D/E Neutralizing Broth - Dey/Engley Neutralizing Broth | AOAC/USP/ISO Compatible

D/E Neutralizing Broth 

Cat No.: AS-1191

What is D/E Neutralizing Broth?

D/E Neutralizing Broth is a broad-spectrum disinfectant neutralization medium used to recover microorganisms exposed to antiseptics, sanitizers, and preservatives. It is specifically formulated for environmental monitoring, disinfectant validation, and antimicrobial efficacy testing.

Originally developed by Dey and Engley (1970), this medium neutralizes residual disinfectants while preserving the viability of stressed bacteria and fungi.

What Does D/E Neutralizing Broth Neutralize?

This formulation inactivates common disinfectant classes including:

• Quaternary ammonium compounds (QACs)

• Phenolic disinfectants

• Halogens (chlorine, iodine)

• Aldehydes (formaldehyde, glutaraldehyde)

• Mercurials

Neutralization is achieved through:

• Lecithin & Polysorbate 80 – neutralize QACs and phenolics

• Sodium Thiosulfate – neutralizes chlorine and iodine

• Sodium Bisulfite – neutralizes aldehydes

• Sodium Thioglycollate – neutralizes mercurial compounds

Why Use D/E Neutralizing Broth?

D/E Broth is used when accurate microbial recovery is required after exposure to disinfectants. Without neutralization, residual sanitizer activity may suppress growth and produce false-negative results.

It is widely used in:

• Hospital and cleanroom environmental monitoring

• Pharmaceutical disinfectant validation

• Food and dairy sanitation verification

• Cosmetic preservative testing

• Water system microbial control studies

How Does Growth Detection Work?

Because of the high lecithin content, turbidity may not reliably indicate growth.

Instead, growth is detected by:

• Color change (purple to yellow) via bromocresol purple indicator

• Pellicle formation in certain organisms (e.g., Pseudomonas spp.)

Regulatory & Testing Standards

D/E Neutralizing Broth is suitable for use in procedures aligned with:

• AOAC disinfectant testing

• USP <51> Antimicrobial Effectiveness Testing

• USP <61> / <62> Microbial Enumeration

• ISO 14698 Environmental Monitoring

• FDA-BAM methods

Composition (per liter)

• Tryptone – 5.0 g

• Yeast Extract – 2.5 g

• Dextrose – 10.0 g

• Sodium Thioglycollate – 1.0 g

• Sodium Thiosulfate – 6.0 g

• Sodium Bisulfite – 2.5 g

• Lecithin – 7.0 g

• Polysorbate 80 – 5.0 g

• Bromocresol Purple – 0.02 g

Final pH: 7.6 ± 0.2 at 25°C

Preparation Instructions

Suspend 39.02 g in 1 liter of purified water.
Heat with agitation until fully dissolved (do not overheat).
Autoclave at 121°C for 15 minutes.
Cool to 45–50°C before use.

Prepared medium should appear clear to slightly opalescent and purple.

Storage Conditions

Dehydrated medium: Store at 10–30°C in a tightly closed container, protected from moisture and light.
Prepared broth: Store at 15–25°C and use within validated shelf life.

Important Notice

For laboratory and research use only.
Not for human or veterinary consumption.
Validate performance for specific strains beyond standard QC organisms.