Overview:
Columbia Agar Base is a highly nutritious, general-purpose dehydrated medium designed for the isolation and cultivation of both non-fastidious and fastidious microorganisms from clinical and non-clinical specimens. First described in 1966 by Ellner et al., it incorporates specialized peptones, yeast extract, and beef extract to provide essential nitrogen, carbon, vitamins, and trace elements, while corn starch serves as an energy reserve and neutralizes toxic metabolites from specimens. When supplemented with 5-10% defibrinated sheep blood, it becomes Columbia Blood Agar, enabling the demonstration of hemolytic reactions and supporting pathogens requiring the X-factor (hemin). The base alone is non-selective, promoting luxuriant growth, typical colony morphology, and pigment production under aerobic conditions at 35-37�C, making it a versatile foundation for selective and enriched media in clinical microbiology labs per CLSI and ISO standards.
Applications:
?? Primary isolation of Gram-positive cocci (e.g., streptococci, staphylococci, enterococci) and Gram-negative rods (e.g., Enterobacteriaceae, Pseudomonas) from blood, urine, and wound specimens
?? Preparation of blood agar or chocolate agar for fastidious pathogens like Haemophilus influenzae and Neisseria spp.
?? Cultivation of fungi (e.g., Candida spp.) and coryneform bacteria in routine diagnostic workflows
?? Base for selective media (e.g., Columbia CNA Agar with antibiotics for Gram-positive selectivity) in food and environmental testing per FDA-BAM
Key Features:
?? Enriched peptone-yeast-beef extract formulation supports rapid, luxuriant growth and enhanced pigment production for >90% recovery of ATCC strains like S. aureus 25923
?? Corn starch neutralizes inhibitory byproducts, improving viability in mixed or contaminated samples
?? Versatile base for supplementation with blood (for hemolysis) or antibiotics (for selectivity); colonies larger and more defined than on standard blood agar
?? Validated in APHA and EU protocols; neutral pH and osmotic balance minimize stress on fastidious organisms
?? Opaque, light amber medium post-autoclaving; compatible with CO? incubation for capnophiles
Composition (per liter):
Pancreatic Digest of Casein � 12.0 g
Peptic Digest of Animal Tissue � 5.0 g
Yeast Extract � 3.0 g
Beef Extract � 3.0 g
Corn Starch � 1.0 g
Sodium Chloride (NaCl) � 5.0 g
Agar � 13.5 g
(Optional: Defibrinated Sheep Blood � 50.0 mL for blood agar variant)
Final pH: 7.3 � 0.2 at 25�C
Preparation:
Suspend 39.5 g of the dehydrated base in 950 mL of purified/distilled water. Heat with gentle agitation to boiling until completely dissolved (do not overheat to avoid starch gelatinization). Autoclave at 121�C (15 psi) for 15 minutes. Cool to 45-50�C in a water bath. For blood agar, aseptically add 50 mL sterile defibrinated sheep blood (5%) and mix thoroughly. Dispense into sterile Petri plates (20-25 mL per plate) or tubes. Allow to solidify at room temperature and dry the surface briefly if needed. The prepared base should appear light amber and clear to slightly opalescent; with blood, it becomes opaque and reddish.
Storage:
Dehydrated medium: Store in a tightly closed container at 10�30�C, protected from moisture, light, and humidity; stable until expiry date (typically 3-5 years).
Prepared plates: Store at 2�8�C in sealed plastic bags; use within 4-8 weeks. Discard if dehydrated, contaminated, discolored, or overgrown.
?? For laboratory and research use only. Not for diagnostic procedures without proper validation. Not for human or veterinary consumption. Handle under biosafety level 2; use Universal Precautions for clinical specimens�wear gloves, lab coat, and eye protection. Autoclave all waste before disposal. Blood supplementation requires sterile technique; test for hemolytic performance with QC strains. Not suitable for strict anaerobes without anaerobic conditions.5.3s