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Sulfite Iron Agar Base | Differential Medium for Sulfite-Reducing Bacteria | AS‑1356
$35.00 AUD
AuSaMicS Life Science • Selective & Differential Culture Media
Sulfite Iron Agar Base
Clostridium perfringens & Sulfite-Reducing Clostridia Detection
The reference selective-differential agar base for enumeration of Clostridium perfringens and sulfite-reducing Clostridia (SRC) in water, food, and environmental samples. Iconic jet-black colony formation via iron-sulfide precipitation delivers unmistakable visual confirmation — a cornerstone of drinking water compliance testing under the ADWG.
Cat #: AS-1356
ISO 14189:2013 Compliant
✓ Australian Stock
⚫ Black Colony Detection
🚀 Same-Day Dispatch: Australian Stock
💧 Water Testing: ADWG / ISO 14189 / AS/NZS 4276.19
🔬 Anaerobic Incubation: 37°C / 24–48 h
🏆 Clostridium Water Specialist
⚫ Jet-Black Colonies — FeS precipitation, unambiguous ID
🧫 SRC & C. perfringens — Dual detection capability
📋 Complete Package — COA + SDS included
⚡ Fast Supply — Ships within 24h
📞 Expert Support — Protocol optimization
Membrane Filtration & Pour Plate
Validated for both MF (APHA/ISO) and pour plate enumeration methods
🔬 Technical Overview & Biochemistry
Sulfite Iron Agar Base is a selective and differential medium designed for the detection, enumeration, and presumptive identification of Clostridium perfringens and other sulfite-reducing Clostridia (SRC) — important faecal indicators and spoilage organisms — in water, food, and environmental samples. The medium exploits two complementary detection mechanisms:
Detection Mechanism — Iron-Sulfide Precipitation:
Sodium Sulfite (Na₂SO₃) — Provides the sulfate/sulfite substrate for sulfite-reducing organisms; also acts as an anaerobic buffer by scavenging residual oxygen within the agar
Ferric Ammonium Citrate / Ferrous Sulfate — Iron source; reacts with biogenic H₂S produced from sulfite reduction to form ferrous sulfide (FeS), an insoluble jet-black precipitate localised within and around colonies
Tryptose / Peptone — Rich nitrogen and carbon source supporting the growth of fastidious anaerobic spore-formers
Agar — Solid matrix; set at minimal concentration to allow diffusion of reaction products, creating characteristic black haloes around positive colonies
Sodium Sulfite (Na₂SO₃) — Provides the sulfate/sulfite substrate for sulfite-reducing organisms; also acts as an anaerobic buffer by scavenging residual oxygen within the agar
Ferric Ammonium Citrate / Ferrous Sulfate — Iron source; reacts with biogenic H₂S produced from sulfite reduction to form ferrous sulfide (FeS), an insoluble jet-black precipitate localised within and around colonies
Tryptose / Peptone — Rich nitrogen and carbon source supporting the growth of fastidious anaerobic spore-formers
Agar — Solid matrix; set at minimal concentration to allow diffusion of reaction products, creating characteristic black haloes around positive colonies
Colony Interpretation: Black colonies surrounded by black precipitate zones = sulfite-reducing Clostridia (presumptive positive). Cream/colourless colonies = non-SRC organisms. No growth = inhibited background flora or absent target.
⚙️ Mode of Action
Clostridium perfringens and related SRC reduce sodium sulfite to hydrogen sulfide (H₂S) via dissimilatory sulfite reductase enzymes active under anaerobic conditions. The liberated H₂S reacts immediately with soluble iron salts (ferric ammonium citrate or ferrous sulfate) dissolved throughout the agar matrix to form insoluble black ferrous sulfide (FeS), producing the characteristic jet-black colouration localised to the colony and its immediate surroundings. Concurrent oxygen scavenging by sodium sulfite within the agar creates a locally reduced microenvironment that favours anaerobic growth, enhancing recovery of even low-density spore populations from water and food matrices without the absolute requirement for external anaerobic jar systems in some protocols.
