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D/E Neutralizing Agar (AS-1190) | Disinfectant Neutralization Medium
$125.00 AUD
Disinfectant Neutralizing Medium · Environmental Monitoring · Antimicrobial Efficacy Testing
D/E Neutralizing Agar (Dey/Engley)
Broad-Spectrum Neutralizing System · AOAC · USP <51>/<61>/<62> · ISO 14698
AOAC Use-Dilution Methods
USP <51> · USP <61>/<62>
ISO 14698-1/2
FDA Aseptic Guidance
Dey & Engley 1970
AuSaMicS
Life Science™
Cat No.
AS-1190
Format
Dehydrated Powder
Final pH
7.6 ± 0.2
Suspension
54.02 g / L
Incubation
35–37 °C / 40–48 h
Overview
D/E Neutralizing Agar (Dey/Engley Neutralizing Agar) is a selective, enriched solid medium developed by Dey and Engley (1970) for the neutralization and recovery of microorganisms exposed to antiseptics and disinfectants in environmental sampling and antimicrobial efficacy testing. It incorporates a comprehensive broad-spectrum neutralizing system capable of inactivating residual chemicals — halogens, mercurials, aldehydes, quaternary ammonium compounds (QACs), and phenolics — without harming viable bacteria, enabling accurate assessment of bactericidal activity.
The bromocresol purple (BCP)–dextrose indicator system differentiates fermentation: Purple gel shifts to Yellow upon acid production, providing presumptive visual indication of microbial growth. D/E Neutralizing Agar complies with AOAC use-dilution methods, USP <51>/<61>/<62>, and ISO 14698 standards.
Neutralizing System — Components & Targets
| Neutralizing Agent | g/L | Target Disinfectant Class | Mechanism |
|---|---|---|---|
| Sodium Thiosulfate | 6.0 | Halogens (Cl&sub2;, I&sub2;, Br&sub2;) | Reductive neutralization — converts active halogen to harmless halide |
| Sodium Thioglycollate | 1.0 | Mercurial compounds, metal biocides | Chelation and reduction — sequesters heavy metal ions |
| Sodium Bisulfite | 2.5 | Aldehydes (glutaraldehyde, formaldehyde) | Reductive addition — inactivates aldehyde groups |
| Lecithin | 7.0 | Phenolics, membrane-active agents | Micellar entrapment — surrounds lipophilic phenolic molecules |
| Polysorbate 80 | 5.0 | QACs, surface-active agents | Competitive surfactant — displaces and sequesters QACs |
| Lecithin + Polysorbate 80 | — | Chlorhexidine, hexachlorophene, bis-phenols | Synergistic neutralization of membrane-disrupting agents |
Combined neutralizing system inactivates > 95% of common disinfectants while supporting reliable growth of stressed Gram-positive and Gram-negative organisms.
Applications
Environmental Monitoring
Recovery of viable bacteria from hospital, cleanroom, and food facility surfaces treated with disinfectants. ISO 14698-1/2; USP <61>/<62>.
Antimicrobial Efficacy
Assessment of bactericidal activity of antiseptics, QACs, phenolics, and halogens per AOAC use-dilution methods (955.11; 964.02; 966.04).
Pharma & Food QC
Microbial recovery from sanitized pharmaceutical surfaces and food/dairy/cosmetic samples post-sanitization. USP <51>; ISO 14644.
