Microbiology: Urea Test

The video tutorial explains the urease test, a biochemical test to determine if bacteria can break down urea into ammonia, which raises the pH and changes the color of phenol red indicator to hot pink. This test is clinically relevant for distinguishing between lactose non-fermenting gram-negative bacilli like Salmonella, Shigella, and Proteus, with only Proteus expressing urease and producing ammonia.

What is the primary purpose of the urease test?

• To identify the presence of gram-positive bacteria

• To measure the oxygen consumption of bacteria

• To check if bacteria can break down urea

• To determine if bacteria can ferment lactose

What does the enzyme urease do in the urease test?

• It ferments lactose into lactic acid

• It oxidizes glucose into carbon dioxide

• It converts ammonia into urea

• It breaks down urea into carbon dioxide and ammonia

How does phenol red indicate a change in pH during the urease test?

• It turns green in neutral conditions

• It turns yellow in acidic and hot pink in alkaline conditions

• It remains colorless in alkaline conditions

• It turns blue in acidic conditions

Which bacteria can be distinguished using the urease test?

• Lactobacillus, Clostridium, and Bacteroides

• Staphylococcus, Streptococcus, and Bacillus

• Salmonella, Shigella, and Proteus

• Escherichia coli, Salmonella, and Shigella

What color change indicates the presence of Proteus in the urease test?

• Yellow

• Hot pink

• Green

• Blue