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Hippurate Test


Hardy Diagnostics Hippurate Test is to be used in the presumptive identification of Gardnerella vaginalis, Campylobacter jejuni, Listeria monocytogenes and group B streptococci, by detecting the ability of the organism to hydrolyze hippurate.


The ability of bacterial species to hydrolyze the compound hippurate was classically tested using ferric chloride indicator to detect benzoic acid, the first byproduct in the hippurate hydrolysis pathway. However, a 2½ hour rapid method as opposed to the 48 hour classical method for detecting hippurate hydrolysis has since been developed. The rapid test employs ninhydrin as the indicator, which detects glycine, the second byproduct of hippurate hydrolysis. The rapid hippurate hydrolysis test has been shown to be as specific and as sensitive as the classical method that detects the benzoic acid byproduct.


Specimen Collection: This product is not intended for primary isolation of patient specimens. This product is used in conjunction with other biochemical tests to identify cultures of isolated organism.

1. To a Hippurate Test tube, add 0.2ml (3-4 drops) of distilled water at a pH of 6.8-7.2.

2. Using a heavy inoculum (a full 10ul loop is adequate) from an 18-24 hour culture, make a heavy suspension of the organism in the Hippurate Reagent with a standard inoculating loop.

3. Incubate the tube for two hours at 35-37 degrees C.

4. During the incubation period, reconstitute the Ninhydrin Indicator Solution in the dropper bottle by adding 2ml of distilled water at a pH of 6.8-7.2. Replace the cap tip and cap, and vigorously shake for one minute. Let stand at room temperature for 30 minutes or until all the substrate has dissolved.

5. After the two hour incubation period, add two drops of the Ninhydrin Indicator Solution to the Hippurate Reagent and organism mixture.

6. Reincubate at 35-37 degrees C. for 30 minutes. Observe the tubes at 10 minute intervals for the appearance of a deep blue color, which is a positive test. The color change will usually appear in 10 to 15 minutes after the Ninhydrin Indicator Solution has been added.


A positive test is indicated by the appearance of a deep blue color in 30 minutes. A negative reaction is indicated by a faint blue color change, or no color change.  

Cat No. HDZ52

Size: 20 tests/kit


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