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Cation-Adjusted Mueller Hinton Broth (CAMHB) AS‑1300 | Microbiology Culture Medium | Ausamics Life Science
$39.00 AUD
Cation-Adjusted Mueller Hinton Broth (CAMHB)
Prepared with Standardized Calcium & Magnesium Supplementation for Antimicrobial Susceptibility Testing | Cat. No. AS-1300
Cat. No. AS-1300 pH 7.3 ± 0.1 ⚠ Critical Ca²⁺ 20–25 mg/L Mg²⁺ 10–12.5 mg/L ✓ CLSI M07 Format ✓ Ca²⁺ & Mg²⁺ Standardized ✓ Low Thymidine/Thymine BD BBL 211438 Equivalent 🇦🇺 Made in Melbourne ⚡ Same-Week Dispatch
20–25 mg/L
Ca²⁺ (Calcium)
10–12.5 mg/L
Mg²⁺ (Magnesium)
7.3 ± 0.1
pH at 25°C — Critical
35 ± 1°C
Incubation — Ambient Air
Cat. No.
AS-1300
pH (25°C)
7.3 ± 0.1
Dissolution
21–22 g/L
Inoculum
5×10⁵ CFU/mL
Read at
16–20 hours
📄 Full DocumentationCOA, TDS & SDS every batch
🇦🇺 Australian StockNo import delays
⚡ Same-Week DispatchMelbourne warehouse
🔬 Technical SupportDirect from our team
Overview
Cation-Adjusted Mueller Hinton Broth (CAMHB, AS-1300) is prepared with standardized calcium and magnesium supplementation for use in broth microdilution and macrodilution Minimum Inhibitory Concentration (MIC) testing of non-fastidious aerobic and facultatively anaerobic bacteria. The formulation follows the composition described in CLSI M07, EUCAST guidelines, and ISO 20776-1 for cation-adjusted broth used in antimicrobial susceptibility testing.
The designation CAMHB (Cation-Adjusted Mueller Hinton Broth) is prepared with standardized divalent cation content targeting Ca²⁺ 20–25 mg/L and Mg²⁺ 10–12.5 mg/L as described in CLSI M07. Users performing validated AST workflows should verify lot performance with appropriate QC organisms. Standardized divalent cation concentrations are important for reproducible MIC results — deviation in either direction can affect MIC values for aminoglycosides, tetracyclines, and polymyxins.
Why Cation Adjustment Is Critical
Ca²⁺ — Calcium
20–25 mg/L
High Ca²⁺ reduces aminoglycoside activity against Pseudomonas aeruginosa by competing with drug binding to LPS. Too low → falsely low MICs (apparent susceptibility). Too high → falsely high MICs (apparent resistance).
Mg²⁺ — Magnesium
10–12.5 mg/L
Same mechanism as Ca²⁺ for aminoglycosides and tetracyclines. Also critical for colistin/polymyxin B MICs — excess Mg²⁺ stabilises LPS and reduces polymyxin binding, causing elevated MICs and false resistance results.
⚠️ pH is equally critical — 7.3 ± 0.1 only. pH below this range causes aminoglycosides and macrolides to appear falsely less active. pH above this range causes opposite effects. Verify pH of every prepared lot before use with a calibrated pH meter. Do not use lots outside the 7.2–7.4 range.
How pH and Cations Affect Individual Antibiotic Classes
Aminoglycosides
Most affected by Ca²⁺ and Mg²⁺. High cations → elevated MICs (false resistance). Testing P. aeruginosa most sensitive to this effect. pH must be 7.2–7.4.
Sulfonamides / TMP
Require low thymidine and thymine in medium. Excess thymidine causes false resistance to trimethoprim-sulfamethoxazole (SXT). MHB is formulated with minimal thymine content.
Polymyxins / Colistin
Mg²⁺ stabilises LPS outer membrane, competing with polymyxin binding. Excess Mg²⁺ → elevated colistin MICs. Standard CAMHB Mg²⁺ range is critical for valid colistin testing.
Tetracyclines
Tetracyclines chelate divalent cations. High Ca²⁺ and Mg²⁺ reduce free drug concentration, increasing apparent MICs. Standard cation levels prevent this interference.
Macrolides
Activity decreases in acidic conditions. pH below 7.2 causes macrolides to appear falsely less active. pH 7.3 ± 0.1 is essential for valid macrolide MICs.
β-Lactams / Fluoroquinolones
Relatively unaffected by cation levels at standard CAMHB ranges. However, pH outside 7.2–7.4 may affect fluoroquinolone activity. Starch neutralises any toxin interference.
