How To Use Blood Agar Plates

 Are you looking for a reliable, easy-to-use method for growing bacteria?

If so, you need a blood agar plate. Blood agar is an enriched type of growth media that contains 5% blood supplement. This makes it an ideal environment for growing fastidious bacteria.

In this article, we will explain how to use blood agar plates to grow bacteria. We will also provide tips on how to store ready-to-use blood agar plates.

Blood Agar

Sheep Blood Agar is a differential as well as an enriched medium. It is used to isolate, cultivate, and detect the haemolytic activity of pathogenic micro-organisms such as Streptococci and Pneumococci. The source of animal blood and the type of base medium used can influence haemolytic patterns. Nucleotidase destroys V factors in sheep blood, preventing Haemophilus species from growing on sheep blood agar unless other micro-organisms, such as Staphylococci, provide the V factors. Small amounts of reducing sugars inhibit the expression of β-haemolysis. Streptococci that are β-haemolytic may develop a green zone or ring of haemolysis.

Several streptococcal species produce substances that lyse the red cell wall, allowing haemoglobin to be released. These substances are known as haemolysins. When streptococcal haemolysins, or streptolysins, are growing on a blood agar plate, their activity can be easily observed. Different Streptococci species have different effects on red blood cells in blood agar.

  • Alpha-haemolytic Streptococci are those that achieve incomplete haemolysis and only partial destruction of the cells that are present around colonies. This type of haemolysis is distinguished by a distinct greening of the agar in the haemolytic zone, and thus this group of streptococci is also known as the "viridian group."

  • In beta-haemolytic species, haemolysins completely destroy red cells in the agar zones surrounding their colonies, and they appear as small, opaque or semi translucent colonies surrounded by clear zones in a red opaque medium. Streptolysin-O, an antigenic oxygen-labile enzyme, and Streptolysin-S, a non-antigenic oxygen-stable enzyme, are the two types of beta lysins produced. When blood agar plates are streaked and simultaneously stabbed to demonstrate subsurface haemolysis by Streptolysin-O in an environment with low oxygen tension, the haemolytic reaction is accelerated. Some Staphylococcus, Escherichia coli, and other bacterial strains may also exhibit beta haemolysis.

  • Some Streptococci species do not produce haemolysins. As a result, when their colonies grow on blood agar, there is no change in the red blood cells around them. These are known as non-haemolytic or gamma-haemolytic Streptococci.

Composition Of Blood Agar

Ingredients

Gms / Ltr

Casein enzymic hydrolysate

14.00

Sodium chloride

5.00

Peptic digest of animal tissue

4.50

Yeast extract

4.500

Sheep Blood

50.00 ml

Agar

12.50

Nutritional components such as pancreatic digest of casein, neutralised peptone, and yeast extract are included in the medium, and the addition of sodium chloride creates an osmotically balanced environment for bacterial cells. The addition of 5% defibrinated sheep blood allows for the determination of haemolytic reactions, which is an important distinguishing feature.

TM Media Blood Agar Plate

TM Media has created ready-to-use culture media plates. They are easy to use and accurate in composition. The perfect consistency and accurate composition give highly reproducible results.



How To Use TM Media Blood Agar Plate?

To use the TM media blood agar plate, first collect the desired sample. This can be done by swabbing the area of interest or by taking a sample from a culture. After this, open the plate in an aseptic environment. Next, streak, inoculate, or surface-spread the test inoculum aseptically onto the blood agar plate. Then, incubate the plate for 24–48 hours. After incubation, examine the plate for colonies of bacteria. The type of bacteria present in the sample will determine the appearance of the colonies.

Storage Conditions

Store the blood agar plates at 2–8 °C. Avoid freezing and overheating. Do not open the plates until you are ready to use them. Do not use plates if they show evidence of microbial contamination, discoloration, drying, cracking, or other signs of deterioration.

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