Microbial Identification Tests: Urea Broth, Gelatin Hydrolysis, EMB, MSA, and MacConkey Agar

Urea Broth tests for

Urease

Urea Broth substrate

Urea

Urea Broth product

Ammonia

Urea Broth positive result

Pink

Urea Broth type

Differential

Nutrient Gelatin tests for

Gelatin Hydrolysis

Nutrient Gelatin substrate

Gelatin

Nutrient Gelatin product

Amino acids

Nutrient Gelatin positive result

Turns liquid

Nutrient Gelatin type

Selective

Eosin Methylene Blue (EMB) tests for

Coliforms (Gram-negative rods)

Eosin Methylene Blue (EMB) substrate

Lactose

Eosin Methylene Blue (EMB) product

Acid

Eosin Methylene Blue (EMB) positive result

Purple, green, or black colonies

Eosin Methylene Blue (EMB) type

Selective & Differential

Mannitol Salt Agar (MSA) tests for

Staphylococcus (Halophiles)

Mannitol Salt Agar (MSA) substrate

Salt / Mannitol

Mannitol Salt Agar (MSA) product

Acid

Mannitol Salt Agar (MSA) positive result

Yellow

Mannitol Salt Agar (MSA) type

Selective & Differential

MacConkey Agar tests for

Coliforms

MacConkey Agar substrate

Lactose

MacConkey Agar product

Acid

MacConkey Agar positive result

Red colonies

MacConkey Agar type

Selective & Differential

Phenol Red Broth tests for?

Carbohydrate fermentation

• Production of an acid or a gas through fermentation

Phenol Red Broth substrate?

Sugars (Glucose, Lactose, Sucrose)

Phenol Red Broth Product?

Pyruvic acid

Phenol Red Broth Positive result?

Yellow

Is Phenol Red Broth Selective or differential?

Differential

MR (MR-VP) broth tests for?

Acids produced in glucose fermentation

• Whether or not it uses glucose to produce an acid/acetoin

MR-VP broth Substrates?

Glucose

MR (MR-VP) broth product?

Acid

VP (MR-VP) broth product?

Acetoin

MR-VP broth positive result?

red

MR (MR-VP) broth reagents?

Methyl red

VP (MR-VP) broth reagents?

Barritt’s A&B

is MR-VP broth selective or differential?

Differential

VP (MR-VP) broth tests for?

Acetonin production from glucose

Sulfide Indole Motility product

Sulfide (H2S)

Sulfide Indole Motility positive result

Turbidity, motile

Sulfide Indole Motility selective or differential?

Differential

Sulfide Indole Motility tests for?

Tryptophan breakdown

Sulfide Indole Motility Substrate

Tryptophan

Sulfide Indole Motility Product

Indole

Sulfide Indole Motility positive result

red

Sulfide Indole Motility reagent

Kovac’s

Sulfide Indole Motility tests for?

Sulfide

Sulfide Indole Motility substrate?

Cystine

Sulfide Indole Motility Product?

Sulfide (H2S)

Sulfide Indole Motility positive result?

Black

O-F glucose tests for?

Oxidation or fermentation

O-F glucose substrate?

Glucose

O-F glucose product?

Acid

O-F glucose positive result?

Yellow

O-F glucose selective or differential?

differential

Triple Sugar Iron (TSI) tests for?

Sugar fermentation and Sulfide

Triple Sugar Iron (TSI) substrate?

Sugars and cystine

Triple Sugar Iron (TSI) product?

Acid and Sulfide (H2S)

Triple Sugar Iron (TSI) positive result when testing for sulfide?

Black

Triple Sugar Iron (TSI) positive result when testing for sugar fermentation?

Yellow

• The butt and the top of the slant are analyzed, A standing for yellow and K standing for red

• Ex. K/A = fermentation of glucose only, A/A = fermentation of glucose and 1 other sugar, K/K = no sugar fermentation

Triple Sugar Iron (TSI) selective or differential?

Differential

Simmon’s Citrate Agar tests for?

Citrate utilization

Simmon’s Citrate Agar substrate?

Citrate

Simmon’s Citrate Agar product?

Ammonia NH4

Simmon’s Citrate Agar positive result?

Blue

Simmon’s Citrate Agar selective or differential?

Differential

Blood Agar tests for?

Hemolysis (bursting of RBCs)

What does hemolysis look like in alpha cells?

Greenish colonies

What does hemolysis look like in beta cells?

Grey/white colonies, zone of clearing

What does hemolysis look like in gamma cells?

No hemolysis

Blood Agar substrate?

Blood cells

Blood Agar selective or differential?

selective

Starch Agar tests for?

Starch hydrolysis

Starch Agar substrate?

Starch

Starch Agar product?

Simple sugar

Starch Agar positive result?

Halo

Starch Agar reagent?

Iodine

Starch Agar differential or selective?

Differential

TSA Catalase tests for?

Catalase

TSA Catalase substrate?

Lactose

TSA Catalase reagent?

H2O2

TSA Catalase product?

Oxygen

TSA Catalase positive result?

Bubbles

TSA Catalase reagents?

H2O2

TSA Catalase selective or differential?

Differential

TSA Oxidase tests for?

Oxidase

TSA Oxidase substrate?

TMPD

TSA Oxidase product?

Reduced cytochrome C

TSA Oxidase positive result?

Purple

TSA Oxidase reagents?

TMPD

TSA Oxidase selective or differential?

Differential