Liofilchem® MIDDLEBROOK 7H11 AGAR BASE

Liofilchem Middlebrook 7H11 Agar Base is a selective, agar-based medium optimized for the isolation, cultivation, and susceptibility testing of Mycobacterium species, particularly Mycobacterium tuberculosis. It is enriched with essential supplements to ensure robust growth and accurate results in clinical and research applications.

Key Features

1. Selective Isolation
   • Designed for the growth of Mycobacterium tuberculosis and other mycobacteria while inhibiting contaminants with malachite green.
2. Enriched with Supplements
   • Requires Middlebrook OADC Supplement and Glycerol Supplement for complete nutrient support.
3. Improved Susceptibility Testing
   • Agar-based formulation allows for more reliable drug susceptibility testing compared to egg-based media like Lowenstein Jensen (LJ), which can inactivate antibiotics.
4. Optimized for Mycobacteria
   • Contains essential growth factors such as oleic acid, albumin, glucose, catalase, and trace ions.
5. Hygroscopic Stability
   • Packaged to prevent moisture absorption and ensure product stability over time.

Composition (per liter)

Supplement Requirements

1. Middlebrook OADC Supplement (Ref. 81035):
   • Contains oleic acid, albumin, dextrose, sodium chloride, and catalase.
   • Provides essential fatty acids, energy sources, and protection from toxic agents.
2. Glycerol Supplement (Ref. 80021):
   • Adds glycerol as an additional carbon and energy source to support Mycobacterial growth.

Preparation Instructions

1. Suspend 20.5 g of powder in 900 mL of distilled water containing 5 mL of glycerol.
2. Heat to boiling and shake until completely dissolved.
3. Sterilize by autoclaving at 121°C for 15 minutes.
4. Cool to 45–50°C.
5. Aseptically add 100 mL of Middlebrook OADC Supplement.
6. Mix thoroughly and pour into sterile Petri dishes or tubes.

Applications

1. Selective Isolation of Mycobacteria
   • Used to isolate and cultivate Mycobacterium tuberculosis from clinical specimens such as sputum, urine, or biopsies.
2. Drug Susceptibility Testing (DST):
   • Enables reliable testing for susceptibility to anti-tuberculosis drugs like isoniazid, rifampicin, ethambutol, and streptomycin.
3. Primary and Pure Cultures
   • Suitable for the cultivation of pure mycobacterial strains in clinical and research settings.
4. Differentiation of Mycobacterium Species
   • Ideal for studying the morphology, pigment production, and colony characteristics of Mycobacterium species.
5. Research Studies
   • Used in antimicrobial resistance studies and epidemiological investigations of tuberculosis infections.

Technique

1. Inoculation:
   • Process clinical specimens following CDC or other established protocols.
   • Use direct inoculation or streaking methods.
2. Incubation:
   • Incubate at 35 ± 2°C for up to 8 weeks in an aerobic atmosphere enriched with 5–10% CO₂.
   • Loosen tube caps during the first week for CO₂ circulation; tighten caps afterward to prevent dehydration.
3. Observation:
   • Examine weekly for growth, pigment production, and colony morphology.
   • Negative cultures do not rule out infection due to sampling errors or processing issues.

Interpretation of Results

Advantages

1. Enhanced Mycobacterial Growth
   • Nutrient-rich formulation supports robust growth of slow-growing Mycobacteria.
2. Reliable for Drug Testing
   • Preferred for antibiotic susceptibility testing due to consistent performance.
3. Selectivity
   • Malachite green suppresses contaminant bacteria, ensuring selectivity for Mycobacteria.
4. Improved Stability
   • Agar-based media are less prone to drug inactivation compared to egg-based alternatives.
5. Flexibility
   • Suitable for primary isolation, pure culture studies, and DST protocols.

Storage Conditions

• Store the dehydrated medium at 10–30°C in a dry environment.
• Keep the prepared medium at 2–8°C, protected from light.
• Use before the expiry date indicated on the label.

Quality Control

Precautions

• For professional use only.
• Handle specimens and cultures using appropriate biosafety precautions.
• Dispose of media and cultures following local and national regulations.

References

1. Murray, P.R., Baron, E.J., Jorgensen, J.H., Landry, M.L., and Pfaller, M.A. (2007). Manual of Clinical Microbiology, 9th Edition.
2. CDC Guidelines for Mycobacterium tuberculosis Laboratory Testing.

The Liofilchem Middlebrook 7H11 Agar Base is a robust and selective medium ideal for isolating, cultivating, and testing susceptibility of Mycobacterium tuberculosis.