Ready-to-use media
Simmons Citrate Agar ISO
Solid medium for verifying citrate utilization by enterobacteria according to the ISO standards.
- Cat. No.
- LC-4001
- Category
- Ready-to-use media
- Format
- 20 tubes
- Storage
- 8 to 25 °C
- Minimum guaranteed shelf life
- 4 months
- Standards
- ISO 10273
- Also available
- Dehydrated medium, 1 format (LC-1014)
Simmons Citrate Agar is the solid version of the classical Koser citrate medium, and can be used in plates format as well as in slanted tubes. Slant tubes can be inoculated by surface streaking or by a deep stab. Although it was originally described as an isolation and identification medium for certain fungi, Edwards and Ewing recommended it for the IMViC (Indole, Methyl red, Voges-Proskauer and Citrate) test. It has the advantage over Koser's medium that readings can be made by the indicator colour change, instead of the turbidity of the medium, which is sometimes difficult to detect.
Key features
Applications
Confirmation of enterobacteria.
Industry
Clinical, food.
Standards
ISO 10273.
Presentation
20 slant tubes, 16 x 113 mm, with 6.2 ± 0.2 mL.
Description and technique
Technique
To ensure an accurate result, use an inoculum as small as possible and ensure the medium is freshly prepared, because if it is very dry, a false result (colour change) may appear, even before inoculation, especially at the bottom of the slant.
The basis of this medium is in the capacity of microorganisms to use citrate as a sole carbon source and ammonium compounds as the only nitrogen source for their growth. Among enterobacteria, these properties are possessed by the following genera: Enterobacter, Klebsiella, Serratia, Citrobacter and some species of Salmonella such as S. schottmuelleri, S. typhimurium, S. arizona etc. Escherichia, Shigella, Salmonella typhi and S. paratyphi are unable to grow on this medium.
Although the test result must be read as growth proceeds, the presence of an indicator makes it easier, as citrate degradation results in an alkaline reaction, which is indicated by the indicator turning an intense blue. This is evident even when the growth is at an early stage.
Precautions
Do not reuse. For professional use only.
Do not use the product if it shows evidence of microbial contamination, discoloration, drying, cracking or other signs of deterioration.
Presentation
| Presentation | 20 slant tubes, 16 x 113 mm |
|---|---|
| Filling | 6.2 ± 0.2 mL |
| Packaging | 1 box with 20 tubes, 16 x 113 mm glass tubes, ink labelled and metal cap. |
Composition
| Ingredient | g/L |
|---|---|
| Magnesium sulfate | 0.20 |
| Monoammonium phosphate | 1.00 |
| Dipotassium phosphate | 1.00 |
| Sodium citrate | 2.00 |
| Sodium chloride | 5.00 |
| Bromothymol blue | 0.08 |
| Agar | 15.00 |
Quality control
Physical/chemical control
| Color | Green |
|---|---|
| pH | 6.8 ± 0.2 at 25 °C |
Microbiological control
Poor inoculum. Loop spreading.
Analytical methodology according to ISO 11133:2014/Amd 1:2018; A2:2020.
Aerobic. Incubation at 35 ± 2 °C, for 24-72 h.
Microbiological control according to ISO 11133:2014/Amd 1:2018.
| Microorganism | Growth |
|---|---|
| Escherichia coliATCC 25922, WDCM 00013 | Inhibited - green medium |
| Ps. aeruginosaATCC 27853, WDCM 00025 | Good - blue medium |
| Enterobacter aerogenesATCC 13048, WDCM 00175 | Good - green to blue colonies |
| Salmonella typhimuriumATCC 14028, WDCM 00031 | Good - green to blue colonies |
| Escherichia coliATCC 8739, WDCM 00012 | Inhibited - green medium |
| Shigella flexneriATCC 12022, WDCM 00126 | Inhibited - green medium |
Sterility control
Incubation 48 h at 30-35 °C and 48 h at 20-25 °C: NO GROWTH.
Check at 7 days after incubation in same conditions.
Bibliography
- APHA-AWWA-WEF (1998) Standard Methods for the examination of water and wastewater. APHA. Washington DC. USA.
- DIN 38411-6 (1991) Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung; Mikrobiologische Verfahren (Gruppe K); Nachweis von Escherichia coli und coliformen Keimen (K6).
- FDA (Food and Drug Administration) (1998). Bacteriological Analytical Manual. 8th ed. Rev. A. AOAC International. Gaithersburg Md. USA.
- HORWITZ, W. (2000) Official Methods of Analysis. 17th ed. AOAC International. Gaithersburg. Md. USA.
- ISO 10273 Standard. (1994) General guidance for the detection of presumptive pathogenic Yersinia enterocolitica.
- ISO/TS 22964 (2006) Milk and milk products - Detection of Enterobacter sakazakii.
- SIMMONS J.S. (1926) A culture medium for differentiating organisms of typhoid-colon aerogenes group and for isolating certain fungi. J. Inf. Dis. 39:209.
What you receive
The product
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