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Rose Bengal Chloramphenicol (RBC) Agar | Selective Yeast & Mould Enumeration
$39.00 AUD
ROSE BENGAL CHLORAMPHENICOL AGAR
Catalogue No. AS-1340
www.ausamics.com.au
AS-1340 Selective Neutral pH Yeasts & Moulds USP <61> · FDA-BAM Ch.18
Rose Bengal Chloramphenicol Agar (RBC)
Selective medium for the enumeration of yeasts and moulds — food, water, environmental, cosmetic, and pharmaceutical microbiology
RBC Agar is a selective fungal enumeration medium widely used for the isolation, cultivation, and counting of yeasts and moulds from food, water, environmental, cosmetic, and pharmaceutical samples. Rose Bengal restricts colony spread and improves recovery of discrete colonies, while chloramphenicol suppresses bacterial contaminants — all at a neutral pH, the defining feature that distinguishes RBC from its dichloran-modified relative, DRBC.
AuSaMicS manufactures RBC Agar in Melbourne, Australia, to the composition established by Jarvis (1973) and Overcast & Weakley, giving reliable fungal recovery and lot-to-lot consistency for routine and regulatory testing.
Performance Snapshot
Final pH7.2 ± 0.2
Incubation25–28°C, 3–5 days
Appearance (powder)Pink, free-flowing
Background colourLight pink — normal
Shelf life (powder)24 months
Formulation accuracy note: RBC Agar has a neutral final pH of 7.2 ± 0.2 at 25°C. This is verified against HiMedia's Rose Bengal Agar Base (M842), whose composition matches this product exactly, and independently against Hardy Diagnostics (7.2 ± 0.3). A pH of 5.6 belongs to DRBC (Dichloran-Rose Bengal Chloramphenicol Agar) — a related but different, dichloran-modified medium with a deliberately lowered pH. The two media are easy to confuse by name; AuSaMicS documentation keeps the two formulations and their pH values clearly distinct.
Testing Workflow
1
SampleFood, water, cosmetic, or pharma sample
2
DilutePrepare decimal dilutions
3
Spread Plate0.1 mL onto RBC surface
4
Incubate25–28°C, 3–5 days (up to 7 for slow growers)
5
CountEnumerate discrete colonies
Principle of the Medium
Origin & Neutral pH Rationale
RBC Agar was formulated by Jarvis (1973) and further modified by Overcast and Weakley, building on Smith and Dawson's 1944 finding that Rose Bengal added to a near-neutral medium supported better fungal recovery than the more acidic media traditionally used for yeast and mould enumeration. This is a deliberate departure from the older, acidified approach — the neutral pH combined with an antibiotic selective agent proved more reliable for supporting fungal growth while restricting bacteria.
Functional Components
Peptone and glucose (dextrose) provide the nutrient base supporting fungal growth. Rose Bengal restricts colony spreading and height — particularly of fast-growing moulds such as Rhizopus — improving recovery of discrete, countable colonies, and is taken up by fungal colonies to aid visual enumeration. Chloramphenicol, a heat-stable, broad-spectrum antibiotic, suppresses bacterial contaminants without inhibiting fungal growth. Potassium phosphate buffers the medium, and magnesium sulfate supplies trace minerals for fungal metabolism.
A light pink background across the prepared medium, due to Rose Bengal, is a normal characteristic and does not indicate medium deterioration or contamination.
Key Applications
Food Microbiology
Enumeration of yeasts and moulds in bakery products, dairy, dried fruits, nuts, and spices.
Environmental Monitoring
Detection of airborne and surface fungal contamination in production areas and cleanrooms.
Water Microbiology
Fungal testing of bottled water, purified water, process water, and cooling systems.
Pharmaceutical & Cosmetic QC
Microbial limit testing of non-sterile cosmetic and pharmaceutical products (USP <61>).
