Liofilchem® SS Agar (Modified)

The Liofilchem® SS Agar (Modified) is a highly selective medium designed for the isolation of Salmonella spp. and certain Shigella spp. from clinical specimens, food, and other types of samples. It provides enhanced growth conditions and improved colony characteristics for salmonellae and shigellae through modifications in bile salt composition and hydrogen sulfide (H₂S) detection components. This medium is an essential tool in diagnostic microbiology and complies with stringent laboratory standards.

Key Features

1. Highly Selective Formulation:
   • Inhibits gram-positive bacteria and many non-target Enterobacteriaceae while allowing the growth of Salmonella and Shigella species.
2. Enhanced Colony Identification:
   • Detects hydrogen sulfide (H₂S)-producing Salmonella colonies with a black center.
   • Differentiates Shigella spp. colonies as light rose to colorless.
3. Optimized Composition:
   • Contains peptone, meat extract, and yeast extract for essential nutrients.
   • Incorporates bile salts and brilliant green for selective inhibition of non-target organisms.
4. Ease of Preparation:
   • Dehydrated format simplifies medium preparation; no autoclaving required.
5. Compliant with Diagnostic Standards:
   • Suitable for clinical, food, and environmental microbiology applications as part of diagnostic workflows.

Specifications

Applications

1. Clinical Microbiology:
   • Isolation and presumptive identification of Salmonella spp. and Shigella spp. from stool specimens, rectal swabs, and other clinical samples.
2. Food Microbiology:
   • Detection of Salmonella and Shigella in food samples for safety and quality control.
3. Environmental Testing:
   • Used in water and environmental testing for Salmonella and Shigella presence.

Methodology

1. Preparation:
   • Suspend 52g of dehydrated powder in 1 liter of distilled or deionized water.
   • Mix thoroughly, heat to boiling, and stir frequently until completely dissolved.
   • Do not autoclave. Cool to 45-50°C and pour into sterile Petri dishes.
2. Inoculation:
   • Use streak plate technique to inoculate the medium.
   • For swabs, roll the swab over a small area of the agar surface before streaking.
3. Incubation:
   • Incubate plates at 35 ± 2°C for 18-24 hours or longer if necessary.
4. Result Interpretation:
   • Salmonella spp.: Transparent colonies with black centers (H₂S production).
   • Shigella spp.: Light rose to colorless colonies.
   • Non-lactose fermenters: Colorless colonies.
   • Coliforms: Small colonies, pink to red in color.

Advantages

1. Enhanced Recovery:
   • Improved growth conditions for Shigella and Salmonella compared to standard SS agar.
2. Reliable H₂S Detection:
   • Enables clear identification of H₂S-producing colonies.
3. Selective Inhibition:
   • Inhibits competing flora to improve specificity for target organisms.
4. Ease of Use:
   • Ready-to-use dehydrated powder with straightforward preparation.

Limitations

• Some Shigella strains may be inhibited or show delayed lactose fermentation.
• Brilliant green may inhibit certain Shigella strains.
• Requires additional biochemical or immunological tests for definitive identification.
• Non-pathogenic organisms may occasionally grow on the medium.

Quality Control

Packaging

• 100g: Ref. 620042 (suitable for smaller laboratories or low-volume usage).
• 500g: Ref. 610042 (standard package for general laboratory needs).
• 5kg: Ref. 6100425 (ideal for high-throughput laboratories).

Why Choose Liofilchem® SS Agar (Modified)?

1. Improved Colony Morphology:
   • Enables better visualization and differentiation of Salmonella and Shigella colonies.
2. Time-Saving Preparation:
   • No autoclaving required, making preparation faster and more convenient.
3. Widely Applicable:
   • Suitable for diverse microbiology settings, including clinical, food, and environmental testing.
4. Trusted Quality:
   • Manufactured by Liofilchem®, known for high-quality microbiological media.

The Liofilchem® SS Agar (Modified) is a reliable, high-performance selective medium for isolating Salmonella spp. and Shigella spp. Its enhanced formulation, selective properties, and ease of preparation make it an invaluable tool for diagnostic microbiology workflows. This medium is ideal for clinical diagnostics, food safety, and environmental monitoring, offering consistent and accurate results.