CN Agar Base – Selective Medium for Pseudomonas aeruginosa Detection (250g)

CN Agar Base (Cetrimide–Nalidixic Acid Agar Base) is a selective culture medium used for the isolation and enumeration of Pseudomonas aeruginosa, particularly by the membrane filtration method. The formulation incorporates cetrimide, which inhibits most bacteria other than Pseudomonas, and requires supplementation with nalidixic acid and glycerol to achieve full selectivity and differentiation.

This medium is widely applied in water quality testing, microbiological analysis, and clinical or pharmaceutical research for the detection of Pseudomonas aeruginosa.

Complete Formula (per liter):

• Pancreatic Digest of Gelatin: 16.0 g

• Tryptone: 10.0 g

• Potassium Sulfate (K₂SO₄): 10.0 g

• Magnesium Chloride (MgCl₂): 1.4 g

• Cetrimide (Cetyltrimethylammonium Bromide): 0.2 g

• Agar: 15.0 g

• Final pH: 7.1 ± 0.2 (25°C)

Preparation & Instructions:

1. Suspend 5.26 g of medium in 100 mL distilled or deionized water.

2. Add 1 mL glycerol.

3. Sterilize by autoclaving at 121°C for 15 minutes or 115°C for 30 minutes.

4. Mix well after sterilization to avoid agar settling at the bottom.

5. Cool to 50°C, then aseptically add 1 vial nalidixic acid solution (1.5 mg/100 mL).

6. Mix thoroughly and pour plates.

7. Allow to solidify before use.

Note: The medium may appear slightly turbid due to the presence of cetrimide.

Packaging & Storage:

• 250 g per bottle

• Shelf life: 3 years

• Storage conditions: Room temperature, dry and tightly sealed