested within the permissible time duration. After use, contaminated materials must be sterilized by autoclaving before discarding.

Mannitol Motility Test Storage

Store the dehydrated medium below 30°C in a tightly closed container and the prepared medium at 2°C-8°C. Avoid freezing and overheating. Use before the expiry date on the label. Once opened keep the powdered medium closed to avoid hydration.

Mannitol Expiration

Refer to the expiration date stamped on the container. The dehydrated medium should be discarded if not free-flowing, or if the appearance has changed from the original color. Expiry applies to the medium in its intact container when stored as directed.

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