Formulation & Specifications
| Component | g/L |
|---|---|
| Peptone (Soy / Casein Digest) | 5.0 |
| Dextrose (Glucose) | 10.0 |
| Monopotassium Phosphate (KH₂PO₄) | 1.0 |
| Magnesium Sulfate (MgSO₄·7H₂O) | 0.5 |
| Rose Bengal | 0.05 |
| Chloramphenicol | 0.1 |
| Agar | 15.0 |
| Total | 31.65 g/L |
Technical Specifications
| Catalogue No. | AS-1340 |
| HS Code | 3821.00.00 |
| Final pH | 7.2 ± 0.2 @ 25°C |
| Incubation | 25–28°C, 3–5 days (up to 7 days) |
| Storage (powder) | 10–30°C, dry |
| Storage (plates) | 2–8°C, protected from light |
Laboratory Preparation
1
Suspend 31.65 g of dehydrated medium in 1 litre of purified water.
2
Heat with agitation and boil for about 1 minute until completely dissolved.
3
Heat-labile chloramphenicol: autoclave the base at 121°C for 15 minutes, cool to 45–50°C, then aseptically add sterile chloramphenicol solution.
4
Heat-stable chloramphenicol format: autoclave the complete medium according to the validated product procedure.
5
Mix thoroughly and pour into sterile Petri plates.
RBC Agar vs DRBC Agar
| Property | RBC Agar (this product) | DRBC Agar |
|---|---|---|
| Final pH | 7.2 ± 0.2 (neutral) | 5.6 ± 0.2 (acidic) |
| Dichloran | Not present | 0.002 g/L — restricts spreading moulds |
| Rose Bengal | 0.05 g/L | 0.025 g/L (halved vs RBC) |
| Colony spread control | Moderate (Rose Bengal only) | Strong (Rose Bengal + dichloran) |
| Best for | General fungal enumeration; higher incubation temperatures; where dichloran's restriction is not wanted | Regulatory yeast/mould counts (ISO 21527-1) where spreading moulds are a major issue |
Both media share the same Rose Bengal-based selectivity principle but are formulated for different situations — always confirm which one your regulatory method specifies.
Typical Recovery Profile
| Organism / Group | Typical Appearance on RBC |
|---|---|
| Yeasts | Smooth, creamy colonies, often off-white to pale pink |
| Moulds | Powdery, filamentous, fuzzy, or pigmented colonies depending on species |
| Bacteria | Generally suppressed by chloramphenicol; occasional resistant strains may appear as pinpoint colonies |
Limitations & Technical Considerations
- No spreading-mould control — unlike DRBC, RBC does not contain dichloran, so fast-spreading moulds such as Rhizopus and Mucor may still overgrow plates at high fungal loads.
- Chloramphenicol format matters — heat-labile chloramphenicol must be added after autoclaving, not before; check your specific product format before preparation.
- Short prepared-plate shelf life — use within 3 months of preparation for optimal recovery.
- Not diagnostic for mycotoxin producers — the medium enumerates yeasts and moulds generally; it does not select for or identify specific toxigenic species.
Cross-Reference / Equivalent Products
| Brand | Equivalent Product | Catalogue No. |
|---|---|---|
| BD Difco (Acumedia) | Rose Bengal Chloramphenicol Agar | 218312 |
| Oxoid (Thermo Scientific) | Rose Bengal Chloramphenicol Agar Base (+ supplement required) | CM0549 |
| Merck / Sigma-Aldrich | Rose Bengal Chloramphenicol Agar (+ supplement required) | 1.00467 |
| HiMedia | Rose Bengal Chloramphenicol Agar | M640 |
| AuSaMicS | RBC Agar | AS-1340 |
Ordering Information
| Catalogue No. | Pack Size | Approx. Yield | Format |
|---|---|---|---|
| AS-1340-500 | 500 g | ≈ 15.8 L prepared medium | Dehydrated powder, bottle |
| AS-1340-2K5 | 2.5 kg | ≈ 79 L prepared medium | Dehydrated powder, bottle |
Yield calculated at 31.65 g/L reconstitution rate.
