Voges–Proskauer or VP is a test used to detect

acetoin Acetoin, also known as 3-hydroxybutanone or acetyl methyl carbinol, is an organic compound with the formula CH3CH(OH)C(O)CH3. It is a colorless liquid with a pleasant, buttery odor. It is chiral. The form produced by bacteria is (''R'')-acetoin. ...

in a

bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

broth culture. The test is performed by adding

alpha-naphthol 1-Naphthol, or α-naphthol, is a fluorescent organic compound with the formula . It is a white solid. It is an isomer of 2-naphthol differing by the location of the hydroxyl group on the naphthalene ring. The naphthols are naphthalene homolog ...

and

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

to the Voges-Proskauer broth, which is a glucose-phosphate broth that has been inoculated with bacteria. A cherry red color indicates a positive result, while a yellow-brown color indicates a negative result. The test depends on the digestion of

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...

to acetylmethylcarbinol. In the presence of oxygen and strong base, the acetylmethylcarbinol is oxidized to diacetyl, which then reacts with guanidine compounds commonly found in the peptone medium of the broth. Alpha-naphthol acts as a color enhancer, but the color change to red can occur without it. Procedure: First, add the alpha-naphthol; then, add the potassium hydroxide. A reversal in the order of the reagents being added may result in a weak-positive or false-negative reaction. VP is one of the four tests of the

IMViC The IMViC tests are a group of individual tests used in microbiology lab testing to identify an organism in the coliform group. A coliform is a gram negative, aerobic, or facultative anaerobic rod, which produces gas from lactose within 48 hour ...

series, which tests for evidence of an enteric bacterium. The other three tests include: the

indole test Indole is an aromatic Heterocyclic compound, heterocyclic organic compound with the formula Carbon, C8Hydrogen, H7Nitrogen, N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indole ...

the

methyl red test Methyl red (2-(''N'',''N''-dimethyl-4-aminophenyl) azobenzenecarboxylic acid), also called C.I. Acid Red 2, is an indicator dye that turns red in acidic solutions. It is an azo dye, and is a dark red crystalline powder. Methyl red is a pH indi ...

and the

citrate test The citrate test detects the ability of an organism to use citrate as the sole source of carbon and energy. Principle Bacteria are inoculated on a medium containing sodium citrate and a pH indicator such as bromothymol blue. The medium also conta ...

Bachoon, Dave S., and Wendy A. Dustman. Microbiology Laboratory Manual. Ed. Michael Stranz. Mason, OH: Cengage Learning, 2008. Exercise 15, "Normal Flora of the Intestinal Tract" Print. VP positive organisms include ''

Enterobacter ''Enterobacter'' is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae. It is the type genus of the order Enterobacterales. Several strains of these bacteria are pat ...

'', ''

Klebsiella ''Klebsiella'' is a genus of Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. ''Klebsiella'' species are found everywhere in nature. This is thought to be due to distinct sublineages developin ...

'', ''

Serratia marcescens ''Serratia marcescens'' () is a species of rod-shaped, Gram-negative bacteria in the family Yersiniaceae. It is a facultative anaerobe and an opportunistic pathogen in humans. It was discovered in 1819 by Bartolomeo Bizio in Padua, Italy.Serra ...

'', '' Hafnia alvei'', ''Vibrio cholerae'' biotype El Tor, and ''

Vibrio alginolyticus ''Vibrio alginolyticus'' is a Gram-negative marine bacterium. It is medically important since it causes otitis and wound infection. It is also present in the bodies of animals such as pufferfish, where it is responsible for the production of ...

''.Bergey's Manual of Systematic Bacteriology, Vol. 1. Baltimore, Williams and Wilkins, 1984. VP negative organisms include ''

Citrobacter ''Citrobacter'' is a genus of Gram-negative coliform bacteria in the family Enterobacteriaceae. The species ''C. amalonaticus'', ''C. koseri'', and ''C. freundii'' can use citrate as a sole carbon source. ''Citrobacter'' species are differentia ...

'' sp., ''

Shigella ''Shigella'' is a genus of bacteria that is Gram-negative, facultative anaerobic, non-spore-forming, nonmotile, rod-shaped, and genetically closely related to ''E. coli''. The genus is named after Kiyoshi Shiga, who first discovered it in 1897. ...

'', ''

Yersinia ''Yersinia'' is a genus of bacteria in the family Yersiniaceae. ''Yersinia'' species are Gram-negative, coccobacilli bacteria, a few micrometers long and fractions of a micrometer in diameter, and are facultative anaerobes. Some members of ''Ye ...

'', '' Edwardsiella'', ''

Salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are ''Salmonella enterica'' and ''Salmonella bongori''. ''S. enterica'' is the type species and is fur ...

'', '' Vibrio furnissii'', ''

Vibrio fluvialis ''Vibrio fluvialis'' is a water-borne bacterium first isolated from patients with severe diarrhoea in Bahrain in the 1970s by A. L. Furniss and his colleagues, and is considered to be an emerging pathogen with the potential to have a significant ...

'', ''

Vibrio vulnificus ''Vibrio vulnificus'' is a species of Gram-negative, motile, curved rod-shaped (bacillus), pathogenic bacteria of the genus ''Vibrio''. Present in marine environments such as estuaries, brackish ponds, or coastal areas, ''V. vulnificus'' is relat ...

'', and ''

Vibrio parahaemolyticus ''Vibrio parahaemolyticus'' (V. parahaemolyticus) is a curved, rod-shaped, Gram-negative bacterium found in the sea and in estuaries which, when ingested, may cause gastrointestinal illness in humans. ''V. parahaemolyticus'' is oxidase positiv ...

''.

History

The reaction was developed by Daniel Wilhelm Otto Voges and

Bernhard Proskauer Bernhard Proskauer (8 January 1851, Ratibor – 24 July 1915, Berlin) was a German chemist and hygienist. He studied chemistry at the University of Berlin, and from 1874 worked as a chemist at the Imperial Health Office in Berlin. In 1885 h ...

, German

bacteriologist A bacteriologist is a microbiologist, or similarly trained professional, in bacteriology -- a subdivision of microbiology that studies bacteria, typically Pathogenic bacteria, pathogenic ones. Bacteriologists are interested in studying and learnin ...

s in 1898 at the Institute for Infectious Diseases.

References

External links

Voges–Proskauer reaction
at Merriam–Webster Online
Voges–Proskauer (VP) Test- Principle, Reagents, Procedure and Result
{{Clinical microbiology techniques Biochemistry detection reactions Microbiology techniques Bacteriology