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Microbiology Lab Final

Terms in this set (85)

2H2O2 > 2H2O + O2 (Hydrogen Peroxide > Water and Oxygen)
Equation for the reaction of catalase
Obligate aerobes, Facultative anaerobes
Types of bacteria that produce catalase
Bubble
In the catalse test, bacteria that are + cause hydrogen peroxide to do this
Pseudomonas aeruginosa, Escherichia coli, Staph. (aureus & epidermidis)
3 catalase positive bacteria
Dextrose (glucose), lactose, sucrose
3 carboydrates that produce enzymes during fermentation and can be tested in the lab
Acid
Product of carbohydrate fermentation
Phenol Red
Indicator that is sensitive to pH and turns yellow in the presence of acid.
Gas tubes in some phenol red tests that collect a bubble of gas if bacteria in them produce gas upon fermentation of carbohydrates
Durham gas tubes
Triple Sugar Iron (TSI)
Agar that contains dextrose, lactose, sucrose, phenol red for pH, and an iron indicator change in an agar slant.
Hydrogen sulfide
This chemical is present if TSI agar turns black
Hydrogen sulfide is produced as a by-product of aerobic respiration in some bacteria because instead of having O2 as the ultimate electron acceptor, they use sulfur
Why is some TSI agar black?
Stab and Streak
Method used to perform a TSI agar test
Broth/Incubation
Method used to perform carbohydrate fermentation tests
Red = negative, Yellow = positive
Colors that signify positive or negative in a Phenol Red carbohydrate fermentation test
Red= negative sugar fermentation, negative H2S, Yellow= positive sugar fermentation
Black= presence of hydrogen sulfide
Colors and what they signify in the result of a triple sugar iron agar test
Mnemonic: C CUT
1. Carbohydrate fermentation tests
2. Cytochrome Oxidase
3. Urease
4. TSI tests
4 tests frequently used to differentiate Gram negative bacteria.
Hemolysis
Virulence factor of some bacteria that aids in differentiating types of Gram + bacteria on blood agar
Hemolysin
Chemical that can break down red blood cells
Beta-hemolytic
Type of bacteria that make hemolysin
Alpha-hemolytic
Bacteria that do not make hemolysin, but do secrete chemicals that turn red blood cells a green color
Gamma-hemolytic
Bacteria that cause no change in blood agar
Differential
Type of media Hemolysis/blood agar test is
Gram + Staphylococci
Most bacteria are prohibited from growth on Mannitol/Salt agar except this one
Mannitol
Sugar in Mannitol/Salt agar
Yellow
Color Mannitol/Salt agar turns when mannitol is fermented by the bacteria on it
Phenol red
Type of pH indicator in Mannitol/Salt agar
1. Mannitol (carb)
2. NaCl (Sodium chloride/salt)
3. Phenol red pH indicator
3 ingredients in Mannitol/Salt agar
Selective & Differential
type of media Mannitol/Salt agar is
Staphylococcus aureus
Bacteria that is positive (turns agar yellow) in Mannitol/Salt agar test
Bacitracin & Optochin (could also use hemolysis/blood agar)
Test used to differentiate between Streptococcus pyogenes and Strep. pneumoniae
Streptococcus pyogenes
Bacitracin sensitive/ Optochin resistant bacteria
Streptococcus pneumoniae
Bacitracin resistant/ Optochin Sensitive bacteria
Gram +
Eosin Methylene Blue (EMB) agar inhibits growth of this type of bacteria
Dyes
What ingredient in Eosin Methylene Blue (EMB) inhibits the growth of Gram Positive bacteria?
Lactose
Sugar source in EMB agar
Dark
Bacteria that ferment lactose on Eosin Methylene Blue (EMB) agar create colonies that appear ________
clear
Bacteria that do not ferment lactose on EMB agar appear ______
Metallic green
Bacteria that produce a large amount of acid appear _________ on EMB agar.
E. coli
Bacteria that appears metallic green in color on EMB agar due to acid production
Selective and Differential
Type of media Eosin Methylene Blue (EMB) agar is
Their only Carbon source
The Citrate test is used to detect bacteria that use citrate for this reason
Bromothymol blue
pH indicator used in citrate test
Green
Color seen in citrate test when pH up to 7.5
Blue
Color seen in citrate test when pH is higher than 7.6
Small amount
How much blue color is necessary to indicate that a citrate test is positive?
