Millipore™ Dey-Engley Neutralizing Agar NutriSelect® Plus, powder, suitable for microbiology, 500g

Dey-Engley Neutralizing Agar (D/E Agar) is a non-selective solid culture medium specifically formulated for the neutralization of residual disinfectants and antiseptics during microbiological testing. Supplied as a powdered medium under the NutriSelect® Plus quality grade, it supports the recovery and enumeration of bacteria that may otherwise be inhibited by antimicrobial residues.

This agar medium is widely used in environmental monitoring, disinfectant efficacy testing, pharmaceutical microbiology, and food & beverage hygiene testing, where accurate assessment of bactericidal activity is critical.

Intended Use

• For microbiological analysis and quality control
• Used in disinfectant and antiseptic efficacy testing
• Suitable for:
  • Environmental monitoring programs
  • Pharmaceutical and cleanroom microbiology
  • Food and beverage hygiene testing
  • Surface and equipment microbiological assessment
• Designed for the recovery of bacteria exposed to disinfectants

Principle of the Medium

Dey-Engley Neutralizing Agar combines a nutrient-rich agar base with multiple chemical neutralizers capable of inactivating a broad spectrum of disinfectants. This ensures that residual antimicrobial agents do not suppress microbial growth during incubation.

Microbial growth is visualized by:

• Colony formation on the agar surface
• Color change of the medium from purple to yellow due to dextrose fermentation
• Surface growth characteristics that aid organism recovery and observation

Disinfectants Neutralized

The formulation effectively neutralizes:

• Quaternary ammonium compounds
• Phenolic disinfectants
• Chlorine and iodine compounds
• Mercurials
• Aldehydes (formaldehyde, glutaraldehyde)
• Peracetic acid (PAA)

Neutralizing agents include:

• Sodium thiosulfate
• Sodium thioglycollate
• Sodium bisulfite
• Lecithin
• Polysorbate 80

Microorganism Suitability

Non-selective medium suitable for recovery of:

• Staphylococcus spp.
• Pseudomonas spp.
• Escherichia coli
• Salmonella spp.
• Other aerobic bacteria exposed to disinfectants

Applications

• Disinfectant validation and bactericidal testing
• Environmental and surface microbiological monitoring
• Pharmaceutical production area testing
• Cleanroom hygiene verification
• Food and beverage sanitation monitoring
• Contact plate and surface sampling workflows

Quality Grade

• NutriSelect® Plus
  • Standard quality control level
  • Designed for routine laboratory and industrial microbiology
  • Cost-effective alternative to premium regulatory grades

Product Specifications

Composition (g/L)

• Casein enzymic hydrolysate – 5.0
• Yeast extract – 2.5
• Dextrose – 10.0
• Agar – 15.0
• Sodium thiosulfate – 6.0
• Sodium thioglycollate – 1.0
• Sodium bisulfite – 2.5
• Lecithin – 7.0
• Polysorbate 80 – 5.0
• Bromocresol purple – 0.02

Preparation & Directions for Use

1. Suspend 54.02 g of powder in 1000 mL of distilled water
2. Heat with frequent agitation and bring to boil to dissolve completely
3. Sterilize by autoclaving at 121 °C for 15 minutes (15 psi)
4. Mix well and dispense into sterile Petri dishes or containers as required

Prepared medium appears purple before inoculation. 

Key Advantages

• Broad-spectrum disinfectant neutralization
• Solid agar format for colony isolation and enumeration
• Supports recovery of disinfectant-stressed bacteria
• Reliable visual growth indication
• Ideal for pharmaceutical and environmental microbiology
• Cost-efficient powdered format

Dey-Engley Neutralizing Agar (NutriSelect® Plus) is a reliable, non-selective solid culture medium for microbiological testing in environments where disinfectants are routinely used. Its strong neutralizing capability and nutrient-rich formulation ensure accurate recovery and detection of bacteria, making it a trusted choice for disinfectant efficacy studies, environmental monitoring, and pharmaceutical quality control laboratories.