Dr.P.B.PRAVEENKUMAR FIRST YEAR POSTGRADUATE DEPARTMENT OF MICROBIOLOGY THANJAVUR MEDICAL COLLEGE THANJAVUR

1. BIOCHEMICAL TESTS
(Oxidase test, Catalase test,
Coagulase test)
Dr. P.B. PRAVEENKUMAR
FIRST YEAR MICROBIOLOGY PG RESIDENT
GOVERNMENT THANJAVUR MEDICAL
COLLEGE

2. OXIDASE TEST
• PRINCIPLE: To determine the presence of
Cytochrome oxidase enzyme which catalyses
the oxidation of reduced cytochrome by
molecular oxygen.

3. HISTORY
• Originally developed to identify all neisseria
species but later used to separate the
Pseudomonadaceae from oxidase(-) of
Enterobacteriaceae.
• Mostly G(+) are oxidase(-)
• Mostly G(-) will give variable reactions except
ENTEROBACTERIACEAE.

4. IDENTIFICATION PURPOSE
Oxidase(+)
• Moraxella
• Neisseria and Vibrio
• Plesiomonas shigelloides
(Aeromonas)
• All brucella species(Except
two)
• All pseudomonas species
(Except one)
• Alcaligenes
• Branhamella (N. Catarrhalis)
Oxidase(-)
• Acinetobacter
• Enterobacteriaceae
• Brucella neotomae
• Brucella ovis
• Pseudomonas maltophilia
• Yersinia

5. BACTERIA RESPIRATION
• All aerobic bacteria obtain their energy by
respiratory chain(Electron transport chain)
which is responsible for production of various
substrates.
• O2 is the final hydrogen acceptor from either
it’s water or hydrogen peroxide depending
on bacterial species.

6. ELECTRON TRANSPORT CHAIN

7. OXIDASE REMOVES
HYDROGEN USE ONLY
OXYGEN!
• All oxidase(+) organisms are either aerobic or
facultative except Vibrio fetus(Campylobacter
pylori) which requires microaerophilic
conditions.

8. ACCORDING TO GORDON AND
MCLEOD....
• Positive oxidase reactions are only limited to
those organisms capable of growing in
presence of oxygen and ability to produce
catalase.
2H2O2 2H2O + O2

9. OBLIGATE ANAEROBIC
ORGANISMS
• Only survive without
oxygen
• So lack cytochrome
oxidase activity
• DEIBEL AND EVANS
showed this in
Lactobacillus.
NO OXYGEN
SURVIVING...NO
OXIDASE ACTIVITY

10. STILL WE ARE BELIEVING OXIDASE
ENZYME IS TWO SEPARATE ENTITY????
Previously we will consider that
Neisseria species were thought to
produce indophenol oxidase.......
Pseudomonas species were thought to
produce cytochrome oxidase.......
After spectrophotometric studies
both oxidases are same.............

11. OTHER NAMES OF CYTOCHROME
OXIDASE
1. Atmungsferment
2. Cytochrome C oxidase
3. Cytochrome Alpha3 oxidase
4. Cytochrome Alpha oxidase
GABY
AND
HADLEY

12. FOUR BACTERIAL PIGMENTS
ACT AS TERMINAL OXIDASE
• Cytochrome oxidase
alpha 1
• Cytochrome oxidase
alpha 2
• Cytochrome oxidase
alpha 3
• Cytochrome O (CO
binding pigment)
• Derived by Castor and
Chance by means of
photochemical methods.
• A mixture of
cytochrome alpha and
alpha 3 having same
protein.. So complex
formed (Cytochrome c
oxidase/Cytochrome
alphaalpha3 )

13. CYTOCHROME C OXIDASE
• Having two molecules of heme A
• Each heme A having one Fe atom which go
and come back between Ferric and Ferrous
ions
Cytochrome-Fe3+ + e- Cytochrome-Fe2+
(Oxidised removal (Reduced gain of
of electrons) electrons)

14. RESPIRATORY ENZYME
(Important bichemical reaction)
Two reduced cytochrome c + 2H+ + 1/2H2O
Cytochrome C
Oxidase
Two oxidized cytochrome c + H2O

15. REAGENTS
• 1. Kovac’s reagent
1% solution of tetramethyl-p-phenylene-
diamine(Less toxic but more expensive
comparing with dimethyl) imparts oxidase(+)
lavender colour initially purplish black
gradually.
Solution is colourless.

