| Technique | HIPPURATE HYDROLYSIS ,(/,)/,( |
| Principle | The test can be a measure of a microbe's ability to use hippurate as a carbon source or of its ability to hydrolyse hippurate to benzoate in which case ferric chloride is added. Ferric chloride precipitate both hippurate and benzoate but the hippurate is more soluble in excess. |
| Cautions | |
| Method | Hippurate broth in inoculated and incubated for 4 days. Incubate an uninoculated broth as a control. To 1 ml volumes of the control roth add 0.2, 0.3, 0.4 and 0.5 ml of ferric chloride solution and shake immediately. With small amounts of ferric chloride a preciptiate occurs; with high amounts the solution remains clear. Determine the minimal volume of acid ferric chloride that gives a clear solult ion. If 1 ml of the inoculated broth forms a preciptate with the minimal amount of ferric chloride, hippurate has been hydrolysed. Alternatively, lightly inoculate slopes of hippurate agar and examine daily for up to 7 days. |
| Results | Hydrolysis of hippurate is indicated by growth and a pink colour due to alkali production |
| Positive control | Klebsiella aerogenes (variable) Streptococcus agalactiae |
| Negative control | Enterobacter cloacae Streptococcus hominis |
| Reagents | |
| Reference |