Frequently Asked Questions
What is RBC Agar used for?
It isolates and enumerates yeasts and moulds from food, water, environmental, cosmetic, and pharmaceutical samples.
What is the correct pH of RBC Agar?
A neutral final pH of 7.2 ± 0.2 at 25°C — a deliberate design feature that supports better fungal recovery than the acidified media traditionally used.
What is the difference between RBC Agar and DRBC Agar?
RBC has a neutral pH (7.2) and no dichloran. DRBC adds dichloran, halves the Rose Bengal concentration, and lowers the pH to 5.6 for tighter control of spreading moulds. See the comparison table above.
Why is a light pink background normal on RBC Agar plates?
Rose Bengal is a dye present throughout the medium, giving prepared plates a light pink background — this is normal and does not indicate deterioration.
How do you prepare RBC Agar with chloramphenicol?
Suspend the dehydrated base in purified water, boil to dissolve, then either autoclave the complete medium (heat-stable format) or autoclave the base alone and aseptically add sterile chloramphenicol after cooling to 45–50°C (heat-labile format).
Common Search Queries This Product Answers
Researchers and procurement teams typically find this page searching for:
- "RBC agar composition" / "Rose Bengal Chloramphenicol Agar formula"
- "RBC agar pH" / "is RBC agar acidic or neutral"
- "RBC vs DRBC agar difference"
- "USP 61 fungal enumeration medium"
- "FDA BAM chapter 18 yeast mould agar"
- "buy RBC agar Australia Melbourne"
Technical Data Sheet
| Product Name | Rose Bengal Chloramphenicol Agar (RBC) |
| Catalogue Number | AS-1340 |
| HS Code | 3821.00.00 |
| Format | Dehydrated powder |
| Manufacturer | AuSaMicS Pty Ltd, Melbourne, Australia |
Intended Use
Selective medium for the isolation and enumeration of yeasts and moulds from food, water, environmental, cosmetic, and pharmaceutical samples.
Mode of Action
Peptone and dextrose support fungal growth. Rose Bengal restricts colony spreading and height, particularly of fast-growing moulds, improving recovery of discrete colonies. Chloramphenicol, a heat-stable broad-spectrum antibiotic, suppresses bacterial contaminants. The neutral pH (7.2 ± 0.2) is a deliberate design feature supporting fungal recovery, distinguishing this medium from acidified alternatives.
Formulation (per litre)
| Ingredient | Quantity | Function |
|---|---|---|
| Peptone (Soy / Casein Digest) | 5.0 g | General nutrient support |
| Dextrose | 10.0 g | Fermentable energy source |
| Monopotassium Phosphate (KH2PO4) | 1.0 g | Buffering component |
| Magnesium Sulfate (MgSO4.7H2O) | 0.5 g | Mineral source |
| Rose Bengal | 0.05 g | Restricts colony spread; aids colony visualisation |
| Chloramphenicol | 0.1 g | Inhibits bacterial contaminants |
| Agar | 15.0 g | Solidifying agent |
Total: 31.65 g/L.
Final pH: 7.2 ± 0.2 at 25°C (neutral). Verified against HiMedia Rose Bengal Agar Base (M842), an exact composition match, and independently against Hardy Diagnostics (7.2 ± 0.3). This is NOT the same as DRBC Agar, which is acidified to pH 5.6 as part of a different, dichloran-modified formulation.
Preparation
Suspend 31.65 g of dehydrated medium in 1 L purified water. Heat with agitation and boil for about 1 minute until completely dissolved. For heat-labile chloramphenicol formats, autoclave the base at 121°C for 15 minutes, cool to 45–50°C, then aseptically add sterile chloramphenicol solution. For heat-stable formats, autoclave the complete medium per the validated procedure. Mix thoroughly and pour into sterile Petri plates.