📊 Clostridium & Anaerobic Detection Media Comparison
🧬 Applications
💧 Drinking Water Compliance
C. perfringens spores are the ADWG indicator for protozoan (Cryptosporidium, Giardia) treatment efficacy — their detection in treated water signals potential treatment failure. Required testing per ADWG 2022 and AS/NZS 4276.19.
🍽️ Food Safety Testing
Enumeration of C. perfringens in cooked and ready-to-eat foods, meat products, gravies, and spices. A critical indicator of temperature abuse and inadequate heating during food processing and catering.
🏭 Wastewater & Environmental
SRC detection in wastewater effluent, biosolids, sludge, and sediment samples. SRC persist far longer than coliforms and provide a historical record of faecal contamination events.
🌾 Irrigation & Agricultural Water
Assessment of irrigation water for C. perfringens spores as a conservative indicator of treatment efficacy and potential pathogen (protozoa) breakthrough risk in horticultural settings.
Additional Laboratory Applications:
- Aquaculture: Water and sediment SRC monitoring in fish farm environments
- NATA Accredited Labs: Routine water and food microbiology testing panels
- Outbreak Investigation: Foodborne illness source tracing
- Pharmaceutical QC: Absence of C. perfringens in non-sterile products
- Research: Anaerobe ecology, spore-former population dynamics
- Council & Utility Labs: Catchment and distribution system monitoring
🇦🇺 C. perfringens as a Drinking Water Indicator — Why It Matters
Clostridium perfringens spores are used in the Australian Drinking Water Guidelines (ADWG 2022) as a conservative indicator of treatment process integrity — specifically, as a surrogate for protozoan parasites (Cryptosporidium and Giardia). Their small size (~1 µm), extreme resistance to chlorine disinfection, and persistence in the environment make them ideal process control sentinels. Detection of C. perfringens in treated water is considered a potential signal of oocyst/cyst passage through filtration barriers.
🛡️ Surrogate for Cryptosporidium & Giardia
🧫 Spores resist chlorination
📋 Required by ADWG 2022 & AS/NZS 4276.19
📋 Recommended Procedure (ISO 14189:2013 / AS/NZS 4276.19)
🔵 Method A — Membrane Filtration
- Filter 100 mL sample through 0.45 µm cellulose nitrate membrane
- Transfer membrane face-down onto surface of prepared Sulfite Iron Agar
- Incubate at 37°C for 24 h under anaerobic conditions
- Count all black colonies — report as CFU/100 mL
- Confirm by heat-shocked subculture (75°C / 15 min) if required
⚫ Method B — Pour Plate
- Prepare SIA at 48–50°C (tempered, pourable)
- Add 1 mL sample to Petri dish; pour 15–20 mL SIA; mix by gentle rotation
- Allow to solidify; overlay with 10–15 mL SIA (thin layer) to maintain anaerobiosis
- Incubate 37°C / 24–48 h in anaerobic jar or pouch
- Count all black colonies; optionally confirm identity by further testing
🫙 Anaerobic Incubation Options
Anaerobic Jars + Gas Pack: Most common — Anaerogen/AnaeroGen sachets in sealed jar; generates CO₂ + scavenges O₂
Anaerobic Pouches: Convenient for small batches; single-use sealed pouches with integral catalyst
Anaerobic Workstation: Ideal for high-throughput labs; maintains <1 ppm O₂ continuously
Self-Contained Overlay (Pour Plate): Sodium sulfite in agar scavenges residual O₂ — reduced atmosphere within pour layers
⚠️ Critical: Strict anaerobic conditions are essential — even brief oxygen exposure during plating inhibits C. perfringens. For water samples requiring spore enumeration only, heat-shock aliquots at 75°C for 15 min before filtration to destroy vegetative cells and select for heat-resistant spores.
💡 Protocol Optimization Guidelines
Preparation:
Dissolve 35.0 g/L in purified water. Heat to dissolve — DO NOT overheat or boil vigorously. Autoclave 121°C / 15 min.
Dissolve 35.0 g/L in purified water. Heat to dissolve — DO NOT overheat or boil vigorously. Autoclave 121°C / 15 min.
pH (25°C):
7.6 ± 0.2 after sterilisation
7.6 ± 0.2 after sterilisation
Pour Temperature:
Pour plates at 48–50°C. Above 50°C risks degrading iron-sulfite reactivity; below 45°C risks premature solidification.
