Phosphate Buffered Saline (for Listeria)

Intended use

Phosphate Buffered Saline is used for preparation of dilutions for Listeria species for further testing from food samples. The composition and performance criteria of this medium are as per specifications laid down in ISO 11290-1:2017 and ISO 11290-2:2017

Composition**

ISO 11290-1:2017 and ISO 11290-2:2017 Specification- Phosphate Buffered Saline (For Listeria)

M2097I- Phosphate Buffered Saline (For Listeria)

Final pH (at 25°C): 7.2±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 18.37 grams ((the equivalent weight of dehydrated medium per litre)) in 1000 ml purified / distilled water. Dispense into tubes or flasks as desired. Heat if necessary to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C)) for 15 minutes.

Principle And Interpretation

Phosphate Buffered Saline is used for preparing dilutions, blanks for the examination of food. This solution gives a pH of 7.2 and also provides sodium and phosphate ions. The composition is as per ISO (3,4).

Type of specimen

Food and animal feeds, environmental samples in the area of food production and food handling.

Specimen Collection and Handling

For samples, follow appropriate techniques for sample collection and processing as per guidelines (3,4). After use, contaminated materials must be sterilized by autoclaving before discarding.

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.

Performance and Evaluation

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

Quality Control

Appearance White to cream homogeneous free flowing powder

Colour and Clarity of prepared medium Colourless clear solution without any precipitate

Reaction Reaction of 1.84% w/v aqueous solution at 25°C. pH : 7.2±0.2

pH 7.00-7.40

Cultural response

Recovery of ±30% of the original count (recovered on Tryptone Soya Agar , M290), when the inoculated sample holding time is 45 minutes to 1 hour at 20-25°C. The plates are incubated at 37 ± 2°C for 18 ± 2 hours.

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. Use before expiry date on the label. 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 (1,2).

Reference

1. Microbiology of Food chain-Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp. Detection method . ISO 11290-1:2017
2. Microbiology of Food chain-Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp. Enumeration method ISO 11290-2:2017
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.