Protocol
for Urease Test:
Stuart’s
Urea Broth :
Ingredient:
Yeast extract: 0.1 g
Potassium phosphate, monobasic: 9.1 g
Potassium phosphate, dibasic: 9.5 g
Urea: 20 g
Phenol red: 0.01 g
Ø Dissolve all ingredients in 1 liter of distilled
water and filter sterilize (0.45-mm pore size). Distribute 3 ml of prepared
broth per sterile tube (13 x 100 mm). Prepared media will have a yellow-orange
color. Store the prepared broth in the refrigerator at 4 to 8oC
until needed. Do not heat the medium as the urea will decompose.
Procudure:
- Use a heavy inoculum from an 18- to 24-hour pure culture to inoculate the broth. Shake the tube gently to suspend the bacteria. Incubate tubes with loosened caps at 35oC. Observe the broth for a color change at 8, 12, 24, and 48 hours. Urease production is indicated by a bright pink (fuchsia) color throughout the broth.
- Rapidly urease-positive Proteeae (Proteus spp., Morganella morganii, and some Providencia stuartiistrains)
for which this medium is differential, will produce a strong positive reaction
as early as 8 hours, but always within 48 hours of incubation. Delayed-positive
organisms (e.g., Enterobacter)
will not produce a positive reaction due to the high buffering capacity of this
medium.
Urease Test