BCP Indicator System
| Uninoculated / non-fermenters | Purple — neutral/alkaline pH, no acid production |
| Fermenters (glucose) | Yellow — acid from glucose fermentation (pH drops below indicator pKa) |
| E. coli ATCC 25922 | Good growth; Yellow colonies (BCP positive fermentation) |
| S. aureus ATCC 25923 | Good growth; Yellow colonies (BCP positive fermentation) |
| P. aeruginosa ATCC 27853 | Good growth; Purple/unchanged (non-fermenter) |
Incubation & Use
| Temperature | 35–37 °C (aerobic) |
| Duration | 40–48 hours; examine at 24 h and 48 h |
| Contact plates | Press dome-shaped surface directly onto sampling area; incubate inverted at 35–37 °C |
| Air sampling | Expose open dome plate for defined time; incubate; count CFU/m³ or CFU/plate |
| Suspension plating | Pour 20–25 mL per plate (slight dome overfill for contact plates; standard 15–20 mL for enumeration) |
Storage & Shelf Life
| Dehydrated Medium | 10–30 °C, tightly closed, protected from moisture, light, and humidity; stable until expiry (typically 3 years) |
| After Opening | Reseal immediately; use desiccant to prevent hygroscopic lump formation |
| Prepared Plates | 2–8 °C, sealed plastic bags; use within 2–4 weeks |
| Do Not Use If | Dehydrated, contaminated, discoloured, or overgrown prepared plates |
For laboratory and research use only. Not for diagnostic procedures without proper validation. Not for human or veterinary consumption. Handle under BSL-2; wear gloves, protective clothing, and eye protection. Autoclave all contaminated materials before disposal.
AuSaMicS Pty Ltd (ABN 56 676 640 467) · For laboratory use only. · 31 Longview CT, Thomastown VIC 3074, Australia · support@ausamics.com · +61 412 520 598 · www.ausamics.com.au
Product Identification
| Product Name | D/E Neutralizing Agar |
| Full Name | Dey/Engley Neutralizing Agar |
| Cat No. | AS-1190 |
| Lot No. | DEN260301 |
| Mfg. Date | March 2026 |
| Retest Date | March 2029 |
| Grade | Microbiological Grade |
Physical Properties
| Appearance (powder) | Pale cream to beige; possible off-white particles (lecithin/polysorbate — normal) |
| Appearance (prepared) | Opaque, purple to reddish-purple opalescent gel; fine white precipitate acceptable |
| pH (prepared, 25 °C) | 7.6 ± 0.2 |
| Agar gel / melt | Gels ~32–34 °C / Melts ~84–86 °C |
| Loss on Drying | ≤ 7.0% w/w |
| Suspension | 54.02 g / L purified water |
Composition per Litre
| Component | Function | Amount (g/L) |
|---|---|---|
| Tryptone | Nitrogen, amino acids — primary nutrient source | 5.0 |
| Yeast Extract | B vitamins, growth factors — supports stressed cell recovery | 2.5 |
| Dextrose (Glucose) | Fermentable carbon source — energy; substrate for BCP indicator | 10.0 |
| Sodium Thiosulfate | Neutralises halogens (Cl&sub2;, I&sub2;, Br&sub2;) | 6.0 |
| Sodium Thioglycollate | Neutralises mercurials and metal-based biocides | 1.0 |
| Sodium Bisulfite | Neutralises aldehydes (glutaraldehyde, formaldehyde) | 2.5 |
| Lecithin | Neutralises phenolics and membrane-active agents | 7.0 |
| Polysorbate 80 | Neutralises QACs and surface-active agents | 5.0 |
| Bromocresol Purple (BCP) | pH indicator — Purple (neutral) → Yellow (acid from fermentation) | 0.02 |
| Agar | Solidifying agent | 15.0 |
| TOTAL | 54.02 g/L |
Preparation Protocol
- 1Suspend 54.02 g of dehydrated D/E Neutralizing Agar in 1 L of purified water.
- 2Heat with frequent agitation to boiling until completely dissolved. Do not overheat — excessive boiling degrades neutralizing agents.
- 3Autoclave at 121 °C (15 psi) for 15 minutes.
- 4Cool to 45–50 °C. Mix gently to resuspend any particulates (white precipitate from lecithin is normal).
- 5Contact plates: Pour 20–25 mL per plate with slight overfill to create a dome shape for direct surface contact sampling.
- 6Standard enumeration plates: Pour 15–20 mL per 90 mm Petri dish.
- 7Allow to solidify at RT. Store at 2–8 °C in sealed bags. Use within 2–4 weeks.