Pour plates at 48–50°C. Above 50°C risks degrading iron-sulfite reactivity; below 45°C risks premature solidification.
Storage (prepared plates):
2–8°C, use within 2 weeks. Protect from light. Dehydrated powder: below 25°C, dry and dark.
2–8°C, use within 2 weeks. Protect from light. Dehydrated powder: below 25°C, dry and dark.
📋 Technical Specifications
| Catalogue Number | AS-1356 |
| Common Name | SIA Base / Iron Sulfite Agar Base |
| Format | Dehydrated powder |
| Reconstitution | 35.0 g/L in purified water |
| pH (25°C) | 7.6 ± 0.2 |
| Incubation Temp | 37°C ± 1°C |
| Incubation Time | 24–48 hours |
| Atmosphere | Anaerobic (strictly required) |
| Positive Result | Jet-black colonies / black precipitate zones |
| Negative Result | Cream / colourless / no growth |
| Key Reagents | Sodium sulfite, ferric ammonium citrate |
| Sterilisation | Autoclave 121°C / 15 min |
| HS Code | 3821.00.00 |
✅ Quality Control Performance
| Test Organism | ATCC | Expected Result | CFU Spec |
|---|---|---|---|
| Clostridium perfringens | 13124 | Black colonies, good growth | ≤100 CFU |
| Clostridium sporogenes | 19404 | Black colonies, growth | ≤100 CFU |
| Escherichia coli | 25922 | Inhibited / cream colonies | ≤100 CFU |
| Enterococcus faecalis | 19433 | No black colonies | ≤100 CFU |
🧪 Typical Formulation (per litre)
| Tryptose | 15.0 g |
| Yeast Extract | 5.0 g |
| Sodium Sulfite (Na₂SO₃) | 0.5 g |
| Ferric Ammonium Citrate | 0.5 g |
| Agar | 14.0 g |
* Formulation may vary slightly between lot numbers. Refer to the current COA for exact composition. Some formulations use ferrous sulfate in place of or alongside ferric ammonium citrate.
📜 Standards & Regulatory Compliance
- ✓ ISO 14189:2013 — Water quality, enumeration of C. perfringens, MF method
- ✓ AS/NZS 4276.19:2005 — Australian Standard, C. perfringens in water
- ✓ ADWG 2022 — Australian Drinking Water Guidelines (NHMRC), treatment process indicator
- ✓ APHA Standard Methods 9060C — SRC enumeration in water
- ✓ ISO 7937:2004 — Enumeration of C. perfringens in food (confirmatory plating)
- ✓ NATA Accreditation — Suitable for NATA-accredited water and food labs
📝 Alternative Names
Sulfite Iron Agar Base (SIA Base)
Sulphite Iron Agar Base
Iron Sulfite Agar
Clostridium perfringens Agar Base
SRC Agar (Sulfite-Reducing Clostridia Agar)
Ferrous Sulfite Agar
🔄 Cross-Reference / Equivalent Products
Cross-references are provided for convenience. Catalogue numbers are trademarks of their respective owners. AuSaMicS products are manufactured and quality-tested independently.
🧬 Complete Anaerobic & Water Safety Testing System
Clostridium & Anaerobe Detection Media
Complete Water Testing Panel
Need Clostridium perfringens Testing Method Support?
Our water and food microbiologists can assist with ISO 14189, AS/NZS 4276.19, and ADWG compliance testing workflows, anaerobic incubation system selection, heat-shock spore enumeration protocols, and NATA documentation.
For laboratory, research, and industrial use only. Not for food, feed, household, cosmetic, therapeutic, or personal use. Results should be interpreted by qualified laboratory personnel in accordance with applicable standard methods. Strictly anaerobic incubation conditions are required for valid results.
AuSaMicS Pty Ltd | ABN: 56 676 640 467 | 31 Longview CT, Thomastown VIC 3074, Australia
www.ausamics.com.au | support@ausamics.com.au | +61 412 520 598
Same-day dispatch • Australian stock • Full documentation included