Plot No. C40, Road No. 21Y, MIDC, Wagle Industrial Estate,
Thane(W)-400604, MH, India.
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Intended use
Dey Engley Neutralizing Agar is used in disinfectant testing where neutralization of the chemical is important for determining its bactericidal activity.
Composition
| Ingredients | g/L |
|---|---|
| Tryptone | 5.000 |
| Yeast extract | 2.500 |
| Dextrose (Glucose) | 10.000 |
| Sodium thiosulphate | 6.000 |
| Sodium thioglycollate | 1.000 |
| Sodium bisulphite | 2.500 |
| Lecithin | 7.000 |
| Polysorbate 80 (Tween 80) | 5.000 |
| Bromocresol purple | 0.020 |
| Agar | 15.000 |
| Final pH (at 25°C) | 7.6±0.2 |
**Formula adjusted, standardized to suit performance parameters
Directions
Dey Engley Neutralizing Agar is a ready to use solid media in glass bottle. The medium is pre-sterilized, hence it does not need sterilization. Medium in the bottle can be melted either by using a pre-heated water bath or any other method. Slightly loosen the cap before melting. When complete melting of medium is observed dispense the medium in tubes as butts /slants or in plates as desired and allow to solidify. If on plate, either streak, inoculate or surface spread the test inoculum (50-100 CFU) aseptically.
Principle And Interpretation
Dey-Engley Neutralizing Agar is formulated as per the procedure described by Engley and Dey (1). A strongly bacteriostatic substance inhibits the growth and reproduction of bacteria without killing them. These bacteria hold the ability to cause infection under favorable conditions. Dey-Engley Neutralizing Agar neutralizes a broad spectrum of antiseptics and disinfectants including quaternary ammonium compounds, phenolic, iodine and chlorine preparations, mercurial, formaldehyde and glutaraldehyde (1).
Tryptone provide nitrogen and carbon source, long chain amino acids, vitamins and other essential nutrients. Dextrose is an energy source. Yeast extract is also a rich source of vitamin B-complex. The present formulation incorporate neutralizing substances for almost all the active products used as antiseptics and disinfectants. Sodium bisulfite neutralizes aldehydes; sodium thioglycollate neutralizes mercurial; sodium thiosulfate neutralizes iodine and chlorine (1); lecithin neutralizes quaternary ammonium compounds; and polysorbate 80, a non-ionic surface-active agent, neutralizes substituted phenolic (2-5). Bromocresol purple is an indicator for dextrose utilization. Due to the high concentration of lecithin in the broth medium, turbidity cannot be used to detect growth. Therefore, bromocresol purple and dextrose are added to the medium. Those organisms that ferment dextrose will turn the medium from purple to yellow (1). For Agar Medium: Dey -Engley Neutralizing Agar medium can be over-filled, producing a meniscus or dome-shaped surface that can be pressed onto a surface for sampling its microbial burden. Incubate the plates, by covering the lids, at an appropriate temperature. The presence of microorganism is determined by the appearance of colonies on the surface of agar medium. Neutralization Test: Growth in Neutralizing Broth and no growth in Neutralizing Broth Base indicate neutralization of disinfectant. To check bactericidal activity, both broth tubes are inoculated on D/E Neutralizing Agar. Positive growth from negative tubes of Neutralizing Broth Base indicates bacteriostatic substance while negative growth indicates a bactericidal disinfectant. All positive tubes should show growth on Dey-Engley Neutralizing Agar.
The control disinfectants used in test procedure are 2% chlorine, 2% formaldehyde, 1% glutaraldehyde, 2% iodine, 2% phenol, 1/750 quaternary ammonium compounds, 1/1000 mercurial etc.
Type of specimen
Environmental samples, Cosmetic products, Pharmaceutical samples
Specimen Collection and Handling
Collection of samples from areas before and after the treatment with disinfectant evaluates cleaning procedures in Sanitation (5,6,7). 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.
Limitations :
- Individual strain of a microorganism may have unique growth requirements with respect to nutrients and physical conditions. Based on which the growth pattern of each varies on a medium and some even may display significant delay.
- Each lot of the medium has been tested for the organisms specified on the COA. It is recommended to users to validate the medium for any specific microorganism other than mentioned in the COA based on the user's unique requirement.
- Further serological and biochemical testing is required for complete identification.
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
Sterile Dey Engley Neutralizing Agar in glass bottle.
Colour medium
Purple to reddish purple coloured
Quantity of medium
100ml of medium in glass bottle.
pH
7.40-7.80
Sterility check
Passes release criteria
Cultural Response
Cultural characteristics observed after an incubation at 35 - 37°C for 40 - 48 hours.
| Organism | Inoculum (CFU) | Growth | Recovery |
|---|---|---|---|
| Escherichia coli ATCC 25922 (00013*) | 50-100 | luxuriant | >=70% |
| Pseudomonas aeruginosa ATCC 27853 (00025*) | 50-100 | luxuriant | >=70% |
| Salmonella Typhimurium ATCC 14028 (00031*) | 50-100 | luxuriant | >=70% |
| Staphylococcus aureus subsp. aureus ATCC 25923 (00034*) | 50-100 | luxuriant | >=70% |
| **Bacillus spizizenii (00003*) ATCC 6633 | 50-100 | luxuriant | >=70% |
| Candida albicans ATCC 10231 (00054*) | 50-100 | luxuriant | >=70% |
| #Aspergillus brasiliensis ATCC 16404 (00053*) | 50-100 | luxuriant | >=50% |
Key: (*) - Corresponding WDCM numbers,
(**) Formerly known as Bacillus subtilis subsp. spizizenii, (#) Formerly known as Aspergillus niger
Storage and Shelf Life
On receipt store between 15-30°C. 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 (8,9).
| Product Name | Dey Engley Neutralizing Agar |
|---|---|
| SKU | SM186C |
| Customized Product Available | No |
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