Voges-Proskauer Assay for Differentiating Biotypes of <i>Vibrio cholerae</i>

Source: Brumfield, K. D., et al., Laboratory Techniques Used to Maintain and Differentiate Biotypes of Vibrio cholerae Clinical and Environmental Isolates. J. Vis. Exp. (2017).This video demonstrates the Voges-Proskauer (VP) test to differentiate among three biotypes of Vibrio cholerae: classical, wild-type El Tor, and El Tor variant. Each culture is inoculated into a glucose-containing medium, incubated, and treated with α-naphthol and potassium hydroxide to detect the presence of acetoin. A pinkish-red color, indicating a positive VP reaction, is observed only in the wild-type El Tor biotype, distinguishing it from the classical and variant types.