16. REAGENTS (cont.)
• 2. Gordon and Mcleod’s reagent
• 1 to 1.5% dimethyl-p-phenylenediamine
hydrochloride/N,N-dimethyl-p-phenylene
diamine monohydrochloride(HCL)/p-
aminodimethylaniline monohydrochloride)
• Solution is light purple.

17. Why p-aminodimethylaniline oxalate
reagent having advantage over others???
• Extremely stable both in powder or solution
forms (Atleast 6 months!!!!)
• No black precipitate while comparing with
Hcl combination of Gordon’s reagent.

18. REAGENTS (Cont.)
• 3. Gaby and Hadley reagent modified by
Ewing and Johnson/Indophenol oxidase
reagent
• Original Nadi reaction from naphthol and
diamine
Reagent A 1% naphthol in 95% Ethyl
alcohol
Reagent B 1% p-aminodimethylaniline
Hcl / dimethyl-p-
phenylenediamine oxalate

19. Why Gaby and Hadley reagent A
alone is an exception??????
• While preparing other reagents we will take 1
gram of reagent in 100 ml of distilled water.
• But for this reagent A of Gaby and Hadley we
will take 1 gram of naphthol in 100 ml
solution of 95% ethyl alcohol...........
• Warm gently and store it in darker place for 15
minutes before usage.........

20. REAGENTS(cont.)
• 4. Carpenter, Suhrland and Morrison
reagent contains 1% p-aminodimethylaniline
oxalate.
• 5. Commercial reagent: Cepti seal Oxidase
reagent
• 6. Oxidase impregnated disc (p-
aminodimethylaniline reagent) :
(6a) Difco: Bacto-differentiation discs
(6b) BBL: Taxo N discs

21. METHODS OF UTILIZATION OF
REAGENT SOLUTIONS
• (A) Direct slant procedure (Indophenol
reagent)
*Using nutrient agar slant and incubate it
for 18 to 24 hours.
*Put positive control as Aeromonas
species.
*Add 2 to 3 drops of both reagents A and
B and tilt it.
*Observe for change in colour to blue.

22. REAGENTS SOLUTIONS (cont.)
• (B) Direct plate procedure
*Add 2 to 3 drops of reagent directly to
few suspected colonies alone without flooding
the entire plate.
*For Kovacs reagent, colour reaction
within 10 to 15 seconds.
*For Gordon and Mcleod’s reagent,
colour reaction within 10 to 30 minutes.

23. REAGENTS SOLUTIONS (cont.)
• (C) Kovac’s indirect filter paper method
*Place a 6 square centimetres of
Whatmann No.1 filter paper in a petri dish.
*Add 2 to 3 drops of Kovac’s reagent to
the centre of the paper.
*With the usage of platinum wire
inoculating needle smear a loopful of the
suspected colony in paper 3 to 6 cm long.
*Positive reaction within 5 to 10 seconds.

24. How is it looks like???????

25. OXIDASE DISCS
• (A) Direct plate procedure
*Moisten the impregnated disc with
sterile distilled water.
*Place disc on few suspected colonies in
plate medium.
*Incubation at 35 degrees for 20 to 30
minutes.
*Initially rose to purple but after 30
minutes red to black.

26. OXIDASE DISCS
• (B) Indirect procedure
*Moisten disc with sterile distilled water.
*Place it in a petri dish.
*Add a loopful of colony growing on a
solid medium.
*Positive reaction occurs within seconds.
*Pink to black.

28. QUALITY CONTROLS
• Escherchia coli (ATCC 25922) – Good
control for negatives
• Neisseria, Pseudomonas(ATCC 27853) and
Aeromonas – Good control for positives
• Easily available and no problems when we
maintained as stock cultures.

29. STORAGE AND REPLACEMENT
• Store it in refrigerator and warm it before use.
• According to Barry and Bernshon reagents should
be freezed at -20 degree. We have to thaw the
reagent before 3 to 4 hrs of usage.
• Once thawed we may use that reagent till one day.
• ONLY REFRIGERATED REAGENTS we can
keep it till maximum 14 days.
• Regular quality control checks should be done
and discard it if comes as negative.

