Liofilchem® Columbia CNA Agar Base

Liofilchem® Columbia CNA Agar Base is a selective medium specifically designed for the isolation and differentiation of Gram-positive bacteria, particularly staphylococci, streptococci, and other Gram-positive organisms. The inclusion of colistin and nalidixic acid suppresses the growth of Gram-negative bacteria, making it ideal for clinical microbiology, food microbiology, and quality control applications.

Key Features

• Selective Isolation: Inhibits Gram-negative bacteria while promoting the growth of Gram-positive organisms.
• Versatile Applications: Suitable for clinical diagnostics, food testing, and pharmaceutical quality control.
• Nutrient-Rich Base: Columbia Agar formulation provides optimal nutrients for a wide variety of Gram-positive organisms.
• Customizable: Can be enriched with 5% sheep blood for differentiating hemolytic reactions.

Typical Formula (g/L)

Principle

The medium is based on the Columbia Agar Base, a rich and versatile formulation. The selective agents colistin and nalidixic acid inhibit Gram-negative organisms by interfering with the integrity of their outer membranes (colistin) and inhibiting DNA gyrase activity (nalidixic acid). This selective environment allows Gram-positive bacteria to grow uninhibited. When enriched with 5% sheep blood, the medium also enables differentiation of hemolytic activity (alpha, beta, or gamma hemolysis).

Preparation

1. Suspend 42.5 g of the dehydrated medium in 1 liter of deionized or distilled water.
2. Heat to boiling with stirring until completely dissolved.
3. Sterilize by autoclaving at 121°C for 15 minutes.
4. Cool to 45–50°C, and if desired, add 5% sterile defibrinated sheep blood to differentiate hemolytic reactions.
5. Pour the medium into sterile Petri dishes and allow it to solidify.

Applications

1. Clinical Microbiology

• Objective: Isolation and identification of Gram-positive pathogens from clinical specimens.
• Application: Commonly used for testing wound swabs, blood cultures, and respiratory specimens to identify staphylococci, streptococci, and enterococci.

2. Food and Beverage Testing

• Objective: Detect Gram-positive bacteria in food and beverage samples as part of microbial quality analysis.
• Application: Screening raw and processed foods for contaminants.

3. Pharmaceutical Microbiology

• Objective: Ensure the microbial quality of non-sterile pharmaceutical products.
• Application: Detect and enumerate Gram-positive bacteria in raw materials and finished products.

4. Veterinary Microbiology

• Objective: Analyze animal samples for Gram-positive bacterial pathogens.
• Application: Identify pathogens in animal-derived products or veterinary specimens.

Performance Characteristics

• Growth Support: Promotes robust growth of Gram-positive organisms, including Staphylococcus aureus, Streptococcus pyogenes, and Enterococcus species.
• Selective Suppression: Effectively inhibits Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa.
• Hemolytic Differentiation (with 5% sheep blood):
  • Alpha Hemolysis: Partial hemolysis, producing a greenish discoloration (e.g., Streptococcus pneumoniae).
  • Beta Hemolysis: Complete hemolysis, resulting in a clear zone around colonies (e.g., Streptococcus pyogenes).
  • Gamma Hemolysis: No hemolysis or change in the medium.

Storage

• Dehydrated Medium: Store at 10–30°C in a dry environment in its original container, tightly closed. Avoid exposure to humidity.
• Prepared Medium: Store at 2–8°C, protected from light.
• Use the medium before the expiration date or discard if contamination or deterioration is observed.

Quality Control

Test Strains and Expected Results

Appearance

• Dehydrated Medium: Free-flowing, homogeneous powder with a light beige color.
• Prepared Medium: Opaque and light amber. When enriched with sheep blood, appears red and opaque.

Precautions

• For professional use only. Operators must be trained in microbiological techniques.
• Read the instructions thoroughly before use.
• Refer to the Safety Data Sheet (SDS) for handling and hazard information.

Packaging

• 500 g Bottle: 610113

Liofilchem® Columbia CNA Agar Base (Ref. 610113) is a robust and reliable medium for isolating and differentiating Gram-positive bacteria. With its selective suppression of Gram-negative organisms and nutrient-rich base, it is an essential tool in clinical, food, pharmaceutical, and veterinary microbiology laboratories.