Dey-Engley Neutralizing HiVeg™ Broth

Principle and Interpretation

These media are prepared by using HiVeg hydrolysate in place of Casein enzymic hydrolysate which are free from BSE/TSE risks. Dey-Engley Neutralizing HiVeg media are modification of the media formulated as per the procedure described by Engley and Dey (1). The Dey-Engley Neutralizing HiVeg media neutralizes a broad spectrum of antiseptics and disinfectants including quaternary ammonium compounds, phenolics, iodine and chlorine preparations, mercurials, formaldehyde and glutaraldehyde. Sodium thioglycollate, sodium thiosulphate, sodium bisulphite, soya lecithin and polysorbate 80 act as neutralizing components. HiVeg hydrolysate, yeast extract and dextrose provide carbon, nitrogen and other essential factors for enhanced growth.

For testing disinfectants, prepare two sets of test tubes, one containing 9 ml Dey-Engley Neutralizing HiVeg Broth (MV1062) and other with 9 ml Dey-Engley Neutralizing HiVeg Broth Base (MV187). Add 1 ml of disinfectant under test. Mix well and allow it to stand for 15 minutes. Inoculate 0.1 ml of 1:100,000 dilution of overnight broth cultures and incubate at 37°C for 48 hours. Growth is indicated by a colour change from purple to yellow or pellicle formation. Growth in Neutralizing HiVeg Broth and no growth in Neutralizing HiVeg Broth Base indicates neutralization of disinfectant. To check bactericidal activity, both broth tubes are inoculated on D/E Neutralizing HiVeg Agar (MV186). Positive growth from negative tubes of Neutralizing HiVeg Broth Base indicates bacteriostatic substance while negative growth indicates a bactericidal disinfectant. All positive tubes should show growth on Dey-Engley Neutralizing HiVeg Agar. The control disinfectants used in test procedure are 2% chlorine, 2% formaldehyde, 1% glutaraldehyde, 2% iodine, 2% phenol, 1/750 quaternary ammonium compounds, 1/1000 mercurials etc.