30. REAGENT ACTION
Two molecules of oxidized cytochrome c
+
Reagent
Coloured compound

31. REAGENT ACTION.........

32. INTERPRETATION FOR
OXIDASE(+)
• Pink...............to...........Maroon.............to..........
.......Finally black colour......
• Pink colour - Viable, able to subculture
• Black colonies – Non viable

33. INTERPRETATION FOR
OXIDASE(-)
• No colour change in colonies
• Only background will be black.

34. DELAYED OXIDASE TEST
MEANS..........
• Within 10 seconds colour formation – O(+)
• Within 10 to 60 seconds colour formation –
Delayed oxidase test
• After 60 seconds colour formation – O(-)

35. REAGENTS IMPREGNATED
OXIDASE TEST STRIPS
• Cytochrome oxidase test strip
• Barry and Bernsohn method (Whatmann No.1
filter paper cut down into strips and dry
rapidly)
• We can test many number of colonies
simultaneously......
• Positive test – Red colour

36. Why kovac’s reagent more sensitive
than Gordon and Mcleod??????
• Ellingsworth first found that Haemophilus
influenzae is negative with Gordon but
positive with Kovac’s..........
• Reason – Tetramethyl-p-phenylenediamine is
more sensitive than Dimethyl-p-
phenylenediamine.......

37. Don’t do oxidase test in glucose
containing medium.....Ok....But why??
• Because it’s fermentation will inhibit oxidase
enzyme activity and results in false negatives.
• OTHER FALSE NEGATIVES:
In mixed culture of Pseudomonas and
Neisseria, inhibitory substance produced by
pseudomonas interferes with oxidase
production by Neisseria

38. FALSE POSITIVES......
• Bordetella pertussis may show false(+) when
cultivated in high conc. of blood.
• Platinum loop needle may contain trace
amount of iron can catalyse oxidase
reagent.....leads to false positive

39. Why can’t we call kovac’s reagent as
simply kovac’s reagent????
• Because there is also a reagent called kovac’s
indole reagent.
• So just to avoid the confusions.....

40. ROLE OF VITAMIN C AND
SUNLIGHT IN KOVAC’S REAGENT
• To avoid auto-oxidation in air, we will add
ascorbic acid in kovac’s reagent
• Colour of the reagent turns into deep blue if it
exposed to sunlight. So keep it in dark
place......

41. MODIFIED OXIDASE METHOD
• Reagent in Dimethyl sulfoxide (DMSO) 6%
solution used for identification of micrococci
species (Positive reaction within 30 seconds)

42. OXIDASE TEST IN SINGLE LINE
• Oxidase test is an oxidising reaction and
oxygen must reach colonies; after flooding
growth or a portion of growth, tilt slants or
plates to permit the reagent to run, exposing
colonies to air..........

43. CATALASE TEST
• PRINCIPLE: To detect the presence of
enzyme catalase in the bacteria which acts on
Hydrogen peroxide to release oxygen........

44. PURPOSE AND DIFFERENTIATION
CATALASE(+)
• Staphylococcus
• Micrococcus
• Bacillus
• Listeria monocytogenes
• Corynebacterium (except
two)
• All moraxella species
(except two)
CATALASE(-)
• Streptococcus
• Clostridium
• Erysipelothrix
• Corynebacterium pyogenes
• Corynebacterium
haemolyticum
• Moraxella bovis
• Kingella kingae(Moraxella
kingii)

45. HISTORY AND MECHANISM
The enzyme catalase is present in most
cytochrome containing aerobic and
facultative anaerobic organisms.
Organisms lacking cytochrome system
also lack the catalase.....
According to Doelle, catalase may interfere
with peroxidase enzymes.....

46. CATALASES AND PEROXIDASES
• Peroxidases are plant enzymes but also found
in milk and leucocytes....
• Catalases are present in animals and plants.
• Iron contained catalases which retain its
oxidized state during enzymatic activity.
• According to Burrows and Moulder non iron
containing catalases are also there.....
• Dacre and Sharpe – Strong and Weak
catalases.

47. Whittenbury Observation
• Two types of catalases: Classical Catalase and
Pseudocatalase
• Classical Catalase: Which decomposes
Hydrogen peroxide and nonsensitive to acid
conditions.
• Pseudocatalase: Which lacks heme prosthetic
group and sensitive to acid pH.
• According to Johnston and Delwiche both
types are present in lactic acid organisms.

