Lab Exam 2 – Flashcards

1. It is looking for the presence of proteases

2. A positive test = Liquefied Medium Negative = solid medium.

3. Pseudomonas aeruginosa

1. Phenol Red is a pH indicator and differentiates between  which  

    organisms produce acid vs non-acid and gas vs non-gas by-products  

    of fermentation 

2. Yellow = Acidic Red = No Fermentation taken place Pink = Alkaline due to peptone degradation) Bubble = Gas Present (C02)

3. Lactose, Sucrose, and Glucose

4. Enterococcus faecalis: all 3 yellow tubes with no gas

    E. Coli:  Sucrose > red w/ no gas

               Lactose > yellow w/ gas

               Glucose > yellow w/ gas

1. Tests for the presence of a protease called casease.

2. Positive = clearing / halo in gar

    Negative = no clearing or halo

1. Spirit blue tests for the presence of Lipases
2. Postive = A clearing in the blue agar indicates   Negative = No clearing, all blue.

1. A quadrant streak is when you streak 1 quadrant and then spread it out through all 4 quadrants on a agar plate
2. To promote and demonstrate greater separation of colonies - look for separation
3. Serratia and E. Coli

1. A radiant streak is when you streak across one quadrant, and then creat 3 - 4 additional perpendicular linear streaks from the origin streak

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MaConkey Agar tests for Enterics, and separates them into 2 groups - Lactose fermenters and non lactose fermenters.

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Lactose Fermenters = Pink, red, purple colonies

Non Lactose Fermenter = Tan / Colorless Colonies

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Mannitol Salt Agar tests for Staphylococcus Aureus specifically.

Positive = Yellow colony or halo

Negative = Red or No Growth

Designed to differentiate bacteria on the basis of glucose, sucrose, and lactose fermentation and sulfur reduction.

Phenol Red is the pH indicator and the Iron in the ferrous sulfate is the Hydrogen Sulfide indicator. 

A red slant and yellow butt indicates that the organism ferments glucose but not lactose. 

Inoculated with a glucose only fermenter, acid by-products lower pH and turn medium yellow.

After a few hours since glucose low concentration, it will be exhausted and alakaline reversion takes place, and NH3 production turns the slant more alkaline.

Acidic slant and butt

Yellow Slant and Yellow butt indicates that the organism is able to ferment Glucose and Lactuse and/or Sucrose and turn the medium yellow through out.

red slant = glucose fermenation

yellow slant = glucose and lactose fermentation

Black = Hydrogen Sulfide

Methyl Red tests for mixed acid fermentation and lowers overall pH. 

MR test: Postive = Red Yellow = Negative

Voges Proskauer Tests for organims that ferments glucose  produces acid and then quickly convert it to acetoin and butanediol.

VP test: Red = Positive Copper = Negative

Reactants used were: Methyl Red for MR test and Reagents A & B for VP

It is used to test for the utilization of Citrate as an organisms sole source of Carbon. (Citrate Permease Enzyme)

Positive = Blue

Negative = Green

It tests for the presence of Urease, which is an enzyme that breaks down Urea. 

Pink = Positive for presence of  Urease

Yellow = Negative for absence Urease

classic positive = Proteus vulgaris 

SIM medium tests for 3 things: Sulfur Reduction, indole production, and motility

Sulfur Reduction: results in Hydrogen Sulfide Production

Black = Positive for Hydrogen Sulfide

Yellow = Negative

Indole Production: 

Red Layer: positive for indole production

Clear Layer: negative for indole production

Motility:

If organisms are spaced and cloudy - positive for motility

Differentiates if an organism contains catalase or not, which breaks down Hydrogen Peroxide and results in a fizzing.

All Staphylococcus = Catalse Positive

All Streptococcus = Catalse Negative

They differentiate between some gram positives and their ability to break down RBC's via Hemolysins.

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Alpha Hemolysis = incomplete lysis and results in a green appearance aroudn the colonys and not much clearing.

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Beta Hemolysis = complete lysis of RBC = complete clearing around the growth as a result of complete lysis of RBCs.

An Agglutination test similar to Blood Typing

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It is Staph Aureus Positive ONLY!

Bile Esculin tests for Group D Enterics - Enterococcus 

Black = Positive

No color change = Negative