Hektoen Enteric Agar
Used for isolation and cultivation of gram-negative enteric microorganisms, especially Shigella, from clinical and nonclinical specimens.
- Description
- Composition
- Quality Control
- Microbial Test Results
Salmonella and Shigella species can be isolated using Hektoen Enteric (HE) agar, a selective and differential medium. For nutritional support, it contains yeast extract and peptone; for carbohydrates, lactose, sucrose, and salicin are used. Bile salts distinguish lactose fermenters from Gram-positive bacteria, as do acid fuchsin and bromothymol blue markers. Hydrogen sulfide generation is detected using ferric ammonium citrate and sodium thiosulfate. Addition of novobiocin may improve selectivity. Enteric pathogens are isolated and differentiated from clinical and dietary samples using hektoen enteric agar.
Storage
Keep the container at 15-30 °C and prepared medium at 2-8 °C.
| Composition | gr/L |
| Proteose Peptone | 15 |
| Yeast Extract | 3 |
| Bile Salt No.3 | 2 |
| Lactose | 14 |
| Sucrose | 14 |
| Salicin | 2 |
| Sodium Chloride | 5 |
| Sodium Thiosulfate | 5 |
| Ferric Ammonium Citrate | 1.5 |
| Bromothymol Blue | 0.05 |
| Acid Fuchsin | 0.08 |
| Agar | 13.5 |
| Final pH at 25°C | 7.7 ± 0.2 |
| Dehydrated Appearance | Light beige, may have a slight green cast, free flowing, homogeneous. |
| Prepared Appearance | Green with yellowish cast, slightly opalescent. |
| Reaction of 7.5% Solution at 25°C | pH 7.7 ± 0.2 |
| Incubate at 35±2 °C for 18 to 24 hours. | ||
| Organism (ATCC) | Recovery | Colony Color |
| Escherichia coli (25922) | Partial inhibition | Salmon-orang may have bile precipitate |
| Enterococcus faecalis (29212) | Marked to complete inhibition | – |
| Salmonella enterica subsp. enterica serotype Typhimurium (14028) | Good | Greenish Blue, W/Black centers |
| Shigella flexneri (12022) | Good | Greenish Blue |























