Midterm Lab review Part 2

What is SBA used for?

• Enriched media which has been supplemented with special nutrients (blood cells)

• Nonselective media: do not have antimicrobial substances, supports the growth of many microorganisms

• Differential media: detection of different types of hemolysis

  • Uses metabolic differences to distinguish microorganisms

  • Hemolytic patterns

What does CNA select for?

Selective for Gram-positive organisms and inhibits gram-negative organisms

What does EMB agar select for?

Selective for Gram-negative organisms and inhibits gram-positive organisms. Differentiates lactose fermentation.

What color is E.coli on EMB?

Green

EMB Agar - green

Strong lactose fermenter; E.coli

EMB Agar - Blue Black

Klebsiella, Lactose fermenter

What color is Klebsiella on EMB?

Blue-black

What color are non-lactose fermenters on EMB?

Colorless

EMB Agar - Colorless

Shigella and Salmonella, Non-lactose fermenters

What does MacConkey agar select for?

Gram-negative rods

What color are lactose fermenters on MAC?

Red/Pink

What color are non-lactose fermenters on MAC?

Colorless

What test differentiates Staph from Strep?

Catalase

What does a positive catalase test look like?

Bubbles

What does a negative catalase test look like?

No bubbles

What does a positive coagulase test indicate?

Clot formation

What does a negative coagulase test indicate?

Liquid

What does a positive CAMP test look like?

Arrowhead

What does a negative CAMP test look like?

No enhanced hemolysis

What does PYR positive indicate?

Pink color

What does PYR negative indicate?

No color

What does hippurate positive indicate?

Purple color

What does huppurate negative indicate?

No color change

What does 6.5% NaCl positive indiciate?

Growth (cloudy/yellow)

What does 6.5% NaCl negative indicate?

No growth

What does bile solubility positive indiciate?

Colony dissolves

What does the bile solubility negative indicate?

Colony remains

What does bile esculin positive indicate?

Black color

What does bile esculin negative indicate?

No color change

What does motility positive look like?

Diffuse growth

What does motility negative look like?

Growth only at stab line

What does DNase positive indicate?

Clear zone

What does DNase negative indicate?

Green

What does ALA positive indicate?

Red fluorescence

What does ALA negative indicate?

Blue/no fluorescence

What does indole positive indicate?

Blue

What does indole negative indicate?

Yellow

What does MR positive indicate?

Red

What does VP Positive?

Pink ring

What does citrate positive indicate?

Blue

What does citrate negative indicate?

Green

What does urease positive indicate?

Pink

What does urease negative indicate?

Yellow

What does lysine positive indicate?

Purple

What does lysine negative indicate?

Yellow

Novobiocin Disk susceptible

Staphylococci Epidermidis

Novobiocin Disk resistant

Staphylococci Saprophyticus

Bacitracin Disk susceptible

Micrococcus sp.

Streptococcaceae Pyogenes GAS

Bacitracin Disk resistant

Staphylococci Epidermidis

Streptococcaceae Agalactiae GBS

CAMP Test

• On SBA

• S. aureus, middle

• Streak "test" organism perpendicular

• CO2 incubator

PYR Positive

Pink on spot paper

PYR Negative

No color on spot paper

Hippurate Hydrolysis

• Detects enzyme hippuricase

• Two methods of detection-Sodium benzoate

  • Ferric choride-Glycine

  • Ninhydrin reagent

PYR

GAS & E. faecalis produce an enzyme which hydrolyzes PYR

6.5% NaCl

Salt Tolerance Test-Some include pH indicator

Bile Solubility

• Bile salts accelerate autolysis in S. pneumo

• Sodium desoxycholate Reagent

Bile Solubility Positive

• Colony dissolves

• S. pneumo

Bile Solubility Negative

• Colony remains

• S. pneumo

Motility Medium

• Semi-solid medium

• W/o TTC indicator

Motility Medium Positive

Hazing past inoculation stab

Motility Medium Negative

Growth in stab, defined border

DNAse Negative

DNA-methyl green complexes remains green

DNAse Positive

Nucleotide-methyl green complexes are colorless

DNAse

• Enzyme that degrades DNA into nucleotide subunits

• DNA methyl green agar

• Streak zig zag onto agar plate or slant (Do NOT stab)

(ALA) Porphyrin test positive

An orange/reddish color (doesn't need X)

(ALA) Porphyrin test negative

No color (may appear blue due to the light) (needs X)

(ALA) Porphyrin test

• Negative: Needs X (can't convert)

• Positive: ALA (Aminolevulinic Acid) to porphobilinogen to porphyrins to hemin

• Interpretation

  • Observe under UV light.

  • A red fluorescence is positive (doesn't need X).

  • A bluish fluorescence is negative (needs X).

Indole

test detects enzyme tryptophanase

Indole Positive

blue spot on paper

Indole Negative

yellow on spot paper

MR/VP

determines the pathway glucose is fermented

MR

Mixed Acid Pathway

MR Positive

tube turns red after MR reagent

MR Negative

tube remains colorless after MR reagent

VP Positive

Pink ring after alpha-naphthol (VP reagent A) and 40% KOH (VP reagent B)

VP Negative

no pink color on top of tube after alpha-naphthol (VP reagent A) and 40% KOH (VP reagent B)

Citrate

• Carbon source

• Bromothymol Blue-Blue is positive

Citrate positive

tube changes from green to blue

Citrate negative

tube remains green

TSI Tube

• Glucose in butt

• Lactose & Sucrose in slant

• Ferrous sulfate Indicator-Phenol Red Indicator-Gas production

TSI Tube K/K

Negative for all sugars, Red on slant and butt

TSI Tube A/A

L+/or S+/ Glucose + Yellow on slant and butt

TSI Tube K/A

L and S negative / Glucose + Red on slant and yellow on butt

TSI Tube Black

H2S positive

Phenylalanine-Phenylalanine Deaminase

Dark green positive

Phenylalanine-Phenylalanine Deaminase positive

after ferric chloride reagent slant turns green

Phenylalanine-Phenylalanine Deaminase negative

after ferric chloride reagent slant has no color change

Urease

• Tests for the enzyme urease

• Urea in agar to Ammonia

• Medium becomes alkaline

• As Ammonia is produced

• pH indictor = Phenol red

Urease Positive

Tube turns pink

Urease Negative

Tube remains yellow

Lysine positive

Broth turns purple

Lysine Negative

Broth remains yellow/no color change