BIOCHEMICAL TEST | Bacterial Identification Technique | Microbiology | Vivek Srinivas |#Bacteriology
Summary
TLDRThis video presentation delves into various biochemical tests for bacterial identification, essential for definitive diagnosis beyond clinical signs. It covers direct microscopic examination, culturing on different media, and a range of biochemical tests including catalase, oxidase, indole, methyl red, Vogus Proskauer, citrate utilization, urease, sugar fermentation, hydrogen sulfide production, and the Triple Sugar Iron (TSI) test. The script also mentions advanced techniques like PCR, DNA sequencing, and phage typing, concluding with the gelatin liquefaction test, providing a comprehensive guide to bacterial identification in laboratories.
Takeaways
- 🔬 The definitive identification of bacteria requires laboratory examination beyond clinical signs and symptoms.
- 📝 Direct microscopic examination and bacterial staining techniques like Gram, acid-fast, negative, spore staining, and motility tests are initial steps in bacterial identification.
- 🌱 Culturing bacteria on different types of media such as differential, selective, enriched, and enrichment broth is essential for further analysis.
- 🧪 Biochemical tests are crucial for identifying the genus and species of bacteria by assessing their enzymatic properties and substrate utilization.
- 🌡 The catalase test differentiates bacteria based on their ability to decompose hydrogen peroxide, producing oxygen bubbles for positive reactions.
- 🟣 The oxidase test detects the presence of the oxidase enzyme, which turns a specific reagent purple in the presence of bacteria.
- 🔴 The indole test identifies bacteria that produce indole as a by-product when metabolizing tryptophan, indicated by a red color change with Kovax reagent.
- 🍬 The methyl red test measures the acidic by-product of glucose fermentation, which changes the indicator to red in a positive test.
- 🍇 The Voges-Proskauer (VP) test detects the production of acetoin from glucose fermentation, resulting in a red color complex with specific reagents.
- 🍋 The citrate utilization test identifies alkaline pH changes due to citrate metabolism, indicated by a color change to Prussian blue.
- 🔄 The IMViC tests (Indole, Methyl Red, Voges-Proskauer, and Citrate) are a set of biochemical tests used to differentiate members of the Enterobacteriaceae family.
- 🧫 The urease test detects bacteria that hydrolyze urea into ammonia and carbon dioxide, causing an alkaline pH shift indicated by a color change to pink.
- 🍯 The sugar fermentation test determines a bacteria's ability to ferment various sugars, producing acid and possibly gas, which can be observed through color change and bubble formation.
- ⚫ The hydrogen sulfide production test detects the formation of black precipitate due to the reaction between hydrogen sulfide and iron salts.
- 🌊 The triple sugar iron (TSI) test evaluates sugar fermentation and hydrogen sulfide production using a medium with three different sugars and an iron salt indicator.
- 🧊 The gelatin liquefaction test detects bacteria that produce gelatinase, an enzyme that breaks down gelatin even at low temperatures, maintaining a liquefied state.
Q & A
What is the primary purpose of biochemical tests in identifying bacteria?
-The primary purpose of biochemical tests is to provide definitive identification of bacteria, which is necessary beyond just clinical signs and symptoms, to identify the causative bacterial agent for infection.
Why is laboratory examination essential for bacterial identification?
-Laboratory examination is essential because it allows for the collection of correct samples and the application of various tests, such as microscopic examination, culturing, biochemical tests, serological tests, molecular techniques, and phage typing, which are necessary for definitive bacterial identification.
What is the principle behind the catalase test for bacterial identification?
-The principle behind the catalase test is that certain bacteria produce the enzyme catalase, which can decompose hydrogen peroxide into water and oxygen. The release of oxygen is observed as bubbles or effervescence, indicating a positive test.
How is the oxidase test performed and what does it indicate?
-The oxidase test is performed by placing a bacterial colony on an oxidase reagent-impregnated disc. If a purple color develops, it indicates the presence of the oxidase enzyme in the bacteria, suggesting a positive test.
What is the purpose of the indole production test and how is it conducted?
-The indole production test is used to detect the presence of the enzyme tryptophanase, which converts tryptophan into indole. The test is conducted by inoculating a bacterial colony into a broth containing tryptophan and adding Kovax reagent; a red color development indicates a positive test due to indole production.
What does the methyl red test indicate about bacterial metabolism?
