Mueller Hinton Broth (MHB)
Mueller Hinton Broth (MHB)
Cation-Adjusted Reference Broth for Antimicrobial Susceptibility Testing
Catalog Number: AS-1300
Overview
Mueller Hinton Broth (MHB), also referred to as Cation-Adjusted Mueller Hinton Broth (CAMHB), is the official international reference liquid medium for broth microdilution and macrodilution Minimum Inhibitory Concentration (MIC) testing of non-fastidious aerobic and facultatively anaerobic bacteria.
It is the mandatory broth specified in CLSI M07, CLSI M100, EUCAST, ISO 20776-1, and all major global antimicrobial susceptibility testing standards.
Applications
• Broth microdilution MIC testing (96-well plates)
• Broth macrodilution MIC determination
• Agar dilution base (when supplemented with 15–17 g/L agar)
• Etest correlation and validation studies
• Routine susceptibility testing of Enterobacteriaceae, Pseudomonas, Acinetobacter, Staphylococcus, and Enterococcus (with supplements)
Key Features & Benefits
• Precisely cation-adjusted calcium and magnesium for reproducible MIC results
• Low thymidine and thymine levels ensure accurate sulfonamide and trimethoprim testing
• Starch neutralizes bacterial toxins that may interfere with antibiotic activity
• Clear, particle-free broth allows easy turbidity and growth assessment
• Fully compliant with CLSI, EUCAST, and ISO reference requirements
Principle of the Medium
Mueller Hinton Broth provides a nutritionally adequate yet controlled environment for antimicrobial susceptibility testing. Precise adjustment of divalent cations (Ca²⁺ and Mg²⁺) is critical for reproducible activity of aminoglycosides, tetracyclines, and polymyxins. Low thymidine and thymine content prevents false resistance results with folate pathway inhibitors, while starch absorbs bacterial toxins that may otherwise inactivate antibiotics.
Typical Composition (per litre)
Beef Infusion Solids – 2.0 g
Acid Hydrolysate of Casein – 17.5 g
Starch – 1.5 g
Final cation content (after sterilisation):
Calcium (Ca²⁺): 20–25 mg/L
Magnesium (Mg²⁺): 10–12.5 mg/L
Final pH: 7.3 ± 0.1 at 25 °C (critical)
Preparation
Dissolve 21.0 g of dehydrated cation-adjusted Mueller Hinton Broth in 1 L purified water.
Heat gently if necessary and mix thoroughly until fully dissolved.
Dispense into tubes or bottles as required.
Sterilise by autoclaving at 121 °C for 15 minutes.
Avoid excessive heating, as divalent cations may precipitate.
Special Modifications
Mueller Hinton Broth + 2–5% lysed horse blood: for Streptococcus spp.
Mueller Hinton Broth + thymidine phosphorylase: for sulfonamide and trimethoprim testing
CAMHB (Cation-Adjusted Mueller Hinton Broth) is the official designation in CLSI and EUCAST standards.
Incubation
Incubate at 35 ± 1 °C in ambient air.
Standard incubation time: 16–20 hours
Extended incubation: 18–24 hours for vancomycin testing of Enterococcus spp.
Storage & Stability
Prepared broth: Store at 2–8 °C and use within 1 month
For extended storage, aliquots may be frozen at −20 °C or −70 °C
Intended Use
For antimicrobial susceptibility testing only.
Not for human, veterinary, pharmaceutical, or therapeutic use.
Quality & Compliance
Manufactured under controlled conditions for batch-to-batch consistency.
Meets performance criteria of CLSI M07/M100, EUCAST, and ISO 20776-1.
Performance comparable to leading international reference media suppliers.
Customs & Trade Information
HS / AHECC Code: 3821.00.00
Prepared culture media for the development or maintenance of microorganisms