Salmonella detection · Step 4 – confirmation
Lysine Iron Agar – lysine decarboxylation and H₂S for Salmonella confirmation
Lysine Iron Agar (LIA) is used in slants together with TSI Agar for the biochemical confirmation of suspect Salmonella colonies. It shows lysine decarboxylation and hydrogen sulfide production.
- Salmonella: purple (alkaline) butt and slant, usually with black H₂S
- Used together with TSI Agar
- Dehydrated powder, 500 g bottle · COLO code PRO7522
How Lysine Iron Agar works
Glucose fermentation first acidifies the butt. Organisms that decarboxylate lysine, such as Salmonella, produce alkaline amines and the butt turns back to purple with bromocresol purple; lysine-negative organisms leave a yellow butt. Ferric ammonium citrate and thiosulfate show H₂S as a black precipitate, and deamination of lysine gives a red slant, typical for Proteus.
Reading the reactions
| Reaction | Appearance |
| Lysine decarboxylation positive | purple butt |
| Lysine decarboxylation negative | yellow butt |
| H₂S production | black precipitate |
| Lysine deamination (Proteus) | red slant |
| Typical Salmonella | purple butt and slant, black H₂S |
Applications and practical notes
Lysine Iron Agar is used together with TSI Agar for the biochemical confirmation of Salmonella in the FDA BAM Chapter 5 procedures. Typical applications include:
- confirmation of suspect colonies from XLD and other selective agars
- differentiation of Salmonella, Proteus and Citrobacter
- food and feed microbiology
- reference laboratories
Working with Lysine Iron Agar: Inoculate the same colony into TSI Agar and Lysine Iron Agar, stabbing the butt twice and streaking the slant. Keep the caps loose and read after 24 h.
Good practice with dehydrated media: keep the bottle tightly closed in a cool, dry place, weigh the powder quickly to avoid moisture uptake, and use fresh distilled or deionised water. Check the pH of each new batch after preparation and before use, and label prepared media with the date. Performance of each lot can be verified with reference strains according to ISO 11133, the standard for the preparation, production, storage and performance testing of culture media.
About the Salmonella culture method: the reference method for Salmonella in the food chain, ISO 6579-1, has four steps: non-selective pre-enrichment, selective enrichment in two broths, plating on two selective agars and confirmation of typical colonies. The FDA BAM Chapter 5 follows the same principle with media adapted to different food types. Rapid tests and identification kits shorten the time to result, but positive screening results are usually confirmed by the culture method. COLO.Science offers products for every step, so that one supplier covers the whole procedure.
Complete sets from one supplier: COLO.Science supplies culture media, supplements, rapid tests, identification kits and QC strains as complete sets for the method you follow. Send us your sample types and standards, and we will prepare an offer with the matching products and documentation.
Lysine Iron Agar is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Lysine Iron Agar, please send us a request.
Where Lysine Iron Agar fits in the Salmonella workflow
- Pre-enrichment – Buffered Peptone Water or Lactose Broth
- Selective enrichment – RVS Broth and MKTTn Broth
- Selective isolation – XLD Agar plus a second selective or chromogenic agar
- Confirmation – TSI, Lysine Iron Agar, Urea Agar, latex and biochemical identification
See the complete Salmonella set in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Lysine Iron Agar, dehydrated | PRO7522 | 500 g |
| Triple Sugar Iron Agar, dehydrated | PRO7439 | 500 g |
| Urea Agar Base, dehydrated | PRO7440 | 500 g |
Product notice: preparation, storage conditions and shelf life are given on the label. Technical data on this page are for orientation; the label and the lot documentation apply. B2B prices are quoted net, excluding VAT.
Sales and technical support
COLO LabExperts
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Quotations and technical support for culture media and microbiology products across our international sales territory. B2B prices are net, excluding VAT.
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Need the complete set for your method?
Send the sample type, target organism and the standard you follow. COLO.Science will put together the media, supplements, QC strains and confirmation tests for the whole procedure.