-The methyl red test indicates whether certain bacteria ferment glucose to produce pyruvic acid, which lowers the pH to acidic levels. The addition of methyl red indicator to the broth changes the color to red in acidic conditions, indicating a positive test.
What is the significance of the Voges-Proskauer (VP) test in bacterial identification?
-The VP test is significant as it detects the production of acetylmethylcarbinol (diacetyl), a neutral byproduct of glucose metabolism in certain bacteria. A positive test shows a red color change when specific reagents are added, indicating the presence of this byproduct.
How does the citrate utilization test help in bacterial identification?
-The citrate utilization test helps in identifying bacteria that can utilize sodium citrate to produce carbonate and bicarbonate, which raises the pH to alkaline levels. A color change to prussian blue in the presence of bromothymol blue indicator indicates a positive test.
What is the principle of the urease test and what does a positive result indicate?
-The principle of the urease test is based on the ability of certain bacteria to produce the enzyme urease, which hydrolyzes urea into ammonia and carbon dioxide, increasing the pH to alkaline levels. A positive result is indicated by a color change to pink due to the presence of phenol red indicator.
What information can be gathered from the sugar fermentation test?
-The sugar fermentation test provides information about the ability of bacteria to ferment specific sugars, producing acid as a byproduct and changing the pH to acidic levels. This can help differentiate between bacterial species based on their metabolic capabilities.
How does the triple sugar iron (TSI) test differentiate between different bacterial species?
-The TSI test differentiates bacterial species by observing their fermentation patterns of three different sugars (glucose, sucrose, and lactose) and their ability to produce hydrogen sulfide. Different reactions, such as color changes and gas production, indicate the metabolic characteristics of the bacteria.
What does the gelatin liquefaction test measure and what is its significance?
-The gelatin liquefaction test measures the ability of certain bacteria to produce the enzyme gelatinase, which breaks down gelatin into amino acids, even at low temperatures. A positive test, where the gelatin remains liquefied at 4 degrees Celsius, indicates the presence of this enzyme.
Outlines
🔬 Bacterial Identification Through Biochemical Testing
This paragraph introduces the necessity of biochemical testing for definitive bacterial identification beyond clinical signs and symptoms. It outlines various laboratory methods, including direct microscopic examination using different staining techniques, culturing on different types of media, biochemical tests, serological tests, molecular techniques like PCR and DNA sequencing, and phage typing. The paragraph emphasizes that without biochemical testing, complete identification of bacteria, such as distinguishing between E. coli, Klebsiella, and Citrobacter, is not feasible.
🧪 Biochemical Tests for Bacterial Identification
This section delves into specific biochemical tests used for bacterial identification, starting with the catalase test, which detects the enzyme catalase that breaks down hydrogen peroxide. It then covers the oxidase test, which identifies bacteria that produce the oxidase enzyme, turning a reagent purple. The indole production test is explained, which detects bacteria that produce indole from tryptophan, changing the Kovax reagent red. The paragraph also describes the methyl red test for glucose fermentation and the Vogus Proskauer test, which detects the production of acetylmethyl carbonyl from glucose fermentation, turning a mixture red.
🌿 Citrate Utilization and Other Biochemical Tests
The paragraph discusses the citrate utilization test, which identifies bacteria that can change pH to alkaline by utilizing sodium citrate. It also explains the IMViC reactions (Indole, Methyl Red, Vogus Proskauer, and Citrate) used for identifying Enterobacteriaceae family members. The urease test is described, which detects bacteria that produce ammonia and carbon dioxide from urea, changing pH to alkaline. The sugar fermentation test is introduced, which determines a bacteria's ability to ferment different sugars, indicated by a color change and possible gas production.
🍬 Sugar Fermentation and Hydrogen Sulfide Production Tests
This paragraph focuses on the sugar fermentation test, explaining how bacteria ferment various sugars and produce acids or gases, detected by a color change or bubble formation. It also introduces the hydrogen sulfide production test, which identifies bacteria that produce hydrogen sulfide, forming a black precipitate with iron salts. The Triple Sugar Iron (TSI) test is detailed, a slant test with three sugars and ferrous sulfate to detect sugar fermentation and hydrogen sulfide production, with different reactions observed for E. coli and Salmonella.
🧊 Gelatin Liquefaction and Summary of Biochemical Tests
The final paragraph describes the gelatin liquefaction test, which detects bacteria that produce gelatinase, an enzyme that breaks down gelatin even at low temperatures. It summarizes the various biochemical tests available for bacterial identification, including their principles and procedures. The paragraph concludes with an invitation to stay tuned for the next video on antimicrobial susceptibility testing and provides a downloadable link to a schematic illustration of the biochemical tests in the video description.
