Triple Sugar Iron Slants

application:

Triple Sugar Iron Slants

medium:

glucose

sucrose

lactose

animal proteins (for carbon and nitrogen)

ferrous sulfate (oxidized sulfur)

sodium thiosulfate (oxidized sulfur)

phenol red

Triple Sugar Iron Slants

differential:

shows differences between fermentation abilities and products

Triple Sugar Iron Slants

results:

yellow slant/yellow butt – glucose and lactose fermentation with acid accumulation in butt

red slant/yellow butt – glucose fermentation with acid production, proteins catabolized aerobically (in slant) with alkaline products (created reversion to red)

red slant/red butt – no fermentation, peptone catabolized aerobically and anerobically in slant and butt

red slant/no change in butt – no fermentation, peptone catabolize aerobically

no change in slant/no change in butt – organism growing slowly or not at all

black precipitate in agar – sulfur reduction (acidic even if yellow color is obscured by black precipitate)

cracks in or lifting of agar – gas production

MacConkey Agar Plates

application:

isolate and differentiate Gram-negative organisms that can ferment lactose

MacConkey Agar Plates

medium:

lactose

bile salts

neutral red

crystal violet

MacConkey Agar Plates

selective:

diffential:

selective:

crystal violet inhibits growth of Gram-positive bacteria

diffential:

neutral red dye is colorless above a pH of 6.8 and red below 6.8

MacConkey Agar Plates

positive test:

growth indicates Gram-negative bacteria

red coloration – lactose fermentation

normal coloration – non lactose fermenting bacteria

Eosin Methylene Blue Plates

application:

used for isolation of fecal coliforms

Eosin Methylene Blue Plates

medium:

peptone (carbon, nitrogen, other nutritional components)

lactose

sucrose

eosin

methylene blue

Eosin Methylene Blue Plates

selective:

inhibits growth of Gram-positive organisms

Eosin Methylene Blue Plates

differential:

coloration of colonies reflects aggressivness of lactose fermentation

Eosin Methylene Blue Plates

positive test:

growth indicates a Gram-negative organism

dark purple or black growth – vigorous lactose fermenters (green metallic sheen usually = E.coli)

pink to dark purple growth – less aggressive lactose fermenters

no color change or color of medium – non fermenters or sucrose fermenters

4 symbols

1 - slant K-alkaline, A-acidic

2 - butt- K-alkaline, A-acidic

3 - H2S production, + or -

4 - gas production, + or -