MacConkey Agar (W/o CV & with 0.15% Bile salts, NaCl) A1 Quality | HX-MEDIA

MacConkey Agar (W/o CV & with 0.15% Bile salts, NaCl) | HX-MEDIA

Product Overview

MacConkey Agar (Without Crystal Violet & with 0.15% Bile Salts, NaCl) is a selective and differential culture medium specially formulated for the isolation, cultivation, and differentiation of Gram-negative enteric bacteria from a wide variety of specimens including clinical, pharmaceutical, food, dairy, water, and environmental samples. This modified version of conventional MacConkey Agar is designed to provide enhanced recovery of sensitive organisms that may otherwise be inhibited by the presence of crystal violet in standard formulations.

The medium contains 0.15% bile salts which inhibit the growth of most Gram-positive organisms while permitting the growth of Gram-negative intestinal bacilli. Since crystal violet is absent, the medium becomes less inhibitory and allows improved recovery of certain delicate enteric pathogens as well as some Gram-positive cocci that may not grow effectively on conventional MacConkey Agar. This characteristic makes the medium useful in applications where broader bacterial recovery is required.

MacConkey Agar functions as a differential medium due to the inclusion of lactose and the pH indicator neutral red. Lactose-fermenting organisms produce acid during fermentation, lowering the pH and causing colonies to appear pink, red, or dark rose-colored, often accompanied by bile precipitation around the colonies. Non-lactose fermenting organisms do not produce acid and therefore form pale, colorless, or transparent colonies. This differentiation enables rapid presumptive identification of coliforms and intestinal pathogens.

MacConkey Agar is nutritionally enriched with peptones that supply essential nitrogenous compounds, vitamins, amino acids, and growth factors necessary for bacterial growth. Sodium chloride maintains osmotic balance, while agar provides a solid surface for colony development and observation of characteristic morphology.

This modified MacConkey Agar is widely used in:

• Clinical microbiology laboratories for isolation of enteric pathogens
• Water and environmental testing for coliform detection
• Food and dairy microbiology for contamination analysis
• Pharmaceutical microbial limit testing
• Research laboratories for selective cultivation studies
• Quality control testing in industrial microbiology

Typical colony appearance on the medium includes:

• Escherichia coli: Pink to dark red colonies due to lactose fermentation
• Klebsiella species: Large mucoid pink colonies
• Salmonella and Shigella species: Colorless transparent colonies
• Proteus species: Pale colonies without swarming
• Pseudomonas species: Colorless non-lactose fermenting colonies

The omission of crystal violet also reduces excessive inhibition and improves the recovery of stressed or injured organisms, making the medium particularly beneficial for samples with low bacterial counts or organisms exposed to environmental stress.

MacConkey Agar (Without CV & with 0.15% Bile Salts, NaCl) is highly valued for its reliability, excellent colony differentiation, reproducibility, and ease of interpretation, making it one of the most commonly used selective differential media in routine microbiological analysis.

🔬 Key Features

• Selective and differential medium for enteric bacteria
• Supports recovery of delicate Gram-negative organisms
• Absence of crystal violet reduces excessive inhibition
• Differentiates lactose fermenters and non-fermenters clearly
• Contains 0.15% bile salts for selective action
• Suitable for routine microbiological testing
• Produces distinct colony morphology for easy interpretation

🎯 Applications

• Isolation of enteric Gram-negative bacteria
• Detection of coliform organisms in food and water samples
• Clinical diagnostic microbiology
• Pharmaceutical quality control testing
• Dairy and environmental microbiology
• Differentiation of lactose fermenting enteric bacteria
• Cultivation of organisms sensitive to crystal violet

🧪 Composition (Typical)

• Peptone : 17.0
• Proteose Peptone : 3.0
• Lactose : 10.0
• Bile Salts : 1.5
• Sodium Chloride : 5.0
• Neutral Red : 0.03
• Agar : 13.5

Final pH: 7.1 ± 0.2 at 25°C

🛠️ How to Use

1. Suspend the required quantity of medium in purified water.
2. Heat with gentle stirring until completely dissolved.
3. Sterilize by autoclaving at 121°C for 15 minutes.
4. Cool to 45–50°C and pour into sterile Petri plates.
5. Allow plates to solidify before inoculation.
6. Incubate inoculated plates at 35–37°C for 18–24 hours.

⏳ Storage & Shelf Life

• Store dehydrated medium below 30°C in a dry environment.
• Keep container tightly closed after use.
• Protect from moisture and direct sunlight.
• Prepared plates should be stored at 2–8°C.
• Use before expiry date for optimum performance.