|
Principle
- Dey-Engley Neutralizing broth is formulated as per the procedure described by Engley and Dey (1970). Media consists of Tryptone, yeast extract, dextrose, sodium thioglycollate, sodium thiosulphate, sodium bisulphite, Lecithin, polysorbate 80, and Bromocresol purple.
- Tryptone and yeast extract provide nitrogen and carbon source, vitamins, and other essential nutrients like vitamins and cofactors. Dextrose is an energy source or carbon source.
- Sodium thioglycollate, sodium thiosulphate, sodium bisulphite, and lecithin, act as neutralizing substances for almost all the active products used as antiseptics and disinfectants in commercial products.
- Sodium thioglycollate neutralizes mercurials; sodium thiosulfate neutralizes iodine and chlorine and Sodium bisulfite neutralizes aldehydes. While lecithin neutralizes quaternary ammonium compounds.
- Polysorbate 80 is used as a non-ionic surface-active agent, which neutralizes substituted phenolics compounds. Bromocresol purple is a pH indicator dye. In the medium, the lecithin is used in high concentration for the neutralization of chemicals the media become a bit hazy and turbidity cannot be measured by spectrophotometer.
- Consequently, bromocresol purple and dextrose are added to the medium. The organisms that ferment dextrose will turn the medium from purple to yellow and the growth of Pseudomonas species, which do not ferment dextrose, can be detected by the formation of a pellicle on the surface of the broth.
|
