Columbia CNA Agar – Selective Medium for Gram-Positive Cocci Isolation (250g)
Selective Columbia CNA Agar for Gram-Positive Cocci Isolation with Blood Supplementation
Clinical-grade Columbia CNA Agar is specifically formulated for the selective isolation of Gram-positive cocci, including Staphylococci and Streptococci. With dual antibiotics (polymyxin & nalidixic acid), this medium effectively inhibits Gram-negative bacteria while supporting enriched growth of target organisms when supplemented with 5% sheep blood.
Key Applications:
🦠 Clinical Microbiology: Selective isolation of pathogenic Gram-positive cocci
🩸 Blood Agar Preparation: Base medium for Columbia CNA blood agar plates
🧫 Antibiotic Resistance Studies: Polymyxin/nalidixic acid combination testing
Critical Technical Features:
✅ Dual Antibiotic Selection: 0.01g/L polymyxin + 0.01g/L nalidixic acid
✅ Nutrient-Rich Formula: 12.0g/L casein peptone + 3.0g/L yeast/beef extracts
✅ Blood Agar Ready: Optimized for 5% defibrinated sheep blood addition
✅ pH-Controlled: 7.3±0.2 at 25°C for consistent performance
Preparation Protocol:
Suspend 42.5g in 1L distilled water
Autoclave at 121°C for 12 minutes
For blood agar: Cool to 50-55°C, add 5% sheep blood aseptically
Essential Step: Pre-solidification mixing prevents agar sedimentation
Complete Formulation (Per Liter):
Pancreatic Digest of Casein: 12.0g
Peptic Digest of Animal Tissue: 5.0g
Yeast Extract: 3.0g
Beef Extract: 3.0g
Maize Starch: 1.0g
Sodium Chloride: 5.0g
Polymyxin: 0.01g
Nalidixic Acid: 0.01g
Agar: 13.5g
