Brain Heart Infusion Agar(BHI) is a nutrient-dense medium used in microbiology to cultivate a wide range of fastidious and non-fastidious microorganisms such as bacteria, yeasts, and molds.
Table of Contents
What is Brain Heart Infusion Agar?
Brain-Heart Infusion(BHI) Agar is a nutrient-rich medium commonly used in microbiology to produce a wide variety of fastidious and non-fastidious microorganisms, such as bacteria, yeasts, and molds. It is particularly useful for developing organisms with complex dietary needs.
Composition of Brain Heart Infusion Agar
Brain Heart Infusion Solids: 7.7 g
These solids are obtained from bovine or porcine brain and heart tissues and are high in nitrogen, vitamins, amino acids, and other essential components.
Peptone: 10.0 g
Peptone is a protein hydrolysate that provides the extra nitrogen, amino acids, and peptides required for microbial development.
Sodium Chloride: 5.0 g
Sodium chloride maintains the medium’s osmotic balance, providing a suitable ionic environment for microbial cells.
Disodium Phosphate: 2.5 g
Disodium phosphate functions as a buffering agent, ensuring that the medium’s pH remains stable.
Agar: 15.0 g
Agar is a solidifying substance that creates a stable environment for microbial development.
Distilled Water: 1 liter
Distilled water is used to dissolve all of the components and create an environment for microbial development.
Principle of Brain Heart Infusion Agar
1. Nutrient Richness
BHI Agar contains brain and heart infusion solids, which provide a rich source of nitrogen, vitamins, amino acids, and other essential nutrients required for microbial growth. Peptone, a protein hydrolysate, further supplements the medium with additional nitrogen and growth factors.
2. Energy Source
BHI Agar contains dextrose (glucose) as a carbohydrate source, which provides energy for microbial metabolism. Microorganisms use glucose as their primary carbon and energy source for growth and reproduction.
3. Osmotic Balance:
To maintain osmotic balance, sodium chloride (NaCl) is added to BHI Agar. Osmotic equilibrium is essential for the normal function of microbial cells because it influences cell volume, turgor pressure, and nutrient intake.
4. pH Stability
Disodium phosphate functions as a buffer, helping to keep the medium’s pH stable. This guarantees that the pH remains in the ideal range for microbial growth and metabolism.
5. Solidifying Agent:
BHI Agar contains agar, a seaweed-derived polysaccharide, which serves as a solidifying agent. When cooled, agar creates a gel matrix that provides a firm surface for microbial growth while also aiding colony isolation and enumeration.
Preparation of Brain Heart Infusion Agar
Brain Heart Infusion (BHI) Agar requires a number of processes to guarantee that the medium is sterile and ready for microbiological culture. The following is a full explanation on how to prepare BHI Agar.
Materials Needed
- BHI Agar powder contains brain heart infusion solids, peptone, sodium chloride, disodium phosphate, dextrose, and agar.
- Distilled water
- Heat source (such as a hot plate or microwave)
- Autoclave
- Sterile Petri dishes
- Sterilized flasks or bottles
- Measuring cylinder
- Magnetic stirrer and stir bar are optional.
- pH meter or indicator strips
Results of Brain Heart Infusion Agar
Colony Morphology
1. Bacteria
- Shape: Colonies might be spherical, uneven, or filamentous.
- Size varies from microscopic to several millimeters in diameter.
- Color varies per species, ranging from colorless to a variety of colors.
- Surface may be smooth, rough, wrinkled, or mucoid.
- Elevation can be flat, elevated, convex, or umbonate (with a raised center).
2. Yeasts
- Shape is typically circular or oval.
- Size: Larger than bacterial colonies, with a smooth, creamy, and shiny appearance.
- Color: Usually white, off-white, or cream, but can vary depending on the species.
3. Molds
- Shape: irregular, filamentous, having a fuzzy or cottony feel.
- Size: Can cover a considerable portion of the plate.
- Color varies greatly depending on the mold species, it can be white, green, black, yellow, or another color
Uses of Brain Heart Infusion (BHI) Agar
1. Cultivation of Fastidious Organisms
BHI Agar promotes the development of fastidious bacteria that demand complex nutrients. This contains germs such as:
- Streptococcus species.
- Neisseria spp.
- Hemophilus spp.
These organisms have high nutritional requirements, which are supplied by the rich nutrient profile of BHI Agar.
2. General Microbial Culture
BHI Agar is appropriate for the culture of a wide range of non-fastidious bacteria, including:
- Bacteria include both Gram-positive and Gram-negative species.
- Yeasts and molds are fungi that flourish in nutrient-rich environments
3. Clinical Diagnostics
BHI Agar is used to isolate and identify pathogens from clinical specimens, such as:
- Blood Urine
- Cerebrospinal Fluid
- Respiratory secretions
4. Antimicrobial Susceptibility Testing
BHI Agar is used to evaluate antibiotic efficacy against specific bacterial strains. This involves:
- The disc diffusion method involves placing antibiotic-impregnated discs on the agar surface to observe zones of inhibition.
- Minimum Inhibitory Concentration (MIC): The lowest concentration of an antibiotic required to suppress observable growth of a bacterium
Frequently Asked Question(FAQ)
What is Brain Heart Infusion (BHI) Agar?
Brain-Heart Infusion (BHI) Agar is a nutrient-rich medium commonly used in microbiology to produce a wide variety of fastidious and non-fastidious microorganisms, such as bacteria, yeasts, and molds.
What are the Uses of Brain Heart Infusion (BHI) Agar?
The uses of Brain Heart Infusion (BHI) Agar are:
1. Cultivation of Fastidious Organisms
2. General Microbial Culture
3. Clinical Diagnostics
4. Antimicrobial Susceptibility Testing
Related Article