Quality Control Specifications
| Parameter | Specification | Method |
|---|---|---|
| Appearance (powder) | Homogeneous; cream to beige; no excessive lumping | Visual inspection |
| pH (prepared, 25 °C) | 7.4 – 7.8 | Potentiometry (ISO 10523) |
| Loss on Drying | ≤ 7.0% w/w | 105 °C / 2 h (gravimetric) |
| Colour (prepared) | Purple to reddish-purple opalescent gel | Visual — plate check |
| Growth + BCP — E. coli ATCC 25922 | Good growth; yellow colonies (BCP+ fermentation); 40–48 h at 37 °C | Growth promotion + BCP test |
| Growth + BCP — S. aureus ATCC 25923 | Good growth; yellow colonies (BCP+ fermentation) | Growth promotion + BCP test |
| Growth + BCP — P. aeruginosa ATCC 27853 | Good growth; purple/unchanged (non-fermenter) | Growth promotion + BCP test |
| Neutralizing efficacy (chlorine 200 ppm) | ≥ 95% neutralization; recovery of viable E. coli | AOAC neutralizer performance |
| Neutralizing efficacy (QAC 400 ppm) | ≥ 95% neutralization; recovery of viable S. aureus | AOAC neutralizer performance |
| Sterility (prepared medium) | No growth at 14 days (35–37 °C) | Incubation sterility check |
Technical References
| Primary Reference | Dey B.P. & Engley F.B. (1970). Prototype formulation of a universal neutralizing medium. J AOAC, 53(4):763–777 |
| AOAC Methods | AOAC 955.11 · 964.02 · 966.04 — Use-dilution methods for disinfectant efficacy |
| USP Standards | USP <51> Antimicrobial Effectiveness Testing · USP <61>/<62> Microbiological Examination |
| ISO Standards | ISO 14698-1/2 — Cleanroom environmental monitoring · ISO 4833 — Food microbiology |
| FDA Guidance | FDA Guidance for Aseptic Processing (2004) — environmental monitoring |
AuSaMicS Pty Ltd (ABN 56 676 640 467) · 31 Longview CT, Thomastown VIC 3074, Australia · support@ausamics.com · +61 412 520 598 · www.ausamics.com.au
Safety Data Sheet — GHS Format (Australian WHS Regulations 2017)
Issue Date: March 2026 · Rev: 1.0
Issue Date: March 2026 · Rev: 1.0
Hazard Notice: This medium contains sodium bisulfite (H302 harmful if swallowed; H317 potential sensitiser) and sodium thioglycollate (H411 toxic to aquatic organisms). Handle with appropriate PPE. Inoculated medium: BSL-2 precautions apply.
Section 1 — Identification
| Product Name | D/E Neutralizing Agar (Dey/Engley) — AS-1190 |
| Other Names | DE Neutralizing Agar; Dey-Engley Neutralizing Agar |
| Intended Use | Microbiological culture medium for disinfectant neutralization — laboratory use only |
| Supplier | AuSaMicS Pty Ltd, 31 Longview CT, Thomastown VIC 3074, Australia |
| Phone / Emergency | +61 412 520 598 · Poisons Centre: 13 11 26 (24h) |
| Email / Web | support@ausamics.com · www.ausamics.com.au |
Section 2 — Hazard Identification
| GHS Classification | H302 (sodium bisulfite — harmful if swallowed) · H317 (sodium bisulfite — may cause allergic skin reaction) · H319 (eye irritation) · H411 (sodium thioglycollate — toxic to aquatic organisms) |
| Signal Word | Warning |
| Precautionary | P260 · P264 · P270 · P280 · P301+P312 · P333+P313 · P391 · P501 |
| Biological Hazard | Inoculated media: BSL-2 organisms possible. Wear gloves, lab coat, eye protection. Use BSC Class II for inoculated work. |
Section 3 — Composition
| Component | CAS No. | Proportion (w/w) | GHS Classification |
|---|---|---|---|
| Agar (bacteriological) | 9002-18-0 | ~27.8% | Not classified |
| Dextrose (Glucose) | 50-99-7 | ~18.5% | Not classified |
| Lecithin (soya) | 8002-43-5 | ~13.0% | Not classified |