48. H2O2 IS TOXIC TO BATERIA......??
• Yes of course.....Hydrogen peroxide
accumulation is very much toxic to bacteria.
• It is an Oxidative end product of aerobic
breakdown of sugars.
• Since it’s toxic, bacteria uses it’s catalase
enzyme to breakdown H2O2.

49. CATALASES VS PEROXIDASES
• At present, it is believed that peroxidases
more predominates than catalases in
elimination of Hydrogen peroxide.
• Optimal pH for catalase activity is 7.0

50. REAGENTS
• 1. Hydrogen peroxide 30%
*Store in a dark bottle
*Keep refrigerated at all times when not
in use.

51. Reagents (cont.)
• 2. Phosphate buffer – pH 7.0
INGREDIENTS QUANTITY
Potassium dihydrogen
phosphate
1.361grams
Anhydrous Disodium
hydrogen phosphate
1.420 grams
Distilled water 1000 ml of distilled
water

52. Reagents (cont.)
• 3. Tween 80,10%
*Add 1 ml of concentrated tween 80 to a
small volume of distilled water in a 10 ml
volumetric flask
*Polyoxyethylene derivative of sorbitan
mono-oleate; a surface active compound

53. QUALITY CONTROLS
POSITIVE CONTROLS NEGATIVE CONTROLS
Staphylococcus
(ATCC 25923)
Streptococcus
Blood agar plate (d/t
catalase in RBCs)
Chocolate agar d/t no
RBCs
Note: Hydrogen peroxide should undergo
quality control check daily or immediately
prior to it’s use............

54. ROUTINE CATALASE TESTS
• At room temperature 25 degree celsius.
• Slide method (Routinely used)
• Tube method

55. SLIDE CATALASE TEST
• With an inoculating needle, pick the centre of
an 18 to 24 hour pure colony on glass slide.
• Exception is colony from blood agar.
• Add a drop of 30% Hydrogen peroxide over
organism on slide.
• Observe for immediate bubbling (Gas
liberation) and Discard the slide.
• These are DO’S IN SLIDE CATALASE
TEST.

56. DONT’S IN SLIDE CATALASE
TEST
• Do not reverse the order of procedure
• Do not mix the culture and Hydrogen
peroxide (Just add a drop of H2O2 on colony
and then just observe!!!!)

57. How it looks like???? Here we go!!!!

58. TUBE CATALASE TEST
• Directly add 1 ml of 3% H2O2 to an 18 to 24
hour heavily inoculated pure agar slant culture.
• Observe for immediate bubbling(Gas
liberation) and observe.

59. Tube catalase test

60. Catalase test for differentiation of Mycobacterium
species (Under controlled pH and temperature)
• Perform procedure under bacteriological hood
(Strict aseptic conditions)
• Add 0.5 ml of phosphate buffer into sterile
screwcap tube.
• Add several loops of Mycobacterium growth
from slant culture 3 to 4 weeks old
• Screw cap down loosely.
• Incubate for 20 to 30 minutes/In 68 degrees
celsius Water bath.

61. Catalase test for Mycobacterium
species(Cont.)
• Cool at room temperature
• Prepare a 1:1 mixture of 10% Tween 80 and
30% H2O2
• Add this mixture in cooled suspension
• Observe for bubble formation.
• Note: ALL MYCOBACTERIUM SPECIES
ARE CATALASE POSITIVE for Routine
catalase test except Isoniazid Resistant
strains.

62. But what’s the interpretation when we will do under
controlled pH and temperature??
Positive
• Mycobacterium avium
Negative
• Some J subgroups of III
nonphotochromogens
• Mycobacterium kanasasii
• Mycobacterium tuberculosis
• Mycobacterium bovis

63. ALTERNATE TESTS
• Capillary tube technique (Method of Fung and
Petrishko)
• Commercial capillary tubes
• 10 ml of 3% Hydrogen peroxide in 50 ml beaker
• Touching centre of colony
0 No bubbles
+ Few bubbles
++ Many bubbles
+++ Gas forcing H2O2 to tip of
tube

64. Disadvantages of capillary tube
method
• Vigorous catalase activity (+++) – Serratia,
Proteus, Providencia
• Moderate catalase activity(++) – Salmonella
• Weak catalase activity/Negative catalase
activity - Enterobacteriaceae

65. Alternate test (cont.)
• Cover slip technique (Method of Taylor and
Achanzar)
• Primarily used for identification of
Enterobacteriaceae.

