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Microbiology Lab flowchart...

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Gram+: Will be purple in color and tells us that the bacteria has a thick peptidoglycan layer.

Gram-Stain: Will show what the cell wall of the bacteria is made of.

Catalase test: This will tell us which bacteria can and can't ferment lactose from the Gram+ bacteria.

NaCl Tolerance test: Selects for bacteria that can tolerate high NaCl concentration.

Bacteria that can tolerate the NaCl: This is the Staph bacteria

MSA: Can ferment mannitol which changes the pH of the agar.

A negative test will produce no color but will still grow on the plate.

Staphylococcus aureus

A positive test will show growth and turn the medium red.

Staphylococcus epidermidis

EMB: Used to differentiate between lactose fermenters and non-fermenters of gram- bacteria.

Negative Catalase testtest: mean that the will appear dark purple Positive Fermenters bacteria cannot ferment lactose. These with a greenish sheen organisms will not bubble when you drop hydrogen peroxide on them.

Positive Catalase test mean that the bacteria can ferment lactose. These organisms will produce bubbles when you drop hydrogen peroxide on them.

NaCl Tolerance test: Selects for bacteria that can tolerate high NaCl concentration.

Gram-: Has a thin peptidoglycan layer which does not allow crystal violet stain to stay within the cell. Will be pink

Negative test: Will result in colorless colonies or may appear the same color of the agar.

Citrate test: Selects for and differentiates bacteria that can use citrate as a sole carbon source, only if there are no other carb. sources available.

Citrate test: Selects for and differentiates bacteria that can use citrate as a sole carbon source, only if there are no other carb. sources available.

Bacteria that cannot tolerate the NaCl: this is the Strep Positive test: Alkaline end produces will result. The medium will turn deep blue

Negative test: No growth will be seen.

Positive test: Alkaline end produces will result. The medium will turn deep blue

Negative test: No growth will be seen.

Blood Agar test: this will show the hemolytic activity of the bacteria, which is the breakdown of red blood cells.

Beta hemolysis: These bacteria will completely utilize the hemoglobin from the red blood cells using hemolysis.

Streptococcus pyogenes

Alpha hemolysis: The incomplete hemolysis of red blood cells. Will leave green halo around colony.

Streptococcus pneumoniae

TSI: Differentiates bacteria based on its ability to ferment glucose, lactose, to produce gas form fermentation process, and or sucrose and ability to reduce sulfur to hydrogen sulfide

No carbs fermented: Red slant/ red butt

Yersinia enterocoliti

Fermentation of glucose, lactose, and/or sucrose: Yellow slant/ yellow butt

Escherichia coli

TSI: Differentiates bacteria based on its ability to ferment glucose, lactose, to produce gas form fermentation process, and or sucrose and ability to reduce sulfur to hydrogen sulfide

Glucose only: Red slant and yellow butt.

Salmonella enterica

Fermentation of glucose, lactose, and/or sucrose: Yellow slant/ yellow butt

Klebsiella pneumoniae...