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Gram Negative Broth, GN Broth
For the selective isolation of Gram-negative intestinal bacteria, especially of Shigella, from all types of materials.
Catalog Number: AS-1244
GN broth, a selective enrichment medium, is used to isolate Shigella and Salmonella from a variety of sample types. It uses peptone as its main source of nutrients, while some Gram-negative bacteria and Gram-positive organisms are inhibited by sodium deoxycholate and sodium citrate. pH stability is maintained by phosphate buffering. Target pathogen recovery is more effective when mannitol concentration is higher than when dextrose concentration is used because it inhibits Proteus growth. To improve isolation performance, GN broth is frequently used in combination with both selective and non-selective agar media.
Storage
Keep the container at 15-30 °C and prepared medium at 2-8 °C.
| Composition | gr/L |
| Tryptose | 20 |
| Sodium Chloride | 5 |
| Sodium Citrate | 5 |
| Dipotassium Hydrogen Phosphate | 4 |
| Mannitol | 2 |
| Potassium dihydrogen Phosphate | 1.5 |
| Glucose | 1 |
| Sodium Deoxycholate | 0.5 |
| Final pH at 25°C | 7.0 ± 0.2 |
| Dehydrated Appearance | Off-white to light tan, free-flowing, homogeneous. |
| Prepared Appearance | Light amber, clear to slightly opalescent. |
| Reaction of 3.9% Solution at 25°C | pH 7.0 ± 0.2 |
| Incubate at 35±2 °C for 18 to 24 hours. | |
| Organism (ATCC) | Recovery |
| Escherichia coli (25922) | Good |
| Enterococcus faecalis (19433) | None to poor |
| Salmonella enterica subsp. enterica serotype Typhimurium (14028) | Good |
| Shigella flexneri (12022) | Good |