67. TWO METHODS OF INTERPRETATION IN
COVER SLIP METHOD
• Frosted appearance of bubbles under cover slip
indicates speed of reaction
• Seeing presence or absence of trapped bubbles

68. ORGANISMS POSITIVE IN 0.5%
COVER SLIP METHOD
• Pseudomonas aeruginosa
• Serratia
• Staphylococcus

69. ALTERNATE TESTS (cont.)
• Colour reaction streak test (Method of
Hanker and Rabin)
• For primarily to differentiate staphylococci and
streptococci

70. REAGENTS
• Stock solutions
DOPAMINE
20 mg/ml in 0.2M
Phosphate buffer
P-phenylenediamine
dihydrochloride
1 mg/ml in 0.2M
phosphate buffer

71. REAGENTS (cont.)
• Working reagent
DOPAMINE 1 ml
P-PHENYLENEDIAMINE
DIHYDROCHLORIDE
1 ml
3% H2O2 2 ml
Dimethyl sulfoxide 1 ml

72. INTERPRETATION OF RESULTS
• After streaking pure bacterial colony on clean
slide and add 1 drop of working reagent
• Formation of highly coloured purple colour
and it may lasts for days so that results may
be rechecked (Advantage!)

73. CHEMISTRY OF REAGENT
FOR BOTH
CATALASES
AND
PEROXIDASES
FOR
PEROXIDASES

74. CRITERIA FOR TAKING CULTURE
IN CATALASE TEST
• It should be a pure culture.
• It must be performed in heavy inoculum.

75. Why 70% ethyl alcohol is needed
while handling Hydrogen peroxide??
• Just to avoid exposure to skin as painful burns
may occur.

76. Why gentle shaking needed for
Hydrogen peroxide before usage??
• Hydrogen peroxide decomposition increases as
the temperature increases due to dissolved
oxygen.....It may create false positive
reactions.

77. COAGULASE TEST
• PRINCIPLE: To test the ability of an
organism to clot plasma by the action of
enzyme coagulase(Staphylocoagulase)

78. USES
• To differentiate staphylococcus aureus from
other staphylococcus species.
• Used as an indication for virulence or
pathogenicity.

79. NORMAL MECHANISM

80. NAMED HYPOTHESIS RELATED
TO COAGULASE TEST
• Oginsky and Umbreit
• Smith
• Burrows and Moulder
• Duthrie
• Dubos and Hirsch
• Soulier, Tager and Zajdel

81. OGINSKY AND UMBREIT
HYPOTHESIS
• Coagulase enzyme may induce alternate
pathway of clotting mechanism either as an
enzyme or or an plasma activator to convert
fibrinogen to fibrin.

82. SMITH HYPOTHESIS
Coagulase (Prothrombin
like substance) +
Plasma(CRF)
Thrombin like
substance
Fibrinogen
to fibrin

83. BURROWS AND MOULDER
HYPOTHESIS
• Procoagulase + Plasma activator Coagulase
Reason for
clotting of plasma

84. DUTHRIE HYPOTHESIS
PROCOAGULASE
BOUND
COAGULASE /
CLUMPING
FACTOR
TUBE
COAGULASE
TEST
SLIDE
COAGULASE
TEST
FREE
COAGULASE
TUBE
COAGULASE
TEST

85. DUBOS AND HIRSCH
HYPOTHESIS
• Every step is same as previously mentioned
mechanisms except one thing.........
• Here PLASMA/CRF doesn’t require
calcium ions to form a clot.

86. SOULIER,TAGER AND ZAJDEL
HYPOTHESIS

87. OVERVIEW OF COAGULASE INDUCED FIBRIN
COATING AND ANTIMICROBIAL DRUGS
• Basically serum is having bactericidal action
against staphylococcus..........
• But when coagulase induced fibrin coated
staphylococcus is present in serum means,
antimicrobial drugs cannot penetrate that
coating......
• BUT THIS MECHANISM WE CANNOT
SEEN IN CONS.