Applications
🧪
Broth Microdilution
96-well plate MIC testing — CLSI M07 reference method
🔬
Broth Macrodilution
Tube MIC determination for research and reference
🧬
Etest Correlation
MIC validation and Etest method correlation studies
💊
Clinical Microbiology
Routine AST of Enterobacteriaceae, Staphylococci, Pseudomonas, Acinetobacter
💊
Agar Dilution Base
Add 15–17 g/L agar for MHA equivalent in agar dilution testing
📊
Pharmaceutical QC
Antibiotic potency testing, antimicrobial preservative efficacy
Supplements for Fastidious Organisms
| Organism / Group | Supplement Required | Concentration | Reference |
|---|---|---|---|
| Streptococcus spp. (including S. pneumoniae) | Lysed horse blood | 2–5% v/v | CLSI M07; EUCAST |
| Haemophilus influenzae | Haemophilus Test Medium (HTM) supplements | Per HTM protocol | CLSI M07 |
| Sulfonamide / TMP testing (any organism) | Thymidine phosphorylase | Per validated protocol | CLSI M07; EUCAST |
| MRSA / oxacillin testing | NaCl supplementation | 2% (w/v) NaCl | CLSI M100 |
| Cefiderocol testing | Iron-depleted CAMHB (ID-CAMHB) | Specific iron depletion protocol | CLSI / EUCAST cefiderocol guidelines |
FAQs
❓ What is the difference between MHB and CAMHB?
In practice, there is no difference when using a quality-manufactured product. CAMHB (Cation-Adjusted Mueller Hinton Broth) is simply the formal designation emphasising that the calcium and magnesium content has been verified and adjusted to the CLSI specification (Ca²⁺ 20–25 mg/L; Mg²⁺ 10–12.5 mg/L). All reputable commercial MHB preparations for MIC testing are cation-adjusted. AS-1300 is CAMHB — the cation content is verified by AAS/ICP for every production lot.
❓ Can I use CO₂ during incubation?
No. CLSI M07 and EUCAST specify incubation at 35 ± 1°C in ambient air only. CO₂ incubation lowers the pH of CAMHB by dissolving as carbonic acid — this directly violates the pH 7.3 ± 0.1 requirement and will invalidate MIC results, particularly for macrolides, aminoglycosides, and pH-sensitive antibiotics. The only exception is for organisms that require CO₂ for growth — in which case, the method is not standard broth microdilution and requires method-specific validation.
❓ What inoculum concentration should I use?
Per CLSI M07 and ISO 20776-1: the final inoculum in each well should be approximately 5 × 10⁵ CFU/mL. Prepare a direct colony suspension or growth suspension equivalent to a 0.5 McFarland standard (~1–2 × 10⁸ CFU/mL), then dilute 1:100 to 1:200 in CAMHB. The final inoculum concentration is critical — too low increases the risk of false susceptibility; too high increases the risk of false resistance.
❓ Why does starch appear in the formula?
Starch (1.5 g/L) acts as a detoxifying agent — it absorbs fatty acids and other bacteriostatic or bactericidal substances (including those from peptone components) that could inhibit bacterial growth or interfere with antibiotic activity. Without starch, certain organisms or antibiotic combinations may give falsely elevated MICs due to non-specific growth inhibition. This is a critical component that distinguishes MHB from simpler nutrient broths.
❓ Is AS-1300 equivalent to BD BBL 211438 and Oxoid CM0405?
Yes — AS-1300 follows the same CLSI/ISO reference formula: Beef Infusion 2.0 g/L, Acid Hydrolysate of Casein 17.5 g/L, Starch 1.5 g/L, pH 7.3 ± 0.1, Ca²⁺ 20–25 mg/L, Mg²⁺ 10–12.5 mg/L. Cation content verified by AAS/ICP per ISO/TS 16782. Full COA supplied with every batch including lot-specific cation concentrations.
