Blood Agar- Composition, Preparation, Uses and Pictures

Blood Agar (BA) are enriched medium used to culture those bacteria or microbes that do not grow easily. Such bacteria are called “fastidious” as they demand a special, enriched nutritional environment as compared to the routine bacteria.

Blood Agar is used to grow a wide range of pathogens particularly those that are more difficult to grow such as Haemophilus influenzae, Streptococcus pneumoniae and Neisseria species. It is also required to detect and differentiate haemolytic bacteria, especially Streptococcus species. It is also a differential media in allowing the detection of hemolysis (destroying the RBC) by cytolytic toxins secreted by some bacteria, such as certain strains of Bacillus, Streptococcus, Enterococcus, Staphylococcus, and Aerococcus

Blood agar can be made selective for certain pathogens by the addition of antibiotics, chemicals or dyes. Examples includes crystal violet blood agar to select Streptococcus pyogens from throat swabs, and kanamycin or neomycin blood agar to select anaerobes from pus.

Composition of Blood Agar

  • 0.5% Peptone
  • 0.3% beef extract/yeast extract
  • 1.5% agar
  • 0.5% NaCl
  • Distilled water

(Since Blood Agar is made from Nutrient Agar, above is the composition of Nutrient Agar)

  • 5% Sheep Blood
  • pH should be from 7.2 to 7.6 (7.4)

Preparation of Blood Agar

  1. Suspend 28 g of nutrient agar powder in 1 litre of distilled water.
  2. Heat this mixture while stirring to fully dissolve all components.
  3. Autoclave the dissolved mixture at 121 degrees Celsius for 15 minutes.
  4. Once the nutrient agar has been autoclaved, allow it to cool but not solidify.
  5. When the agar has cooled to 45-50 °C, Add 5% (vol/vol) sterile defibrinated blood that has been warmed to room temperature and mix gently but well.
  6. Avoid Air bubbles.
  7. Dispense into sterile plates while liquid.

Uses of Blood Agar

  1. Blood Agar is a general purpose enriched medium often used to grow fastidious organisms
  2. To differentiate bacteria based on their hemolytic properties (β-hemolysis, α-hemolysis and γ-hemolysis (or non-hemolytic)).

    Read more about Haemolysis and its types.

Pictures of Blood Agar


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32 thoughts on “Blood Agar- Composition, Preparation, Uses and Pictures”

  1. Hi, do we need to test the blood whether it is free from extraneous viruses. it the virus is presence, can we use it for blood agar preparation?

    • Brucella grows on standard laboratory media, like sheep or chocolate agar, and in most blood culture systems. The bacteria is strictly aerobic, nonhemolytic, oxidase positive, and produce a large amount of urease. Brucella is detected in blood cultures after 3 to 4 days of incubation.

    • no please you should not use blood from EDTA to prepare blood agar because it shows a very low number of colonies and wrong hemolytic zone (about 6mm) instead of <5mm, though its capable of giving accurate type of hemolysis (beta,gamma,alpha).

  2. Please how do you prepare trypticase soy agar with 5% sheep blood.

    And is blood agar selective for the identification and isolation of Helicobacter pylori?

    • Hey may I know
      What culture plates have to be used in order to grow the following bacteria

      1) bacillus Cerus
      2) clostridium perfringens
      3) listeria
      4) Aeromonas
      5) brucella
      6) staph
      7) cornybacterium

      Can a few plates encompass all these? Thank you

      • Hey,

        for Aeromonas I would recommend Ryan medium, GSP agar and LB. For Staphylococcus and Brucella – Tryptic Soy Agar.

      • Hi Desmond,

        Please find the below mentioned answers

        1) Bacillus cerus – TSA Tryptic Soy agar
        2) clostridium perfringens – Pefringens agar (Anaerobic Condition)
        3) listeria sp – (Brain Heart Infusion (BHI)
        4) Aeromonas – Aeromonas Agar
        5) Brucella sp – Brucella agar
        6) Staphylococcus sp – Baired Parker agar
        7) Cornybacterium sp – Hoyle’s medium

    • Because also the human blood it contain alot of nutrients which can be used for blood agar production hence are where food stored in form of amnio acid from protein,fatty acid and grecelo from lipid and fat and minerals

  3. How to prepare 10% crystal violet blood agar to contain 1in 250000 final dilution of crystal violet …materials provided:10% crystal violet 1ml, sterile molten nutrient agar 20mls ,sterile petridish.

  4. hello, Sagar
    can we use human blood instead of sheep blood for media preparation??
    does it make any change??

    Please reply.


    • No human blood can’t be used because of pathological status of human we take vegetables meat by which both may be containing antbiotic which may hinder the growth of cultured bacteria or microbes

      • Please human blood can be but you must first know that the one whose blood you using is not on any drugs like antibiotics or something that can kill the microbes.

    • How to prepare 5% blood agar given 5mls of sterile defibrinated blood, 20mls of sterile molten nutrient agar and one petri dish

    • No ,we can’t use the human blood because human blood Many antibiotic drugs or vaccine that inhabited the growth of microorganisms.
      Thank you……

      • At high temperature (50°C), vaccine residues and drugs are expected to have been deactivated.
        In a standard laboratory setting with blood bank facility, expired blood from the bank are the best for Blood Agar production.

  5. I am worried that your information on the type of organisms that grow on BAP (blood agar plates)might have come from a source that has very little experience in microbiology. The only time I have observed Haemophilus influenzae growing on BAP is when it is sateliting around a Staph.aureus colony. BAP alone does not support the growth of H.influenzae.

    microbiologist in California


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