| Sodium Thiosulfate | 10102-17-7 | ~11.1% | Not classified at supplied conc. |
| Polysorbate 80 | 9005-65-6 | ~9.3% | Not classified |
| Sodium Bisulfite | 7631-90-5 | ~4.6% | H302 · H317 · H319 · H335 |
| Tryptone | — | ~9.3% | Not classified |
| Yeast Extract | 8013-01-2 | ~4.6% | Not classified |
| Sodium Thioglycollate | 367-51-1 | ~1.9% | H302 · H312 · H332 · H411 |
| Bromocresol Purple | 115-40-2 | < 0.1% | Not classified at supplied conc. |
Sections 4–8 — First Aid, Fire, Spill, Handling, PPE
| Inhalation | Remove to fresh air. Sodium bisulfite dust: potential sensitiser — seek advice if symptomatic. |
| Skin Contact | Wash with soap and water ≥ 15 min. Sodium bisulfite: H317 sensitiser — seek advice if reaction develops. |
| Eye Contact | Rinse immediately with copious water ≥ 15 min. Seek medical attention. |
| Ingestion | Do not induce vomiting. Rinse mouth. Sodium bisulfite H302 — seek medical advice. Contact Poisons Centre: 13 11 26. |
| Flash Point | Not applicable (non-flammable powder). H&sub2;S possible from thioglycollate on strong heating. |
| Spill (chemical) | Avoid dust. Collect with HEPA vacuum or damp cloth. Dispose per Section 13. |
| Spill (inoculated) | BIOHAZARD: Apply 1% hypochlorite; contact time ≥ 30 min. Autoclave all waste. Report per biosafety policy. |
| Engineering Controls | Local exhaust ventilation when weighing. BSC Class II for all inoculated work. |
| Respiratory PPE | P2 / FFP2 dust mask when generating significant dust (sodium bisulfite sensitiser) |
| Hand Protection | Nitrile gloves — double-glove for inoculated work |
| Eye / Face | Safety glasses; splash goggles for inoculated work |
| Biosafety Level | BSL-2 containment required per AS/NZS 2243.3:2010 when culturing potentially pathogenic organisms |
Sections 9–16 — Properties, Stability, Toxicology, Disposal, Regulatory
| Physical State | Solid (powder); opaque purple-reddish gel when prepared |
| pH (prepared) | 7.6 ± 0.2 |
| Stability | Stable at 10–30 °C, dry, protected. Incompatible with strong oxidising agents; concentrated acids (releases SO&sub2; from bisulfite). |
| Acute Oral Toxicity | Sodium bisulfite H302 — harmful if swallowed at high dose. Others: low acute toxicity (GRAS components). |
| Skin Sensitisation | Sodium bisulfite H317 — may cause allergic skin reaction in sensitised individuals. Apply ALARA. |
| Aquatic Toxicity | Sodium thioglycollate H411 — toxic to aquatic organisms with long-lasting effects. Prevent discharge to waterways. |
| Waste Disposal | Inoculated medium: autoclave 121 °C / 30 min as biohazardous waste. Uninoculated: autoclave then dispose as chemical waste. Sodium thioglycollate — environmental hazard; licensed contractor for bulk disposal. |
| Transport | Not regulated as dangerous goods in standard laboratory quantities. Sodium thioglycollate: check regulations for bulk commercial shipments. |
| AICS (Australia) | All components listed on Australian Inventory of Chemical Substances |
| SUSMP Schedule | Not scheduled for laboratory use |
| WHS Regulations | Contains hazardous chemicals (sodium bisulfite H302/H317; sodium thioglycollate H411) — WHS Regulations 2017 apply |
| SDS Prepared By | AuSaMicS Pty Ltd — Technical & Quality Department · March 2026 · Rev 1.0 |
AuSaMicS Pty Ltd (ABN 56 676 640 467) · 31 Longview CT, Thomastown VIC 3074, Australia · support@ausamics.com · +61 412 520 598 · www.ausamics.com.au
This SDS is prepared in accordance with Australian WHS Regulations and GHS (7th Rev.). For laboratory use only.