Cross-Reference / Equivalents
| Manufacturer | Product Name | Cat. No. |
|---|---|---|
| BD BBL | Mueller Hinton II Broth (Cation-Adjusted) | 211438 |
| BD Difco | Mueller Hinton Broth | 275730 |
| Sigma-Aldrich / Merck | Mueller Hinton Broth 2, Cation-Adjusted | 90922 |
| Thermo Scientific / Oxoid | Mueller Hinton Broth | CM0405 |
| Liofilchem | Mueller Hinton II Broth (MH II Broth) | 610015 |
| HiMedia | Mueller Hinton Broth No. 2 | M391 |
Related Products
Product Specifications
| Product Name | Mueller Hinton Broth (MHB / CAMHB) |
| Catalogue Number | AS-1300 |
| Synonyms | CAMHB; Cation-Adjusted Mueller Hinton Broth; CA-MHB; MH Broth; Mueller Hinton Broth |
| Standards | Follows composition guidelines of CLSI M07 | EUCAST | ISO 20776-1 | ISO/TS 16782 |
| Equivalents | BD BBL 211438 | BD Difco 275730 | Sigma 90922 | Oxoid CM0405 | Liofilchem 610015 |
| Medium Type | Non-selective liquid broth — MIC testing reference medium |
| Dissolution | 21–22 g/L in purified water (refer to batch label for exact amount) |
| Final pH at 25°C | 7.3 ± 0.1 — CRITICAL. Verify every lot before use. pH 7.2–7.4 acceptable range. |
| Ca²⁺ content | 20–25 mg/L — verified by AAS or ICP per ISO/TS 16782 |
| Mg²⁺ content | 10–12.5 mg/L — verified by AAS or ICP per ISO/TS 16782 |
| Sterilisation | Autoclave 121°C for 10–15 minutes. DO NOT OVERHEAT — excess heat may precipitate divalent cations and alter pH. |
| Appearance (powder) | Light yellow to beige, free-flowing, hygroscopic powder |
| Appearance (prepared) | Pale to light yellow, clear solution without precipitate |
| Incubation | 35 ± 1°C for 16–20 hours in ambient air — NO CO₂ |
| Inoculum | ~5 × 10⁵ CFU/mL final concentration (0.5 McFarland → 1:100–1:200 dilution) |
| Storage (powder) | Cool, dry, tightly sealed; protected from moisture and light |
| Storage (prepared broth) | 2–8°C up to 1 month; aliquots may be frozen at −20°C or −70°C |
| HS Tariff Code | 3821.00.00 |
Formula — Per Litre (CLSI M07 / BD BBL 211438 Reference)
| Ingredient | g / L | Function |
|---|---|---|
| Beef Infusion Solids (Beef Extract) | 2.0 | Amino acids, vitamins, minerals, growth factors — balanced nutrient base for diverse organism growth |
| Acid Hydrolysate of Casein | 17.5 | Primary nitrogen source — free amino acids; low thymidine/thymine content essential for accurate SXT MIC results |
| Starch | 1.5 | Detoxifying agent — adsorbs fatty acids and bacteriostatic substances; prevents non-specific growth inhibition that would falsely elevate MICs |
| Calcium salts (added) | Adjusted | Final Ca²⁺ target: 20–25 mg/L per CLSI M07 / ISO/TS 16782 |
| Magnesium salts (added) | Adjusted | Final Mg²⁺ target: 10–12.5 mg/L per CLSI M07 / ISO/TS 16782 |
| Dissolution | 21–22 g/L | pH 7.3 ± 0.1 at 25°C | Autoclave 121°C / 10–15 min | DO NOT OVERHEAT |
⚠️ DO NOT OVERHEAT during autoclaving. Prolonged or excessive heat causes precipitation of divalent cation salts, reducing Ca²⁺ and Mg²⁺ in solution and potentially shifting pH. Use the shortest validated autoclave cycle (typically 10–15 minutes at 121°C). Mix well before dispensing post-sterilisation.
Preparation Protocol
1
Suspend 21–22 g (per label) of dehydrated CAMHB (AS-1300) in 1 litre of purified or deionised water. Mix thoroughly.
2
Heat gently if necessary to dissolve. Most lots dissolve without boiling. Do not overheat.
3
Dispense into tubes, bottles, or 96-well plates as required.
4
Sterilise by autoclaving at 121°C for 10–15 minutes. Do not exceed the stated cycle.
5
Allow to cool. Verify pH of each lot with a calibrated pH meter: acceptable range 7.2–7.4. Discard lots outside this range.
6
Store at 2–8°C. Use within 1 month or freeze aliquots at −20°C / −70°C for extended storage.
