DNase Test Agar Base w/ methyl green

M1419
DNase Test Agar Base w/ methyl green
DNase Test Agar is recommended for the detection of deoxyribonuclease activity of bacteria and fungi, and especially for
identification of pathogenic Staphylococci.
Composition**
Ingredients
Gms / Litre
Tryptose
Deoxyribonucleic acid (DNA)
Sodium chloride
Methyl green
Agar
Final pH ( at 25°C)
**Formula adjusted, standardized to suit performance parameters
20.000
2.000
5.000
0.050
15.000
7.3±0.2
Directions
Suspend 42.05 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving
at 15 lbs pressure (121°C) for 15 minutes. Mix well and pour into sterile Petri plates.
Principle And Interpretation
DNase test Agar is used for detecting deoxyribonuclease activity of bacteria and fungi and particularly for identification
of pathogenic Staphylococci (1). DNase producing organisms exhibit clear zone around growth against green background.
Reagent addition is not required (2). This medium is based on modification of the procedure for detecting DNase-producing
bacteria as per Smith, Hanoch, and Rhoden (4) and Jefferies, Holtman and Guse (3). The medium supports growth of both
gram positive and gram-negative bacteria.
Tryptose serves as nitrogenous source for the organisms. DNase produced by microorganisms depolymerizes the DNA substrate
in the medium. Methyl green fades into a colourless compound producing distinct clear zones surrounding colonies (or band/
spot inocula) in an otherwise green coloured medium. Methyl green requires a highly polymerized DNA substrate (5) and it
combines with polymerized DNA forming a stable, green complex at pH 7.5 (6,7,8). As hydrolysis progresses, methyl green
is released and when not combined at this pH it fades and becomes a colourless compound. Therefore clear zones are observed
(7,9).
Quality Control
Appearance
Light yellow to greeenish yellow homogeneous free flowing powder
Gelling
Firm, comparable with 1.5% Agar gel
Colour and Clarity of prepared medium
Green coloured, clear to slightly opalescent gel forms in Petri plates
Reaction
Reaction of 4.2% w/v aqueous solution at 25°C. pH : 7.3±0.2
pH
7.10-7.50
Cultural Response
M1419: Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours
Organism
Inoculum
(CFU)
Please refer disclaimer Overleaf.
Growth
DNase Activity
HiMedia Laboratories
Technical Data
Serratia marcescens ATCC 50-100
8100
luxuriant
Staphylococcus aureus
ATCC 25923
50-100
luxuriant
Staphylococcus epidermidis 50-100
ATCC 12228
Streptococcus pyogenes
50-100
ATCC 19615
luxuriant
luxuriant
positive, clear
halo around the
growth.
positive, clear
halo around the
growth.
negative
reaction
positive, clear
halo around the
growth.
Storage and Shelf Life
Store below 30°C in tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label.
Reference
1. Macfaddin, J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Volume1 Williams,
Wilkins, Baltimore.
2. Schreier 1969. Am. J. Clin. Pathol. 51:711.
3. Smith, P.B., Hancock, G. A., and Rhoden, D. L (1969) Appl. Microbiol., 18,991.
4. Jeffries C.D.; Holtman, D.F.; and Guse, D.G (1957) J. Bacteriol., 73, 590.
5. Lachica, R.V.F. and Deibel, R. H (1969). Appl. Environ, Microbiol., 32 (4), 633.
6. Kurnick, N.B (1947). Cold Spring Harbor Symp. Quant. Biol., 12, 141.
7. Kurnick, N.B (1950) Arch. Biochem., 29, 41.
8. Kurnick, N.B and Foster, M. (1950) J. Gen. Microbiol. 33. 243.
9. Kurnick, N.B and Foster, M. (1950) J. Gen. Physiol. 34, 147.
Revision : 1 / 2011
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User must ensure suitability of the product(s) in their application prior to use. Products conform solely to the information contained in
this and other related HiMedia™ publications. The information contained in this publication is based on our research and development
work and is to the best of our knowledge true and accurate. HiMedia™ Laboratories Pvt Ltd reserves the right to make changes to
specifications and information related to the products at any time. Products are not intended for human or animal or therapeutic use but
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