Triple Sugar Iron Agar
a rich medium designed to differentiate bacteria on the basis of glucose fermentation, lactose fermentation, sucrose fermentation, and sulfur reduction
What does triple sugar iron agar contain?
animal proteins as sources of carbon and nitrogen,
ferrous sulfate and sodium thiosulfate as sources of oxidized sulfur
______ is the pH indicator and _____ is the hydrogen sulfide indicator
How is triple sugar iron agar prepared?
in a shallow agar slant with a deep butt. it is inoculated by a stab in the agar butt followed by a fishtail streak of the slant
Incubation period for triple sugar iron agar
18-24 hrs for carbohydrate fermentation
48 hrs for hydrogen sulfide reactions
TSIA is inoculated with a glucose only fermenter. As the glucose diminishes, the organisms located in the aerobic region (slant) will break down amino acids, producing NH3 and raising the pH. This process takes 18-24 hours and only occurs in the slant because of the anaerobic conditions in the butt.
TSIA slant with a red slant and yellow butt indicates what?
that the organism ferments glucose but not lactose
Organisms that ferment both glucose and lactose/sucrose do what to the medium?
turn it yellow throughout
_______ produced by fermentation of any of the carbs will appear as fissures in the medium or will lift the agar off the bottom of the tube
Why is hydrogen sulfide produced?
by the reduction of thiosulfate in the medium or by the breakdown of cysteine in the peptone
black precipitate in the medium is an indication of what?
sulfur reduction and fermentation
red slant indicates what?
yellow slant indicates what?
red - glucose fermentation
yellow - glucose and lactose fermentation