HiMedia Laboratories GmbH, Marie-Curie-Str. 3, 64683, Einhausen, Germany.
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Intended use
Recommended for detection of deoxyribonuclease activity of microorganisms.
Composition**
| Ingredients | Gms / Litre |
|---|---|
| Tryptose | 20.000 |
| Deoxyribonucleic acid (DNA) | 2.000 |
| Sodium chloride | 5.000 |
| Toluidine blue | 0.100 |
| Agar | 15.000 |
| Final pH (at 25°C) | 7.3±0.2 |
**Formula adjusted, standardized to suit performance parameters
Directions
Either streak, inoculate or surface spread the test inoculum (50-100 CFU) aseptically on the plate.
Principle And Interpretation
DNase Test Agar w/ toluidine blue is used for detecting deoxyribonuclease activity of bacteria and fungi and particularly for identification of pathogenic Staphylococci. With added toluidine blue, it is used in differentiation and identification of non-pigmented Serratia species isolated from clinical sources that might be improperly identified as Enterobacter and Klebsiella species. DNase activity was observed by Weckman and Catlin (8) in Micrococci and found the correlation with coagulase activity as coagulase positive species were DNase positive. Di Salvo (2) confirmed the results of Weckman and Catlin and observed accurate correlation of DNase and coagulase activity. In his experiment Di Salvo incorporated DNA and calcium chloride to activate DNase enzyme. Schreier modified DNase medium by adding toluidine blue (6). Modified medium achieved faster identification of Serratia marcescens and could differentiate Serratia from other members of the Enterobacteriaceae
Tryptose provide essential nutrients. DNase depolymerizes the DNA resulting in the formation of a clear zone around the microbial growth which is visualized by flooding the plate with hydrochloric acid (7).
When toluidine blue is added to the medium itself, DNase activity results in the production of a bright pink reaction due to the metachromatic property of toluidine blue. Some strains of Staphylococci may be inhibited on DNase Test Agar due to toluidine blue.
Type of specimen
Food and dairy samples.
Specimen Collection and Handling:
For food and dairy samples, follow appropriate techniques for sample collection and processing as per guidelines (1,5,9).
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 organisms differ in their growth requirement and may show variable growth patterns on the medium
- 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 confirmatory tests for the identification should be carried out.
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 DNase Test Agar Plate w/ Toluidine Blue in 90mm disposable plates.
Colour of medium
Blue coloured
Quantity of medium
25ml of medium in disposable plate
Reaction
7.10-7.50
Sterility Test
Passes release criteria
Cultural Response
Cultural characteristics observed after an incubation at 35 - 37°C for 18 - 24 hours.
| Organism | Inoculum (CFU) | Growth | D-Nase Activity |
|---|---|---|---|
| Serratia marcescens ATCC 8100 | 50-100 | luxuriant | positive reaction, pink to red zone around the growth |
| Staphylococcus aureus subsp.aureus ATCC 25923 (00034*) | 50-100 | luxuriant | positive reaction, pink to red zone around the growth |
| Staphylococcus epidermidis ATCC 12228 (00036*) | 50-100 | luxuriant | negative reaction |
| Streptococcus pyogenes ATCC 19615 | 50-100 | luxuriant | positive reaction, pink to red zone around the growth |
Key: *Corresponding WDCM numbers.
Storage and Shelf Life
On receipt store between 2-8°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 (3,4).
| Product Name | DNase Test Agar Plate w/ Toluidine Blue |
|---|---|
| SKU | MP1041 |
| Customized Product Available | No |
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