88. HEMOLYSIN PRODUCTION
COWAN All C(+) strains produce
either alpha or beta
hemolysin or both
BURROWS AND MOULDER Either alpha or gamma
hemolysin associated with
coagulase activity
YOUNG AND LEITNER No correlation at all
WECKMAN AND CATLIN Production of
deoxyribonucleases along with
coagulase

89. ANTIGENIC SUBTYPES
RAMMELKAMP, DUTHRIE AND
ZEN-YOJI
Seven antigenic subtypes
MIALE TYPES A,B,C,D
SMITH TYPES I AND II

90. REAGENTS

91. METHOD OF PREPARATION OF
REAGENT
• Commercial plasma
• Fresh plasma from whole blood
(CentrifugeTake supernatant Store it in
sterile container)
• Fresh fibrinogen (Centrifuge Take the
precipitate  Make up(Dilution) to 5 times of
sterile distilled water)

92. Why are we adding heparin or EDTA
with plasma in special???
• Simply, reason is that citrate utilising
organisms creates delayed coagulase reaction
which leads to false positive coagulase
test(Clot formation).
• So by means of adding 5 ml of heparin 
inhibit coagulation by citrate utilisation Test
is more specific for staphylococcus.

93. QUALITY CONTROL
• Positive quality control – Staphylococcus
aureus (ATCC 25923)
• Negative quality control – Staphylococcus
epidermidis

94. PLASMA COAGULABILITY
CHECK
• Add one drop of 5% calcium chloride
solution to 0.5ml aliquot of plasma (1:2
dilution) and a clot should form.

95. STORAGE
• Dehydrated plasma vials  Refrigerator (4
degree celsius)
• Reconstituted plasma vials  Freezer (-20
degree celsius)

96. PLASMA QUALITY CHECK
CRITERIA
• CRF/Plasma concentration is highest in human
plasma followed by Pig>Rabbit>Horse>
Bovine>Chicken>Sheep.
MUST CONTAINS SUFFICIENT AMOUNT OF CRF CONCENTRATION AND
FIBRINOGEN
FAIRLY FREE OF FIBRINOLYTIC ACTIVITY (BY MEANS OF
STAPHYLOKINASE ENZYME AND MULLER FACTOR PLASMIN)
REASONABLY FREE OF INHIBITORS (PROTEASES)

97. WHY RABBIT PLASMA IS PREFERRED
OVER HUMAN PLASMA??
• Clot is firm and it’s rate of coagulation is faster
(Rabbit plasma)
• Antibodies in human plasma will inhibit
coagulase production by staphylococcus.

98. Why dilution of human plasma
preferred??
• Because bacteriostatic action against
staphylococcus is eliminated by dilution of
human plasma......

99. Why diabetics more prone to infections
caused by staphylococcus???
• Yearsly and Carter proved that a slight
increase in coagulase activity in diabetic
plasma over human plasma...
• So we should control diabetics as much as
possible with the help of insulin/OHA.

100. SLIDE COAGULASE TEST
• Place a drop of distilled water in glass slide.
• Emulsify it using heavy suspension of 18 to
24 hour culture of staphylococcus
• Gently mix with small loop of fresh human
plasma and mixture should be homogenous.
• Set up positive and negative controls in same
slide
• Observe for clump formation

102. INTERPRETATION

103. TUBE COAGULASE TEST

105. INTERPRETATION
(A) POSITIVE TEST: Clot or distinct fibrin
threads formed.
Complete clot: Clot throughout tube.
Partial clot: Clot doesn’t extend throughout
fluid column.
(B) NEGATIVE TEST: No clot formation,
suspension remains homogenous.

106. RAPID TEST: Staph strip
• Strips impregnated with lyophilized rabbit
plasma with EDTA
• Results of both screening and tube tests with
as single inoculum

107. ALTERNATE TESTS
1. Pour plate coagulase test
Method of Parisi, Baldwin and Sottile
* Detects coagulase production
* BHI or YETS agar (Trypticase soy broth) and
0.3% yeast extract
* Plasma preferably swine pig plasma;
Alternatively rabbit.
Correlation with standard test tube(Excellent)
* No plasma – Parisi recommended not to use
plasma

108. ALTERNATE TESTS (cont.)
2. Tube coagulase thermonuclease test
Method of Barry, Lachica and Atchison
* Detects free coagulase and heat stable
nuclease
* BHI broth, EDTA plasma and DNA agar
TDA technique (Toluidine Blue
Deoxyribonucleic acid)
* Correlation with standard tube test.

109. ALTERNATE TESTS (cont.)
3. Coagulase-mannitol agar plate test
* Detects free and bound coagulase
* Mannitol fermentation
* Contents: Human blood plasma and
Mannitol
* Disadvantage: Too many false positives

110. THANK YOU