Mindmap
Keywords
💡Biochemical test
💡Bacterial staining techniques
💡Culturing
💡Gram-negative bacilli
💡Enzyme activity
💡Sugar fermentation
💡pH indicator
💡Serological test
💡Molecular techniques
💡Phage typing
💡IMViC reactions
Highlights
Laboratory examination is essential for definitive bacterial identification beyond clinical signs and symptoms.
Different bacterial staining techniques like gram staining, acid-fast staining, and negative staining are used for microscopic examination.
Bacterial culture media types include differential, selective, enriched media, and enrichment broth for bacterial growth.
Biochemical tests are crucial for identifying bacterial genus, species, and sometimes subspecies.
The catalase test detects the presence of the catalase enzyme, which breaks down hydrogen peroxide.
The oxidase test identifies bacteria that produce the oxidase enzyme, changing a reagent to a purple color complex.
Indole production test detects bacteria that produce indole from tryptophan, forming a red ring with Kovax reagent.
Methyl red test indicates glucose fermentation by detecting a change to an acidic pH and a red color.
Voges-Proskauer test detects the production of diacetyl from glucose fermentation, turning a mixture red.
Citrate utilization test identifies bacteria that utilize sodium citrate, changing pH to alkaline and turning bromothymol blue to prussian blue.
IMViC reactions, a set of four biochemical tests, are used for identifying members of the Enterobacteriaceae family.
Urease test detects bacteria that hydrolyze urea to ammonia and carbon dioxide, changing pH to alkaline and turning phenol red to pink.
Sugar fermentation test determines which sugars a bacteria can ferment, producing acid and changing pH to acidic.
Hydrogen sulfide production test detects the production of hydrogen sulfide, forming a black precipitate with iron salts.
Triple sugar iron (TSI) test checks for sugar fermentation and hydrogen sulfide production in a single test.
Gelatin liquefaction test detects bacteria that produce gelatinase, breaking down gelatin even at low temperatures.
A downloadable link for schematic illustrations of different biochemical tests is available in the video description.
Upcoming video presentations will cover antimicrobial susceptibility testing.
Transcripts
[Music]
in this video presentation we will see
about the different biochemical test for
the identification of the bacteria
the diagnosis of the bacterial infection
can be done based on the clinical signs
and the symptoms of the disease but it
gives only the tentative identification
but for the definitive identification
the laboratory examination is necessary
by the laboratory examination we can
identify the causative bacterial agent
for the infection but for that the
correct sample from the patient has to
be collected based on the clinical signs
first the collected sample can be
subjected for the direct microscopic
examination by performing the different
bacterial staining techniques like the
gram staining the acid fast staining the
negative staining the spore staining and
the motility test
next by culturing the bacteria onto the
different types of bacterial culture
media like the differential media the
selective media the enriched media and
the enrichment broth and next by the
biochemical tests this tests will be
detailed in this video presentation
next by the serological test like the
slide agglutination test the tube
agglutination test and the microscopic
agglutination test and next by using
molecular techniques like the pcr
followed by the dna sequencing and
lastly the phage typing that is the
bacterial identification by using the
bacteriophages these are the laboratory
methods and the strategy followed for
the bacterial identification only by the
microscopic examination and by the
culturing technique the complete
identity of the bacteria is not possible
for instance the bacteria producing the
pink colonies on the mcconkey's agar
when subjected to the microscopic
examination will shows the gram-negative
bacilli which may be the e coli the
klebsiella or the citrobacter so the
genus and species level bacterial
identification is achieved by subjecting
the bacterial culture to various
biochemical tests and other techniques
the biochemical test this helps in the
identification of the bacterial genus
and the species sometimes even the
subspecies too this is achieved by
subjecting the bacterial culture to the
various biochemical tests
the various bacteria has its inherent
property to produce the different types
of the enzymes and the substances in
addition the various bacteria also has
its inherent property to ferment or to
utilize the different types of the
sugars and the substrates the yield the
different types of by-products this can
be identified by subjecting the
bacterial culture to the various
biochemical tests
first we see about the catalase test the
principle certain bacteria produce the
enzyme the catalase this enzyme along
with the hydrogen peroxide capable of
decomposing the hydrogen peroxide to the
water and the oxygen the release of the
oxygen is observed as the bubbles or the
effervescence formation this is the
principle behind the catalase test
the procedure take a glass slide
place 0.5 ml of the hydrogen peroxide
