Columbia CNA Agar (Colistin Nalidixic Acid Agar) | Selective Medium for Gram‑Positive Bacteria | AS‑1182

$145.00 AUD

AuSaMicS Life Science • Selective Media

Columbia CNA Agar

Columbia Colistin Nalidixic Acid Agar for Selective Isolation of Gram-Positive Cocci

Columbia CNA Agar is a selective medium for Gram-positive bacteria, especially Staphylococcus, Streptococcus, and Enterococcus. Built on a highly nutritive Columbia agar base and commonly used with 5% sheep blood, it supports strong recovery and clear haemolytic reactions while suppressing most Gram-negative bacilli.

AS-1182 Gram-Positive Selective ✓ Blood Agar Compatible Haemolysis Readout

🧫 Selective recovery of Gram-positive cocci 🩸 Typically used with 5% sheep blood 🔬 Strong clinical microbiology positioning

🏆 Gram-Positive Recovery Specialist

🦠 Targets staphylococci, streptococci, enterococci

⚗️ Colistin + nalidixic acid selectivity

📋 COA + SDS available

🩸 Excellent haemolysis visualization with blood

🏥 Ideal for mixed clinical specimens

Key Advantage

Suppresses Gram-negative overgrowth while preserving haemolytic detail

🔬 Principle of the Medium

Columbia CNA Agar is based on the nutrient-rich Columbia agar system, then made selective by adding colistin and nalidixic acid. Colistin disrupts susceptible Gram-negative cell membranes, while nalidixic acid inhibits DNA replication in many Gram-negative bacilli. This makes the medium highly useful when Gram-negative background flora would otherwise overgrow Gram-positive pathogens.

When supplemented with 5% blood, the medium supports luxuriant growth of Gram-positive cocci and gives sharply defined haemolytic reactions, making it especially valuable for recovery of Staphylococcus, haemolytic Streptococcus, and Enterococcus.

            Columbia base + colistin + nalidixic acid + blood

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            Inhibits Gram-negative bacilli

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            Enhances selective recovery of Gram-positive cocci

🧬 Applications

🏥 Clinical Isolation

Designed for selective isolation of Gram-positive cocci from mixed clinical specimens where Gram-negative organisms may otherwise mask clinically important growth.

🩸 Haemolysis Differentiation

Commonly used as a blood-containing selective plate to show haemolytic reactions of streptococci and related Gram-positive pathogens.

🧫 Mixed Flora Samples

Particularly helpful for specimens where Proteus, Pseudomonas, Klebsiella, and other Gram-negative bacteria tend to overgrow on conventional blood agar.

🔬 Routine Gram-Positive Workflows

Useful in routine microbiology for recovery of staphylococci, haemolytic streptococci, enterococci, and related Gram-positive organisms from non-sterile materials.

📊 Comparative Gram-Positive Isolation Media Guide

Medium	Primary Role	Best Use	Key Advantage
Columbia CNA Agar	Selective Gram-positive recovery	Mixed clinical specimens with blood	Combines strong growth support with Gram-negative inhibition
Blood Agar	General enriched cultivation	Broad primary recovery	Excellent haemolysis display but limited selectivity
PEA Blood Agar	Selective Gram-positive medium	Gram-positive recovery, especially anaerobes	Alternative selective mechanism via phenylethyl alcohol
Mannitol Salt Agar	Selective/differential staphylococcal medium	Salt-tolerant staphylococci	Good for mannitol reaction, narrower target scope

💡 Practical Notes

Medium Type:
Selective Columbia agar base

Typical Supplementation:
Usually used with 5% sheep blood

Main Target Group:
Staphylococci, streptococci, enterococci

Commercial Positioning:
Best for customers needing selective blood agar for Gram-positive cocci

📋 Technical Specifications

Product	Columbia CNA Agar
Alternative Name	Columbia Colistin Nalidixic Acid Agar
Cat. No.	AS-1182
Format	Dehydrated powder / blood agar base format
Medium Type	Selective Gram-positive isolation agar
Typical Selective Agents	Colistin 10 mg/L and nalidixic acid 15 mg/L are common published levels for the base format
Base Formula Notes	Common Columbia CNA base listings include peptones, beef heart digest or tryptic digests, corn starch, sodium chloride, and agar
Typical pH	About 7.3 ± 0.2 at 25°C
Supplementation	Often supplemented with 5% sheep blood
Storage	Typically stored dry at 2–25°C or 10–30°C depending on supplier format
HS Code	3821.00.00

🧫 Target Recovery Profile

✓ Staphylococci
✓ Haemolytic streptococci
✓ Enterococci
✓ Reduced overgrowth from many Gram-negative bacilli

✅ Quality

✓ Strong Gram-positive recovery on rich Columbia base
✓ Excellent haemolysis visualization with blood supplementation
✓ COA issued per lot

Disclaimer: For laboratory and research use only. Not for household, food, or therapeutic use.