The most meticulous organisms that have a high nutritional requirements can be developed using infusion media. Meat infusions were among the first media utilized to cultivate bacteria. Huntoon created a medium with fresh beef heart and peptone that was later named the Heart Infusion Aggar. He showed that it can be utilized to help support the growth of fastidious nutritional microorganisms, without the need for enrichment like blood from animals. Heart Infusion Agar can be used as a general-purpose growth medium. It is recommended for cultivation of fastidious and nutritious microorganisms and as a medium for basal growth that can be used for a wide range of purposes.
Principle of Heart Infusion Agar
The infusion of beef heart and tryptose offer the necessary nutrients for pathogenic bacteria. Beef heart infusions provide amino acids and nitrogenous compounds essential for the growth of fastidious nutritional bacteria. Sodium chloride supplies essential electrolytes and helps maintain osmotic equilibrium. Agar is an agent that solidifies.
Composition of Heart Infusion Agar
|Beef heart, infusion form||500.0|
Final pH (at 25°C): 7.4 ± 0.2
Preparation and Method of Use of Heart Infusion Agar
- Suspend 40 grams of the mixture in 1000ml of distillate water.
- Bring the temperature to a boil to completely dissolve the medium.
- Sterilize with autoclaving with 15 lbs pressurization (121degC) over 15 mins.
- If desired , 5% v/v defibrinated sterile blood can be added.
- Mix thoroughly and disperse according to your preference.
- Innoculate your specimen and color it as quickly as is possible after it has received at the laboratory.
- If the material is grown using a single swab place the swab on an area of the agar’s surface and streak to isolate.
- Incubate aerobically or with 5-10% CO2 at 33 to 37 degrees Celsius for 18-24 hours.
- Look for the typical colony the morphology
Result Interpretation on Heart Infusion Agar
|Escherichia coli||luxuriant growth; beta hemolysis|
|Staphylococcus aureus||Good-luxuriant growth; beta hemolysis|
|Neisseria meningitides||Luxuriant growth; no hemolysis|
|Streptococcus pneumoniae||Good growth; alpha hemolysis|
|Streptococcus pyogenes||Good growth; alpha hemolysis; beta hemolysis|
Uses of Heart Infusion Agar
- It is suggested to the use in qualitative methods for the isolation of a large range of microorganisms with a high degree of speed.
- It is also used to cultivate Vibrio as well as Streptococci.
- It is employed for large-scale cultivation of bacteria that is required for the preparation of vaccines.
- With the addition of blood, Heart Infusion Aggar is a good way to research hemolytic reactions.
- It is also possible to supplement by horse serum, glucose and antibiotics to cultivate an array of microorganisms.
- It was employed for the isolation and quantification of hemolytic Streptococci within milk.
- The agar-deep fill could be utilized for an oxygen-based gradient in order to assess the oxygen needs of the inoculum, by watching the area in which the growth is most prominent.
- It is suggested that immunological, biochemical mass spectrometry or molecular tests be conducted on pure-cultured colonies to confirm the identity of the colony.
- Due to the different needs for nutrition of certain organisms, occasionally isolated species may be found that fail to develop or are not able to grow in this medium.