OXOID SS Agar (Salmonella-Shigella Agar)

OXOID SS Agar (Salmonella-Shigella Agar) – Selective & Differential Medium

OXOID SS Agar is a high-quality selective and differential culture medium specifically designed for the isolation and differentiation of Salmonella and Shigella species from clinical, food, and environmental samples. Produced by Oxoid, this medium is widely used in microbiology laboratories for its precision and reliability.

 What is SS Agar?

Salmonella-Shigella (SS) Agar is a selective medium that inhibits most Gram-positive and many Gram-negative bacteria, allowing the growth of enteric pathogens. It also differentiates lactose fermenters from non-fermenters and detects hydrogen sulfide (H₂S) production.

 Key Features

• Selective – Inhibits Gram-positive bacteria and non-target Gram-negatives
• Differential – Distinguishes lactose fermenters from non-fermenters
• H₂S Detection – Black-centered colonies indicate H₂S-producing organisms (e.g., Salmonella)
• Reliable & Reproducible – Ideal for diagnostic, food, and environmental labs

 Composition (Typical per Liter)

• Peptone: 13.0 g
• Lactose: 10.0 g
• Bile salts: 5.0 g
• Sodium citrate: 1.0 g
• Neutral red: 0.03 g
• Ferric citrate: 1.0 g
• Agar: 15.0 g
• Final pH: 7.1 ± 0.2 at 25°C

 Principle of the Medium

• Lactose Fermenters → produce acid → colonies appear red or pink
• Non-Lactose Fermenters → colonies appear colorless
• H₂S-Producing Bacteria → black-centered colonies (e.g., Salmonella)
• Bile salts & sodium citrate → inhibit unwanted bacteria

 Applications

• Clinical Diagnostics – Isolation of Salmonella and Shigella from stool and clinical specimens
• Food & Water Testing – Detection of enteric pathogens
• Environmental Microbiology – Monitoring contamination in surfaces and water
• Pharmaceutical QC – Microbial limit testing

 Directions for Use

1. Dissolve the required amount of SS Agar powder in distilled water.
2. Heat to dissolve completely.
3. Sterilize by autoclaving at 121°C for 15 minutes.
4. Cool to 45–50°C and pour into sterile Petri dishes.
5. Allow to solidify before inoculation.

 Storage & Shelf Life

• Store in a cool, dry place (10–30°C)
• Protect from moisture and light
• Keep container tightly closed

 Precautions

• For laboratory use only
• Maintain strict aseptic technique
• Avoid overheating, which may affect selectivity and indicator performance

 Why Choose OXOID SS Agar?

With Oxoid quality assurance, SS Agar provides accurate differentiation, selective growth, and consistent results, making it a preferred choice for enteric pathogen detection worldwide.