Hardy Diagnostics HUGO


Cat. no. K108 D/E Neutralizing Broth, 16x125mm Tube, 10ml 20 tubes/box
Cat. no. U75 D/E Neutralizing Broth, 180ml Wide Mouth Jar, 90ml 12 jars/box
Cat. no. U76 D/E Neutralizing Broth, 1L Polycarbonate Bottle, 750ml 10 bottles/box
Cat. no. U332 D/E Neutralizing Broth, 60ml Polypropylene Bottle, 45ml 25 bottles/box


Hardy Diagnostics D/E Neutralizing Broth is utilized to neutralize antiseptics and disinfectants as well as to detect organisms remaining after treatment. This broth is especially suited for environmental sampling where neutralization of the chemical is important to determining the bactericidal activity.

This product is not intended to be used for the diagnosis of human disease.


D/E Neutralizing Broth, also known as Dey-Engley Neutralizing Broth, is capable of neutralizing a broad spectrum of antiseptic and disinfectant chemicals including quaternary ammonium compounds, phenolics, iodine, chlorine preparations, mercurials, formaldehyde and glutaraldehyde. It can determine the bactericidal capability of disinfectants and therefore is well suited for environmental sampling.

D/E Neutralizing Broth contains various neutralizing agents: lecithin, Tween®, sodium thiosulfate, and sodium bisulfite. Lecithin neutralizes quaternary ammonia compounds while phenolic disinfectants and hexachlorophene are neutralized by Tween®. Together, lecithin and Tween® neutralize ethanol. Sodium thiosulfate neutralizes iodine and chlorine, where as sodium bisulfite neutralizes formaldehyde and gluteraldehyde.

Complete neutralization of disinfectants is vital as disinfectant carryover can cause a false no-growth test result. D/E Neutralizing media effectively neutralizes the inhibitory effects of disinfectant carryover, allowing differentiation between bacteriostasis and the true bactericidal action of disinfectants.

In addition to neutralizing agents, this media contains ingredients that enhance the growth of a wide variety of microorganisms. Pancreatic digest of casein provides the carbon and nitrogen sources. Yeast extract provides vitamins and growth factors required for growth. Dextrose is added as a fermentable carbohydrate source. Bromcresol purple is added to the media as a colormetric indicator to demonstrate the production of acid from dextrose.


Ingredients per liter of deionized water:*

Dextrose 10.0gm
Lecithin 7.0gm
Sodium Thiosulfate 6.0gm
Pancreatic Digest of Casein 5.0gm
Tween® 80 5.0gm
Yeast Extract 2.5gm
Sodium Bisulfite 2.5gm
Sodium Thioglycollate 1.0gm
Monopotassium Phosphate 0.1gm
Bromcresol Purple 0.02gm

Final pH 7.6 +/- 0.3 at 25°C.

* Adjusted and/or supplemented as required to meet performance criteria.


Storage: Upon receipt store at 2-8ºC. away from direct light. Media should not be used if there are any signs of deterioration, discoloration, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat and freezing.



Specimen Collection: Consult listed references for appropriate methods for the collection of specimens from environmental and industrial sources.

Method of Use: Refer to listed references of test protocols and additional procedures using this media. Inoculate the media as desired and incubate with caps loosened, under aerobic conditions at 35ºC. for 24-48 hours.


Colonies of dextrose fermenting microorganisms will cause the media to turn yellow in color.

Consult listed references for information pertaining to colony morphology and biochemical tests required for identification.(1-5)



Standard microbiological supplies and equipment such as loops, other culture media, swabs, applicator sticks, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Bacillus subtilis
ATCC® 6633
A 40-48hr 35°C Aerobic Growth; usually no color change
Escherichia coli
ATCC® 25922
A 40-48hr 35°C Aerobic Growth; yellow color change
Pseudomonas aeruginosa
ATCC® 9027
A 40-48hr 35°C Aerobic Growth; no color change
Salmonella enterica
ATCC® 14028
A 40-48hr 35°C Aerobic Growth; yellow color change
Staphylococcus aureus
ATCC® 6538
A 40-48hr 35°C Aerobic Growth; yellow color change
Additional test organism for Cat. no. U332
Streptococcus mutans
ATCC® 35668
A 40-48hr 35°C Aerobic Growth; yellow color change

User Quality Control


D/E Neutralizing Broth should appear opaque, with an even suspension of particulates, and lavender to purple in color.

B. subtilis growing in D/E Neutralizing Broth E. coli growing in D/E Neutralizing Broth

Bacillus subtilis (ATCC® 6633) growing in D/E Neutralizing Broth (Cat. no. K108). Incubated aerobically for 24 hours at 35ºC. No color change to yellow was indicative as negative for acid production from dextrose.

Escherichia coli (ATCC® 25922) growing in D/E Neutralizing Broth (Cat. no. K108). Incubated aerobically for 24 hours at 35ºC. The yellow color change was indicative as positive for acid production from dextrose.


1. U.S. Food and Drug Administration. Bacteriological Analytical Manual. AOAC, Arlington, VA.

2. American Public Health Association. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

3. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods, APHA, Washington, D.C.

4. American Public Health Association. Standard Methods for the Examination of Water and Wastewater, APHA, Washington, D.C.

5. United States Pharmacopoeia and National Formulary (USP-NF). Rockville, MD: United States Pharmacopeial Convention.

ATCC is a registered trademark of the American Type Culture Collection.
Tween is a registered trademark of ICI Americas, Inc.