Liofilchem® Biggy (Nickerson) Agar

Liofilchem® Biggy (Nickerson) Agar is a selective and differential medium developed for the detection and presumptive identification of Candida spp. from clinical specimens such as sputum, vaginal swabs, tissues, and skin scrapings.

The medium, also known as Bismuth Glucose Glycine Yeast (BiGGY) Agar, was originally formulated by Nickerson to differentiate Candida species based on colony morphology and pigmentation. Certain Candida spp. reduce bismuth and sulphite, forming brown to black colonies, often with characteristic metallic sheens or color diffusion patterns.

This medium is intended as an aid in diagnosis, with further confirmatory tests required for complete identification.

Key Features

• Selective and Differential: Formulated to inhibit bacterial contaminants and distinguish Candida spp. by colony color and morphology.
• Rapid Presumptive Identification: Characteristic pigmentation patterns help differentiate C. albicans, C. tropicalis, and C. krusei.
• Ready-to-Use or Dehydrated Formats: Available as plates, bottles, tubes, and powder for versatile laboratory use.
• Non-Autoclavable Formula: Preserves selective properties by preparation under controlled heating (do not autoclave).
• Compliant with IVDR 2017/746: Manufactured under ISO 13485-certified quality systems.
• Validated for clinical diagnostics — in vitro diagnostic (IVD) use by trained laboratory professionals.

Principle of the Method

• Yeast Extract provides amino acids, vitamins, and minerals to support fungal growth.
• Glucose serves as the fermentable carbohydrate and primary energy source.
• Glycine stimulates fungal growth and enhances colony pigmentation.
• Bismuth Ammonium Citrate and Sodium Sulphite act as differential and selective agents; their reduction by Candida spp. leads to brown-to-black pigmentation.
• Agar provides the solid matrix for colony isolation.

Pigment intensity and colony appearance vary by species due to differential reduction and metabolic activity.

Typical Formula (per litre)

Formula adjusted and/or supplemented as required to meet performance specifications.

Preparation

Dehydrated Medium

1. Suspend 47 g of powder in 1 L of distilled or deionized water.
2. Heat gently with frequent agitation until fully dissolved.
3. Do not autoclave.
4. Pour into sterile Petri dishes once cooled to 45–50°C.

Bottled Medium

1. Melt in a water bath at 100°C (loosely capped) until fully liquefied.
2. Tighten the cap, invert gently to ensure homogeneity.
3. Cool to 45–50°C, mix without foaming, and pour into Petri dishes.

Test Procedure

1. Allow plates to equilibrate to room temperature and ensure the agar surface is dry.
2. Inoculate directly by streaking the specimen or spreading from an enrichment culture to obtain isolated colonies.
3. Incubate plates aerobically at 22.5 ± 2.5°C for up to 5 days.
4. Observe colony morphology and pigmentation.

Interpretation of Results

Note: Variations may occur depending on strain and incubation conditions. Additional biochemical or molecular tests are recommended for confirmation.

Quality Control

Appearance (Dehydrated): Free-flowing, homogeneous, light beige

Appearance (Prepared): Opalescent, light amber

Storage and Stability

• Store dehydrated medium at 10–30°C in a dry, tightly closed container.
• Store prepared bottles/plates at 10–25°C, away from light.
• Avoid rapid temperature shifts to prevent condensation.
• Shelf life:
  • Dehydrated medium: 4 years
  • Bottles: 2 years
  • Tubes: 1 year
  • Ready-to-use plates: 6 months

Warnings and Precautions

• For in vitro diagnostic use (IVD).
• Professional use only: Operators must be trained in clinical microbiology techniques.
• Handle all clinical specimens as potentially infectious.
• Avoid cross-contamination between samples.
• Do not mix reagents from different lots.
• Refer to Safety Data Sheet (SDS) before use.
• Dispose of all biological waste according to national and local regulations.

Performance Characteristics

• Verified against standard Candida control strains.
• Complies with IVDR 2017/746 performance requirements.
• Productivity ratio (PR ≥ 0.5) equivalent to ≥50% recovery efficiency.
• Demonstrated selectivity against bacterial contaminants (E. coli, S. aureus).

Ordering Information

The Liofilchem® Biggy (Nickerson) Agar provides a reliable, selective, and differential medium for the isolation and presumptive identification of Candida species from clinical specimens. By exploiting the reduction of bismuth and sulphite to form pigmented colonies, it allows visual differentiation among C. albicans, C. tropicalis, C. krusei, and related species. Its ready-to-use formats and consistent quality make it ideal for clinical, veterinary, and research microbiology laboratories.