MICROBIO LAB EX. 7-8

Blood agar

Non-inhibitory, non-selective

Blood agar

uses sheeps blood

sheeps blood

provides a rich medium for bacterial growth

Blood agar

5% defibrinated sheep’s blood

Alpha Hemolysis

indistinct zone of partially lysed red cells, (green or brownish discoloration)

Beta Hemolysis

a clear zone of complete lysis of red cells

Gamma Hemolysis

Non hemolytic, no change in red cells

Beta toxin

causes/produces alpha hemolysis

Alpha toxin

causes/produces beta hemolysis

Nutrient broth/agar

Non-selective, all purpose

Nutrient broth/agar

commonly used in the laboratory as a medium for stock bacterial cultures

Eosin Methylene Blue (EMB)

Selective/Differential

MacConkey’s Agar (MAC)

Selective/Differential

Mannitol Salt Agar (MSA)

Selective/Differential

Mannitol Salt Agar (MSA)

used as a media for Staphylococcus

Mannitol Salt Agar (MSA)

fermenters will cause a yellow color around the colony

Eosin Methylene Blue (EMB)

used to enrich for and differentiate (enteric) gram negative organisms

MacConkey’s Agar (MAC)

used to enrich for and differentiate (enteric) gram negative organisms

MacConkey’s Agar (MAC)

fermentors are dark pink ( with a precipitate visible)

Eosin Methylene Blue (EMB)

fermenters will create a dark green metallic sheen

E. coli

lactose fermenter

Eosin Methylene Blue (EMB)

substrate: lactose

Eosin Methylene Blue (EMB)

inhibitor: eosin Y + methylene blue

Mannitol Salt Agar (MSA)

inhibitor: salt

Mannitol Salt Agar (MSA)

substrate: mannitol

Mannitol Salt Agar (MSA)

pH indicator: phenol red

MacConkey’s Agar (MAC)

inhibitor: crystal violet & bile salts

MacConkey’s Agar (MAC)

pH indicator: neutral red

• acid= pink to red

• alkaline= yellow/colorless

Phenol Red Tubes

Indicator:

• acid= yellow

• alkaline= red

Triple Sugar Iron (TSI)

contains glucose, lactose, sucrose

Triple Sugar Iron (TSI)

substrate: triple sugar

• slant= lactose & sucrose

• butt= glucose

Triple Sugar Iron (TSI)

pH indicator: phenol red

• acid= yellow

• alkaline= red

Salmonella Shigella Agar (SSA)

inhibitor: bile salts, brilliant green dye

Salmonella Shigella Agar (SSA)

pH indicator: neutral red

• acid= pink to red

• alkaline= yellow/colorless

Sulfur Indole Motility (SIM)

differential test

Indole

Kovac’s reagent is added and reacts

Simmon Citrate Agar (SCA)

pH indicator: bromthymol blue

• green= acid

• prussian blue= alkaline

Sheep, rabbit, human

viable sources of blood for blood agar

Methyl Red Test

detects acid production from glucose fermentation

Methyl Red Test

pH indicator: methyl red

• acid= red

• alkaline= yellow

MacConkey’s Agar (MAC)

fermenters will create pink to red colonies

Salmonella Shigella Agar (SSA)

salmonella forms colorless spherical colony with black precipitate at the center “fish eye colony”

Salmonella Shigella Agar (SSA)

Shigella only colorless colony

Triple Sugar Iron (TSI)

E. coli: whole tube yellow, gas at butt

(can ferment all 3 sugars)

Triple Sugar Iron (TSI)

Shigella: yellow butt, red slant

(ferments glucose only)

Triple Sugar Iron (TSI)

Salmonella: black

TSI Tubes, Methyl Red- Voges Proskauer

Tests that use phenol red as pH indicator