Key Scientific has found that modifications in the original procedure can produce more clear cut reactions as well as shorten the incubation period. Key's rapid V-P test can be used in place of any standard V-P test. Since the pyruvate to acetoin conversion occurs more efficiently at a slightly acid pH, the tablets contain dextrose to insure adequate acid formation.

Voges-Proskauer Tablets contain 10 mg. of sodium pyruvate per tablet with dextrose and other inert ingredients. WEE-TABS contain 1 mg. sodium pyruvate.

Voges-Proskauer Tablets do not contain any material known at this time to be hazardous.

Alpha-Naphthol Tablets contain 200 mg. of alpha naphthol per tablet. Alpha-naphthol is harmful if inhaled, ingested, or absorbed through the skin, and causes severe irritation. In case of exposure, immediately flood eyes and skin with large amounts of water and remove contaminated apparel. Wash contaminated clothing before reusing.

Voges-Proskauer tests require preliminary growth on appropriate media. Consult a manual such as the Manual for Clinical Microbiology for this information. Each item is sold separately.

K660 Voges Proskauer-50/bottle

K1660 WEE-TAB-28 ready-to-use tubes.

K675 Alpha-Naphthol Tablets-10 each

The following items are also required but not provided:

Test tubes

Loop for colony transfer

Distilled water

Isopropyl alcohol

40% KOH

Dissolve 1 alpha-naphthol tablet in 5 ml. of isopropyl alcohol. This makes enough for 15-20 tests and must be made fresh daily.

(1) Place 1 V-P Tablet and 1 ml. of distilled water into a test tube.

(2) Inoculate heavily with either 2-3 drops of a heavy suspension of the organism to be tested or with a heavy loopful of organism directly from the plate. Best results require a final suspension of at least a #3 McFarland.

(3) Incubate at 37C for 6-8 hours, but no more than 8 hours. Inoculating the V-P tube and refrigerating overnight for incubation the next day will not adversely affect the test.

(4) After incubation, add 3 drops of 40% KOH and mix by gently shaking.

(5) Next add 2 drops of alpha-naphthol reagent. The reagent will form a thin layer on the surface of the liquid. Allow the tube to stand up to 30 minutes, observing periodically for the appearance of a cherry red color.

WEE-TAB: Setup with 5 drops of the suspension or add 5 drops of water to tube for direct inoculation. WEE-TABs should incubate 3-4 hours. Use only 1 drop KOH and 1 drop Alpha-naphthol.

In a positive V-P test, the acetoin will react with alpha-naphthol in the alkaline environment provided by the KOH to produce a cherry red color. The color develops first at the surface and then spreads gradually into the lower part of the tube. In a strong reaction the color appears almost immediately but weaker ones may take 20-30 minutes. No color change, or the appearance of a copper color is a negative result.

KEY Voges-Proskauer Tablets should be tested prior to use with organisms which produce known reactions. The Manual for Clinical Microbiology suggests Enterobacter aerogenes for positives and E. coli for negative. Finished tests should be discarded in a manner appropriate for biohazardous materials

Store unused tablets and desiccant tightly sealed at room temperature.

Serratia marcescens +

Serratia liquifaciens +

Klebsiella pneumoniae +

Klebsiella oxytoca +

Enterobacter aerogenes +

Enterobacter cloacae +

Proteus mirabilis +

Proteus vulgaris -

E. coli -

Salmonella -

Shigella -

Citrobacter freundii -

Morganella morganii -

Yersinia enterocolitica -

1) Manual of Clinical Microbiology, Fifth Edition, Chapter 120, "Quality Control" and Chapter 122, "Reagents and Stains"

2) Bailey and Scott's Diagnostic Microbiology, Seventh Edition, Chapter 27, "Enterobacteraceae"

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