Rose Bengal Chloramphenicol (RBC) Agar | Selective Yeast & Mould Enumeration
Rose Bengal Chloramphenicol Agar
RBC Agar • Selective medium for yeasts and molds
Rose Bengal Chloramphenicol Agar (RBC Agar) is a selective fungal enumeration medium widely used for the isolation, cultivation, and counting of yeasts and molds from food, water, environmental, cosmetic, and pharmaceutical samples. Rose bengal restricts colony spread and improves recovery of discrete colonies, while chloramphenicol suppresses bacterial contaminants.
Fungal Recovery Medium
Product Overview
Rose Bengal Chloramphenicol Agar is formulated for the selective isolation and enumeration of yeasts and molds in mixed microbial populations. The medium is particularly valuable where fungi must be recovered in the presence of bacterial flora or rapidly spreading molds.
Rose bengal limits colony size and helps prevent overgrowth by fast-spreading molds, improving the recovery of slow-growing colonies. Chloramphenicol acts as a broad-spectrum bacteriostatic agent to suppress bacterial interference. The slightly acidic pH further enhances selectivity in favor of fungi.
RBC Agar is suitable for routine fungal testing across food microbiology, environmental monitoring, water microbiology, pharmaceutical quality control, and cosmetic microbiology.
Principle of the Medium
RBC Agar combines nutrient support with selective inhibition to improve fungal recovery and plate readability:
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Rose Bengal restricts colony spreading
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Chloramphenicol inhibits bacterial contaminants
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Low pH improves fungal selectivity
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Discrete yeast and mold colonies for clearer enumeration
🧫 Applications
🍞 Food Microbiology
Enumeration of yeasts and molds in bakery products, dairy products, dried fruits, nuts, spices, and other foods.
🏭 Environmental Monitoring
Detection of airborne and surface fungal contamination in production areas, cleanrooms, and controlled environments.
Water Microbiology
Fungal testing of bottled water, purified water, process water, and cooling systems where yeast and mold recovery is required.
Pharmaceutical & Cosmetic QC
Microbial limit testing of non-sterile cosmetic and pharmaceutical products where fungal selectivity is important.
Pathogenic & Environmental Fungi
Isolation and recovery of fungi such as Candida, Aspergillus, Penicillium, and other yeasts and molds.
📊 Key Features
Rose bengal helps control rapidly spreading molds and improves colony separation.
Chloramphenicol reduces bacterial interference during fungal enumeration.
Low final pH supports fungal recovery while discouraging bacterial growth.
Discrete colony morphology helps improve counting accuracy and plate readability.
Applicable to food, water, environmental, cosmetic, and pharmaceutical microbiology.
Widely recognized in international fungal enumeration practices.
🧪 Composition (per litre)
🧭 Preparation
- Suspend 31.65 g of dehydrated medium in 1 litre of purified water.
- Heat with agitation and boil for about 1 minute until completely dissolved.
- If using a heat-labile chloramphenicol format, do not autoclave the complete medium with chloramphenicol.
- Option A: Autoclave the base medium at 121 °C for 15 minutes, cool to 45–50 °C, then aseptically add sterile chloramphenicol solution.
- Option B: If using a commercial heat-stable chloramphenicol formulation, autoclave according to the validated product procedure.
- Mix thoroughly and pour into sterile Petri plates.
💡 Interpretation
Typically smooth, creamy colonies, often off-white to pale pink.
Usually powdery, filamentous, fuzzy, or pigmented colonies depending on the species.
Generally suppressed by chloramphenicol and the acidic pH.
A light pink medium background due to rose bengal is normal.
📋 Technical Specifications
| Product Name | Rose Bengal Chloramphenicol Agar |
| Short Name | RBC Agar |
| Catalogue Number | AS-1340 |
| Medium Type | Selective fungal agar |
| Primary Use | Enumeration and isolation of yeasts and molds |
| Selective Agents | Rose Bengal, Chloramphenicol |
| Final pH | 5.6 ± 0.2 at 25 °C |
| Incubation | 25–28 °C for 3–5 days |
| Extended Incubation | Up to 7 days for slow growers |
| HS Code | 3821.00.00 |
Incubation Guidance
- ✓ Standard enumeration: 25–28 °C
- ✓ Typical incubation: 3–5 days
- ✓ Slow-growing fungi: up to 7 days
- ✓ Protect prepared plates from excessive light exposure
✅ Typical Recovery Profile
- ✓ Yeasts: creamy, smooth colonies
- ✓ Molds: filamentous, fuzzy, or powdery colonies
- ✓ Bacterial interference reduced
- ✓ Supports stressed or slow-growing fungi
📚 Common Reference Alignment
- ✓ ISO 21527-1 / ISO 21527-2
- ✓ USP <61>
- ✓ FDA-BAM Chapter 18
- ✓ Routine fungal enumeration workflows
❄️ Storage
- ✓ Dehydrated medium: 10–30 °C, dry and tightly sealed
- ✓ Prepared plates: 2–8 °C
- ✓ Protect prepared medium from light
- ✓ Use within 3 months for optimal recovery
📄 Available Documentation
🧬 Related Fungal Microbiology Products
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