Listeria Motility Medium

Intended Use:

Recommended for testing motility of Listeria monocytogenes. The composition and performance criteria of this media is as per the specification laid down in ISO 11290-2:2017.

Composition**

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 29.6 grams in 1000 ml purified / distilled water. Heat to boiling to dissolve the medium completely. Dispense in tubes and sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Allow the tubed medium to cool in an upright position.

Principle And Interpretation

Bacterial motility is one of the important determinants in making a final species identification. Bacteria move by means of flagella, the number and location of which vary among different species. Semisolid media in tubes are most commonly employed for detecting motility. Motility media have agar concentration of 0.4% or less. The motility test is interpreted by making a macroscopic examination of medium for a diffused zone of growth flaring out from the line of inoculation. Listeria monocytogenes requires room temperature incubation before motility develops, since in some organisms; flagellar proteins develop more rapidly at lower temperatures (room temperature) such as in L.monocytogenes and Yersinia enterocolitica. Listeria Motility Medium is formulated in accordance with ISO Committee specification (1) for the determination of motility by L. monocytogenes.

Tryptone and peptone serves as a source of nitrogen and carbon compounds, long chain amino acids and vitamins as source of growth nutrients.

Type of specimen

Isolated Microorganisms

Specimen Collection and Handling

The motility of L.monocytogenes is best demonstrated by stab inoculating two tubes of semisolid medium and incubating one at room temperature (20 - 25°C) and the other at 35°C. Motility is better observed at room temperature (2). An umbrella-like zone of growth 2 to 5 mm below the surface of the medium is characteristic of L. monocytogenes. Motility at 35°C incubation is either absent or extremely sluggish.

Warning and Precautions

Read the label before opening the container. Wear protective gloves/protective clothing/eye protection/face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

• Well isolated colonies must be used for detection of motility.

Performance and Evaluation

Performance of the medium is expected when used as per the direction on the label within the expiry period when storedat recommended temperature.

Quality Control

Appearance Cream to yellow homogeneous free flowing powder

Gelling Semisolid, comparable with 0.35% Agar gel.

Colour and Clarity of prepared medium Light yellow coloured, clear to slightly opalescent gel forms in tubes as butts

Reaction Reaction of 2.96% w/v aqueous solution at 25°C. pH: 7.3±0.2

pH 7.10-7.50

Cultural Response Cultural characteristics observed after an incubation at 22-30°C for 48± 2hours.

Key: (*) Corresponding WDCM numbers.

Storage and Shelf Life

Store between 10-30°C in a tightly closed container and the prepared medium at 15-30°C. Use before expiry date on the label. On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product. Improper storage of the product may lead to lump formation. Store in dry ventilated area protected from extremes of temperature and sources of ignition. Seal the container tightly after use. Product performance is best if used within stated expiry period.

Disposal

User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with sample must be decontaminated and disposed of in accordance with current laboratory techniques (3,4).

Reference

1. Microbiology of the food chain — Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp. - Part 2, Enumeration method ; ISO 11290-2:2017.
2. Bailey and Scotts Diagnostic Microbiology, 1986, 7th Ed., The C.V. Mosby Co., St. Louis.
3. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition.
4. Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual of Clinical Microbiology, 11th Edition. Vol. 1.