DN’ase agar provides a convenient means of identify
ing potentially pathogenic staphylococci, based on
the ability of coagulase-positive
species to split DNA. DN’ases produced by the organ
isms hydrolyse the DNA molecule to a mixture of sma
ller mono and poly nucleotides.
DiSalvo observed perfect correlation between coagul
ase activity and DN’ase production using
strains from clinical specimens.
Other publications have also reported a close corre
Method for reconstitution
Weigh 39 grams of powder, disperse in 1 litre of de
ionised water. Allow to soak for 10 minutes, swirl
to mix then sterilise by autoclaving at
121°C for 15 minutes. Allow to cool to 47°C then po
ur into Petri dishes.
Pale cream, clear.
7.3 ± 0.2
Minimum Q.C. organisms:
Storage of Prepared Medium:
Plates – up to 7 days: at 2-8°C in the dark. Capped
container – up to 1 month at 4°C in the dark.
Use a heavy inoculum on a small area. Four or more
organisms can be tested on one 90mm Petri dish.
37°C aerobically for 18-24 hours.
Having obtained good growth, flood the plate with 1
N hydrochloric acid. This will precipitate the DNA
in the medium. DN’ase
producing organisms will be surrounded by a clear a
rea where the DNA has been broken down into fractio
ns which are not precipitated
by the Hydrochloric acid. Gram positive, catalase p
ositive cocci that produce DN’ase can be provisiona
lly classified as
confirmed by tube coagluase or thermostable DN’ase
tests. DN.’ase is also produced by some Gram negati
ve bacilli such as
Some corynebacteria and streptococci may also produ
Baird-Parker, A. C. 1965. The classification of sta
phylococci and micrococci from world-wide sources.
J. Gen. Microbiol. 38, 363-387.
Black, W. A., Hodgson, R. and McKechnie, A. 1971.
DiSalvo, J. W. 1958 Deoxyribunuclease and coagulase
activity of micrococci. Med. Tech. Bull. U.S. Arme
d Forces Med. J. 9, 191.
Martin, W. J and Ewing, W. H. 1967. The deoxryibonu
clease test as applied to certain gram-negative bac
teria. Can. J. Microbiol. 13, 616-
Messinova, O. V., Yusupova, D. V. and Shamsutdinov,
N. S. 1963. Deoxyribonuclease activity of Coryneba
cterium and its relation to
virulence. Fed. Proc. 22, T1033.
Streitfeld, M. M., Hoffmann, E. M. and Janklow, H.
M. 1962. Evaluation of extracellular deoxyribonucle
ase activity in Pseudomonas.
J. Bacteriol. 84, 77. Wannamaker, L. W. 1964. Strep
tococcal deoxryribonuclease, pp. 140-165. J. W. Uhr
(ed.). The Streptococcus,
Rheumatic Fever, Glomerulophritis. Baltimore: Willi
ams & Williams.
Weckman, B. G. and Catlin, B. W. 1957 Deoxryribonuc
lease activity of micrococci from clinical sources.
J. Bacteriol. 73, 747-753.
Zierdt, C. H. and Golde, D. W. 1970. Deoxryribonucl
ease-positive Staphylococcus epidermidis strains. A
ppl. Microbiol. 20(1), 54-57.