over the slide then emulsify the
bacterial colony to the hydrogen
peroxide if there is no bubbles or no
effervescence observed indicates the
test is negative
the example the streptococcus bacterial
organism negative for the catalase test
in contrast if the bacterial colony once
emulsified with the hydrogen peroxide
produce bubbles or effervescence
indicates the test is positive the
example the staphylococcus bacterial
organism positive for the catalase test
this is the procedure for the catalase
test
this is the photograph showing the
positive and the negative test result of
the catalase test
next the oxidase test the principle
certain bacteria produce the enzyme the
oxidase this enzyme along with the
oxidase reagent consisting of one
percent
tetramethylparaphenyldiamine
dihydrochloride capable of turning into
the endophenol this into phenyl is a
purple color complex this is the
principle behind the oxidase test
the procedure take the oxidase disc this
disc is the oxidase reagent impregnated
disc now place the bacterial colony over
the oxidase disc if there is no color
development observed indicates the test
is negative the example the e coli
bacterial organism negative for the
oxidase test in contrast following
addition of the bacterial colony over
the oxidase disc produces the purple
color indicates the test is positive the
example the pseudomonas bacterial
organism positive for the oxidase test
this is the procedure for the oxidase
test
this is the photograph showing the
positive and the negative test result of
the oxidase test
next the indole production test or the
indole ring test the principle
certain bacteria produce the enzyme the
tryptophanase this enzyme in presence of
the tryptophan capable of utilizing the
tryptophan to yield the indole as the
by-product
next this indole by-product once mixed
with the kovax reagent develop a red
color complex this is observed as the
red ring this is also referred as the
indole ring this is the principle behind
the indo-ring test
the procedure this test is performed in
the test tube with the liquid broth
containing the tryptophan now take the
bacterial colony inoculate into this
broth incubate for 24 to 48 hours
following incubation add the covax
reagent along the side the formation of
red ring which indicates the test is
positive due to indole production the
example the e coli bacterial organism
positive for the indole test
in contrast following addition of the
covax reagent if there is no red ring
formation which indicates the test is
negative for the endoproduction the
example the salmonella bacterial
organism negative for the endo test this
is the procedure for the endo test
this is the photograph showing the
positive and the negative test result of
the indole production or the indole ring
test
next the methyl red test also
abbreviated as the mr test the principle
certain bacteria in presence of the
glucose ferment the glucose to yield the
pyruvic acid as the byproduct this
changes the ph 2 acidic from the initial
neutral ph
next this acidic ph along with the
methyl red indicator develops the red
color this is the principle behind the
methyl red test
the procedure this test is performed in
the glucose phosphate broth with the
neutral ph
now take the bacterial colony inoculate
into this broth incubate for 24 to 48
hours following incubation add the
methyl red indicator to it the
development of red color which indicates
the test is positive due to acidic ph
the example the e coli bacterial
organism positive for the mr test
in contrast following addition of the
methyl red indicator if there is no
color change which indicates the test is
negative for the mr test the example the
klebsiella pneumoniae bacterial organism
negative for the mr test this is the
procedure for the methyl red test
this is the photograph showing the
positive and the negative test result of
the methyl red test
next the vogus prosper test also
abbreviated as the vp test the principle
certain bacteria in presence of the
glucose ferment the glucose to the acid
and then subsequently metabolize to
yield a neutral byproduct the acetyl
methyl carbonyl which is an acetoin
compound
next this acidoin compound along with
the 40 potassium hydroxide and the 5
alpha naphthal to form the red color
complex the diacetyl derivative this is
the principle behind the vogus prosper
test
the procedure this test is performed in
the glucose phosphate broth now take the
bacterial colony inoculate into this
broth incubate for 48 hours
following incubation add the 5 alpha
naphthal and the 40 potassium hydroxide
to it the development of the red color
which indicates the test is positive due
to the diacetyl formation the example
the klebsiella pneumoniae bacterial
organism positive for the vp test
in contrast following addition of the 5
alpha naphthal and the 40 potassium
hydroxide if there is no color change
which indicates the test is negative for
the vp test the example the e coli
bacterial organism negative for the vp
test
this is the procedure for the vp test
this is the photograph showing the
positive and the negative test result of
the vp test
in general the vp test is done in
conjugation with the mr test the
bacterial organisms showing the mr test
positive will give the vp test negative
and the bacterial organisms showing the
