Ready-to-use media
Lysine Iron Agar
Differential medium for enterobacteria.
- Cat. No.
- LC-4007
- Category
- Ready-to-use media
- Format
- 20 tubes
- Storage
- 8 to 25 °C
- Minimum guaranteed shelf life
- 3 months
- Also available
- Dehydrated medium, 1 format (LC-1044)
LIA medium permits differentiation of Enterobacteriaceae based on their capacity to deaminate and decarboxylate lysine and produce hydrogen sulfide.
Key features
Applications
Differentiation of enterobacteria and Salmonella arizonae.
Industry
Food.
Presentation
20 slant tubes, 16 x 113 mm, with 7.5 ± 0.3 mL.
Packaging
1 box with 20 tubes, 16 x 113 mm glass tubes, ink labelled and metal cap.
Description and technique
Description
It was developed for the identification of strains of Salmonella arizonae, especially those with rapid fermentation of lactose. In TSI, the lactose fermenting strains produce an acidification of the medium that prevents the production of hydrogen sulfide. In Lysine Iron Agar, Salmonella species are identified by their ability to decarboxylate lysine and produce hydrogen sulfide.
Gelatin peptone and yeast extract are sources of nitrogen, carbon, vitamins and minerals. Ferric ammonium citrate and sodium thiosulfate are indicators of hydrogen sulfide production, with the formation of a black precipitate of iron sulfide. Bromocresol purple is a pH indicator. The fermentable sugar is glucose and fermentation causes acidification of the bottom of the tube, which turns yellow. Lysine is the substrate of lysine decarboxylase and lysine deaminase. The decarboxylation of lysine alkalinizes the medium, which changes to purple. Deamination of lysine leads to the formation of red or orange compounds in the presence of oxygen (at the medium surface).
Acidification of the bottom of the tube in lysine decarboxylase negative strains may prevent detection of hydrogen sulfide production. Therefore, Proteus species producing hydrogen sulfide cannot blacken the medium.
Technique
From a single colony, using an inoculating needle, stab the butt and make a streak on the inclined surface.
The tubes are incubated under aerobic conditions (with cap unscrewed) at 35 ± 2 °C for 24 h.
Presentation
| Presentation | 20 slant tubes, 16 x 113 mm |
|---|---|
| Filling | 7.5 ± 0.3 mL |
| Packaging | 1 box with 20 tubes, 16 x 113 mm glass tubes, ink labelled and metal cap. |
Composition
| Ingredient | g/L |
|---|---|
| Gelatin peptone | 5.00 |
| Yeast extract | 3.00 |
| Dextrose | 1.00 |
| Lysine | 10.0 |
| Ammonium ferric citrate | 0.50 |
| Sodium thiosulfate | 0.04 |
| Bromocresol purple | 0.02 |
| Agar | 15.00 |
Quality control
Physical/chemical control
| Color | Violet |
|---|---|
| pH | 6.7 ± 0.2 at 25 °C |
Microbiological control
Inoculate by stabbing the butt + streak the slant.
Aerobiosis. Incubation at 35 ± 2 °C, reading after 18-24 hours.
| Microorganism | Growth |
|---|---|
| Escherichia coliATCC 25922, WDCM 00013 | A. slant/bottom: purple; H₂S (-) |
| Proteus mirabilisATCC 43071 | A. slant: red; A. butt: yellow-ochre; H₂S (-) |
| Salmonella typhimuriumATCC 14028, WDCM 00031 | A. slant/bottom: purple; H₂S (+) |
| Shigella flexneriATCC 12022, WDCM 00126 | A. slant: purple; A. bottom: yellow-ochre; H₂S (-) |
Sterility control
Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.
Check at 7 days after incubation in same conditions.
Bibliography
- ATLAS, R.M., L.C. PARKS (1993) Handbook of Microbiological Media. CRC Press, Inc. London.
- DOWNES, F.P. & K. ITO (2001) Compendium of methods for the microbiological examination of foods. 4th ed. APHA. Washington.
- EDWARS, P.R., & FIFE, MARY A. (1961) Lysine-Iron Agar in the detection of Arizona cultures. Appl. Microbiol 99, 478-480.
- EWING, J. (1982) Edwars and Ewing's identification of Enterobacteriaceae. 4th ed. Elsevier Sci. Pub. Co. Inc. N.Y.
- HORWITZ, W. (2000) Official Methods of Analysis. 17th ed. AOAC International. Gaithersburg. MD. USA.
- MARSHALL, R.T. (1992) Methods for the examination of dairy products. 16th ed. APHA. Washington.
- MacFADDIN, J.F. (1985) Media for the isolation, cultivation, identification and maintenance of medical bacteria. William & Wilkins. Baltimore.
What you receive
The product
Shipped under controlled temperature when the product requires it.
Lot certificate
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Frequently asked questions
Can I ask for formats other than those listed?
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