Question

Typically, urea broth is filter-sterilized because autoclaving breaks down the urea. However, even unsterilized broth rarely produces false-positive results. Why do you think this is true?

Answer 1

Urea broth is typically filter-sterilized to avoid breaking down the urea. However, unsterilized broth rarely produces false-positive results because the presence of urease-producing bacteria is necessary for a positive test result.

Step-by-step explanation:

Urea broth is typically filter-sterilized because autoclaving breaks down the urea. However, even unsterilized broth rarely produces false-positive results. This is because the urease enzyme produced by bacteria hydrolyzes the urea in the broth, resulting in the release of ammonia. The increase in ammonia raises the pH of the broth, which is detected by a pH indicator. Even without sterilization, the presence of urease-producing bacteria is necessary for a positive test result. Therefore, unsterilized broth rarely produces false-positive results.

Answer 2

When organisms use urea, ammonia is generated during incubation, which makes the reaction of these media alkaline

Step-by-step explanation:

Urea broth preparation:

Suspend 3.87 grams of the medium in 100 ml of distilled water without heating. When the powder dissolves, sterilize by filtration. Dispense quantities of 0.5 to 2 ml in small sterile tubes. Larger volumes may be used but the reactions will be slower. Do not sterilize in autoclave.

Do not boil the medium.

If no filter is available, the medium can be sterilized at 100-110 ° C for 10 minutes. If the medium is prepared and inoculated immediately, it provides good results without sterilization.