Salmonella Shigella Agar A1 Quality – HX-Media

Salmonella Shigella Agar – HX-Media

Product Overview

Salmonella Shigella Agar (SS Agar) is a highly selective and differential solid microbiological culture medium formulated for the isolation, differentiation, and presumptive identification of enteric pathogens, particularly Salmonella spp. and Shigella spp. It is widely employed in clinical laboratories, food and beverage industries, water testing facilities, and public health laboratories for the detection of these pathogens in complex samples such as stool, food products, dairy items, and environmental water sources.

The medium is specifically designed to handle samples containing mixed microbial populations, where pathogenic organisms are often present in low numbers alongside abundant normal flora. To address this, Salmonella Shigella Agar incorporates potent selective agents such as bile salts, sodium citrate, and brilliant green dye, which effectively inhibit Gram-positive bacteria and a large proportion of non-pathogenic Gram-negative organisms. This selective suppression reduces background interference and enhances the recovery and visibility of target pathogens.

In addition to its selectivity, Salmonella Shigella Agar is a differential medium, allowing microorganisms to be distinguished based on their biochemical behavior. The presence of lactose and the pH indicator neutral red enables differentiation between lactose-fermenting and non-lactose-fermenting organisms. Lactose fermenters produce acid, resulting in pink to red colonies, whereas non-fermenters remain colorless or transparent.

A key feature of Salmonella Shigella Agar is its ability to detect hydrogen sulfide (H₂S) production, an important characteristic of many Salmonella species. The medium contains sodium thiosulfate as the sulfur source and ferric citrate as an indicator, which react to form a black precipitate (ferrous sulfide) in H₂S-producing colonies. This results in the formation of colorless colonies with black centers, providing a strong visual clue for presumptive identification.

The medium’s formulation ensures the development of distinct and easily interpretable colony morphology, making it highly effective for rapid screening and preliminary diagnosis. However, due to its strong inhibitory nature, certain strains—particularly some Shigella species—may exhibit reduced growth or may require the use of less selective media in parallel for optimal recovery.

Salmonella Shigella Agar is an essential tool in microbial quality control, epidemiological surveillance, and outbreak investigations, where accurate and early detection of enteric pathogens is critical. It supports laboratories in achieving reliable, reproducible, and efficient results, forming an important part of standard microbiological testing protocols.

Overall, Salmonella Shigella Agar remains a trusted and widely used medium that combines strong selectivity with clear differentiation, enabling effective isolation and presumptive identification of clinically and industrially significant enteric pathogens.

🔬 Key Features

• Highly selective for enteric pathogens
• Differential for lactose fermentation and H₂S production
• Provides distinct colony morphology for easy identification
• Suppresses non-pathogenic intestinal flora
• Suitable for clinical, food, and environmental samples
• Reliable for screening and presumptive diagnosis

🎯 Applications

• Isolation of Salmonella and Shigella from stool samples
• Food safety testing (meat, dairy, processed foods)
• Water quality analysis
• Environmental monitoring
• Public health surveillance and outbreak investigations
• Routine use in diagnostic laboratories

🧪 Composition (Typical)

• Peptones: 10 g/L

• Lactose: 10 g/L

• Bile Salts & Sodium Citrate: 8.5 g/L

• Sodium Thiosulfate: 8.5 g/L

• Ferric Citrate: 1 g/L

• Neutral Red: 0.025 g/L

• Brilliant Green: 0.00033 g/L

• Agar: 13.5–15 g/L

• pH: 7.0 ± 0.2

🛠️ How to Use

1. Suspend required quantity in distilled water
2. Heat gently with agitation to dissolve completely
3. Avoid autoclaving (to maintain selectivity)
4. Cool to about 45–50°C
5. Pour into sterile Petri plates
6. Allow to solidify
7. Inoculate sample using streaking technique
8. Incubate at 35–37°C for 18–24 hours
9. Observe colony characteristics for identification

⏳Storage and Shelf Life

• Store in a cool, dry place (10–30°C)
• Protect from moisture and light
• Store at 2–8°C
• Avoid dehydration and contamination
• 2–3 years (dehydrated medium)

👍 Ideal For

✔ Clinical microbiology labs

✔ Food & water testing labs

✔ Public health and environmental labs

✔ Pathogen isolation workflows