Literature & References
| # | Reference |
|---|---|
| 1 | CLSI. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically. CLSI Standard M07. Current edition. Wayne, PA: CLSI. [Primary reference — CAMHB specification] |
| 2 | CLSI. Performance Standards for Antimicrobial Susceptibility Testing. CLSI Supplement M100. Current edition. Wayne, PA: CLSI. |
| 3 | EUCAST. Breakpoint Tables for Interpretation of MICs and Zone Diameters. European Committee on Antimicrobial Susceptibility Testing; current version. eucast.org |
| 4 | ISO 20776-1:2019. Clinical laboratory testing and in vitro diagnostic test systems — Susceptibility testing of infectious agents. Geneva: ISO; 2019. |
| 5 | ISO/TS 16782:2016. Clinical laboratory testing — Criteria for acceptable lots of dehydrated Mueller-Hinton agar and broth for antimicrobial susceptibility testing. Geneva: ISO; 2016. |
| 6 | Mueller JH, Hinton J. A protein-free medium for primary isolation of the Gonococcus and Meningococcus. Proc Soc Exp Biol Med. 1941;48:330–333. [Original medium description] |
📄 Full 16-section GHS SDS available (Australian WHS Regulations 2023 / GHS 7th Edition) — support@ausamics.com.au
Section 1 — Identification
| Product Name | Mueller Hinton Broth (MHB / CAMHB) |
| Catalogue No. | AS-1300 |
| Intended Use | Cation-adjusted liquid medium for antimicrobial susceptibility testing applications (MIC determination). Laboratory use only. |
| Supplier | AuSaMicS Pty Ltd | ABN 56 676 640 467 |
| Address | 31 Longview CT, Thomastown VIC 3074, Australia |
| Emergency | Poisons Information Centre: 13 11 26 (24 hr) |
| Phone | +61 412 520 598 | support@ausamics.com.au |
Section 2 — Hazard Identification (GHS 7th Ed / WHS 2023)
| GHS Classification | NOT classified as a hazardous substance under Australian WHS Regulations 2023. All components are food-grade or GRAS at supplied concentrations. |
| Signal Word | None required |
| Other Hazards | Combustible powder. Hygroscopic — absorbs moisture rapidly. Dust may cause mild respiratory irritation during bulk weighing. |
Composition
| Component | g/L | CAS | Hazard |
|---|---|---|---|
| Beef Infusion Solids | 2.0 | Mixture | Not hazardous |
| Acid Hydrolysate of Casein | 17.5 | 65072-00-6 | Not hazardous |
| Starch | 1.5 | 9005-84-9 | Not hazardous |
| Calcium / Magnesium salts | Adjusted | Various | Not hazardous at use level |
| PPE | P1 respirator when weighing bulk powder (hygroscopic — clumping possible); safety glasses; nitrile gloves; lab coat |
| Storage (powder) | Cool, dry, tightly sealed. Hygroscopic — keep container closed except during weighing. |
| Waste (inoculated broth) | Autoclave 121°C / 15 min before disposal as microbiological waste per institutional biosafety procedures |
| Transport | Not dangerous goods — ADG, IMDG, IATA |
| Regulatory | Australian WHS Regulations 2023 | GHS 7th Edition | AICIS compliant |
Quality Specifications
| Parameter | Specification | Method |
|---|---|---|
| Appearance (powder) | Light yellow to beige, free-flowing, hygroscopic powder | Visual |
| Appearance (prepared) | Pale to light yellow, clear without precipitate | Visual after dissolution |
| pH (prepared, 25°C) | 7.3 ± 0.1 — CRITICAL. Acceptable range 7.2–7.4. | pH meter (calibrated) |
| Ca²⁺ (Calcium) | 20–25 mg/L | Atomic Absorption Spectrophotometry (AAS) or ICP per ISO/TS 16782 |
| Mg²⁺ (Magnesium) | 10–12.5 mg/L | AAS or ICP per ISO/TS 16782 |
| Moisture Content | ≤5.0% (w/w) | Loss on drying |
| Clarity | Clear solution; no precipitate post-sterilisation | Visual inspection |
| Growth — E. coli ATCC 25922 | Good growth; MIC of ampicillin in expected range when tested against CLSI M100 QC guidelines | CLSI M07 QC method |
| Growth — S. aureus ATCC 29213 | Good growth; MIC of oxacillin in expected range when tested against CLSI M100 QC guidelines | CLSI M07 QC method |
| Growth — P. aeruginosa ATCC 27853 | Good growth; aminoglycoside MICs within CLSI QC range | CLSI M07 QC method |
| Batch COA | Lot-specific including Ca²⁺ and Mg²⁺ values | Included with every order |
Cation Verification Statement
AS-1300 is prepared with standardized calcium and magnesium supplementation targeting Ca²⁺ 20–25 mg/L and Mg²⁺ 10–12.5 mg/L as described in CLSI M07. Cation content is reported on the batch Certificate of Analysis. Users should verify lot performance with appropriate QC organisms before routine use in validated AST workflows.
Manufacturing & Documentation
Manufactured by AuSaMicS Pty Ltd
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Formulated per CLSI M07 / ISO 20776-1 / BD BBL 211438 reference specification
✓ Ca²⁺ and Mg²⁺ verified by AAS/ICP — lot values on COA
✓ pH verified 7.3 ± 0.1 every batch
✓ Starch 1.5 g/L — CLSI-specified detoxifier
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Formulated per CLSI M07 / ISO 20776-1 / BD BBL 211438 reference specification
✓ Ca²⁺ and Mg²⁺ verified by AAS/ICP — lot values on COA
✓ pH verified 7.3 ± 0.1 every batch
✓ Starch 1.5 g/L — CLSI-specified detoxifier
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch
⚠️ For antimicrobial susceptibility testing and laboratory research use only. Not for human, veterinary, pharmaceutical, or therapeutic use. Verify new lots with appropriate QC organisms before routine use in validated AST workflows.