Incubation Conditions
| Parameter | Condition |
|---|---|
| Temperature | 25–28°C |
| Time | 3–5 days standard; up to 7 days for slow-growing fungi |
| Light | Protect prepared plates from excessive light exposure |
Storage & Shelf Life
| Dehydrated medium | 10–30°C, dry, tightly sealed — 24 months |
| Prepared plates | 2–8°C, protected from light — use within 3 months for optimal recovery |
Literature & References
- Jarvis, B. (1973). Comparison of an improved rose bengal-chlortetracycline agar with other media for the selective isolation and enumeration of moulds and yeasts in foods. Journal of Applied Bacteriology, 36, 723–727.
- Smith, N.R., Dawson, V.T. (1944). The bacteriostatic action of rose bengal in media used for the plate count of soil fungi. Soil Science, 58(6), 467–471.
- United States Pharmacopeia. USP <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests.
- U.S. Food and Drug Administration. Bacteriological Analytical Manual (BAM), Chapter 18: Yeasts, Moulds and Mycotoxins.
For laboratory use only. Product suitability should be verified by the user under validated sample preparation, incubation, recovery, and regulatory testing conditions. AuSaMicS Pty Ltd accepts no liability for results obtained outside the stated preparation and storage conditions.
Safety Data Sheet — Summary
This is a summary view. The full 16-section GHS-compliant Safety Data Sheet (Australian format) is provided as a downloadable Word document alongside this page.
| Product Name | RBC Agar, AS-1340 |
| Recommended Use | Laboratory culture medium (dehydrated) |
| Manufacturer | AuSaMicS Pty Ltd, Melbourne, Victoria, Australia |
| GHS Classification | Contains chloramphenicol — see Section 2 of full SDS |
| Signal Word | Warning |
Hazard Summary
The dehydrated medium contains chloramphenicol, an antibiotic with known potential for serious blood disorders (aplastic anaemia) with repeated or prolonged exposure. Avoid generating and inhaling dust. May cause mechanical irritation to eyes and respiratory tract. Full precautions are detailed in the complete SDS.
First Aid
| Route | Response |
|---|---|
| Inhalation | Move to fresh air. Seek medical attention if irritation persists or if a significant dust exposure occurred. |
| Skin Contact | Wash with soap and water. |
| Eye Contact | Rinse thoroughly with water for several minutes. Seek medical advice if irritation persists. |
| Ingestion | Rinse mouth. Seek medical advice. |
Full SDS (16 GHS sections, chloramphenicol hazard details, handling, disposal, transport and regulatory information) is provided as a separate Word document — see downloads.
Certificate of Analysis — Sample Format
Each batch is supplied with a lot-specific Certificate of Analysis. A representative COA is provided as a downloadable Word document; the batch-specific COA accompanies your shipment.
| Product Name | Rose Bengal Chloramphenicol Agar (RBC) |
| Catalogue Number | AS-1340 |
| Batch/Lot Number | Assigned per production batch |
| Manufacture Date | Assigned per production batch |
| Retest / Expiry Date | 24 months from manufacture |
Quality Control Results (Representative)
| Test | Specification | Result |
|---|---|---|
| Appearance (powder) | Pink, free-flowing | Conforms |
| Final pH (25°C) | 7.2 ± 0.2 | Conforms |
| Gel firmness | Firm, pink-coloured gel | Conforms |
| Aspergillus niger ATCC 16404 recovery | Good growth | Conforms |
| Candida albicans ATCC 10231 recovery | Good growth | Conforms |
| Escherichia coli ATCC 25922 (inhibition control) | Inhibited / no growth | Conforms |
| Sterility (uninoculated control) | No growth | Conforms |
This tab shows a representative format. The lot-specific Certificate of Analysis issued with your order carries the actual batch number, manufacture/expiry dates, and signed QC results.
The information provided is accurate to the best of AuSaMicS Pty Ltd's knowledge at the time of publication. Product specifications may be updated without notice. For laboratory use only. Product suitability should be verified by the user under validated sample preparation, incubation, recovery, and regulatory testing conditions.