mr test negative will give the vp test
positive therefore in general these two
test results are vice versa for the
bacteria
next the citrate utilization test
the principle certain bacteria in
presence of the sodium citrate utilize
the citrate the yield the carbonate and
the bicarbonate as the byproduct this
changes the ph to alkaline from the
initial neutral ph this is the principle
behind the citrate utilization test
the procedure this test is performed in
the test tube with the agar slant
prepared with the simon citrate agar
containing the sodium citrate and the
bromothymol blue as the indicator this
bromothymol blue indicator at neutral ph
appears as the deep forest green
now take the bacterial colony inoculate
into this agar slant incubate for 24 to
48 hours
following incubation if the agar slant
turns to the prussian blue which
indicates the test is positive due to
the changes in the ph 2 alkaline because
of the yield of the carbonate and the
bicarbonate as the byproduct this
bromothymol blue indicator at alkaline
ph appears as the prussian blue the
example the salmonella bacterial
organism positive for the citrate test
in contrast following incubation if
there is no color change which indicates
the test is negative for the citrate
utilization test the example the e coli
bacterial organism this is the procedure
for the citrate utilization test
this is the photograph showing the
positive and the negative test result of
the citrate utilization test
the imvik reactions there are the set of
four biochemical tests they are commonly
employed in the identification of the
members of the family anterobacteria ce
bacteria the four biochemical tests are
the indo-ring test the methyl red test
the vogus prosker test and the citrate
utilization test the letter i is only
for the rhyming purpose the e coli
bacteria gives plus plus minus minus for
the invic reactions the salmonella
bacteria gives minus plus minus plus for
the invic reactions the klebsiella
bacteria gives minus minus plus plus for
the invic reactions so immvic reactions
are employed in the identification of
the members of the family enterobacteria
ce bacteria
next the urease test also referred as
the urea hydrolysis test the principle
certain bacteria produce the enzyme the
urease this enzyme in presence of the
urea capable of hydrolyzing the urea the
yield the ammonia and the carbon dioxide
as the byproduct this byproduct changes
the ph 2 alkaline from the initial
neutral ph this is the principle behind
the urease test the procedure this test
is performed in the test tube with the
agar slant containing the urea and the
phenyl red as the indicator this phenol
red indicator at neutral ph appears as
the orange now take the bacterial colony
inoculate into this agar slant incubate
for 24 to 48 hours
following incubation if the agar slant
turns to the pink which indicates the
test is positive due to the changes in
the ph 2 alkaline because of the yield
of the ammonia and the carbon dioxide as
the byproduct this phenol red indicator
at alkaline ph appears as the pink the
example the staphylococcus bacterial
organism positive for the urease test
in contrast following incubation if
there is no color change which indicates
the test is negative for the urease test
the example the e coli bacterial
organism negative for the urease test
this is the procedure for the urease
test
this is the photograph showing the
positive and the negative test result of
the urease test
next the sugar fermentation test
each bacteria has the ability to ferment
certain sugars and not ferment certain
sugars to find out the sugar
fermentation of the particular bacteria
this test is done
the principle the bacteria in presence
of the certain sugar the sugar may be
glucose or sucrose or lactose or maltose
or galactose or mannose or any other
sugars this bacteria in presence of the
certain sugar ferment the yield the acid
as the byproduct this changes the ph 2
acidic from the initial neutral ph
next this acid along with the androte's
indicator changes to the pink color due
to acidic ph
some bacteria may also releases the
gases along with the acids this is
observed as the bubble formation this is
the principle behind the sugar
fermentation test
the procedure this test is performed in
the broth containing sugar with the
durham's tube inside it the sugar may be
glucose or sucrose or lactose or maltose
or galactose or mannose or any other
sugars that can be added to the broth
for instance this broth is added with
the lactose thereby to check the
bacteria for the lactose fermentation
now take the bacterial colony inoculate
into this broth incubate for 24 to 48
hours
following incubation add the andronte's
indicator to it the development of the
pink color indicates the test is
positive for the lactose fermentation
due to the acid production
sometimes the bubble formation may be
observed in the durham's tube indicates
the gas production the example the e
coli bacterial organism positive for the
lactose fermentation
in contrast following addition of the
androtes indicator if there is no color
change which indicates the test is
negative for the lactose fermentation
the example the salmonella bacterial
organism negative for the lactose
fermentation this is the procedure for