Gram Negative Enterics
The Methyl Red/Voges-Proskauer Test differentiates between these types of bacteria
Mixed acids
Causes Methyl Red to turn red
Peptone, glucose, Phosphate buffer
Contents of MRVP broth
Red
Color Voges-Proskaeur test turns when positive
Acetoin & 2,3 butandiol
2 products detected in the Voges-Proskaeur Test
Cytochrome Oxidase
Enzyme present if the paper in a Cytochrome oxidase test turns purple/blue
Pseudomonas aeruginosa
Example bacteria that is Cytochrome oxidase positive
Iodine
Chemical that causes starch to turn brown-black if present in Amylase test
Clear around colonies
How amylase positive bacteria appear on Amylase positive test result
Breaks down urea to ammonia and CO2
Purpose of urease enzyme
Pink
Color urease agar turns when urease is present
Alkaline pH of ammonia
What causes the pink color in urease agar?
Stab and Streak
Method used to perform urease test
Lactose, sucrose, dextrose tests. Middle is negative.
What type of tests and which tube(s) has/have negative result?
Triple Sugar Iron (TSI) test, Hydrogen sulfide, yellow = +
(agar inside tubes) What test? What causes one tube to turn black? What color is positive?
Alpha hemolysis, E. coli or Strep. Pneumoniae
What type of reaction? Possible bacteria this could be?
Beta hemolysis, Streptococcus pyogenes
What type of reaction? Possible bacteria this could be?
Gamma hemolysis, Streptococcus lactis
Mannitol Salt agar, Yellow = +, Staphylococcus aureas = +
Type of test? Color that = positive result? Example positive
Simmons Citrate, B = +
Type of test? Which tube is +?
Red tube =+. Acids.
Methyl Red test. Which one is positive? For what is it positive?
Red tube = +. Acetoin & 2,3 butandiol
Voges-Proskaeur test. Which one is positive? For what is it positive?
Cytochrome Oxidase Test. B is +.
Type of test? What is positive?
Amylase Test. Clear + positive.
Type of test? What indicates a positive result?
Urease test. Right tube (Pink) = +.
Type of test? Which tube is +?
1. Prepare smear/heat fix 2. Cover with crystal violet (1 minute), rinse (distilled water) 3. Iodine mordant for 1 minute, rinse 4. Gram decolorizer (aprox 5-10 seconds), rinse 5. Gram safranin (30 sec), rinse and dry.
5 Steps of a Gram stain
1. Divide plate into thirds 2. Obtain swab of bacteria 3. Streak bacteria in zig zag in section one. 3. Drag from section one and zig zag in section two at 90 degree angle 4. Drag from section two and zig zag in section three at 90 degree angle from section 2.
4 Steps of Streak plate
Obtain individual colonies of bacteria
Goal of a streak plate
Obtain an entire yard of bacteria
Goal of a spread plate
1. Use swab to fill 3/4 of plate 2. Turn plate 1/4 turn, turn swab, repeat fill 3. Turn plate another 1/4 turn, turn swab, repeat fill
Steps of making a spread plate
a key for the identification of organisms based on a series of choices between alternative characteristics
Define Dichotomous key
AMC BOB
1. Amylase
2. Mannitol Salt
3. Catalase
4. Bacitracin
5. Optochin
6. Blood hemolysis
6 Tests commonly run on Gram positive bacteria
E TV SLUMS
1. EMB (Eosin Methylene Blue)
2. TSI
3. VP
4. Sucrose
5. Lactose
6. Urease
7. Methyl Red
8. Simmons Citrate
8 Tests commonly run on Gram negative bacteria
Pseudomonas aeruginosa
Oxidase positive bacteria example
E. coli
Oxidase negative bacteria example
Enzyme that is an electron carrier in the electron transport chain. Present in bacteria that utilize oxygen.
Cytochrome oxidase
Kovak's reagent
Reagent for cytochrome oxidase test
Hydrogen peroxide
Reagent for catalase test
Iodine
Reagent for amylase test
Formation of ammonia when bacteria ferments citrate
What causes that bromothymol blue to turn blue in a citrate test?
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