Blood Agar Base No. 2
CAT: AS‑1145
Overview
Blood Agar Base No. 2 (CAT: AS‑1145) is a highly enriched, non‑selective solid medium base formulated to produce exceptionally wide and clear haemolytic zones when supplemented with 5–10% defibrinated blood (sheep or horse). Recognized as one of the best general‑purpose blood agars, it is widely used for the isolation and differentiation of fastidious pathogens, particularly Streptococcus pyogenes, S. agalactiae, S. pneumoniae, Listeria monocytogenes, and haemolytic staphylococci. Its extra‑rich nutrient content supports larger colonies and sharper β‑haemolysis compared with standard Blood Agar Base, making it the preferred choice in many European and Asian clinical laboratories.
Applications
Primary isolation of β‑haemolytic streptococci (groups A, B, C, G).
Optimum demonstration of haemolysis, especially wide zones of S. pyogenes.
Cultivation of Listeria, Corynebacterium, Neisseria, Haemophilus.
Standard medium for CAMP test, chocolate agar, and selective streptococcal media.
Official reference in Oxoid CM271, HiMedia M834, BD 297848.
Key Features
Extra meat infusion + selected peptones → luxuriant growth and wide clear haemolysis zones.
Consistently produces β‑haemolysis >6–10 mm with group A streptococci.
Preferred over ordinary Blood Agar Base when maximum haemolysis clarity is required.
Transparent agar surface for easy colony and haemolysis observation.
Composition (per liter)
Proteose Peptone: 15.0 g
Liver Digest: 2.5 g
Yeast Extract: 5.0 g
Meat Infusion: 10.0 g (equivalent)
Sodium Chloride: 5.0 g
Agar: 14.5 g
Final pH: 7.4 ± 0.2 at 25 °C
Supplement: Add 50–100 mL/L sterile defibrinated blood (5–10%) at 45–50 °C.
Preparation
Suspend 52.0 g dehydrated base in 1 L purified water. Mix well and boil to dissolve completely. Autoclave at 121 °C for 15 minutes. Cool to 45–50 °C, add 5–10% sterile blood with gentle mixing (avoid foaming), and pour plates immediately (~20 mL per 90 mm plate).
Typical Haemolysis (24 h at 35–37 °C, 5% CO₂)
S. pyogenes: very wide, clear β‑haemolysis (often >10 mm).
S. agalactiae: narrow β or double‑zone haemolysis.
S. pneumoniae: α‑haemolysis (green).
Listeria monocytogenes: narrow β‑haemolysis.
Storage
Dehydrated base: Store in a cool, dry place below 30 °C.
Prepared blood agar plates: Store at 2–8 °C in sealed bags; use within 3–4 weeks depending on blood source.
Intended Use
For clinical and veterinary diagnostic microbiology. Not intended for diagnostic or therapeutic use in humans or animals.
