Liofilchem® Yersinia Selective Agar Base

Liofilchem Yersinia Selective Agar Base is a selective and differential medium designed for the isolation and identification of Yersinia enterocolitica from clinical, food, and environmental samples. The complete medium (CIN agar) is prepared by supplementing this base with Yersinia Supplement (ref. 81039) containing cefsulodin, irgasan (triclosan), and novobiocin, which enhance selectivity. This medium is recommended by ISO 10273 for detecting presumptive pathogenic Y. enterocolitica in food, animal feed, and water samples.

Key Features and Applications

• Selective Isolation: Inhibits most Gram-positive and enteric Gram-negative bacteria using sodium deoxycholate, crystal violet, and supplements.
• Differentiation: Differentiates between mannitol-fermenting and non-fermenting bacteria using mannitol as the fermentable carbohydrate and neutral red as a pH indicator.
• Standardized Method: Adheres to ISO 10273 for detecting pathogenic Y. enterocolitica in food production and handling areas.
• High Specificity: Supports the growth of Y. enterocolitica while suppressing other Gram-negative and Gram-positive bacteria.

Composition (g/L)

• Enzymatic Digest of Gelatin: 17.0 (source of amino acids, nitrogen, and carbon).
• Enzymatic Digest of Casein and Animal Tissues: 3.0 (provides essential nutrients).
• Yeast Extract: 2.0 (source of vitamins, particularly B-group).
• Sodium Chloride: 1.0 (maintains osmotic balance).
• Sodium Pyruvate: 2.0 (enhances growth and recovery of stressed cells).
• Magnesium Sulfate: 0.01 (stimulates enzymatic activities).
• Mannitol: 20.0 (fermentable carbohydrate for differentiation).
• Sodium Deoxycholate: 0.5 (selective agent against Gram-positive bacteria).
• Crystal Violet: 0.001 (inhibits Gram-positive bacteria).
• Neutral Red: 0.03 (pH indicator).
• Agar: 14.0 (solidifying agent).
• Final pH: 7.4 ± 0.2 at 25°C.

Preparation Instructions

1. Suspend 59.6 g of Yersinia Selective Agar Base powder in 1 liter of deionized or distilled water.
2. Heat to boiling and shake until completely dissolved.
3. Sterilize in an autoclave at 121°C for 15 minutes.
4. Cool the medium to 45-50°C.
5. Aseptically add the contents of 2 vials (6 ml) of Yersinia Supplement (ref. 81039), prepared as directed.
6. Mix well and pour into sterile Petri dishes.

Testing Technique

1. Sample Preparation: Inoculate the medium using:
   • Direct Plating: Streak the sample onto the agar surface.
   • Enrichment Method (ISO Protocol): Pre-enrich the sample in Peptone Sorbitol Bile (PSB) broth for 48-72 hours at 22-25°C with agitation, or 5 days without agitation.
2. Incubation: Incubate plates aerobically at 30 ± 1°C for 18-24 hours.
3. Colony Observation:
   • Mannitol-fermenting bacteria (e.g., Y. enterocolitica): Red-centered colonies surrounded by a transparent zone ("bull’s-eye" appearance).
   • Non-fermenting bacteria: Colorless, translucent colonies.

Results Interpretation

• Positive Test: Characteristic "bull’s-eye" colonies indicate mannitol fermentation.
• Negative Test: Translucent or colorless colonies indicate non-fermenting bacteria.
• Note: Some Serratia, Citrobacter, or Enterobacter strains may mimic Y. enterocolitica. Final identification requires biochemical confirmation.

Applications

• Food and Beverage Industry: Detect pathogenic Y. enterocolitica in food production and processing environments.
• Water Testing: Evaluate water samples for potential contamination by pathogenic Y. enterocolitica.
• Clinical Diagnostics: Isolate Yersinia enterocolitica from human specimens.
• Environmental Monitoring: Test for Yersinia contamination in environmental samples.

Product Specifications

• Format: Dehydrated powder in plastic bottles.
• Packaging Options:
  • Ref. 610111: 500 g bottle
  • Ref. 620111: 100 g bottle
• pH of Prepared Medium: 7.4 ± 0.2 at 25°C
• Appearance:
  • Powder: Free-flowing, homogeneous, pink-beige to beige.
  • Prepared Medium: Slightly opalescent, reddish-orange.

Storage and Shelf Life

• Storage: Store the powder at 10-30°C in a dry environment. Prepared plates should be stored at 2-8°C away from light.
• Shelf Life:
  • Powder: 4 years from the date of manufacture.
  • Prepared Plates: 6 months.

Quality Control

• Microbiological Control:
  • Yersinia enterocolitica (WDCM 00038): Good growth, "bull’s-eye" colonies with red center.
  • Escherichia coli (WDCM 00012): Partially or totally inhibited.
  • Staphylococcus aureus (WDCM 00034): Inhibited.
• Incubation Conditions: 18-24 h at 30 ± 1°C aerobically.

Warnings and Precautions

• For in vitro diagnostic use only.
• Operators must be trained in laboratory procedures.
• Handle according to SDS (Safety Data Sheet) guidelines.
• Dispose of waste following national and local regulations.

Compliance and Standards

• ISO 10273:2003: Horizontal method for detecting presumptive pathogenic Yersinia enterocolitica.
• EN ISO 11133: Microbiology of food, animal feed, and water – Testing of culture media.

This detailed description provides comprehensive information about Liofilchem Yersinia Selective Agar Base, covering its composition, preparation, applications, and compliance with international standards.