| Technique | CITRATE UTILIZATION ,(/,)/,( |
| Principle | The citrate utilization test
measures the ability of a microbe to use citrate as the
SOLE carbon source. see also IMViC tests |
| Cautions | Therefore the tubes must be chemically clean and the inoculum should be as small as possible to avoid carry-over of m edium. Use a straight wire instead of a loop, inoculate from an aqueous suspension, and sub-culturel all positives to a second tube of the same medium |
| Method | Simmon's citrate and Koser's citrate
media are commonly used for this test. Other citrate
media, such as Christensens's, contain additional
nutrients and do not test the ability of the organism to
use citrate as the sole carbon source. Microbes are inoculated onto Simmons citrate by making a single streak over the surface of a slope. |
| Results | If after 2-3 days the slope is the original green colour citrate is not utilized. If the slant has changed to a blue colour and there is a streak of growth citrate is utilized as the sole carbon source. Simmons citrate only contains salts, citric acid and bromothymol blue pH indicator. An organism that grows on Koser's or Simmon's citrate will grow on Christensen's medium but the reverse may not be true |
| Positive control | |
| Negative control | |
| Reagents | |
| Reference |