This SDS is prepared in accordance with Australian WHS Regulations and GHS (7th Rev.). For laboratory use only.
Product Details
| Product Name | D/E Neutralizing Agar |
| Catalog No. | AS-1190 |
| Lot No. | DEN260301 |
| Mfg. Date | March 2026 |
| Retest Date | March 2029 |
| Grade | Microbiological Grade |
Document Information
| COA No. | COA-AS-1190-L001 |
| Issue Date | March 2026 |
| Issued By | AuSaMicS Quality Control |
| Test Ref. | ISO 11133 / AOAC / USP <61> |
Test Results & Analytical Data
| Test Parameter | Specification | Method | Result | Status |
|---|---|---|---|---|
| Appearance (powder) | Homogeneous; cream to beige; no excessive lumping | Visual inspection | Conforms | PASS |
| Colour (prepared medium) | Purple to reddish-purple opalescent gel | Visual — plate check | Conforms | PASS |
| pH (prepared, 25 °C) | 7.4 – 7.8 | Potentiometry (ISO 10523) | 7.6 | PASS |
| Gel strength (prepared) | Firm gel; opalescence and white precipitate acceptable | Visual — plate check | Firm | PASS |
| Loss on Drying | ≤ 7.0% w/w | 105 °C / 2 h (gravimetric) | 4.2% | PASS |
| Solubility (54.02 g/L) | Complete dissolution with heating + agitation | Suspension + heating | Complete | PASS |
| BCP indicator (pH shift) | Purple → Yellow upon acid production from glucose | Fermentation test (E. coli) | Positive | PASS |
| Growth — E. coli ATCC 25922 | Good growth; yellow colonies (BCP+); 40–48 h at 37 °C | Growth promotion test | Good growth | PASS |
| Growth — S. aureus ATCC 25923 | Good growth; yellow colonies (BCP+); 40–48 h at 37 °C | Growth promotion test | Good growth | PASS |
| Growth — P. aeruginosa ATCC 27853 | Good growth; purple/unchanged (non-fermenter) | Growth promotion test | Good growth | PASS |
| Neutralizing efficacy — chlorine (200 ppm) | ≥ 95% neutralization; recovery of viable E. coli | AOAC neutralizer performance | ≥ 95% | PASS |
| Neutralizing efficacy — QAC (400 ppm) | ≥ 95% neutralization; recovery of viable S. aureus | AOAC neutralizer performance | ≥ 95% | PASS |
| Sterility (prepared medium) | No growth at 14 days (35–37 °C) | Incubation sterility check | No growth | PASS |
| ISO 11133 / AOAC Compliance | Full conformance with D/E neutralizing agar performance criteria | Compositional + performance review | Conforms | CONFORM |
Conclusion: Lot DEN260301 fully meets all release specifications for D/E Neutralizing Agar. Neutralizing efficacy confirmed for halogens and QACs. Growth promotion and BCP indicator system verified with E. coli ATCC 25922, S. aureus ATCC 25923, and P. aeruginosa ATCC 27853. This lot is RELEASED for use.
Quality Control Analyst
AuSaMicS Quality Control Department
Date: March 2026 | Signature: _______________
Quality Manager
AuSaMicS Pty Ltd
Date: March 2026 | Signature: _______________
AuSaMicS Pty Ltd (ABN 56 676 640 467) warrants this product meets specifications at time of manufacture. For laboratory and research use only. Not for diagnostic procedures without proper validation. · 31 Longview CT, Thomastown VIC 3074, Australia · support@ausamics.com · +61 412 520 598 · www.ausamics.com.au
AuSaMicS Pty Ltd · ABN 56 676 640 467 · 31 Longview CT, Thomastown VIC 3074, Australia · support@ausamics.com · +61 412 520 598 · www.ausamics.com.au