the sugar fermentation test
next the hydrogen sulfide production
test
the principle certain bacteria produce
substance like the hydrogen sulfide this
hydrogen sulfide along with the iron
salts like ferrous sulfate and ferric
ammonium salt to form the ferrous
sulfide as the end product
this is observed as the black
precipitate this is the principle behind
the hydrogen sulfide production test
next the triple sugar iron test also
referred as the tsi test the procedure
this test is performed in the test tube
with the agar slant prepared with the
tsi agar containing the three sugars the
glucose the sucrose and the lactose to
check the bacteria for the sugar
fermentation for these three sugars and
also contain the ferrous sulfate salt to
check the bacteria for the hydrogen
sulfide production and contain the
indicator the phenyl red this phenol red
indicator at neutral ph appears as
orange generally the top slanting
portion of the agar is referred as the
slant and the bottom portion of the agar
is referred as the butt
the three sugars present in the tsi agar
are in different concentration such as
the glucose 0.1 percent the sucrose one
percent and the lactose one percent this
is about the tsi agar now take the
bacterial colony inoculate into this
agar slant incubate for 24 to 48 hours
following incubation the agar slant may
turns to this type of reaction this type
of reaction is observed in the e coli
that is the yellow slant due to acidic
ph at the slant portion and the yellow
butt due to acidic ph at the butt
portion
and the bubble cracks and the
displacement of the agar due to the gas
production
since the e coli ferments all the three
sugars present in the media so a large
amount of acids are produced which turns
the phenol red indicator to yellow both
at the butt portion and at the slant
portion this type of reaction is
observed in the e coli
following incubation the agar slant may
turns to this type of reaction this type
of reaction is observed in the
salmonella that is the red slant due to
alkaline ph at the slant portion and the
yellow butt due to acidic ph at the butt
portion and also we can observe the
presence of the black precipitate due to
hydrogen sulfide production remember the
butt portion comparatively contain more
glucose compared to the slant portion
since the salmonella ferments only
glucose present in the media a small
amount of the acid is produced which
turns the phenol red indicator to yellow
only at the butt portion this type of
reaction is observed in the salmonella
these are some of the reactions observed
in the tsi agar starting from the left
the uninoculated dsi agar the middle the
e coli inoculated dsi agar and the right
the salmonella inoculated dsi agar
this is the photograph showing the
reactions observed in the tsi agar the
left the uninoculated dsi agar the
middle the e coli inoculated dsi agar
and the right the salmonella inoculated
dsi agar
therefore the e coli ferments all the
three sugars present in the media and
turns the phenol red indicator to yellow
both the butt portion and the slant
portion but the salmonella ferments only
glucose present in the media and turns
the phenol red indicator to yellow only
the butt portion
next the gelatin liquefaction test also
referred as the gelatin hydrolysis test
in this experiment the gelatin will be
used before that we will see about the
property of the gelatin the gelatin at
high temperature that is at temperature
above 25 degrees celsius it liquefies in
contrast the gelatin at low temperature
that is at temperature below 15 degrees
celsius it solidifies this is the
property of the
gelatin now we will see about the
principle of this test
certain bacteria produce the enzyme the
gelatin is this is the proteolytic
enzyme this enzyme in presence of the
gelatin capable of breaking down the
gelatin into the individual amino acids
as the end product this liquefies the
gelatin and remain liquefied even at
four degrees celsius that is remain
liquefied even at the chilling
temperature this is the principle behind
the gelatin liquefaction test
the procedure this test is performed in
the test tube prepared with the nutrient
gelatin medium now take the bacterial
colony inoculate into this gelatin
medium incubate for the 48 hours
following incubation if the medium
remains liquefied even at the 4 degrees
celsius indicates the test is positive
due to the liquefaction of the gelatin
the example the staphylococcus aureus
bacterial organism positive for the
gelatin liquefaction test
in contrast following incubation if the
medium remains solidified at the 4
degree celsius indicates the test is
negative due to the gelatin is not
hydrolyzed by the bacteria the example
the e coli bacterial organism negative
for the gelatin liquefaction test this
is the procedure for the gelatin
liquefaction test
this is the photograph showing the
positive and the negative test result of
the gelatin liquefaction test
the schematic illustration of the
different biochemical test is available
as the downloadable link in the below
youtube description in next video
presentation we will see about the
antimicrobial susceptibility test stay
tuned to this youtube channel hope the
lecture is informative and useful
thank you
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