Andrade’s Indicator, also known as Andzed Indicator, is composed of acid fuchsin and alkali. It appears pale yellow to pale straw-colored liquid. It turns pink/rose-red under acidic conditions and yellow/light yellow under alkaline conditions. Its pH transition range is approximately pH 5.0 (pink) to pH 8.0 (yellow). In routine interpretation, it is red near pH 5.5 and yellow near pH 7.5.
Main applications:
① Bacterial carbohydrate fermentation test: for detection of acid production from glucose, lactose, sucrose, mannitol and other sugars or sugar alcohols (e.g., Andrade Peptone Water, BAM M13 carbohydrate broths).
② Medium for urinary bacterial isolation: used in CLED Agar with Andrade's Indicator to differentiate lactose fermenters (pink) from non-fermenters (yellow-green).
③ Teaching and food microbiological testing: used in carbohydrate fermentation tubes specified in standards such as SN/T 0168.
This product is used for microbial carbohydrate metabolism assays. Bacteria capable of fermenting sugars, alcohols and glycosides to produce acid will turn the medium red.
For research use only. Not for clinical diagnosis or other applications.
Procedure (for reference only):
1.Before use, confirm that this product is a light yellow to pale straw-colored liquid. If it is red, add an appropriate amount of sodium hydroxide and let it stand for 24 h until the color meets the requirements before use.
2.After basal peptone water (pH 7.2 ± 0.2) is sterilized and cooled, add 10 mL of indicator per 1 L of basal medium (i.e., 1%).
3.Prepare sugars separately as 5%–10% sterile filtrates, add at a final concentration of 0.5%–1%, and dispense into small tubes (use Durham tubes to check gas production).
4.Incubate at 35–37 ℃ for 18–24 h and observe changes in color and characteristics: turning red or pink indicates acid production; no change to yellow-red indicates no fermentation; bubbles in the inverted tube indicate gas production.
Precautions:
1.This product has not been sterilized. If strict sterility is required, please filter it under aseptic conditions before use.
2.Sufficient decolorization is required: light yellow and transparent is preferable. If it is purple-red or red, the background will be too red and the endpoint will be difficult to distinguish.
3.The pH of the basal medium must be adjusted to 7.2 ± 0.2. After sterilization, add the indicator under aseptic conditions at 50–60 ℃.
4.Do not over-incubate: CLED plates cultured for >24 h may be turned pink overall by dominant fermenting bacteria, masking non-fermenting colonies.
5.Do not mix with BTB, as this may cause color interpretation conflicts: some CLED media contain both bromothymol blue + Andrade. Use the pink halo around local colonies as the criterion for fermentation, and do not judge only by the overall color.
6.After opening the reagent, please use it as soon as possible to prevent affecting subsequent experimental results.
7.For your safety and health, please wear a laboratory coat and disposable gloves during operation.
